app: fix automatic window decoration action processing

This commit adapts the use of the automatic window decorations to the
event processing changes introduced in v0.4.0. You must update widget
state before laying it out, not after. Doing so after (as this code used
to do) results in discarding updates.

Fixes: https://todo.sr.ht/~eliasnaur/gio/542
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>

.builds/apple.yml

@@ -8,16 +8,21 @@ packages:
  - libxml2-dev
  - libssl-dev
  - libz-dev
- - llvm-dev # for cctools
+ - llvm-dev # cctools
- - uuid-dev ## for cctools
+ - uuid-dev # cctools
+ - ninja-build # cctools
+ - systemtap-sdt-dev # cctools
+ - libbsd-dev # cctools
+ - linux-libc-dev # cctools
  - libplist-utils # for gogio
 sources:
  - https://git.sr.ht/~eliasnaur/applesdks
  - https://git.sr.ht/~eliasnaur/gio
  - https://git.sr.ht/~eliasnaur/giouiorg
- - https://github.com/tpoechtrager/cctools-port.git
+ - https://github.com/tpoechtrager/cctools-port
- - https://github.com/tpoechtrager/apple-libtapi.git
+ - https://github.com/tpoechtrager/apple-libtapi
- - https://github.com/mackyle/xar.git
+ - https://github.com/tpoechtrager/apple-libdispatch
+ - https://github.com/mackyle/xar
 environment:
    APPLE_TOOLCHAIN_ROOT: /home/build/appletools
    PATH: /home/build/sdk/go/bin:/home/build/go/bin:/usr/bin
@@ -42,6 +47,11 @@ tasks:
  - install_appletoolchain: |
      cd giouiorg
      go build -o $APPLE_TOOLCHAIN_ROOT/tools ./cmd/appletoolchain
+ - build_libdispatch: |
+     cd apple-libdispatch
+     cmake -G Ninja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_INSTALL_PREFIX=$APPLE_TOOLCHAIN_ROOT/libdispatch .
+     ninja
+     ninja install
  - build_xar: |
      cd xar/xar
      ac_cv_lib_crypto_OpenSSL_add_all_ciphers=yes CC=clang ./autogen.sh --prefix=/usr
@@ -53,7 +63,7 @@ tasks:
      ./install.sh
  - build_cctools: |
      cd cctools-port/cctools
-     ./configure --prefix $APPLE_TOOLCHAIN_ROOT/toolchain --with-libtapi=$APPLE_TOOLCHAIN_ROOT/libtapi --target=x86_64-apple-darwin19
+     ./configure --target=x86_64-apple-darwin19 --prefix $APPLE_TOOLCHAIN_ROOT/toolchain --with-libtapi=$APPLE_TOOLCHAIN_ROOT/libtapi --with-libdispatch=$APPLE_TOOLCHAIN_ROOT/libdispatch --with-libblocksruntime=$APPLE_TOOLCHAIN_ROOT/libdispatch
      make install
  - test_macos: |
      cd gio

.builds/linux.yml

@@ -67,11 +67,6 @@ tasks:
      CGO_ENABLED=1 GOARCH=386 go test ./...
      GOOS=windows go test -exec=wine ./...
      GOOS=js GOARCH=wasm go build -o /dev/null ./...
- - install_chrome: |
-     curl -s https://dl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
-     sudo sh -c 'echo "deb [arch=amd64] https://dl-ssl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list'
-     sudo apt-get -qq update
-     sudo apt-get -qq install -y google-chrome-stable
  - install_jdk8: |
      curl -so jdk.deb "https://cdn.azul.com/zulu/bin/zulu8.42.0.21-ca-jdk8.0.232-linux_amd64.deb"
      sudo apt-get -qq install -y -f ./jdk.deb

app/d3d11_windows.go

@@ -60,10 +60,10 @@ func (c *d3d11Context) RenderTarget() (gpu.RenderTarget, error) {
 }
 
 func (c *d3d11Context) Present() error {
-	err := c.swchain.Present(1, 0)
+	return wrapErr(c.swchain.Present(1, 0))
-	if err == nil {
+}
-		return nil
+
-	}
+func wrapErr(err error) error {
 	if err, ok := err.(d3d11.ErrorCode); ok {
 		switch err.Code {
 		case d3d11.DXGI_STATUS_OCCLUDED:
@@ -84,7 +84,7 @@ func (c *d3d11Context) Refresh() error {
 	}
 	c.releaseFBO()
 	if err := c.swchain.ResizeBuffers(0, 0, 0, d3d11.DXGI_FORMAT_UNKNOWN, 0); err != nil {
-		return err
+		return wrapErr(err)
 	}
 	c.width = width
 	c.height = height

app/doc.go

@@ -12,16 +12,16 @@ Create a new Window by calling NewWindow. On mobile platforms or when Gio
 is embedded in another project, NewWindow merely connects with a previously
 created window.
 
-A Window is run by receiving events from its Events channel. The most
+A Window is run by calling NextEvent in a loop. The most important event is
-important event is FrameEvent that prompts an update of the window
+FrameEvent that prompts an update of the window contents.
-contents and state.
 
 For example:
 
 	import "gioui.org/unit"
 
 	w := app.NewWindow()
-	for e := range w.Events() {
+	for {
+		e := w.NextEvent()
 		if e, ok := e.(system.FrameEvent); ok {
 			ops.Reset()
 			// Add operations to ops.
@@ -50,7 +50,8 @@ For example, to display a blank but otherwise functional window:
 	func main() {
 		go func() {
 			w := app.NewWindow()
-			for range w.Events() {
+			for {
+				w.NextEvent()
 			}
 		}()
 		app.Main()

app/internal/windows/windows.go

@@ -47,6 +47,13 @@ type WndClassEx struct {
 	HIconSm       syscall.Handle
 }
 
+type Margins struct {
+	CxLeftWidth    int32
+	CxRightWidth   int32
+	CyTopHeight    int32
+	CyBottomHeight int32
+}
+
 type Msg struct {
 	Hwnd     syscall.Handle
 	Message  uint32
@@ -69,6 +76,21 @@ type MinMaxInfo struct {
 	PtMaxTrackSize Point
 }
 
+type NCCalcSizeParams struct {
+	Rgrc  [3]Rect
+	LpPos *WindowPos
+}
+
+type WindowPos struct {
+	HWND            syscall.Handle
+	HWNDInsertAfter syscall.Handle
+	x               int32
+	y               int32
+	cx              int32
+	cy              int32
+	flags           uint32
+}
+
 type WindowPlacement struct {
 	length           uint32
 	flags            uint32
@@ -245,6 +267,7 @@ const (
 	WM_MOUSEHWHEEL          = 0x020E
 	WM_NCACTIVATE           = 0x0086
 	WM_NCHITTEST            = 0x0084
+	WM_NCCALCSIZE           = 0x0083
 	WM_PAINT                = 0x000F
 	WM_QUIT                 = 0x0012
 	WM_SETCURSOR            = 0x0020
@@ -323,6 +346,7 @@ var (
 	_DispatchMessage             = user32.NewProc("DispatchMessageW")
 	_EmptyClipboard              = user32.NewProc("EmptyClipboard")
 	_GetWindowRect               = user32.NewProc("GetWindowRect")
+	_GetClientRect               = user32.NewProc("GetClientRect")
 	_GetClipboardData            = user32.NewProc("GetClipboardData")
 	_GetDC                       = user32.NewProc("GetDC")
 	_GetDpiForWindow             = user32.NewProc("GetDpiForWindow")
@@ -379,6 +403,9 @@ var (
 	_ImmReleaseContext       = imm32.NewProc("ImmReleaseContext")
 	_ImmSetCandidateWindow   = imm32.NewProc("ImmSetCandidateWindow")
 	_ImmSetCompositionWindow = imm32.NewProc("ImmSetCompositionWindow")
+
+	dwmapi                        = syscall.NewLazySystemDLL("dwmapi")
+	_DwmExtendFrameIntoClientArea = dwmapi.NewProc("DwmExtendFrameIntoClientArea")
 )
 
 func AdjustWindowRectEx(r *Rect, dwStyle uint32, bMenu int, dwExStyle uint32) {
@@ -430,6 +457,14 @@ func DispatchMessage(m *Msg) {
 	_DispatchMessage.Call(uintptr(unsafe.Pointer(m)))
 }
 
+func DwmExtendFrameIntoClientArea(hwnd syscall.Handle, margins Margins) error {
+	r, _, _ := _DwmExtendFrameIntoClientArea.Call(uintptr(hwnd), uintptr(unsafe.Pointer(&margins)))
+	if r != 0 {
+		return fmt.Errorf("DwmExtendFrameIntoClientArea: %#x", r)
+	}
+	return nil
+}
+
 func EmptyClipboard() error {
 	r, _, err := _EmptyClipboard.Call()
 	if r == 0 {
@@ -444,6 +479,12 @@ func GetWindowRect(hwnd syscall.Handle) Rect {
 	return r
 }
 
+func GetClientRect(hwnd syscall.Handle) Rect {
+	var r Rect
+	_GetClientRect.Call(uintptr(hwnd), uintptr(unsafe.Pointer(&r)))
+	return r
+}
+
 func GetClipboardData(format uint32) (syscall.Handle, error) {
 	r, _, err := _GetClipboardData.Call(uintptr(format))
 	if r == 0 {

app/internal/xkb/xkb_unix.go

@@ -242,6 +242,9 @@ func convertKeysym(s C.xkb_keysym_t) (string, bool) {
 	if 'a' <= s && s <= 'z' {
 		return string(rune(s - 'a' + 'A')), true
 	}
+	if C.XKB_KEY_KP_0 <= s && s <= C.XKB_KEY_KP_9 {
+		return string(rune(s - C.XKB_KEY_KP_0 + '0')), true
+	}
 	if ' ' < s && s <= '~' {
 		return string(rune(s)), true
 	}
@@ -255,8 +258,6 @@ func convertKeysym(s C.xkb_keysym_t) (string, bool) {
 		n = key.NameRightArrow
 	case C.XKB_KEY_Return:
 		n = key.NameReturn
-	case C.XKB_KEY_KP_Enter:
-		n = key.NameEnter
 	case C.XKB_KEY_Up:
 		n = key.NameUpArrow
 	case C.XKB_KEY_Down:
@@ -297,9 +298,9 @@ func convertKeysym(s C.xkb_keysym_t) (string, bool) {
 		n = key.NameF11
 	case C.XKB_KEY_F12:
 		n = key.NameF12
-	case C.XKB_KEY_Tab, C.XKB_KEY_KP_Tab, C.XKB_KEY_ISO_Left_Tab:
+	case C.XKB_KEY_Tab, C.XKB_KEY_ISO_Left_Tab:
 		n = key.NameTab
-	case 0x20, C.XKB_KEY_KP_Space:
+	case 0x20:
 		n = key.NameSpace
 	case C.XKB_KEY_Control_L, C.XKB_KEY_Control_R:
 		n = key.NameCtrl
@@ -309,6 +310,64 @@ func convertKeysym(s C.xkb_keysym_t) (string, bool) {
 		n = key.NameAlt
 	case C.XKB_KEY_Super_L, C.XKB_KEY_Super_R:
 		n = key.NameSuper
+
+	case C.XKB_KEY_KP_Space:
+		n = key.NameSpace
+	case C.XKB_KEY_KP_Tab:
+		n = key.NameTab
+	case C.XKB_KEY_KP_Enter:
+		n = key.NameEnter
+	case C.XKB_KEY_KP_F1:
+		n = key.NameF1
+	case C.XKB_KEY_KP_F2:
+		n = key.NameF2
+	case C.XKB_KEY_KP_F3:
+		n = key.NameF3
+	case C.XKB_KEY_KP_F4:
+		n = key.NameF4
+	case C.XKB_KEY_KP_Home:
+		n = key.NameHome
+	case C.XKB_KEY_KP_Left:
+		n = key.NameLeftArrow
+	case C.XKB_KEY_KP_Up:
+		n = key.NameUpArrow
+	case C.XKB_KEY_KP_Right:
+		n = key.NameRightArrow
+	case C.XKB_KEY_KP_Down:
+		n = key.NameDownArrow
+	case C.XKB_KEY_KP_Prior:
+		// not supported
+		return "", false
+	case C.XKB_KEY_KP_Next:
+		// not supported
+		return "", false
+	case C.XKB_KEY_KP_End:
+		n = key.NameEnd
+	case C.XKB_KEY_KP_Begin:
+		n = key.NameHome
+	case C.XKB_KEY_KP_Insert:
+		// not supported
+		return "", false
+	case C.XKB_KEY_KP_Delete:
+		n = key.NameDeleteForward
+	case C.XKB_KEY_KP_Multiply:
+		n = "*"
+	case C.XKB_KEY_KP_Add:
+		n = "+"
+	case C.XKB_KEY_KP_Separator:
+		// not supported
+		return "", false
+	case C.XKB_KEY_KP_Subtract:
+		n = "-"
+	case C.XKB_KEY_KP_Decimal:
+		// TODO(dh): does a German keyboard layout also translate the numpad key to XKB_KEY_KP_DECIMAL? Because in
+		// German, the decimal is a comma, not a period.
+		n = "."
+	case C.XKB_KEY_KP_Divide:
+		n = "/"
+	case C.XKB_KEY_KP_Equal:
+		n = "="
+
 	default:
 		return "", false
 	}

app/os_android.go

@@ -953,18 +953,18 @@ func Java_org_gioui_GioView_onKeyEvent(env *C.JNIEnv, class C.jclass, handle C.j
 //export Java_org_gioui_GioView_onTouchEvent
 func Java_org_gioui_GioView_onTouchEvent(env *C.JNIEnv, class C.jclass, handle C.jlong, action, pointerID, tool C.jint, x, y, scrollX, scrollY C.jfloat, jbtns C.jint, t C.jlong) {
 	w := cgo.Handle(handle).Value().(*window)
-	var typ pointer.Type
+	var kind pointer.Kind
 	switch action {
 	case C.AMOTION_EVENT_ACTION_DOWN, C.AMOTION_EVENT_ACTION_POINTER_DOWN:
-		typ = pointer.Press
+		kind = pointer.Press
 	case C.AMOTION_EVENT_ACTION_UP, C.AMOTION_EVENT_ACTION_POINTER_UP:
-		typ = pointer.Release
+		kind = pointer.Release
 	case C.AMOTION_EVENT_ACTION_CANCEL:
-		typ = pointer.Cancel
+		kind = pointer.Cancel
 	case C.AMOTION_EVENT_ACTION_MOVE:
-		typ = pointer.Move
+		kind = pointer.Move
 	case C.AMOTION_EVENT_ACTION_SCROLL:
-		typ = pointer.Scroll
+		kind = pointer.Scroll
 	default:
 		return
 	}
@@ -994,7 +994,7 @@ func Java_org_gioui_GioView_onTouchEvent(env *C.JNIEnv, class C.jclass, handle C
 		return
 	}
 	w.callbacks.Event(pointer.Event{
-		Type:      typ,
+		Kind:      kind,
 		Source:    src,
 		Buttons:   btns,
 		PointerID: pointer.ID(pointerID),

app/os_darwin.go

@@ -6,7 +6,7 @@ package app
 #include <Foundation/Foundation.h>
 
 __attribute__ ((visibility ("hidden"))) void gio_wakeupMainThread(void);
-__attribute__ ((visibility ("hidden"))) CFTypeRef gio_createDisplayLink(uintptr_t handle);
+__attribute__ ((visibility ("hidden"))) CFTypeRef gio_createDisplayLink(void);
 __attribute__ ((visibility ("hidden"))) void gio_releaseDisplayLink(CFTypeRef dl);
 __attribute__ ((visibility ("hidden"))) int gio_startDisplayLink(CFTypeRef dl);
 __attribute__ ((visibility ("hidden"))) int gio_stopDisplayLink(CFTypeRef dl);
@@ -42,7 +42,7 @@ static CFTypeRef newNSString(unichar *chars, NSUInteger length) {
 import "C"
 import (
 	"errors"
-	"runtime/cgo"
+	"sync"
 	"sync/atomic"
 	"time"
 	"unicode/utf16"
@@ -70,6 +70,9 @@ type displayLink struct {
 	running uint32
 }
 
+// displayLinks maps CFTypeRefs to *displayLinks.
+var displayLinks sync.Map
+
 var mainFuncs = make(chan func(), 1)
 
 // runOnMain runs the function on the main thread.
@@ -121,25 +124,25 @@ func stringToNSString(str string) C.CFTypeRef {
 	return C.newNSString(chars, C.NSUInteger(len(u16)))
 }
 
-func NewDisplayLink(callback func()) (*displayLink, error) {
+func newDisplayLink(callback func()) (*displayLink, error) {
 	d := &displayLink{
 		callback: callback,
 		done:     make(chan struct{}),
 		states:   make(chan bool),
 		dids:     make(chan uint64),
 	}
-	h := cgo.NewHandle(d)
+	dl := C.gio_createDisplayLink()
-	dl := C.gio_createDisplayLink(C.uintptr_t(h))
 	if dl == 0 {
 		return nil, errors.New("app: failed to create display link")
 	}
-	go d.run(dl, h)
+	go d.run(dl)
 	return d, nil
 }
 
-func (d *displayLink) run(dl C.CFTypeRef, h cgo.Handle) {
+func (d *displayLink) run(dl C.CFTypeRef) {
 	defer C.gio_releaseDisplayLink(dl)
-	defer h.Delete()
+	displayLinks.Store(dl, d)
+	defer displayLinks.Delete(dl)
 	var stopTimer *time.Timer
 	var tchan <-chan time.Time
 	started := false
@@ -200,10 +203,14 @@ func (d *displayLink) SetDisplayID(did uint64) {
 }
 
 //export gio_onFrameCallback
-func gio_onFrameCallback(dl C.CFTypeRef, handle C.uintptr_t) {
+func gio_onFrameCallback(ref C.CFTypeRef) {
-	d := cgo.Handle(handle).Value().(*displayLink)
+	d, exists := displayLinks.Load(ref)
-	if atomic.LoadUint32(&d.running) != 0 {
+	if !exists {
-		d.callback()
+		return
+	}
+	dl := d.(*displayLink)
+	if atomic.LoadUint32(&dl.running) != 0 {
+		dl.callback()
 	}
 }
 

app/os_ios.go

@@ -117,7 +117,7 @@ func onCreate(view, controller C.CFTypeRef) {
 	w := &window{
 		view: view,
 	}
-	dl, err := NewDisplayLink(func() {
+	dl, err := newDisplayLink(func() {
 		w.draw(false)
 	})
 	if err != nil {
@@ -236,16 +236,16 @@ func onText(view, str C.CFTypeRef) {
 
 //export onTouch
 func onTouch(last C.int, view, touchRef C.CFTypeRef, phase C.NSInteger, x, y C.CGFloat, ti C.double) {
-	var typ pointer.Type
+	var kind pointer.Kind
 	switch phase {
 	case C.UITouchPhaseBegan:
-		typ = pointer.Press
+		kind = pointer.Press
 	case C.UITouchPhaseMoved:
-		typ = pointer.Move
+		kind = pointer.Move
 	case C.UITouchPhaseEnded:
-		typ = pointer.Release
+		kind = pointer.Release
 	case C.UITouchPhaseCancelled:
-		typ = pointer.Cancel
+		kind = pointer.Cancel
 	default:
 		return
 	}
@@ -253,7 +253,7 @@ func onTouch(last C.int, view, touchRef C.CFTypeRef, phase C.NSInteger, x, y C.C
 	t := time.Duration(float64(ti) * float64(time.Second))
 	p := f32.Point{X: float32(x), Y: float32(y)}
 	w.w.Event(pointer.Event{
-		Type:      typ,
+		Kind:      kind,
 		Source:    pointer.Touch,
 		PointerID: w.lookupTouch(last != 0, touchRef),
 		Position:  p,

app/os_ios.m

@@ -123,6 +123,9 @@ static void handleTouches(int last, UIView *view, NSSet<UITouch *> *touches, UIE
 
 @implementation GioView
 NSArray<UIKeyCommand *> *_keyCommands;
++ (void)onFrameCallback:(CADisplayLink *)link {
+       gio_onFrameCallback((__bridge CFTypeRef)link);
+}
 + (Class)layerClass {
     return gio_layerClass();
 }
@@ -227,23 +230,8 @@ NSArray<UIKeyCommand *> *_keyCommands;
 }
 @end
 
-@interface DisplayLinkHandle : NSObject {
+CFTypeRef gio_createDisplayLink(void) {
-}
+	CADisplayLink *dl = [CADisplayLink displayLinkWithTarget:[GioView class] selector:@selector(onFrameCallback:)];
-@property uintptr_t handle;
-@end
-
-@implementation DisplayLinkHandle {
-}
-
-- (void)onFrameCallback:(CADisplayLink *)link {
-	gio_onFrameCallback((__bridge CFTypeRef)link, _handle);
-}
-@end
-
-CFTypeRef gio_createDisplayLink(uintptr_t handle) {
-	DisplayLinkHandle *h = [DisplayLinkHandle alloc];
-	h.handle = handle;
-	CADisplayLink *dl = [CADisplayLink displayLinkWithTarget:h selector:@selector(onFrameCallback:)];
 	dl.paused = YES;
 	NSRunLoop *runLoop = [NSRunLoop mainRunLoop];
 	[dl addToRunLoop:runLoop forMode:[runLoop currentMode]];

app/os_js.go

@@ -275,7 +275,7 @@ func (w *window) addEventListeners() {
 		}
 		w.touches = w.touches[:0]
 		w.w.Event(pointer.Event{
-			Type:   pointer.Cancel,
+			Kind:   pointer.Cancel,
 			Source: pointer.Touch,
 		})
 		return nil
@@ -398,7 +398,7 @@ func modifiersFor(e js.Value) key.Modifiers {
 	return mods
 }
 
-func (w *window) touchEvent(typ pointer.Type, e js.Value) {
+func (w *window) touchEvent(kind pointer.Kind, e js.Value) {
 	e.Call("preventDefault")
 	t := time.Duration(e.Get("timeStamp").Int()) * time.Millisecond
 	changedTouches := e.Get("changedTouches")
@@ -426,7 +426,7 @@ func (w *window) touchEvent(typ pointer.Type, e js.Value) {
 			Y: float32(y) * scale,
 		}
 		w.w.Event(pointer.Event{
-			Type:      typ,
+			Kind:      kind,
 			Source:    pointer.Touch,
 			Position:  pos,
 			PointerID: pid,
@@ -448,7 +448,7 @@ func (w *window) touchIDFor(touch js.Value) pointer.ID {
 	return pid
 }
 
-func (w *window) pointerEvent(typ pointer.Type, dx, dy float32, e js.Value) {
+func (w *window) pointerEvent(kind pointer.Kind, dx, dy float32, e js.Value) {
 	e.Call("preventDefault")
 	x, y := e.Get("clientX").Float(), e.Get("clientY").Float()
 	rect := w.cnv.Call("getBoundingClientRect")
@@ -476,7 +476,7 @@ func (w *window) pointerEvent(typ pointer.Type, dx, dy float32, e js.Value) {
 		btns |= pointer.ButtonTertiary
 	}
 	w.w.Event(pointer.Event{
-		Type:      typ,
+		Kind:      kind,
 		Source:    pointer.Mouse,
 		Buttons:   btns,
 		Position:  pos,

app/os_macos.go

@@ -192,6 +192,10 @@ static CFTypeRef windowForView(CFTypeRef viewRef) {
 }
 
 static void raiseWindow(CFTypeRef windowRef) {
+	NSRunningApplication *currentApp = [NSRunningApplication currentApplication];
+	if (![currentApp isActive]) {
+		[currentApp activateWithOptions:(NSApplicationActivateAllWindows | NSApplicationActivateIgnoringOtherApps)];
+	}
 	NSWindow* window = (__bridge NSWindow *)windowRef;
 	[window makeKeyAndOrderFront:nil];
 }
@@ -297,7 +301,9 @@ func (w *window) contextView() C.CFTypeRef {
 
 func (w *window) ReadClipboard() {
 	cstr := C.readClipboard()
-	defer C.CFRelease(cstr)
+	if cstr != 0 {
+		defer C.CFRelease(cstr)
+	}
 	content := nsstringToString(cstr)
 	w.w.Event(clipboard.Event{Text: content})
 }
@@ -365,11 +371,11 @@ func (w *window) Configure(options []Option) {
 		case Minimized:
 			C.unhideWindow(window)
 		case Maximized:
+			if C.isWindowZoomed(window) != 0 {
+				C.zoomWindow(window)
+			}
 		}
 		w.config.Mode = Windowed
-		if C.isWindowZoomed(window) != 0 {
-			C.zoomWindow(window)
-		}
 		w.setTitle(prev, cnf)
 		if prev.Size != cnf.Size {
 			w.config.Size = cnf.Size
@@ -523,8 +529,10 @@ func gio_onMouse(view, evt C.CFTypeRef, cdir C.int, cbtn C.NSInteger, x, y, dx,
 		btn = pointer.ButtonPrimary
 	case 1:
 		btn = pointer.ButtonSecondary
+	case 2:
+		btn = pointer.ButtonTertiary
 	}
-	var typ pointer.Type
+	var typ pointer.Kind
 	switch cdir {
 	case C.MOUSE_MOVE:
 		typ = pointer.Move
@@ -548,7 +556,7 @@ func gio_onMouse(view, evt C.CFTypeRef, cdir C.int, cbtn C.NSInteger, x, y, dx,
 		panic("invalid direction")
 	}
 	w.w.Event(pointer.Event{
-		Type:      typ,
+		Kind:      typ,
 		Source:    pointer.Mouse,
 		Time:      t,
 		Buttons:   w.pointerBtns,
@@ -788,13 +796,13 @@ func configFor(scale float32) unit.Metric {
 //export gio_onClose
 func gio_onClose(view C.CFTypeRef) {
 	w := mustView(view)
-	w.displayLink.Close()
 	w.w.Event(ViewEvent{})
-	deleteView(view)
 	w.w.Event(system.DestroyEvent{})
+	w.displayLink.Close()
+	w.displayLink = nil
+	deleteView(view)
 	C.CFRelease(w.view)
 	w.view = 0
-	w.displayLink = nil
 }
 
 //export gio_onHide
@@ -882,7 +890,7 @@ func newOSWindow() (*window, error) {
 		scale:  scale,
 		redraw: make(chan struct{}, 1),
 	}
-	dl, err := NewDisplayLink(func() {
+	dl, err := newDisplayLink(func() {
 		select {
 		case w.redraw <- struct{}{}:
 		default:

app/os_macos.m

@@ -92,24 +92,30 @@ static void handleMouse(NSView *view, NSEvent *event, int typ, CGFloat dx, CGFlo
 - (void)mouseUp:(NSEvent *)event {
 	handleMouse(self, event, MOUSE_UP, 0, 0);
 }
-- (void)middleMouseDown:(NSEvent *)event {
-	handleMouse(self, event, MOUSE_DOWN, 0, 0);
-}
-- (void)middleMouseUp:(NSEvent *)event {
-	handleMouse(self, event, MOUSE_UP, 0, 0);
-}
 - (void)rightMouseDown:(NSEvent *)event {
 	handleMouse(self, event, MOUSE_DOWN, 0, 0);
 }
 - (void)rightMouseUp:(NSEvent *)event {
 	handleMouse(self, event, MOUSE_UP, 0, 0);
 }
+- (void)otherMouseDown:(NSEvent *)event {
+	handleMouse(self, event, MOUSE_DOWN, 0, 0);
+}
+- (void)otherMouseUp:(NSEvent *)event {
+	handleMouse(self, event, MOUSE_UP, 0, 0);
+}
 - (void)mouseMoved:(NSEvent *)event {
 	handleMouse(self, event, MOUSE_MOVE, 0, 0);
 }
 - (void)mouseDragged:(NSEvent *)event {
 	handleMouse(self, event, MOUSE_MOVE, 0, 0);
 }
+- (void)rightMouseDragged:(NSEvent *)event {
+	handleMouse(self, event, MOUSE_MOVE, 0, 0);
+}
+- (void)otherMouseDragged:(NSEvent *)event {
+	handleMouse(self, event, MOUSE_MOVE, 0, 0);
+}
 - (void)scrollWheel:(NSEvent *)event {
 	CGFloat dx = -event.scrollingDeltaX;
 	CGFloat dy = -event.scrollingDeltaY;
@@ -193,14 +199,14 @@ static void handleMouse(NSView *view, NSEvent *event, int typ, CGFloat dx, CGFlo
 static GioWindowDelegate *globalWindowDel;
 
 static CVReturn displayLinkCallback(CVDisplayLinkRef dl, const CVTimeStamp *inNow, const CVTimeStamp *inOutputTime, CVOptionFlags flagsIn, CVOptionFlags *flagsOut, void *handle) {
-	gio_onFrameCallback(dl, (uintptr_t)handle);
+	gio_onFrameCallback(dl);
 	return kCVReturnSuccess;
 }
 
-CFTypeRef gio_createDisplayLink(uintptr_t handle) {
+CFTypeRef gio_createDisplayLink(void) {
 	CVDisplayLinkRef dl;
 	CVDisplayLinkCreateWithActiveCGDisplays(&dl);
-	CVDisplayLinkSetOutputCallback(dl, displayLinkCallback, (void *)(handle));
+	CVDisplayLinkSetOutputCallback(dl, displayLinkCallback, nil);
 	return dl;
 }
 

app/os_wayland.go

@@ -791,7 +791,7 @@ func gio_onTouchDown(data unsafe.Pointer, touch *C.struct_wl_touch, serial, t C.
 		Y: fromFixed(y) * float32(w.scale),
 	}
 	w.w.Event(pointer.Event{
-		Type:      pointer.Press,
+		Kind:      pointer.Press,
 		Source:    pointer.Touch,
 		Position:  w.lastTouch,
 		PointerID: pointer.ID(id),
@@ -807,7 +807,7 @@ func gio_onTouchUp(data unsafe.Pointer, touch *C.struct_wl_touch, serial, t C.ui
 	w := s.touchFoci[id]
 	delete(s.touchFoci, id)
 	w.w.Event(pointer.Event{
-		Type:      pointer.Release,
+		Kind:      pointer.Release,
 		Source:    pointer.Touch,
 		Position:  w.lastTouch,
 		PointerID: pointer.ID(id),
@@ -825,7 +825,7 @@ func gio_onTouchMotion(data unsafe.Pointer, touch *C.struct_wl_touch, t C.uint32
 		Y: fromFixed(y) * float32(w.scale),
 	}
 	w.w.Event(pointer.Event{
-		Type:      pointer.Move,
+		Kind:      pointer.Move,
 		Position:  w.lastTouch,
 		Source:    pointer.Touch,
 		PointerID: pointer.ID(id),
@@ -844,7 +844,7 @@ func gio_onTouchCancel(data unsafe.Pointer, touch *C.struct_wl_touch) {
 	for id, w := range s.touchFoci {
 		delete(s.touchFoci, id)
 		w.w.Event(pointer.Event{
-			Type:   pointer.Cancel,
+			Kind:   pointer.Cancel,
 			Source: pointer.Touch,
 		})
 	}
@@ -869,7 +869,7 @@ func gio_onPointerLeave(data unsafe.Pointer, p *C.struct_wl_pointer, serial C.ui
 	s.serial = serial
 	if w.inCompositor {
 		w.inCompositor = false
-		w.w.Event(pointer.Event{Type: pointer.Cancel})
+		w.w.Event(pointer.Event{Kind: pointer.Cancel})
 	}
 }
 
@@ -917,21 +917,21 @@ func gio_onPointerButton(data unsafe.Pointer, p *C.struct_wl_pointer, serial, t,
 			}
 		}
 	}
-	var typ pointer.Type
+	var kind pointer.Kind
 	switch state {
 	case 0:
 		w.pointerBtns &^= btn
-		typ = pointer.Release
+		kind = pointer.Release
 		// Move or resize gestures no longer applies.
 		w.inCompositor = false
 	case 1:
 		w.pointerBtns |= btn
-		typ = pointer.Press
+		kind = pointer.Press
 	}
 	w.flushScroll()
 	w.resetFling()
 	w.w.Event(pointer.Event{
-		Type:      typ,
+		Kind:      kind,
 		Source:    pointer.Mouse,
 		Buttons:   w.pointerBtns,
 		Position:  w.lastPos,
@@ -1573,7 +1573,7 @@ func (w *window) flushScroll() {
 		return
 	}
 	w.w.Event(pointer.Event{
-		Type:      pointer.Scroll,
+		Kind:      pointer.Scroll,
 		Source:    pointer.Mouse,
 		Buttons:   w.pointerBtns,
 		Position:  w.lastPos,
@@ -1596,7 +1596,7 @@ func (w *window) onPointerMotion(x, y C.wl_fixed_t, t C.uint32_t) {
 		Y: fromFixed(y) * float32(w.scale),
 	}
 	w.w.Event(pointer.Event{
-		Type:      pointer.Move,
+		Kind:      pointer.Move,
 		Position:  w.lastPos,
 		Buttons:   w.pointerBtns,
 		Source:    pointer.Mouse,

app/os_windows.go

@@ -32,11 +32,6 @@ type ViewEvent struct {
 	HWND uintptr
 }
 
-type winDeltas struct {
-	width  int32
-	height int32
-}
-
 type window struct {
 	hwnd        syscall.Handle
 	hdc         syscall.Handle
@@ -55,7 +50,6 @@ type window struct {
 	animating bool
 	focused   bool
 
-	deltas     winDeltas
 	borderSize image.Point
 	config     Config
 }
@@ -192,22 +186,12 @@ func createNativeWindow() (*window, error) {
 // It reads the window style and size/position and updates w.config.
 // If anything has changed it emits a ConfigEvent to notify the application.
 func (w *window) update() {
-	r := windows.GetWindowRect(w.hwnd)
+	cr := windows.GetClientRect(w.hwnd)
-	size := image.Point{
+	w.config.Size = image.Point{
-		X: int(r.Right - r.Left - w.deltas.width),
+		X: int(cr.Right - cr.Left),
-		Y: int(r.Bottom - r.Top - w.deltas.height),
+		Y: int(cr.Bottom - cr.Top),
 	}
 
-	// Check the window mode.
-	style := windows.GetWindowLong(w.hwnd, windows.GWL_STYLE)
-	if style&windows.WS_OVERLAPPEDWINDOW == 0 {
-		size = image.Point{
-			X: int(r.Right - r.Left),
-			Y: int(r.Bottom - r.Top),
-		}
-	}
-	w.config.Size = size
-
 	w.borderSize = image.Pt(
 		windows.GetSystemMetrics(windows.SM_CXSIZEFRAME),
 		windows.GetSystemMetrics(windows.SM_CYSIZEFRAME),
@@ -275,7 +259,7 @@ func windowProc(hwnd syscall.Handle, msg uint32, wParam, lParam uintptr) uintptr
 		w.pointerButton(pointer.ButtonTertiary, false, lParam, getModifiers())
 	case windows.WM_CANCELMODE:
 		w.w.Event(pointer.Event{
-			Type: pointer.Cancel,
+			Kind: pointer.Cancel,
 		})
 	case windows.WM_SETFOCUS:
 		w.focused = true
@@ -304,7 +288,7 @@ func windowProc(hwnd syscall.Handle, msg uint32, wParam, lParam uintptr) uintptr
 		x, y := coordsFromlParam(lParam)
 		p := f32.Point{X: float32(x), Y: float32(y)}
 		w.w.Event(pointer.Event{
-			Type:      pointer.Move,
+			Kind:      pointer.Move,
 			Source:    pointer.Mouse,
 			Position:  p,
 			Buttons:   w.pointerBtns,
@@ -325,6 +309,28 @@ func windowProc(hwnd syscall.Handle, msg uint32, wParam, lParam uintptr) uintptr
 		// The system destroys the HWND for us.
 		w.hwnd = 0
 		windows.PostQuitMessage(0)
+	case windows.WM_NCCALCSIZE:
+		if w.config.Decorated {
+			// Let Windows handle decorations.
+			break
+		}
+		// No client areas; we draw decorations ourselves.
+		if wParam != 1 {
+			return 0
+		}
+		// lParam contains an NCCALCSIZE_PARAMS for us to adjust.
+		place := windows.GetWindowPlacement(w.hwnd)
+		if !place.IsMaximized() {
+			// Nothing do adjust.
+			return 0
+		}
+		// Adjust window position to avoid the extra padding in maximized
+		// state. See https://devblogs.microsoft.com/oldnewthing/20150304-00/?p=44543.
+		// Note that trying to do the adjustment in WM_GETMINMAXINFO is ignored by Windows.
+		szp := (*windows.NCCalcSizeParams)(unsafe.Pointer(uintptr(lParam)))
+		mi := windows.GetMonitorInfo(w.hwnd)
+		szp.Rgrc[0] = mi.WorkArea
+		return 0
 	case windows.WM_PAINT:
 		w.draw(true)
 	case windows.WM_SIZE:
@@ -344,18 +350,26 @@ func windowProc(hwnd syscall.Handle, msg uint32, wParam, lParam uintptr) uintptr
 		}
 	case windows.WM_GETMINMAXINFO:
 		mm := (*windows.MinMaxInfo)(unsafe.Pointer(uintptr(lParam)))
+		var bw, bh int32
+		if w.config.Decorated {
+			r := windows.GetWindowRect(w.hwnd)
+			cr := windows.GetClientRect(w.hwnd)
+			bw = r.Right - r.Left - (cr.Right - cr.Left)
+			bh = r.Bottom - r.Top - (cr.Bottom - cr.Top)
+		}
 		if p := w.config.MinSize; p.X > 0 || p.Y > 0 {
 			mm.PtMinTrackSize = windows.Point{
-				X: int32(p.X) + w.deltas.width,
+				X: int32(p.X) + bw,
-				Y: int32(p.Y) + w.deltas.height,
+				Y: int32(p.Y) + bh,
 			}
 		}
 		if p := w.config.MaxSize; p.X > 0 || p.Y > 0 {
 			mm.PtMaxTrackSize = windows.Point{
-				X: int32(p.X) + w.deltas.width,
+				X: int32(p.X) + bw,
-				Y: int32(p.Y) + w.deltas.height,
+				Y: int32(p.Y) + bh,
 			}
 		}
+		return 0
 	case windows.WM_SETCURSOR:
 		w.cursorIn = (lParam & 0xffff) == windows.HTCLIENT
 		if w.cursorIn {
@@ -446,23 +460,18 @@ func (w *window) hitTest(x, y int) uintptr {
 	if w.config.Mode == Fullscreen {
 		return windows.HTCLIENT
 	}
-	p := f32.Pt(float32(x), float32(y))
-	if a, ok := w.w.ActionAt(p); ok && a == system.ActionMove {
-		return windows.HTCAPTION
-	}
 	if w.config.Mode != Windowed {
 		// Only windowed mode should allow resizing.
 		return windows.HTCLIENT
 	}
+	// Check for resize handle before system actions; otherwise it can be impossible to
+	// resize a custom-decorations window when the system move area is flush with the
+	// edge of the window.
 	top := y <= w.borderSize.Y
 	bottom := y >= w.config.Size.Y-w.borderSize.Y
 	left := x <= w.borderSize.X
 	right := x >= w.config.Size.X-w.borderSize.X
 	switch {
-	default:
-		fallthrough
-	case !top && !bottom && !left && !right:
-		return windows.HTCLIENT
 	case top && left:
 		return windows.HTTOPLEFT
 	case top && right:
@@ -480,6 +489,11 @@ func (w *window) hitTest(x, y int) uintptr {
 	case right:
 		return windows.HTRIGHT
 	}
+	p := f32.Pt(float32(x), float32(y))
+	if a, ok := w.w.ActionAt(p); ok && a == system.ActionMove {
+		return windows.HTCAPTION
+	}
+	return windows.HTCLIENT
 }
 
 func (w *window) pointerButton(btn pointer.Buttons, press bool, lParam uintptr, kmods key.Modifiers) {
@@ -487,15 +501,15 @@ func (w *window) pointerButton(btn pointer.Buttons, press bool, lParam uintptr,
 		windows.SetFocus(w.hwnd)
 	}
 
-	var typ pointer.Type
+	var kind pointer.Kind
 	if press {
-		typ = pointer.Press
+		kind = pointer.Press
 		if w.pointerBtns == 0 {
 			windows.SetCapture(w.hwnd)
 		}
 		w.pointerBtns |= btn
 	} else {
-		typ = pointer.Release
+		kind = pointer.Release
 		w.pointerBtns &^= btn
 		if w.pointerBtns == 0 {
 			windows.ReleaseCapture()
@@ -504,7 +518,7 @@ func (w *window) pointerButton(btn pointer.Buttons, press bool, lParam uintptr,
 	x, y := coordsFromlParam(lParam)
 	p := f32.Point{X: float32(x), Y: float32(y)}
 	w.w.Event(pointer.Event{
-		Type:      typ,
+		Kind:      kind,
 		Source:    pointer.Mouse,
 		Position:  p,
 		Buttons:   w.pointerBtns,
@@ -539,7 +553,7 @@ func (w *window) scrollEvent(wParam, lParam uintptr, horizontal bool, kmods key.
 		}
 	}
 	w.w.Event(pointer.Event{
-		Type:      pointer.Scroll,
+		Kind:      pointer.Scroll,
 		Source:    pointer.Mouse,
 		Position:  p,
 		Buttons:   w.pointerBtns,
@@ -669,9 +683,6 @@ func (w *window) Configure(options []Option) {
 	swpStyle := uintptr(windows.SWP_NOZORDER | windows.SWP_FRAMECHANGED)
 	winStyle := uintptr(windows.WS_OVERLAPPEDWINDOW)
 	style &^= winStyle
-	if !w.config.Decorated {
-		winStyle = 0
-	}
 	switch w.config.Mode {
 	case Minimized:
 		style |= winStyle
@@ -684,41 +695,44 @@ func (w *window) Configure(options []Option) {
 		showMode = windows.SW_SHOWMAXIMIZED
 
 	case Windowed:
-		windows.SetWindowText(w.hwnd, w.config.Title)
 		style |= winStyle
 		showMode = windows.SW_SHOWNORMAL
-		// Get target for client areaa size.
+		// Get target for client area size.
 		width = int32(w.config.Size.X)
 		height = int32(w.config.Size.Y)
 		// Get the current window size and position.
 		wr := windows.GetWindowRect(w.hwnd)
-		// Set desired window size.
-		wr.Right = wr.Left + width
-		wr.Bottom = wr.Top + height
-		// Convert from client size to window size.
-		r := wr
-		windows.AdjustWindowRectEx(&r, uint32(style), 0, dwExStyle)
-		// Calculate difference between client and full window sizes.
-		w.deltas.width = r.Right - wr.Right + wr.Left - r.Left
-		w.deltas.height = r.Bottom - wr.Bottom + wr.Top - r.Top
-		// Set new window size and position.
 		x = wr.Left
 		y = wr.Top
-		width = r.Right - r.Left
+		if w.config.Decorated {
-		height = r.Bottom - r.Top
+			// Compute client size and position. Note that the client size is
+			// equal to the window size when we are in control of decorations.
+			r := windows.Rect{
+				Right:  width,
+				Bottom: height,
+			}
+			windows.AdjustWindowRectEx(&r, uint32(style), 0, dwExStyle)
+			width = r.Right - r.Left
+			height = r.Bottom - r.Top
+		}
+		if !w.config.Decorated {
+			// Enable drop shadows when we draw decorations.
+			windows.DwmExtendFrameIntoClientArea(w.hwnd, windows.Margins{-1, -1, -1, -1})
+		}
 
 	case Fullscreen:
+		swpStyle |= windows.SWP_NOMOVE | windows.SWP_NOSIZE
 		mi := windows.GetMonitorInfo(w.hwnd)
 		x, y = mi.Monitor.Left, mi.Monitor.Top
 		width = mi.Monitor.Right - mi.Monitor.Left
 		height = mi.Monitor.Bottom - mi.Monitor.Top
-		showMode = windows.SW_SHOW
+		showMode = windows.SW_SHOWMAXIMIZED
 	}
 	windows.SetWindowLong(w.hwnd, windows.GWL_STYLE, style)
 	windows.SetWindowPos(w.hwnd, 0, x, y, width, height, swpStyle)
 	windows.ShowWindow(w.hwnd, showMode)
 
-	w.w.Event(ConfigEvent{Config: w.config})
+	w.update()
 }
 
 func (w *window) WriteClipboard(s string) {

app/os_x11.go

@@ -547,7 +547,7 @@ func (h *x11EventHandler) handleEvents() bool {
 		case C.ButtonPress, C.ButtonRelease:
 			bevt := (*C.XButtonEvent)(unsafe.Pointer(xev))
 			ev := pointer.Event{
-				Type:   pointer.Press,
+				Kind:   pointer.Press,
 				Source: pointer.Mouse,
 				Position: f32.Point{
 					X: float32(bevt.x),
@@ -557,7 +557,7 @@ func (h *x11EventHandler) handleEvents() bool {
 				Modifiers: w.xkb.Modifiers(),
 			}
 			if bevt._type == C.ButtonRelease {
-				ev.Type = pointer.Release
+				ev.Kind = pointer.Release
 			}
 			var btn pointer.Buttons
 			const scrollScale = 10
@@ -569,7 +569,7 @@ func (h *x11EventHandler) handleEvents() bool {
 			case C.Button3:
 				btn = pointer.ButtonSecondary
 			case C.Button4:
-				ev.Type = pointer.Scroll
+				ev.Kind = pointer.Scroll
 				// scroll up or left (if shift is pressed).
 				if ev.Modifiers == key.ModShift {
 					ev.Scroll.X = -scrollScale
@@ -578,7 +578,7 @@ func (h *x11EventHandler) handleEvents() bool {
 				}
 			case C.Button5:
 				// scroll down or right (if shift is pressed).
-				ev.Type = pointer.Scroll
+				ev.Kind = pointer.Scroll
 				if ev.Modifiers == key.ModShift {
 					ev.Scroll.X = +scrollScale
 				} else {
@@ -587,11 +587,11 @@ func (h *x11EventHandler) handleEvents() bool {
 			case 6:
 				// http://xahlee.info/linux/linux_x11_mouse_button_number.html
 				// scroll left.
-				ev.Type = pointer.Scroll
+				ev.Kind = pointer.Scroll
 				ev.Scroll.X = -scrollScale * 2
 			case 7:
 				// scroll right
-				ev.Type = pointer.Scroll
+				ev.Kind = pointer.Scroll
 				ev.Scroll.X = +scrollScale * 2
 			default:
 				continue
@@ -607,7 +607,7 @@ func (h *x11EventHandler) handleEvents() bool {
 		case C.MotionNotify:
 			mevt := (*C.XMotionEvent)(unsafe.Pointer(xev))
 			w.w.Event(pointer.Event{
-				Type:    pointer.Move,
+				Kind:    pointer.Move,
 				Source:  pointer.Mouse,
 				Buttons: w.pointerBtns,
 				Position: f32.Point{

app/window.go

@@ -61,6 +61,8 @@ type Window struct {
 	// actions are the actions waiting to be performed.
 	actions chan system.Action
 
+	// out is where the platform backend delivers events bound for the
+	// user program.
 	out      chan event.Event
 	frames   chan *op.Ops
 	frameAck chan struct{}
@@ -107,6 +109,16 @@ type Window struct {
 	}
 
 	imeState editorState
+
+	// event stores the state required for processing and delivering events
+	// from NextEvent. If we had support for range over func, this would
+	// be the iterator state.
+	eventState struct {
+		created     bool
+		initialOpts []Option
+		wakeup      func()
+		timer       *time.Timer
+	}
 }
 
 type editorState struct {
@@ -185,7 +197,7 @@ func NewWindow(options ...Option) *Window {
 	w.imeState.compose = key.Range{Start: -1, End: -1}
 	w.semantic.ids = make(map[router.SemanticID]router.SemanticNode)
 	w.callbacks.w = w
-	go w.run(options)
+	w.eventState.initialOpts = options
 	return w
 }
 
@@ -195,11 +207,6 @@ func decoHeightOpt(h unit.Dp) Option {
 	}
 }
 
-// Events returns the channel where events are delivered.
-func (w *Window) Events() <-chan event.Event {
-	return w.out
-}
-
 // update the window contents, input operations declare input handlers,
 // and so on. The supplied operations list completely replaces the window state
 // from previous calls.
@@ -713,7 +720,7 @@ func (w *Window) waitAck(d driver) {
 		select {
 		case f := <-w.driverFuncs:
 			f(d)
-		case w.out <- event.Event(nil):
+		case w.out <- theFlushEvent:
 			// A dummy event went through, so we know the application has processed the previous event.
 			return
 		case <-w.immediateRedraws:
@@ -747,7 +754,7 @@ func (w *Window) waitFrame(d driver) *op.Ops {
 		case frame := <-w.frames:
 			// The client called FrameEvent.Frame.
 			return frame
-		case w.out <- event.Event(nil):
+		case w.out <- theFlushEvent:
 			// The client ignored FrameEvent and continued processing
 			// events.
 			return nil
@@ -881,7 +888,6 @@ func (w *Window) processEvent(d driver, e event.Event) bool {
 		if err := w.validateAndProcess(d, viewSize, e2.Sync, wrapper, signal); err != nil {
 			w.destroyGPU()
 			w.out <- system.DestroyEvent{Err: err}
-			close(w.out)
 			close(w.destroy)
 			break
 		}
@@ -890,7 +896,6 @@ func (w *Window) processEvent(d driver, e event.Event) bool {
 	case system.DestroyEvent:
 		w.destroyGPU()
 		w.out <- e2
-		close(w.out)
 		close(w.destroy)
 	case ViewEvent:
 		w.out <- e2
@@ -899,6 +904,7 @@ func (w *Window) processEvent(d driver, e event.Event) bool {
 		w.decorations.Config = e2.Config
 		e2.Config = w.effectiveConfig()
 		w.out <- e2
+	case wakeupEvent:
 	case event.Event:
 		handled := w.queue.q.Queue(e2)
 		if e, ok := e.(key.Event); ok && !handled {
@@ -938,43 +944,51 @@ func (w *Window) processEvent(d driver, e event.Event) bool {
 	return true
 }
 
-func (w *Window) run(options []Option) {
+// NextEvent blocks until an event is received from the window, such as
-	if err := newWindow(&w.callbacks, options); err != nil {
+// [io/system.FrameEvent]. It blocks forever if called after [io/system.DestroyEvent]
-		w.out <- system.DestroyEvent{Err: err}
+// has been returned.
-		close(w.out)
+func (w *Window) NextEvent() event.Event {
-		close(w.destroy)
+	state := &w.eventState
-		return
+	if !state.created {
+		state.created = true
+		if err := newWindow(&w.callbacks, state.initialOpts); err != nil {
+			close(w.destroy)
+			return system.DestroyEvent{Err: err}
+		}
 	}
-	var wakeup func()
-	var timer *time.Timer
 	for {
 		var (
 			wakeups <-chan struct{}
 			timeC   <-chan time.Time
 		)
-		if wakeup != nil {
+		if state.wakeup != nil {
 			wakeups = w.wakeups
-			if timer != nil {
+			if state.timer != nil {
-				timeC = timer.C
+				timeC = state.timer.C
 			}
 		}
 		select {
 		case t := <-w.scheduledRedraws:
-			if timer != nil {
+			if state.timer != nil {
-				timer.Stop()
+				state.timer.Stop()
 			}
-			timer = time.NewTimer(time.Until(t))
+			state.timer = time.NewTimer(time.Until(t))
-		case <-w.destroy:
+		case e := <-w.out:
-			return
+			// Receiving a flushEvent indicates to the platform backend that
+			// all previous events have been processed by the user program.
+			if _, ok := e.(flushEvent); ok {
+				break
+			}
+			return e
 		case <-timeC:
 			select {
 			case w.redraws <- struct{}{}:
-				wakeup()
+				state.wakeup()
 			default:
 			}
 		case <-wakeups:
-			wakeup()
+			state.wakeup()
-		case wakeup = <-w.wakeupFuncs:
+		case state.wakeup = <-w.wakeupFuncs:
 		}
 	}
 }
@@ -1022,9 +1036,9 @@ func (w *Window) decorate(d driver, e system.FrameEvent, o *op.Ops) (size, offse
 		Metric:      e.Metric,
 		Constraints: layout.Exact(e.Size),
 	}
-	style.Layout(gtx)
 	// Update the window based on the actions on the decorations.
-	w.Perform(deco.Actions())
+	w.Perform(deco.Update(gtx))
+	style.Layout(gtx)
 	// Offset to place the frame content below the decorations.
 	decoHeight := gtx.Dp(w.decorations.Config.decoHeight)
 	if w.decorations.currentHeight != decoHeight {
@@ -1165,3 +1179,14 @@ func Decorated(enabled bool) Option {
 		cnf.Decorated = enabled
 	}
 }
+
+// flushEvent is sent to detect when the user program
+// has completed processing of all prior events. Its an
+// [io/event.Event] but only for internal use.
+type flushEvent struct{}
+
+func (t flushEvent) ImplementsEvent() {}
+
+// theFlushEvent avoids allocating garbage when sending
+// flushEvents.
+var theFlushEvent flushEvent

gesture/gesture.go

@@ -39,18 +39,18 @@ type Hover struct {
 func (h *Hover) Add(ops *op.Ops) {
 	pointer.InputOp{
 		Tag:   h,
-		Types: pointer.Enter | pointer.Leave,
+		Kinds: pointer.Enter | pointer.Leave,
 	}.Add(ops)
 }
 
-// Hovered returns whether a pointer is inside the area.
+// Update state and report whether a pointer is inside the area.
-func (h *Hover) Hovered(q event.Queue) bool {
+func (h *Hover) Update(q event.Queue) bool {
 	for _, ev := range q.Events(h) {
 		e, ok := ev.(pointer.Event)
 		if !ok {
 			continue
 		}
-		switch e.Type {
+		switch e.Kind {
 		case pointer.Leave, pointer.Cancel:
 			if h.entered && h.pid == e.PointerID {
 				h.entered = false
@@ -87,10 +87,10 @@ type Click struct {
 }
 
 // ClickEvent represent a click action, either a
-// TypePress for the beginning of a click or a
+// KindPress for the beginning of a click or a
-// TypeClick for a completed click.
+// KindClick for a completed click.
 type ClickEvent struct {
-	Type      ClickType
+	Kind      ClickKind
 	Position  image.Point
 	Source    pointer.Source
 	Modifiers key.Modifiers
@@ -99,7 +99,7 @@ type ClickEvent struct {
 	NumClicks int
 }
 
-type ClickType uint8
+type ClickKind uint8
 
 // Drag detects drag gestures in the form of pointer.Drag events.
 type Drag struct {
@@ -136,15 +136,15 @@ const (
 )
 
 const (
-	// TypePress is reported for the first pointer
+	// KindPress is reported for the first pointer
 	// press.
-	TypePress ClickType = iota
+	KindPress ClickKind = iota
-	// TypeClick is reported when a click action
+	// KindClick is reported when a click action
 	// is complete.
-	TypeClick
+	KindClick
-	// TypeCancel is reported when the gesture is
+	// KindCancel is reported when the gesture is
 	// cancelled.
-	TypeCancel
+	KindCancel
 )
 
 const (
@@ -163,7 +163,7 @@ const touchSlop = unit.Dp(3)
 func (c *Click) Add(ops *op.Ops) {
 	pointer.InputOp{
 		Tag:   c,
-		Types: pointer.Press | pointer.Release | pointer.Enter | pointer.Leave,
+		Kinds: pointer.Press | pointer.Release | pointer.Enter | pointer.Leave,
 	}.Add(ops)
 }
 
@@ -177,24 +177,24 @@ func (c *Click) Pressed() bool {
 	return c.pressed
 }
 
-// Events returns the next click events, if any.
+// Update state and return the click events.
-func (c *Click) Events(q event.Queue) []ClickEvent {
+func (c *Click) Update(q event.Queue) []ClickEvent {
 	var events []ClickEvent
 	for _, evt := range q.Events(c) {
 		e, ok := evt.(pointer.Event)
 		if !ok {
 			continue
 		}
-		switch e.Type {
+		switch e.Kind {
 		case pointer.Release:
 			if !c.pressed || c.pid != e.PointerID {
 				break
 			}
 			c.pressed = false
 			if !c.entered || c.hovered {
-				events = append(events, ClickEvent{Type: TypeClick, Position: e.Position.Round(), Source: e.Source, Modifiers: e.Modifiers, NumClicks: c.clicks})
+				events = append(events, ClickEvent{Kind: KindClick, Position: e.Position.Round(), Source: e.Source, Modifiers: e.Modifiers, NumClicks: c.clicks})
 			} else {
-				events = append(events, ClickEvent{Type: TypeCancel})
+				events = append(events, ClickEvent{Kind: KindCancel})
 			}
 		case pointer.Cancel:
 			wasPressed := c.pressed
@@ -202,7 +202,7 @@ func (c *Click) Events(q event.Queue) []ClickEvent {
 			c.hovered = false
 			c.entered = false
 			if wasPressed {
-				events = append(events, ClickEvent{Type: TypeCancel})
+				events = append(events, ClickEvent{Kind: KindCancel})
 			}
 		case pointer.Press:
 			if c.pressed {
@@ -224,7 +224,7 @@ func (c *Click) Events(q event.Queue) []ClickEvent {
 				c.clicks = 1
 			}
 			c.clickedAt = e.Time
-			events = append(events, ClickEvent{Type: TypePress, Position: e.Position.Round(), Source: e.Source, Modifiers: e.Modifiers, NumClicks: c.clicks})
+			events = append(events, ClickEvent{Kind: KindPress, Position: e.Position.Round(), Source: e.Source, Modifiers: e.Modifiers, NumClicks: c.clicks})
 		case pointer.Leave:
 			if !c.pressed {
 				c.pid = e.PointerID
@@ -254,7 +254,7 @@ func (s *Scroll) Add(ops *op.Ops, bounds image.Rectangle) {
 	oph := pointer.InputOp{
 		Tag:          s,
 		Grab:         s.grab,
-		Types:        pointer.Press | pointer.Drag | pointer.Release | pointer.Scroll,
+		Kinds:        pointer.Press | pointer.Drag | pointer.Release | pointer.Scroll,
 		ScrollBounds: bounds,
 	}
 	oph.Add(ops)
@@ -268,9 +268,8 @@ func (s *Scroll) Stop() {
 	s.flinger = fling.Animation{}
 }
 
-// Scroll detects the scrolling distance from the available events and
+// Update state and report the scroll distance along axis.
-// ongoing fling gestures.
+func (s *Scroll) Update(cfg unit.Metric, q event.Queue, t time.Time, axis Axis) int {
-func (s *Scroll) Scroll(cfg unit.Metric, q event.Queue, t time.Time, axis Axis) int {
 	if s.axis != axis {
 		s.axis = axis
 		return 0
@@ -281,7 +280,7 @@ func (s *Scroll) Scroll(cfg unit.Metric, q event.Queue, t time.Time, axis Axis)
 		if !ok {
 			continue
 		}
-		switch e.Type {
+		switch e.Kind {
 		case pointer.Press:
 			if s.dragging {
 				break
@@ -368,12 +367,12 @@ func (d *Drag) Add(ops *op.Ops) {
 	pointer.InputOp{
 		Tag:   d,
 		Grab:  d.grab,
-		Types: pointer.Press | pointer.Drag | pointer.Release,
+		Kinds: pointer.Press | pointer.Drag | pointer.Release,
 	}.Add(ops)
 }
 
-// Events returns the next drag events, if any.
+// Update state and return the drag events.
-func (d *Drag) Events(cfg unit.Metric, q event.Queue, axis Axis) []pointer.Event {
+func (d *Drag) Update(cfg unit.Metric, q event.Queue, axis Axis) []pointer.Event {
 	var events []pointer.Event
 	for _, e := range q.Events(d) {
 		e, ok := e.(pointer.Event)
@@ -381,7 +380,7 @@ func (d *Drag) Events(cfg unit.Metric, q event.Queue, axis Axis) []pointer.Event
 			continue
 		}
 
-		switch e.Type {
+		switch e.Kind {
 		case pointer.Press:
 			if !(e.Buttons == pointer.ButtonPrimary || e.Source == pointer.Touch) {
 				continue
@@ -444,16 +443,16 @@ func (a Axis) String() string {
 	}
 }
 
-func (ct ClickType) String() string {
+func (ct ClickKind) String() string {
 	switch ct {
-	case TypePress:
+	case KindPress:
-		return "TypePress"
+		return "KindPress"
-	case TypeClick:
+	case KindClick:
-		return "TypeClick"
+		return "KindClick"
-	case TypeCancel:
+	case KindCancel:
-		return "TypeCancel"
+		return "KindCancel"
 	default:
-		panic("invalid ClickType")
+		panic("invalid ClickKind")
 	}
 }
 

gesture/gesture_test.go

@@ -26,16 +26,16 @@ func TestHover(t *testing.T) {
 	r.Frame(ops)
 
 	r.Queue(
-		pointer.Event{Type: pointer.Move, Position: f32.Pt(30, 30)},
+		pointer.Event{Kind: pointer.Move, Position: f32.Pt(30, 30)},
 	)
-	if !h.Hovered(r) {
+	if !h.Update(r) {
 		t.Fatal("expected hovered")
 	}
 
 	r.Queue(
-		pointer.Event{Type: pointer.Move, Position: f32.Pt(50, 50)},
+		pointer.Event{Kind: pointer.Move, Position: f32.Pt(50, 50)},
 	)
-	if h.Hovered(r) {
+	if h.Update(r) {
 		t.Fatal("expected not hovered")
 	}
 }
@@ -75,7 +75,7 @@ func TestMouseClicks(t *testing.T) {
 			r.Frame(&ops)
 			r.Queue(tc.events...)
 
-			events := click.Events(&r)
+			events := click.Update(&r)
 			clicks := filterMouseClicks(events)
 			if got, want := len(clicks), len(tc.clicks); got != want {
 				t.Fatalf("got %d mouse clicks, expected %d", got, want)
@@ -92,7 +92,7 @@ func TestMouseClicks(t *testing.T) {
 
 func mouseClickEvents(times ...time.Duration) []event.Event {
 	press := pointer.Event{
-		Type:    pointer.Press,
+		Kind:    pointer.Press,
 		Source:  pointer.Mouse,
 		Buttons: pointer.ButtonPrimary,
 	}
@@ -101,7 +101,7 @@ func mouseClickEvents(times ...time.Duration) []event.Event {
 		press := press
 		press.Time = t
 		release := press
-		release.Type = pointer.Release
+		release.Kind = pointer.Release
 		events = append(events, press, release)
 	}
 	return events
@@ -110,7 +110,7 @@ func mouseClickEvents(times ...time.Duration) []event.Event {
 func filterMouseClicks(events []ClickEvent) []ClickEvent {
 	var clicks []ClickEvent
 	for _, ev := range events {
-		if ev.Type == TypeClick {
+		if ev.Kind == KindClick {
 			clicks = append(clicks, ev)
 		}
 	}

go.mod

@@ -5,7 +5,7 @@ go 1.19
 require (
 	eliasnaur.com/font v0.0.0-20230308162249-dd43949cb42d
 	gioui.org/cpu v0.0.0-20210817075930-8d6a761490d2
-	gioui.org/shader v1.0.6
+	gioui.org/shader v1.0.8
 	github.com/go-text/typesetting v0.0.0-20230803102845-24e03d8b5372
 	golang.org/x/exp v0.0.0-20221012211006-4de253d81b95
 	golang.org/x/exp/shiny v0.0.0-20220827204233-334a2380cb91

go.sum

@@ -3,8 +3,8 @@ eliasnaur.com/font v0.0.0-20230308162249-dd43949cb42d/go.mod h1:OYVuxibdk9OSLX8v
 gioui.org/cpu v0.0.0-20210808092351-bfe733dd3334/go.mod h1:A8M0Cn5o+vY5LTMlnRoK3O5kG+rH0kWfJjeKd9QpBmQ=
 gioui.org/cpu v0.0.0-20210817075930-8d6a761490d2 h1:AGDDxsJE1RpcXTAxPG2B4jrwVUJGFDjINIPi1jtO6pc=
 gioui.org/cpu v0.0.0-20210817075930-8d6a761490d2/go.mod h1:A8M0Cn5o+vY5LTMlnRoK3O5kG+rH0kWfJjeKd9QpBmQ=
-gioui.org/shader v1.0.6 h1:cvZmU+eODFR2545X+/8XucgZdTtEjR3QWW6W65b0q5Y=
+gioui.org/shader v1.0.8 h1:6ks0o/A+b0ne7RzEqRZK5f4Gboz2CfG+mVliciy6+qA=
-gioui.org/shader v1.0.6/go.mod h1:mWdiME581d/kV7/iEhLmUgUK5iZ09XR5XpduXzbePVM=
+gioui.org/shader v1.0.8/go.mod h1:mWdiME581d/kV7/iEhLmUgUK5iZ09XR5XpduXzbePVM=
 github.com/go-text/typesetting v0.0.0-20230803102845-24e03d8b5372 h1:FQivqchis6bE2/9uF70M2gmmLpe82esEm2QadL0TEJo=
 github.com/go-text/typesetting v0.0.0-20230803102845-24e03d8b5372/go.mod h1:evDBbvNR/KaVFZ2ZlDSOWWXIUKq0wCOEtzLxRM8SG3k=
 github.com/go-text/typesetting-utils v0.0.0-20230616150549-2a7df14b6a22 h1:LBQTFxP2MfsyEDqSKmUBZaDuDHN1vpqDyOZjcqS7MYI=

gpu/gpu.go

@@ -68,22 +68,40 @@ type renderer struct {
 	pather        *pather
 	packer        packer
 	intersections packer
+	layers        packer
+	layerFBOs     fboSet
 }
 
 type drawOps struct {
-	profile     bool
+	profile      bool
-	reader      ops.Reader
+	reader       ops.Reader
-	states      []f32.Affine2D
+	states       []f32.Affine2D
-	transStack  []f32.Affine2D
+	transStack   []f32.Affine2D
-	vertCache   []byte
+	layers       []opacityLayer
-	viewport    image.Point
+	opacityStack []int
-	clear       bool
+	vertCache    []byte
-	clearColor  f32color.RGBA
+	viewport     image.Point
-	imageOps    []imageOp
+	clear        bool
-	pathOps     []*pathOp
+	clearColor   f32color.RGBA
-	pathOpCache []pathOp
+	imageOps     []imageOp
-	qs          quadSplitter
+	pathOps      []*pathOp
-	pathCache   *opCache
+	pathOpCache  []pathOp
+	qs           quadSplitter
+	pathCache    *opCache
+}
+
+type opacityLayer struct {
+	opacity float32
+	parent  int
+	// depth of the opacity stack. Layers of equal depth are
+	// independent and may be packed into one atlas.
+	depth int
+	// opStart and opEnd denote the range of drawOps.imageOps
+	// that belong to the layer.
+	opStart, opEnd int
+	// clip of the layer operations.
+	clip  image.Rectangle
+	place placement
 }
 
 type drawState struct {
@@ -127,7 +145,12 @@ type imageOp struct {
 	clip     image.Rectangle
 	material material
 	clipType clipType
-	place    placement
+	// place is either a placement in the path fbos or intersection fbos,
+	// depending on clipType.
+	place placement
+	// layerOps is the number of operations this
+	// operation replaces.
+	layerOps int
 }
 
 func decodeStrokeOp(data []byte) float32 {
@@ -154,17 +177,25 @@ type material struct {
 	// For materialTypeColor.
 	color f32color.RGBA
 	// For materialTypeLinearGradient.
-	color1 f32color.RGBA
+	color1  f32color.RGBA
-	color2 f32color.RGBA
+	color2  f32color.RGBA
+	opacity float32
 	// For materialTypeTexture.
 	data    imageOpData
+	tex     driver.Texture
 	uvTrans f32.Affine2D
 }
 
+const (
+	filterLinear  = 0
+	filterNearest = 1
+)
+
 // imageOpData is the shadow of paint.ImageOp.
 type imageOpData struct {
 	src    *image.RGBA
 	handle interface{}
+	filter byte
 }
 
 type linearGradientOpData struct {
@@ -182,6 +213,7 @@ func decodeImageOp(data []byte, refs []interface{}) imageOpData {
 	return imageOpData{
 		src:    refs[0].(*image.RGBA),
 		handle: handle,
+		filter: data[1],
 	}
 }
 
@@ -222,8 +254,6 @@ func decodeLinearGradientOp(data []byte) linearGradientOpData {
 	}
 }
 
-type clipType uint8
-
 type resource interface {
 	release()
 }
@@ -273,6 +303,9 @@ type blitUniforms struct {
 	transform     [4]float32
 	uvTransformR1 [4]float32
 	uvTransformR2 [4]float32
+	opacity       float32
+	fbo           float32
+	_             [2]float32
 }
 
 type colorUniforms struct {
@@ -284,7 +317,7 @@ type gradientUniforms struct {
 	color2 f32color.RGBA
 }
 
-type materialType uint8
+type clipType uint8
 
 const (
 	clipTypeNone clipType = iota
@@ -292,6 +325,8 @@ const (
 	clipTypeIntersection
 )
 
+type materialType uint8
+
 const (
 	materialColor materialType = iota
 	materialLinearGradient
@@ -391,6 +426,8 @@ func (g *gpu) frame(target RenderTarget) error {
 	g.coverTimer.begin()
 	g.renderer.uploadImages(g.cache, g.drawOps.imageOps)
 	g.renderer.prepareDrawOps(g.cache, g.drawOps.imageOps)
+	g.drawOps.layers = g.renderer.packLayers(g.drawOps.layers)
+	g.renderer.drawLayers(g.cache, g.drawOps.layers, g.drawOps.imageOps)
 	d := driver.LoadDesc{
 		ClearColor: g.drawOps.clearColor,
 	}
@@ -400,7 +437,7 @@ func (g *gpu) frame(target RenderTarget) error {
 	}
 	g.ctx.BeginRenderPass(defFBO, d)
 	g.ctx.Viewport(0, 0, viewport.X, viewport.Y)
-	g.renderer.drawOps(g.cache, g.drawOps.imageOps)
+	g.renderer.drawOps(g.cache, false, image.Point{}, g.renderer.blitter.viewport, g.drawOps.imageOps)
 	g.coverTimer.end()
 	g.ctx.EndRenderPass()
 	g.cleanupTimer.begin()
@@ -424,19 +461,41 @@ func (g *gpu) Profile() string {
 }
 
 func (r *renderer) texHandle(cache *resourceCache, data imageOpData) driver.Texture {
+	type cachekey struct {
+		filter byte
+		handle any
+	}
+	key := cachekey{
+		filter: data.filter,
+		handle: data.handle,
+	}
+
 	var tex *texture
-	t, exists := cache.get(data.handle)
+	t, exists := cache.get(key)
 	if !exists {
 		t = &texture{
 			src: data.src,
 		}
-		cache.put(data.handle, t)
+		cache.put(key, t)
 	}
 	tex = t.(*texture)
 	if tex.tex != nil {
 		return tex.tex
 	}
-	handle, err := r.ctx.NewTexture(driver.TextureFormatSRGBA, data.src.Bounds().Dx(), data.src.Bounds().Dy(), driver.FilterLinearMipmapLinear, driver.FilterLinear, driver.BufferBindingTexture)
+
+	var minFilter, magFilter driver.TextureFilter
+	switch data.filter {
+	case filterLinear:
+		minFilter, magFilter = driver.FilterLinearMipmapLinear, driver.FilterLinear
+	case filterNearest:
+		minFilter, magFilter = driver.FilterNearest, driver.FilterNearest
+	}
+
+	handle, err := r.ctx.NewTexture(driver.TextureFormatSRGBA,
+		data.src.Bounds().Dx(), data.src.Bounds().Dy(),
+		minFilter, magFilter,
+		driver.BufferBindingTexture,
+	)
 	if err != nil {
 		panic(err)
 	}
@@ -464,15 +523,18 @@ func newRenderer(ctx driver.Device) *renderer {
 	if cap := 8192; maxDim > cap {
 		maxDim = cap
 	}
+	d := image.Pt(maxDim, maxDim)
 
-	r.packer.maxDims = image.Pt(maxDim, maxDim)
+	r.packer.maxDims = d
-	r.intersections.maxDims = image.Pt(maxDim, maxDim)
+	r.intersections.maxDims = d
+	r.layers.maxDims = d
 	return r
 }
 
 func (r *renderer) release() {
 	r.pather.release()
 	r.blitter.release()
+	r.layerFBOs.delete(r.ctx, 0)
 }
 
 func newBlitter(ctx driver.Device) *blitter {
@@ -747,8 +809,7 @@ func (r *renderer) packStencils(pops *[]*pathOp) {
 			ops = ops[:len(ops)-1]
 			continue
 		}
-		sz := image.Point{X: p.clip.Dx(), Y: p.clip.Dy()}
+		place, ok := r.packer.add(p.clip.Size())
-		place, ok := r.packer.add(sz)
 		if !ok {
 			// The clip area is at most the entire screen. Hopefully no
 			// screen is larger than GL_MAX_TEXTURE_SIZE.
@@ -760,6 +821,83 @@ func (r *renderer) packStencils(pops *[]*pathOp) {
 	*pops = ops
 }
 
+func (r *renderer) packLayers(layers []opacityLayer) []opacityLayer {
+	// Make every layer bounds contain nested layers; cull empty layers.
+	for i := len(layers) - 1; i >= 0; i-- {
+		l := layers[i]
+		if l.parent != -1 {
+			b := layers[l.parent].clip
+			layers[l.parent].clip = b.Union(l.clip)
+		}
+		if l.clip.Empty() {
+			layers = append(layers[:i], layers[i+1:]...)
+		}
+	}
+	// Pack layers.
+	r.layers.clear()
+	depth := 0
+	for i := range layers {
+		l := &layers[i]
+		// Only layers of the same depth may be packed together.
+		if l.depth != depth {
+			r.layers.newPage()
+		}
+		place, ok := r.layers.add(l.clip.Size())
+		if !ok {
+			// The layer area is at most the entire screen. Hopefully no
+			// screen is larger than GL_MAX_TEXTURE_SIZE.
+			panic(fmt.Errorf("layer size %v is larger than maximum texture size %v", l.clip.Size(), r.layers.maxDims))
+		}
+		l.place = place
+	}
+	return layers
+}
+
+func (r *renderer) drawLayers(cache *resourceCache, layers []opacityLayer, ops []imageOp) {
+	if len(r.layers.sizes) == 0 {
+		return
+	}
+	fbo := -1
+	r.layerFBOs.resize(r.ctx, driver.TextureFormatSRGBA, r.layers.sizes)
+	for i := len(layers) - 1; i >= 0; i-- {
+		l := layers[i]
+		if fbo != l.place.Idx {
+			if fbo != -1 {
+				r.ctx.EndRenderPass()
+				r.ctx.PrepareTexture(r.layerFBOs.fbos[fbo].tex)
+			}
+			fbo = l.place.Idx
+			f := r.layerFBOs.fbos[fbo]
+			r.ctx.BeginRenderPass(f.tex, driver.LoadDesc{Action: driver.LoadActionClear})
+		}
+		v := image.Rectangle{
+			Min: l.place.Pos,
+			Max: l.place.Pos.Add(l.clip.Size()),
+		}
+		r.ctx.Viewport(v.Min.X, v.Min.Y, v.Max.X, v.Max.Y)
+		f := r.layerFBOs.fbos[fbo]
+		r.drawOps(cache, true, l.clip.Min.Mul(-1), l.clip.Size(), ops[l.opStart:l.opEnd])
+		sr := f32.FRect(v)
+		uvScale, uvOffset := texSpaceTransform(sr, f.size)
+		uvTrans := f32.Affine2D{}.Scale(f32.Point{}, uvScale).Offset(uvOffset)
+		// Replace layer ops with one textured op.
+		ops[l.opStart] = imageOp{
+			clip: l.clip,
+			material: material{
+				material: materialTexture,
+				tex:      f.tex,
+				uvTrans:  uvTrans,
+				opacity:  l.opacity,
+			},
+			layerOps: l.opEnd - l.opStart - 1,
+		}
+	}
+	if fbo != -1 {
+		r.ctx.EndRenderPass()
+		r.ctx.PrepareTexture(r.layerFBOs.fbos[fbo].tex)
+	}
+}
+
 func (d *drawOps) reset(viewport image.Point) {
 	d.profile = false
 	d.viewport = viewport
@@ -768,6 +906,8 @@ func (d *drawOps) reset(viewport image.Point) {
 	d.pathOpCache = d.pathOpCache[:0]
 	d.vertCache = d.vertCache[:0]
 	d.transStack = d.transStack[:0]
+	d.layers = d.layers[:0]
+	d.opacityStack = d.opacityStack[:0]
 }
 
 func (d *drawOps) collect(root *op.Ops, viewport image.Point) {
@@ -866,6 +1006,27 @@ loop:
 			state.t = d.transStack[n-1]
 			d.transStack = d.transStack[:n-1]
 
+		case ops.TypePushOpacity:
+			opacity := ops.DecodeOpacity(encOp.Data)
+			parent := -1
+			depth := len(d.opacityStack)
+			if depth > 0 {
+				parent = d.opacityStack[depth-1]
+			}
+			lidx := len(d.layers)
+			d.layers = append(d.layers, opacityLayer{
+				opacity: opacity,
+				parent:  parent,
+				depth:   depth,
+				opStart: len(d.imageOps),
+			})
+			d.opacityStack = append(d.opacityStack, lidx)
+		case ops.TypePopOpacity:
+			n := len(d.opacityStack)
+			idx := d.opacityStack[n-1]
+			d.layers[idx].opEnd = len(d.imageOps)
+			d.opacityStack = d.opacityStack[:n-1]
+
 		case ops.TypeStroke:
 			quads.key.strokeWidth = decodeStrokeOp(encOp.Data)
 
@@ -958,7 +1119,7 @@ loop:
 			mat := state.materialFor(bnd, off, partialTrans, bounds)
 
 			rect := state.cpath == nil || state.cpath.rect
-			if bounds.Min == (image.Point{}) && bounds.Max == d.viewport && rect && mat.opaque && (mat.material == materialColor) {
+			if bounds.Min == (image.Point{}) && bounds.Max == d.viewport && rect && mat.opaque && (mat.material == materialColor) && len(d.opacityStack) == 0 {
 				// The image is a uniform opaque color and takes up the whole screen.
 				// Scrap images up to and including this image and set clear color.
 				d.imageOps = d.imageOps[:0]
@@ -971,6 +1132,15 @@ loop:
 				clip:     bounds,
 				material: mat,
 			}
+			if n := len(d.opacityStack); n > 0 {
+				idx := d.opacityStack[n-1]
+				lb := d.layers[idx].clip
+				if lb.Empty() {
+					d.layers[idx].clip = img.clip
+				} else {
+					d.layers[idx].clip = lb.Union(img.clip)
+				}
+			}
 
 			d.imageOps = append(d.imageOps, img)
 			if clipData != nil {
@@ -1000,7 +1170,9 @@ func expandPathOp(p *pathOp, clip image.Rectangle) {
 }
 
 func (d *drawState) materialFor(rect f32.Rectangle, off f32.Point, partTrans f32.Affine2D, clip image.Rectangle) material {
-	var m material
+	m := material{
+		opacity: 1.,
+	}
 	switch d.matType {
 	case materialColor:
 		m.material = materialColor
@@ -1040,10 +1212,11 @@ func (d *drawState) materialFor(rect f32.Rectangle, off f32.Point, partTrans f32
 }
 
 func (r *renderer) uploadImages(cache *resourceCache, ops []imageOp) {
-	for _, img := range ops {
+	for i := range ops {
+		img := &ops[i]
 		m := img.material
 		if m.material == materialTexture {
-			r.texHandle(cache, m.data)
+			img.material.tex = r.texHandle(cache, m.data)
 		}
 	}
 }
@@ -1053,10 +1226,10 @@ func (r *renderer) prepareDrawOps(cache *resourceCache, ops []imageOp) {
 		m := img.material
 		switch m.material {
 		case materialTexture:
-			r.ctx.PrepareTexture(r.texHandle(cache, m.data))
+			r.ctx.PrepareTexture(m.tex)
 		}
 
-		var fbo stencilFBO
+		var fbo FBO
 		switch img.clipType {
 		case clipTypeNone:
 			continue
@@ -1069,24 +1242,26 @@ func (r *renderer) prepareDrawOps(cache *resourceCache, ops []imageOp) {
 	}
 }
 
-func (r *renderer) drawOps(cache *resourceCache, ops []imageOp) {
+func (r *renderer) drawOps(cache *resourceCache, isFBO bool, opOff image.Point, viewport image.Point, ops []imageOp) {
 	var coverTex driver.Texture
-	for _, img := range ops {
+	for i := 0; i < len(ops); i++ {
+		img := ops[i]
+		i += img.layerOps
 		m := img.material
 		switch m.material {
 		case materialTexture:
-			r.ctx.BindTexture(0, r.texHandle(cache, m.data))
+			r.ctx.BindTexture(0, m.tex)
 		}
-		drc := img.clip
+		drc := img.clip.Add(opOff)
 
-		scale, off := clipSpaceTransform(drc, r.blitter.viewport)
+		scale, off := clipSpaceTransform(drc, viewport)
-		var fbo stencilFBO
+		var fbo FBO
 		switch img.clipType {
 		case clipTypeNone:
 			p := r.blitter.pipelines[m.material]
 			r.ctx.BindPipeline(p.pipeline)
 			r.ctx.BindVertexBuffer(r.blitter.quadVerts, 0)
-			r.blitter.blit(m.material, m.color, m.color1, m.color2, scale, off, m.uvTrans)
+			r.blitter.blit(m.material, isFBO, m.color, m.color1, m.color2, scale, off, m.opacity, m.uvTrans)
 			continue
 		case clipTypePath:
 			fbo = r.pather.stenciler.cover(img.place.Idx)
@@ -1105,11 +1280,11 @@ func (r *renderer) drawOps(cache *resourceCache, ops []imageOp) {
 		p := r.pather.coverer.pipelines[m.material]
 		r.ctx.BindPipeline(p.pipeline)
 		r.ctx.BindVertexBuffer(r.blitter.quadVerts, 0)
-		r.pather.cover(m.material, m.color, m.color1, m.color2, scale, off, m.uvTrans, coverScale, coverOff)
+		r.pather.cover(m.material, isFBO, m.color, m.color1, m.color2, scale, off, m.uvTrans, coverScale, coverOff)
 	}
 }
 
-func (b *blitter) blit(mat materialType, col f32color.RGBA, col1, col2 f32color.RGBA, scale, off f32.Point, uvTrans f32.Affine2D) {
+func (b *blitter) blit(mat materialType, fbo bool, col f32color.RGBA, col1, col2 f32color.RGBA, scale, off f32.Point, opacity float32, uvTrans f32.Affine2D) {
 	p := b.pipelines[mat]
 	b.ctx.BindPipeline(p.pipeline)
 	var uniforms *blitUniforms
@@ -1119,18 +1294,23 @@ func (b *blitter) blit(mat materialType, col f32color.RGBA, col1, col2 f32color.
 		uniforms = &b.colUniforms.blitUniforms
 	case materialTexture:
 		t1, t2, t3, t4, t5, t6 := uvTrans.Elems()
-		b.texUniforms.blitUniforms.uvTransformR1 = [4]float32{t1, t2, t3, 0}
-		b.texUniforms.blitUniforms.uvTransformR2 = [4]float32{t4, t5, t6, 0}
 		uniforms = &b.texUniforms.blitUniforms
+		uniforms.uvTransformR1 = [4]float32{t1, t2, t3, 0}
+		uniforms.uvTransformR2 = [4]float32{t4, t5, t6, 0}
 	case materialLinearGradient:
 		b.linearGradientUniforms.color1 = col1
 		b.linearGradientUniforms.color2 = col2
 
 		t1, t2, t3, t4, t5, t6 := uvTrans.Elems()
-		b.linearGradientUniforms.blitUniforms.uvTransformR1 = [4]float32{t1, t2, t3, 0}
-		b.linearGradientUniforms.blitUniforms.uvTransformR2 = [4]float32{t4, t5, t6, 0}
 		uniforms = &b.linearGradientUniforms.blitUniforms
+		uniforms.uvTransformR1 = [4]float32{t1, t2, t3, 0}
+		uniforms.uvTransformR2 = [4]float32{t4, t5, t6, 0}
 	}
+	uniforms.fbo = 0
+	if fbo {
+		uniforms.fbo = 1
+	}
+	uniforms.opacity = opacity
 	uniforms.transform = [4]float32{scale.X, scale.Y, off.X, off.Y}
 	p.UploadUniforms(b.ctx)
 	b.ctx.DrawArrays(0, 4)

gpu/internal/rendertest/render_test.go

@@ -359,6 +359,73 @@ func TestImageRGBA(t *testing.T) {
 	})
 }
 
+func TestImageRGBA_ScaleLinear(t *testing.T) {
+	run(t, func(o *op.Ops) {
+		w := newWindow(t, 128, 128)
+		defer clip.Rect{Max: image.Pt(128, 128)}.Push(o).Pop()
+		op.Affine(f32.Affine2D{}.Scale(f32.Point{}, f32.Pt(64, 64))).Add(o)
+
+		im := image.NewRGBA(image.Rect(0, 0, 2, 2))
+		im.Set(0, 0, colornames.Red)
+		im.Set(1, 0, colornames.Green)
+		im.Set(0, 1, colornames.White)
+		im.Set(1, 1, colornames.Black)
+
+		op := paint.NewImageOp(im)
+		op.Filter = paint.FilterLinear
+		op.Add(o)
+
+		paint.PaintOp{}.Add(o)
+
+		if err := w.Frame(o); err != nil {
+			t.Error(err)
+		}
+	}, func(r result) {
+		r.expect(0, 0, colornames.Red)
+		r.expect(8, 8, colornames.Red)
+
+		// TODO: this currently seems to do srgb scaling
+		// instead of linear rgb scaling,
+		r.expect(64-4, 0, color.RGBA{R: 197, G: 87, B: 0, A: 255})
+		r.expect(64+4, 0, color.RGBA{R: 175, G: 98, B: 0, A: 255})
+
+		r.expect(127, 0, colornames.Green)
+		r.expect(127-8, 8, colornames.Green)
+	})
+}
+
+func TestImageRGBA_ScaleNearest(t *testing.T) {
+	run(t, func(o *op.Ops) {
+		w := newWindow(t, 128, 128)
+		op.Affine(f32.Affine2D{}.Scale(f32.Point{}, f32.Pt(64, 64))).Add(o)
+
+		im := image.NewRGBA(image.Rect(0, 0, 2, 2))
+		im.Set(0, 0, colornames.Red)
+		im.Set(1, 0, colornames.Green)
+		im.Set(0, 1, colornames.White)
+		im.Set(1, 1, colornames.Black)
+
+		op := paint.NewImageOp(im)
+		op.Filter = paint.FilterNearest
+		op.Add(o)
+
+		paint.PaintOp{}.Add(o)
+
+		if err := w.Frame(o); err != nil {
+			t.Error(err)
+		}
+	}, func(r result) {
+		r.expect(0, 0, colornames.Red)
+		r.expect(8, 8, colornames.Red)
+
+		r.expect(64-4, 0, colornames.Red)
+		r.expect(64+4, 0, colornames.Green)
+
+		r.expect(127, 0, colornames.Green)
+		r.expect(127-8, 8, colornames.Green)
+	})
+}
+
 func TestGapsInPath(t *testing.T) {
 	ops := new(op.Ops)
 	var p clip.Path
@@ -413,6 +480,22 @@ func TestGapsInPath(t *testing.T) {
 	})
 }
 
+func TestOpacity(t *testing.T) {
+	run(t, func(ops *op.Ops) {
+		opc1 := paint.PushOpacity(ops, .3)
+		// Fill screen to exercize the glClear optimization.
+		paint.FillShape(ops, color.NRGBA{R: 255, A: 255}, clip.Rect{Max: image.Pt(1024, 1024)}.Op())
+		opc2 := paint.PushOpacity(ops, .6)
+		paint.FillShape(ops, color.NRGBA{G: 255, A: 255}, clip.Rect{Min: image.Pt(20, 10), Max: image.Pt(64, 128)}.Op())
+		opc2.Pop()
+		opc1.Pop()
+		opc3 := paint.PushOpacity(ops, .6)
+		paint.FillShape(ops, color.NRGBA{G: 255, A: 255}, clip.Rect{Min: image.Pt(50+20, 10), Max: image.Pt(50+64, 128)}.Op())
+		opc3.Pop()
+	}, func(r result) {
+	})
+}
+
 // lerp calculates linear interpolation with color b and p.
 func lerp(a, b f32color.RGBA, p float32) f32color.RGBA {
 	return f32color.RGBA{

gpu/path.go

@@ -58,7 +58,7 @@ type coverUniforms struct {
 	uvCoverTransform [4]float32
 	uvTransformR1    [4]float32
 	uvTransformR2    [4]float32
-	_                float32
+	fbo              float32
 }
 
 type stenciler struct {
@@ -90,10 +90,10 @@ type intersectUniforms struct {
 }
 
 type fboSet struct {
-	fbos []stencilFBO
+	fbos []FBO
 }
 
-type stencilFBO struct {
+type FBO struct {
 	size image.Point
 	tex  driver.Texture
 }
@@ -247,10 +247,10 @@ func newStenciler(ctx driver.Device) *stenciler {
 	return st
 }
 
-func (s *fboSet) resize(ctx driver.Device, sizes []image.Point) {
+func (s *fboSet) resize(ctx driver.Device, format driver.TextureFormat, sizes []image.Point) {
 	// Add fbos.
 	for i := len(s.fbos); i < len(sizes); i++ {
-		s.fbos = append(s.fbos, stencilFBO{})
+		s.fbos = append(s.fbos, FBO{})
 	}
 	// Resize fbos.
 	for i, sz := range sizes {
@@ -273,7 +273,7 @@ func (s *fboSet) resize(ctx driver.Device, sizes []image.Point) {
 			if sz.X > max {
 				sz.X = max
 			}
-			tex, err := ctx.NewTexture(driver.TextureFormatFloat, sz.X, sz.Y, driver.FilterNearest, driver.FilterNearest,
+			tex, err := ctx.NewTexture(format, sz.X, sz.Y, driver.FilterNearest, driver.FilterNearest,
 				driver.BufferBindingTexture|driver.BufferBindingFramebuffer)
 			if err != nil {
 				panic(err)
@@ -340,15 +340,15 @@ func (s *stenciler) beginIntersect(sizes []image.Point) {
 	// 8 bit coverage is enough, but OpenGL ES only supports single channel
 	// floating point formats. Replace with GL_RGB+GL_UNSIGNED_BYTE if
 	// no floating point support is available.
-	s.intersections.resize(s.ctx, sizes)
+	s.intersections.resize(s.ctx, driver.TextureFormatFloat, sizes)
 }
 
-func (s *stenciler) cover(idx int) stencilFBO {
+func (s *stenciler) cover(idx int) FBO {
 	return s.fbos.fbos[idx]
 }
 
 func (s *stenciler) begin(sizes []image.Point) {
-	s.fbos.resize(s.ctx, sizes)
+	s.fbos.resize(s.ctx, driver.TextureFormatFloat, sizes)
 }
 
 func (s *stenciler) stencilPath(bounds image.Rectangle, offset f32.Point, uv image.Point, data pathData) {
@@ -375,11 +375,11 @@ func (s *stenciler) stencilPath(bounds image.Rectangle, offset f32.Point, uv ima
 	}
 }
 
-func (p *pather) cover(mat materialType, col f32color.RGBA, col1, col2 f32color.RGBA, scale, off f32.Point, uvTrans f32.Affine2D, coverScale, coverOff f32.Point) {
+func (p *pather) cover(mat materialType, isFBO bool, col f32color.RGBA, col1, col2 f32color.RGBA, scale, off f32.Point, uvTrans f32.Affine2D, coverScale, coverOff f32.Point) {
-	p.coverer.cover(mat, col, col1, col2, scale, off, uvTrans, coverScale, coverOff)
+	p.coverer.cover(mat, isFBO, col, col1, col2, scale, off, uvTrans, coverScale, coverOff)
 }
 
-func (c *coverer) cover(mat materialType, col f32color.RGBA, col1, col2 f32color.RGBA, scale, off f32.Point, uvTrans f32.Affine2D, coverScale, coverOff f32.Point) {
+func (c *coverer) cover(mat materialType, isFBO bool, col f32color.RGBA, col1, col2 f32color.RGBA, scale, off f32.Point, uvTrans f32.Affine2D, coverScale, coverOff f32.Point) {
 	var uniforms *coverUniforms
 	switch mat {
 	case materialColor:
@@ -399,6 +399,10 @@ func (c *coverer) cover(mat materialType, col f32color.RGBA, col1, col2 f32color
 		c.texUniforms.uvTransformR2 = [4]float32{t4, t5, t6, 0}
 		uniforms = &c.texUniforms.coverUniforms
 	}
+	uniforms.fbo = 0
+	if isFBO {
+		uniforms.fbo = 1
+	}
 	uniforms.transform = [4]float32{scale.X, scale.Y, off.X, off.Y}
 	uniforms.uvCoverTransform = [4]float32{coverScale.X, coverScale.Y, coverOff.X, coverOff.Y}
 	c.pipelines[mat].UploadUniforms(c.ctx)

internal/egl/egl.go

@@ -62,6 +62,7 @@ func (c *Context) Release() {
 		eglDestroyContext(c.disp, c.eglCtx.ctx)
 		c.eglCtx = nil
 	}
+	eglTerminate(c.disp)
 	c.disp = nilEGLDisplay
 }
 

internal/ops/ops.go

@@ -14,14 +14,25 @@ import (
 
 type Ops struct {
 	// version is incremented at each Reset.
-	version int
+	version uint32
 	// data contains the serialized operations.
 	data []byte
 	// refs hold external references for operations.
 	refs []interface{}
+	// stringRefs provides space for string references, pointers to which will
+	// be stored in refs. Storing a string directly in refs would cause a heap
+	// allocation, to store the string header in an interface value. The backing
+	// array of stringRefs, on the other hand, gets reused between calls to
+	// reset, making string references free on average.
+	//
+	// Appending to stringRefs might reallocate the backing array, which will
+	// leave pointers to the old array in refs. This temporarily causes a slight
+	// increase in memory usage, but this, too, amortizes away as the capacity
+	// of stringRefs approaches its stable maximum.
+	stringRefs []string
 	// nextStateID is the id allocated for the next
 	// StateOp.
-	nextStateID int
+	nextStateID uint32
 	// multipOp indicates a multi-op such as clip.Path is being added.
 	multipOp bool
 
@@ -40,9 +51,10 @@ const (
 	TypeMacro OpType = iota + firstOpIndex
 	TypeCall
 	TypeDefer
-	TypePushTransform
 	TypeTransform
 	TypePopTransform
+	TypePushOpacity
+	TypePopOpacity
 	TypeInvalidate
 	TypeImage
 	TypePaint
@@ -72,30 +84,30 @@ const (
 	TypeSemanticDesc
 	TypeSemanticClass
 	TypeSemanticSelected
-	TypeSemanticDisabled
+	TypeSemanticEnabled
 	TypeSnippet
 	TypeSelection
 	TypeActionInput
 )
 
 type StackID struct {
-	id   int
+	id   uint32
-	prev int
+	prev uint32
 }
 
 // StateOp represents a saved operation snapshot to be restored
 // later.
 type StateOp struct {
-	id      int
+	id      uint32
-	macroID int
+	macroID uint32
 	ops     *Ops
 }
 
 // stack tracks the integer identities of stack operations to ensure correct
 // pairing of their push and pop methods.
 type stack struct {
-	currentID int
+	currentID uint32
-	nextID    int
+	nextID    uint32
 }
 
 type StackKind uint8
@@ -111,6 +123,7 @@ const (
 	ClipStack StackKind = iota
 	TransStack
 	PassStack
+	OpacityStack
 	_StackKind
 )
 
@@ -124,11 +137,12 @@ const (
 	TypeMacroLen            = 1 + 4 + 4
 	TypeCallLen             = 1 + 4 + 4 + 4 + 4
 	TypeDeferLen            = 1
-	TypePushTransformLen    = 1 + 4*6
 	TypeTransformLen        = 1 + 1 + 4*6
 	TypePopTransformLen     = 1
+	TypePushOpacityLen      = 1 + 4
+	TypePopOpacityLen       = 1
 	TypeRedrawLen           = 1 + 8
-	TypeImageLen            = 1
+	TypeImageLen            = 1 + 1
 	TypePaintLen            = 1
 	TypeColorLen            = 1 + 4
 	TypeLinearGradientLen   = 1 + 8*2 + 4*2
@@ -156,7 +170,7 @@ const (
 	TypeSemanticDescLen     = 1
 	TypeSemanticClassLen    = 2
 	TypeSemanticSelectedLen = 2
-	TypeSemanticDisabledLen = 2
+	TypeSemanticEnabledLen  = 2
 	TypeSnippetLen          = 1 + 4 + 4
 	TypeSelectionLen        = 1 + 2*4 + 2*4 + 4 + 4
 	TypeActionInputLen      = 1 + 1
@@ -183,8 +197,12 @@ func Reset(o *Ops) {
 	for i := range o.refs {
 		o.refs[i] = nil
 	}
+	for i := range o.stringRefs {
+		o.stringRefs[i] = ""
+	}
 	o.data = o.data[:0]
 	o.refs = o.refs[:0]
+	o.stringRefs = o.stringRefs[:0]
 	o.nextStateID = 0
 	o.version++
 }
@@ -248,11 +266,11 @@ func AddCall(o *Ops, callOps *Ops, pc PC, end PC) {
 	bo.PutUint32(data[13:], uint32(end.refs))
 }
 
-func PushOp(o *Ops, kind StackKind) (StackID, int) {
+func PushOp(o *Ops, kind StackKind) (StackID, uint32) {
 	return o.stacks[kind].push(), o.macroStack.currentID
 }
 
-func PopOp(o *Ops, kind StackKind, sid StackID, macroID int) {
+func PopOp(o *Ops, kind StackKind, sid StackID, macroID uint32) {
 	if o.macroStack.currentID != macroID {
 		panic("stack push and pop must not cross macro boundary")
 	}
@@ -265,12 +283,26 @@ func Write1(o *Ops, n int, ref1 interface{}) []byte {
 	return o.data[len(o.data)-n:]
 }
 
+func Write1String(o *Ops, n int, ref1 string) []byte {
+	o.data = append(o.data, make([]byte, n)...)
+	o.stringRefs = append(o.stringRefs, ref1)
+	o.refs = append(o.refs, &o.stringRefs[len(o.stringRefs)-1])
+	return o.data[len(o.data)-n:]
+}
+
 func Write2(o *Ops, n int, ref1, ref2 interface{}) []byte {
 	o.data = append(o.data, make([]byte, n)...)
 	o.refs = append(o.refs, ref1, ref2)
 	return o.data[len(o.data)-n:]
 }
 
+func Write2String(o *Ops, n int, ref1 interface{}, ref2 string) []byte {
+	o.data = append(o.data, make([]byte, n)...)
+	o.stringRefs = append(o.stringRefs, ref2)
+	o.refs = append(o.refs, ref1, &o.stringRefs[len(o.stringRefs)-1])
+	return o.data[len(o.data)-n:]
+}
+
 func Write3(o *Ops, n int, ref1, ref2, ref3 interface{}) []byte {
 	o.data = append(o.data, make([]byte, n)...)
 	o.refs = append(o.refs, ref1, ref2, ref3)
@@ -278,7 +310,7 @@ func Write3(o *Ops, n int, ref1, ref2, ref3 interface{}) []byte {
 }
 
 func PCFor(o *Ops) PC {
-	return PC{data: len(o.data), refs: len(o.refs)}
+	return PC{data: uint32(len(o.data)), refs: uint32(len(o.refs))}
 }
 
 func (s *stack) push() StackID {
@@ -354,6 +386,14 @@ func DecodeTransform(data []byte) (t f32.Affine2D, push bool) {
 	return f32.NewAffine2D(a, b, c, d, e, f), push
 }
 
+func DecodeOpacity(data []byte) float32 {
+	if OpType(data[0]) != TypePushOpacity {
+		panic("invalid op")
+	}
+	bo := binary.LittleEndian
+	return math.Float32frombits(bo.Uint32(data[1:]))
+}
+
 // DecodeSave decodes the state id of a save op.
 func DecodeSave(data []byte) int {
 	if OpType(data[0]) != TypeSave {
@@ -381,9 +421,10 @@ var opProps = [0x100]opProp{
 	TypeMacro:            {Size: TypeMacroLen, NumRefs: 0},
 	TypeCall:             {Size: TypeCallLen, NumRefs: 1},
 	TypeDefer:            {Size: TypeDeferLen, NumRefs: 0},
-	TypePushTransform:    {Size: TypePushTransformLen, NumRefs: 0},
 	TypeTransform:        {Size: TypeTransformLen, NumRefs: 0},
 	TypePopTransform:     {Size: TypePopTransformLen, NumRefs: 0},
+	TypePushOpacity:      {Size: TypePushOpacityLen, NumRefs: 0},
+	TypePopOpacity:       {Size: TypePopOpacityLen, NumRefs: 0},
 	TypeInvalidate:       {Size: TypeRedrawLen, NumRefs: 0},
 	TypeImage:            {Size: TypeImageLen, NumRefs: 2},
 	TypePaint:            {Size: TypePaintLen, NumRefs: 0},
@@ -413,23 +454,23 @@ var opProps = [0x100]opProp{
 	TypeSemanticDesc:     {Size: TypeSemanticDescLen, NumRefs: 1},
 	TypeSemanticClass:    {Size: TypeSemanticClassLen, NumRefs: 0},
 	TypeSemanticSelected: {Size: TypeSemanticSelectedLen, NumRefs: 0},
-	TypeSemanticDisabled: {Size: TypeSemanticDisabledLen, NumRefs: 0},
+	TypeSemanticEnabled:  {Size: TypeSemanticEnabledLen, NumRefs: 0},
 	TypeSnippet:          {Size: TypeSnippetLen, NumRefs: 2},
 	TypeSelection:        {Size: TypeSelectionLen, NumRefs: 1},
 	TypeActionInput:      {Size: TypeActionInputLen, NumRefs: 0},
 }
 
-func (t OpType) props() (size, numRefs int) {
+func (t OpType) props() (size, numRefs uint32) {
 	v := opProps[t]
-	return int(v.Size), int(v.NumRefs)
+	return uint32(v.Size), uint32(v.NumRefs)
 }
 
-func (t OpType) Size() int {
+func (t OpType) Size() uint32 {
-	return int(opProps[t].Size)
+	return uint32(opProps[t].Size)
 }
 
-func (t OpType) NumRefs() int {
+func (t OpType) NumRefs() uint32 {
-	return int(opProps[t].NumRefs)
+	return uint32(opProps[t].NumRefs)
 }
 
 func (t OpType) String() string {
@@ -440,12 +481,14 @@ func (t OpType) String() string {
 		return "Call"
 	case TypeDefer:
 		return "Defer"
-	case TypePushTransform:
-		return "PushTransform"
 	case TypeTransform:
 		return "Transform"
 	case TypePopTransform:
 		return "PopTransform"
+	case TypePushOpacity:
+		return "PushOpacity"
+	case TypePopOpacity:
+		return "PopOpacity"
 	case TypeInvalidate:
 		return "Invalidate"
 	case TypeImage:

internal/ops/reader.go

@@ -26,8 +26,8 @@ type EncodedOp struct {
 // Key is a unique key for a given op.
 type Key struct {
 	ops     *Ops
-	pc      int
+	pc      uint32
-	version int
+	version uint32
 }
 
 // Shadow of op.MacroOp.
@@ -39,8 +39,8 @@ type macroOp struct {
 
 // PC is an instruction counter for an operation list.
 type PC struct {
-	data int
+	data uint32
-	refs int
+	refs uint32
 }
 
 type macro struct {
@@ -128,7 +128,7 @@ func (r *Reader) Decode() (EncodedOp, bool) {
 				if nrefs != 1 {
 					panic("internal error: unexpected number of macro refs")
 				}
-				deferData := Write1(&r.deferOps, n, refs[0])
+				deferData := Write1(&r.deferOps, int(n), refs[0])
 				copy(deferData, data)
 				r.pc.data += n
 				r.pc.refs += nrefs
@@ -154,8 +154,8 @@ func (r *Reader) Decode() (EncodedOp, bool) {
 				r.pc = op.endpc
 			} else {
 				// Treat an incomplete macro as containing all remaining ops.
-				r.pc.data = len(r.ops.data)
+				r.pc.data = uint32(len(r.ops.data))
-				r.pc.refs = len(r.ops.refs)
+				r.pc.refs = uint32(len(r.ops.refs))
 			}
 			continue
 		}
@@ -171,8 +171,8 @@ func (op *opMacroDef) decode(data []byte) {
 	}
 	bo := binary.LittleEndian
 	data = data[:TypeMacroLen]
-	op.endpc.data = int(int32(bo.Uint32(data[1:])))
+	op.endpc.data = bo.Uint32(data[1:])
-	op.endpc.refs = int(int32(bo.Uint32(data[5:])))
+	op.endpc.refs = bo.Uint32(data[5:])
 }
 
 func (m *macroOp) decode(data []byte, refs []interface{}) {
@@ -183,8 +183,8 @@ func (m *macroOp) decode(data []byte, refs []interface{}) {
 	data = data[:TypeCallLen]
 
 	m.ops = refs[0].(*Ops)
-	m.start.data = int(int32(bo.Uint32(data[1:])))
+	m.start.data = bo.Uint32(data[1:])
-	m.start.refs = int(int32(bo.Uint32(data[5:])))
+	m.start.refs = bo.Uint32(data[5:])
-	m.end.data = int(int32(bo.Uint32(data[9:])))
+	m.end.data = bo.Uint32(data[9:])
-	m.end.refs = int(int32(bo.Uint32(data[13:])))
+	m.end.refs = bo.Uint32(data[13:])
 }

io/clipboard/clipboard.go

@@ -30,7 +30,7 @@ func (h ReadOp) Add(o *op.Ops) {
 }
 
 func (h WriteOp) Add(o *op.Ops) {
-	data := ops.Write1(&o.Internal, ops.TypeClipboardWriteLen, &h.Text)
+	data := ops.Write1String(&o.Internal, ops.TypeClipboardWriteLen, h.Text)
 	data[0] = byte(ops.TypeClipboardWrite)
 }
 

io/key/key.go

@@ -323,8 +323,7 @@ func (h InputOp) Add(o *op.Ops) {
 	if h.Tag == nil {
 		panic("Tag must be non-nil")
 	}
-	filter := h.Keys
+	data := ops.Write2String(&o.Internal, ops.TypeKeyInputLen, h.Tag, string(h.Keys))
-	data := ops.Write2(&o.Internal, ops.TypeKeyInputLen, h.Tag, &filter)
 	data[0] = byte(ops.TypeKeyInput)
 	data[1] = byte(h.Hint)
 }
@@ -343,7 +342,7 @@ func (h FocusOp) Add(o *op.Ops) {
 }
 
 func (s SnippetOp) Add(o *op.Ops) {
-	data := ops.Write2(&o.Internal, ops.TypeSnippetLen, s.Tag, &s.Text)
+	data := ops.Write2String(&o.Internal, ops.TypeSnippetLen, s.Tag, s.Text)
 	data[0] = byte(ops.TypeSnippet)
 	bo := binary.LittleEndian
 	bo.PutUint32(data[1:], uint32(s.Range.Start))

io/pointer/doc.go

@@ -8,7 +8,7 @@ object such as a finger.
 The InputOp operation is used to declare a handler ready for pointer
 events. Use an event.Queue to receive events.
 
-# Types
+# Kinds
 
 Only events that match a specified list of types are delivered to a handler.
 
@@ -20,7 +20,7 @@ Leave, or Scroll):
 
 	pointer.InputOp{
 		Tag:   h,
-		Types: pointer.Press | pointer.Drag | pointer.Release,
+		Kinds: pointer.Press | pointer.Drag | pointer.Release,
 	}.Add(ops)
 
 Cancel events are always delivered.

io/pointer/pointer.go

@@ -18,7 +18,7 @@ import (
 
 // Event is a pointer event.
 type Event struct {
-	Type   Type
+	Kind   Kind
 	Source Source
 	// PointerID is the id for the pointer and can be used
 	// to track a particular pointer from Press to
@@ -32,8 +32,10 @@ type Event struct {
 	Time time.Duration
 	// Buttons are the set of pressed mouse buttons for this event.
 	Buttons Buttons
-	// Position is the position of the event, relative to
+	// Position is the coordinates of the event in the local coordinate
-	// the current transformation, as set by op.TransformOp.
+	// system of the receiving tag. The transformation from global window
+	// coordinates to local coordinates is performed by the inverse of
+	// the effective transformation of the tag.
 	Position f32.Point
 	// Scroll is the scroll amount, if any.
 	Scroll f32.Point
@@ -51,7 +53,7 @@ type PassOp struct {
 type PassStack struct {
 	ops     *ops.Ops
 	id      ops.StackID
-	macroID int
+	macroID uint32
 }
 
 // InputOp declares an input handler ready for pointer
@@ -61,8 +63,8 @@ type InputOp struct {
 	// Grab, if set, request that the handler get
 	// Grabbed priority.
 	Grab bool
-	// Types is a bitwise-or of event types to receive.
+	// Kinds is a bitwise-or of event types to receive.
-	Types Type
+	Kinds Kind
 	// ScrollBounds describe the maximum scrollable distances in both
 	// axes. Specifically, any Event e delivered to Tag will satisfy
 	//
@@ -73,8 +75,8 @@ type InputOp struct {
 
 type ID uint16
 
-// Type of an Event.
+// Kind of an Event.
-type Type uint
+type Kind uint
 
 // Priority of an Event.
 type Priority uint8
@@ -169,7 +171,7 @@ const (
 const (
 	// A Cancel event is generated when the current gesture is
 	// interrupted by other handlers or the system.
-	Cancel Type = (1 << iota) >> 1
+	Cancel Kind = (1 << iota) >> 1
 	// Press of a pointer.
 	Press
 	// Release of a pointer.
@@ -243,7 +245,7 @@ func (op InputOp) Add(o *op.Ops) {
 	if b := op.ScrollBounds; b.Min.X > 0 || b.Max.X < 0 || b.Min.Y > 0 || b.Max.Y < 0 {
 		panic(fmt.Errorf("invalid scroll range value %v", b))
 	}
-	if op.Types>>16 > 0 {
+	if op.Kinds>>16 > 0 {
 		panic(fmt.Errorf("value in Types overflows uint16"))
 	}
 	data := ops.Write1(&o.Internal, ops.TypePointerInputLen, op.Tag)
@@ -252,19 +254,19 @@ func (op InputOp) Add(o *op.Ops) {
 		data[1] = 1
 	}
 	bo := binary.LittleEndian
-	bo.PutUint16(data[2:], uint16(op.Types))
+	bo.PutUint16(data[2:], uint16(op.Kinds))
 	bo.PutUint32(data[4:], uint32(op.ScrollBounds.Min.X))
 	bo.PutUint32(data[8:], uint32(op.ScrollBounds.Min.Y))
 	bo.PutUint32(data[12:], uint32(op.ScrollBounds.Max.X))
 	bo.PutUint32(data[16:], uint32(op.ScrollBounds.Max.Y))
 }
 
-func (t Type) String() string {
+func (t Kind) String() string {
 	if t == Cancel {
 		return "Cancel"
 	}
 	var buf strings.Builder
-	for tt := Type(1); tt > 0; tt <<= 1 {
+	for tt := Kind(1); tt > 0; tt <<= 1 {
 		if t&tt > 0 {
 			if buf.Len() > 0 {
 				buf.WriteByte('|')
@@ -275,7 +277,7 @@ func (t Type) String() string {
 	return buf.String()
 }
 
-func (t Type) string() string {
+func (t Kind) string() string {
 	switch t {
 	case Press:
 		return "Press"

io/pointer/pointer_test.go

@@ -8,7 +8,7 @@ import (
 
 func TestTypeString(t *testing.T) {
 	for _, tc := range []struct {
-		typ Type
+		typ Kind
 		res string
 	}{
 		{Cancel, "Cancel"},

io/router/key_test.go

@@ -30,11 +30,6 @@ func TestKeyWakeup(t *testing.T) {
 	if evts := r.Events(handler); len(evts) != 1 {
 		t.Errorf("no Focus event for newly registered key.InputOp")
 	}
-	// Verify that r.Events does trigger a redraw.
-	r.Frame(&ops)
-	if _, wake := r.WakeupTime(); !wake {
-		t.Errorf("key.FocusEvent event didn't trigger a redraw")
-	}
 }
 
 func TestKeyMultiples(t *testing.T) {
@@ -279,7 +274,7 @@ func TestFocusScroll(t *testing.T) {
 	key.InputOp{Tag: h}.Add(ops)
 	pointer.InputOp{
 		Tag:          h,
-		Types:        pointer.Scroll,
+		Kinds:        pointer.Scroll,
 		ScrollBounds: image.Rect(-100, -100, 100, 100),
 	}.Add(ops)
 	// Test that h is scrolled even if behind another handler.
@@ -305,7 +300,7 @@ func TestFocusClick(t *testing.T) {
 	key.InputOp{Tag: h}.Add(ops)
 	pointer.InputOp{
 		Tag:   h,
-		Types: pointer.Press | pointer.Release,
+		Kinds: pointer.Press | pointer.Release,
 	}.Add(ops)
 	cl.Pop()
 	r.Frame(ops)

io/router/pointer.go

@@ -66,7 +66,7 @@ type pointerHandler struct {
 	area      int
 	active    bool
 	wantsGrab bool
-	types     pointer.Type
+	types     pointer.Kind
 	// min and max horizontal/vertical scroll
 	scrollRange image.Rectangle
 
@@ -242,7 +242,7 @@ func (c *pointerCollector) newHandler(tag event.Tag, events *handlerEvents) *poi
 		c.q.handlers[tag] = h
 		// Cancel handlers on (each) first appearance, but don't
 		// trigger redraw.
-		events.AddNoRedraw(tag, pointer.Event{Type: pointer.Cancel})
+		events.AddNoRedraw(tag, pointer.Event{Kind: pointer.Cancel})
 	}
 	h.active = true
 	h.area = areaID
@@ -268,16 +268,16 @@ func (c *pointerCollector) inputOp(op pointer.InputOp, events *handlerEvents) {
 	areaID := c.currentArea()
 	area := &c.q.areas[areaID]
 	area.semantic.content.tag = op.Tag
-	if op.Types&(pointer.Press|pointer.Release) != 0 {
+	if op.Kinds&(pointer.Press|pointer.Release) != 0 {
 		area.semantic.content.gestures |= ClickGesture
 	}
-	if op.Types&pointer.Scroll != 0 {
+	if op.Kinds&pointer.Scroll != 0 {
 		area.semantic.content.gestures |= ScrollGesture
 	}
 	area.semantic.valid = area.semantic.content.gestures != 0
 	h := c.newHandler(op.Tag, events)
 	h.wantsGrab = h.wantsGrab || op.Grab
-	h.types = h.types | op.Types
+	h.types = h.types | op.Kinds
 	h.scrollRange = op.ScrollBounds
 }
 
@@ -309,11 +309,11 @@ func (c *pointerCollector) semanticSelected(selected bool) {
 	area.semantic.content.selected = selected
 }
 
-func (c *pointerCollector) semanticDisabled(disabled bool) {
+func (c *pointerCollector) semanticEnabled(enabled bool) {
 	areaID := c.currentArea()
 	area := &c.q.areas[areaID]
 	area.semantic.valid = true
-	area.semantic.content.disabled = disabled
+	area.semantic.content.disabled = !enabled
 }
 
 func (c *pointerCollector) cursor(cursor pointer.Cursor) {
@@ -432,39 +432,42 @@ func (q *pointerQueue) semanticIDFor(content semanticContent) SemanticID {
 	return id.id
 }
 
-func (q *pointerQueue) ActionAt(pos f32.Point) (system.Action, bool) {
+func (q *pointerQueue) ActionAt(pos f32.Point) (action system.Action, hasAction bool) {
-	for i := len(q.hitTree) - 1; i >= 0; i-- {
+	q.hitTest(pos, func(n *hitNode) bool {
-		n := &q.hitTree[i]
-		hit, _ := q.hit(n.area, pos)
-		if !hit {
-			continue
-		}
 		area := q.areas[n.area]
-		return area.action, area.action != 0
+		if area.action != 0 {
-	}
+			action = area.action
-	return 0, false
+			hasAction = true
+			return false
+		}
+		return true
+	})
+	return action, hasAction
 }
 
-func (q *pointerQueue) SemanticAt(pos f32.Point) (SemanticID, bool) {
+func (q *pointerQueue) SemanticAt(pos f32.Point) (semID SemanticID, hasSemID bool) {
 	q.assignSemIDs()
-	for i := len(q.hitTree) - 1; i >= 0; i-- {
+	q.hitTest(pos, func(n *hitNode) bool {
-		n := &q.hitTree[i]
-		hit, _ := q.hit(n.area, pos)
-		if !hit {
-			continue
-		}
 		area := q.areas[n.area]
 		if area.semantic.id != 0 {
-			return area.semantic.id, true
+			semID = area.semantic.id
+			hasSemID = true
+			return false
 		}
-	}
+		return true
-	return 0, false
+	})
+	return semID, hasSemID
 }
 
-func (q *pointerQueue) opHit(pos f32.Point) ([]event.Tag, pointer.Cursor) {
+// hitTest searches the hit tree for nodes matching pos. Any node matching pos will
+// have the onNode func invoked on it to allow the caller to extract whatever information
+// is necessary for further processing. onNode may return false to terminate the walk of
+// the hit tree, or true to continue. Providing this algorithm in this generic way
+// allows normal event routing and system action event routing to share the same traversal
+// logic even though they are interested in different aspects of hit nodes.
+func (q *pointerQueue) hitTest(pos f32.Point, onNode func(*hitNode) bool) pointer.Cursor {
 	// Track whether we're passing through hits.
 	pass := true
-	hits := q.scratch[:0]
 	idx := len(q.hitTree) - 1
 	cursor := pointer.CursorDefault
 	for idx >= 0 {
@@ -483,12 +486,23 @@ func (q *pointerQueue) opHit(pos f32.Point) ([]event.Tag, pointer.Cursor) {
 		} else {
 			idx = n.next
 		}
+		if !onNode(n) {
+			break
+		}
+	}
+	return cursor
+}
+
+func (q *pointerQueue) opHit(pos f32.Point) ([]event.Tag, pointer.Cursor) {
+	hits := q.scratch[:0]
+	cursor := q.hitTest(pos, func(n *hitNode) bool {
 		if n.tag != nil {
 			if _, exists := q.handlers[n.tag]; exists {
 				hits = addHandler(hits, n.tag)
 			}
 		}
-	}
+		return true
+	})
 	q.scratch = hits[:0]
 	return hits, cursor
 }
@@ -588,7 +602,7 @@ func (q *pointerQueue) Frame(events *handlerEvents) {
 
 func (q *pointerQueue) dropHandler(events *handlerEvents, tag event.Tag) {
 	if events != nil {
-		events.Add(tag, pointer.Event{Type: pointer.Cancel})
+		events.Add(tag, pointer.Event{Kind: pointer.Cancel})
 	}
 	for i := range q.pointers {
 		p := &q.pointers[i]
@@ -635,11 +649,11 @@ func (q *pointerQueue) Deliver(areaIdx int, e pointer.Event, events *handlerEven
 			continue
 		}
 		h := q.handlers[n.tag]
-		if e.Type&h.types == 0 {
+		if e.Kind&h.types == 0 {
 			continue
 		}
 		e := e
-		if e.Type == pointer.Scroll {
+		if e.Kind == pointer.Scroll {
 			if sx == 0 && sy == 0 {
 				break
 			}
@@ -649,7 +663,7 @@ func (q *pointerQueue) Deliver(areaIdx int, e pointer.Event, events *handlerEven
 		}
 		e.Position = q.invTransform(h.area, e.Position)
 		events.Add(n.tag, e)
-		if e.Type != pointer.Scroll {
+		if e.Kind != pointer.Scroll {
 			break
 		}
 	}
@@ -669,7 +683,7 @@ func (q *pointerQueue) SemanticArea(areaIdx int) (semanticContent, int) {
 }
 
 func (q *pointerQueue) Push(e pointer.Event, events *handlerEvents) {
-	if e.Type == pointer.Cancel {
+	if e.Kind == pointer.Cancel {
 		q.pointers = q.pointers[:0]
 		for k := range q.handlers {
 			q.dropHandler(events, k)
@@ -680,14 +694,14 @@ func (q *pointerQueue) Push(e pointer.Event, events *handlerEvents) {
 	p := &q.pointers[pidx]
 	p.last = e
 
-	switch e.Type {
+	switch e.Kind {
 	case pointer.Press:
 		q.deliverEnterLeaveEvents(p, events, e)
 		p.pressed = true
 		q.deliverEvent(p, events, e)
 	case pointer.Move:
 		if p.pressed {
-			e.Type = pointer.Drag
+			e.Kind = pointer.Drag
 		}
 		q.deliverEnterLeaveEvents(p, events, e)
 		q.deliverEvent(p, events, e)
@@ -721,7 +735,7 @@ func (q *pointerQueue) deliverEvent(p *pointerInfo, events *handlerEvents, e poi
 	var sx, sy = e.Scroll.X, e.Scroll.Y
 	for _, k := range p.handlers {
 		h := q.handlers[k]
-		if e.Type == pointer.Scroll {
+		if e.Kind == pointer.Scroll {
 			if sx == 0 && sy == 0 {
 				return
 			}
@@ -729,7 +743,7 @@ func (q *pointerQueue) deliverEvent(p *pointerInfo, events *handlerEvents, e poi
 			sx, e.Scroll.X = setScrollEvent(sx, h.scrollRange.Min.X, h.scrollRange.Max.X)
 			sy, e.Scroll.Y = setScrollEvent(sy, h.scrollRange.Min.Y, h.scrollRange.Max.Y)
 		}
-		if e.Type&h.types == 0 {
+		if e.Kind&h.types == 0 {
 			continue
 		}
 		e := e
@@ -744,7 +758,7 @@ func (q *pointerQueue) deliverEvent(p *pointerInfo, events *handlerEvents, e poi
 
 func (q *pointerQueue) deliverEnterLeaveEvents(p *pointerInfo, events *handlerEvents, e pointer.Event) {
 	var hits []event.Tag
-	if e.Source != pointer.Mouse && !p.pressed && e.Type != pointer.Press {
+	if e.Source != pointer.Mouse && !p.pressed && e.Kind != pointer.Press {
 		// Consider non-mouse pointers leaving when they're released.
 	} else {
 		hits, q.cursor = q.opHit(e.Position)
@@ -776,9 +790,9 @@ func (q *pointerQueue) deliverEnterLeaveEvents(p *pointerInfo, events *handlerEv
 			continue
 		}
 		h := q.handlers[k]
-		e.Type = pointer.Leave
+		e.Kind = pointer.Leave
 
-		if e.Type&h.types != 0 {
+		if e.Kind&h.types != 0 {
 			e := e
 			e.Position = q.invTransform(h.area, e.Position)
 			events.Add(k, e)
@@ -790,9 +804,9 @@ func (q *pointerQueue) deliverEnterLeaveEvents(p *pointerInfo, events *handlerEv
 		if _, found := searchTag(p.entered, k); found {
 			continue
 		}
-		e.Type = pointer.Enter
+		e.Kind = pointer.Enter
 
-		if e.Type&h.types != 0 {
+		if e.Kind&h.types != 0 {
 			e := e
 			e.Position = q.invTransform(h.area, e.Position)
 			events.Add(k, e)

io/router/pointer_test.go

@@ -14,6 +14,7 @@ import (
 	"gioui.org/io/event"
 	"gioui.org/io/key"
 	"gioui.org/io/pointer"
+	"gioui.org/io/system"
 	"gioui.org/io/transfer"
 	"gioui.org/op"
 	"gioui.org/op/clip"
@@ -32,11 +33,6 @@ func TestPointerWakeup(t *testing.T) {
 	}
 	// However, adding a handler queues a Cancel event.
 	assertEventPointerTypeSequence(t, r.Events(handler), pointer.Cancel)
-	// Verify that r.Events does trigger a redraw.
-	r.Frame(&ops)
-	if _, wake := r.WakeupTime(); !wake {
-		t.Errorf("pointer.Cancel event didn't trigger a redraw")
-	}
 }
 
 func TestPointerDrag(t *testing.T) {
@@ -49,12 +45,12 @@ func TestPointerDrag(t *testing.T) {
 	r.Queue(
 		// Press.
 		pointer.Event{
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(50, 50),
 		},
 		// Move outside the area.
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(150, 150),
 		},
 	)
@@ -71,12 +67,12 @@ func TestPointerDragNegative(t *testing.T) {
 	r.Queue(
 		// Press.
 		pointer.Event{
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(-50, -50),
 		},
 		// Move outside the area.
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(-150, -150),
 		},
 	)
@@ -91,15 +87,15 @@ func TestPointerGrab(t *testing.T) {
 
 	types := pointer.Press | pointer.Release
 
-	pointer.InputOp{Tag: handler1, Types: types, Grab: true}.Add(&ops)
+	pointer.InputOp{Tag: handler1, Kinds: types, Grab: true}.Add(&ops)
-	pointer.InputOp{Tag: handler2, Types: types}.Add(&ops)
+	pointer.InputOp{Tag: handler2, Kinds: types}.Add(&ops)
-	pointer.InputOp{Tag: handler3, Types: types}.Add(&ops)
+	pointer.InputOp{Tag: handler3, Kinds: types}.Add(&ops)
 
 	var r Router
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(50, 50),
 		},
 	)
@@ -109,7 +105,7 @@ func TestPointerGrab(t *testing.T) {
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Release,
+			Kind:     pointer.Release,
 			Position: f32.Pt(50, 50),
 		},
 	)
@@ -125,15 +121,15 @@ func TestPointerGrabSameHandlerTwice(t *testing.T) {
 
 	types := pointer.Press | pointer.Release
 
-	pointer.InputOp{Tag: handler1, Types: types, Grab: true}.Add(&ops)
+	pointer.InputOp{Tag: handler1, Kinds: types, Grab: true}.Add(&ops)
-	pointer.InputOp{Tag: handler1, Types: types}.Add(&ops)
+	pointer.InputOp{Tag: handler1, Kinds: types}.Add(&ops)
-	pointer.InputOp{Tag: handler2, Types: types}.Add(&ops)
+	pointer.InputOp{Tag: handler2, Kinds: types}.Add(&ops)
 
 	var r Router
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(50, 50),
 		},
 	)
@@ -142,7 +138,7 @@ func TestPointerGrabSameHandlerTwice(t *testing.T) {
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Release,
+			Kind:     pointer.Release,
 			Position: f32.Pt(50, 50),
 		},
 	)
@@ -159,10 +155,10 @@ func TestPointerMove(t *testing.T) {
 
 	// Handler 1 area: (0, 0) - (100, 100)
 	r1 := clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops)
-	pointer.InputOp{Tag: handler1, Types: types}.Add(&ops)
+	pointer.InputOp{Tag: handler1, Kinds: types}.Add(&ops)
 	// Handler 2 area: (50, 50) - (100, 100) (areas intersect).
 	r2 := clip.Rect(image.Rect(50, 50, 200, 200)).Push(&ops)
-	pointer.InputOp{Tag: handler2, Types: types}.Add(&ops)
+	pointer.InputOp{Tag: handler2, Kinds: types}.Add(&ops)
 	r2.Pop()
 	r1.Pop()
 
@@ -171,21 +167,21 @@ func TestPointerMove(t *testing.T) {
 	r.Queue(
 		// Hit both handlers.
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(50, 50),
 		},
 		// Hit handler 1.
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(49, 50),
 		},
 		// Hit no handlers.
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(100, 50),
 		},
 		pointer.Event{
-			Type: pointer.Cancel,
+			Kind: pointer.Cancel,
 		},
 	)
 	assertEventPointerTypeSequence(t, r.Events(handler1), pointer.Cancel, pointer.Enter, pointer.Move, pointer.Move, pointer.Leave, pointer.Cancel)
@@ -198,7 +194,7 @@ func TestPointerTypes(t *testing.T) {
 	r1 := clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops)
 	pointer.InputOp{
 		Tag:   handler,
-		Types: pointer.Press | pointer.Release,
+		Kinds: pointer.Press | pointer.Release,
 	}.Add(&ops)
 	r1.Pop()
 
@@ -206,21 +202,58 @@ func TestPointerTypes(t *testing.T) {
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(50, 50),
 		},
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(150, 150),
 		},
 		pointer.Event{
-			Type:     pointer.Release,
+			Kind:     pointer.Release,
 			Position: f32.Pt(150, 150),
 		},
 	)
 	assertEventPointerTypeSequence(t, r.Events(handler), pointer.Cancel, pointer.Press, pointer.Release)
 }
 
+func TestPointerSystemAction(t *testing.T) {
+	t.Run("simple", func(t *testing.T) {
+		var ops op.Ops
+		r1 := clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops)
+		system.ActionInputOp(system.ActionMove).Add(&ops)
+		r1.Pop()
+
+		var r Router
+		r.Frame(&ops)
+		assertActionAt(t, r, f32.Pt(50, 50), system.ActionMove)
+	})
+	t.Run("covered by another clip", func(t *testing.T) {
+		var ops op.Ops
+		r1 := clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops)
+		system.ActionInputOp(system.ActionMove).Add(&ops)
+		clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops).Pop()
+		r1.Pop()
+
+		var r Router
+		r.Frame(&ops)
+		assertActionAt(t, r, f32.Pt(50, 50), system.ActionMove)
+	})
+	t.Run("uses topmost action op", func(t *testing.T) {
+		var ops op.Ops
+		r1 := clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops)
+		system.ActionInputOp(system.ActionMove).Add(&ops)
+		r2 := clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops)
+		system.ActionInputOp(system.ActionClose).Add(&ops)
+		r2.Pop()
+		r1.Pop()
+
+		var r Router
+		r.Frame(&ops)
+		assertActionAt(t, r, f32.Pt(50, 50), system.ActionClose)
+	})
+}
+
 func TestPointerPriority(t *testing.T) {
 	handler1 := new(int)
 	handler2 := new(int)
@@ -230,14 +263,14 @@ func TestPointerPriority(t *testing.T) {
 	r1 := clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops)
 	pointer.InputOp{
 		Tag:          handler1,
-		Types:        pointer.Scroll,
+		Kinds:        pointer.Scroll,
 		ScrollBounds: image.Rectangle{Max: image.Point{X: 100}},
 	}.Add(&ops)
 
 	r2 := clip.Rect(image.Rect(0, 0, 100, 50)).Push(&ops)
 	pointer.InputOp{
 		Tag:          handler2,
-		Types:        pointer.Scroll,
+		Kinds:        pointer.Scroll,
 		ScrollBounds: image.Rectangle{Max: image.Point{X: 20}},
 	}.Add(&ops)
 	r2.Pop()
@@ -246,7 +279,7 @@ func TestPointerPriority(t *testing.T) {
 	r3 := clip.Rect(image.Rect(0, 100, 100, 200)).Push(&ops)
 	pointer.InputOp{
 		Tag:          handler3,
-		Types:        pointer.Scroll,
+		Kinds:        pointer.Scroll,
 		ScrollBounds: image.Rectangle{Min: image.Point{X: -20, Y: -40}},
 	}.Add(&ops)
 	r3.Pop()
@@ -256,25 +289,25 @@ func TestPointerPriority(t *testing.T) {
 	r.Queue(
 		// Hit handler 1 and 2.
 		pointer.Event{
-			Type:     pointer.Scroll,
+			Kind:     pointer.Scroll,
 			Position: f32.Pt(50, 25),
 			Scroll:   f32.Pt(50, 0),
 		},
 		// Hit handler 1.
 		pointer.Event{
-			Type:     pointer.Scroll,
+			Kind:     pointer.Scroll,
 			Position: f32.Pt(50, 75),
 			Scroll:   f32.Pt(50, 50),
 		},
 		// Hit handler 3.
 		pointer.Event{
-			Type:     pointer.Scroll,
+			Kind:     pointer.Scroll,
 			Position: f32.Pt(50, 150),
 			Scroll:   f32.Pt(-30, -30),
 		},
 		// Hit no handlers.
 		pointer.Event{
-			Type:     pointer.Scroll,
+			Kind:     pointer.Scroll,
 			Position: f32.Pt(50, 225),
 		},
 	)
@@ -310,7 +343,7 @@ func TestPointerEnterLeave(t *testing.T) {
 	// Hit both handlers.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(50, 50),
 		},
 	)
@@ -323,7 +356,7 @@ func TestPointerEnterLeave(t *testing.T) {
 	// Leave the second area by moving into the first.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(45, 45),
 		},
 	)
@@ -334,7 +367,7 @@ func TestPointerEnterLeave(t *testing.T) {
 	// Move, but stay within the same hit area.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(40, 40),
 		},
 	)
@@ -344,7 +377,7 @@ func TestPointerEnterLeave(t *testing.T) {
 	// Move outside of both inputs.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(300, 300),
 		},
 	)
@@ -354,7 +387,7 @@ func TestPointerEnterLeave(t *testing.T) {
 	// Check that a Press event generates Enter Events.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(125, 125),
 		},
 	)
@@ -365,12 +398,12 @@ func TestPointerEnterLeave(t *testing.T) {
 	r.Queue(
 		// Leave
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(25, 25),
 		},
 		// Enter
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(50, 50),
 		},
 	)
@@ -380,7 +413,7 @@ func TestPointerEnterLeave(t *testing.T) {
 	// Check that a Release event generates Enter/Leave Events.
 	r.Queue(
 		pointer.Event{
-			Type: pointer.Release,
+			Kind: pointer.Release,
 			Position: f32.Pt(25,
 				25),
 		},
@@ -408,15 +441,15 @@ func TestMultipleAreas(t *testing.T) {
 	// Hit first area, then second area, then both.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(25, 25),
 		},
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(150, 150),
 		},
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(50, 50),
 		},
 	)
@@ -432,11 +465,11 @@ func TestPointerEnterLeaveNested(t *testing.T) {
 
 	// Handler 1 area: (0, 0) - (100, 100)
 	r1 := clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops)
-	pointer.InputOp{Tag: handler1, Types: types}.Add(&ops)
+	pointer.InputOp{Tag: handler1, Kinds: types}.Add(&ops)
 
 	// Handler 2 area: (25, 25) - (75, 75) (nested within first).
 	r2 := clip.Rect(image.Rect(25, 25, 75, 75)).Push(&ops)
-	pointer.InputOp{Tag: handler2, Types: types}.Add(&ops)
+	pointer.InputOp{Tag: handler2, Kinds: types}.Add(&ops)
 	r2.Pop()
 	r1.Pop()
 
@@ -445,7 +478,7 @@ func TestPointerEnterLeaveNested(t *testing.T) {
 	// Hit both handlers.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(50, 50),
 		},
 	)
@@ -457,7 +490,7 @@ func TestPointerEnterLeaveNested(t *testing.T) {
 	// Leave the second area by moving into the first.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(20, 20),
 		},
 	)
@@ -467,7 +500,7 @@ func TestPointerEnterLeaveNested(t *testing.T) {
 	// Move, but stay within the same hit area.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(10, 10),
 		},
 	)
@@ -477,7 +510,7 @@ func TestPointerEnterLeaveNested(t *testing.T) {
 	// Move outside of both inputs.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(200, 200),
 		},
 	)
@@ -487,7 +520,7 @@ func TestPointerEnterLeaveNested(t *testing.T) {
 	// Check that a Press event generates Enter Events.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(50, 50),
 		},
 	)
@@ -497,7 +530,7 @@ func TestPointerEnterLeaveNested(t *testing.T) {
 	// Check that a Release event generates Enter/Leave Events.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Release,
+			Kind:     pointer.Release,
 			Position: f32.Pt(20, 20),
 		},
 	)
@@ -516,7 +549,7 @@ func TestPointerActiveInputDisappears(t *testing.T) {
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(25, 25),
 		},
 	)
@@ -527,7 +560,7 @@ func TestPointerActiveInputDisappears(t *testing.T) {
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(25, 25),
 		},
 	)
@@ -549,21 +582,21 @@ func TestMultitouch(t *testing.T) {
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type:      pointer.Press,
+			Kind:      pointer.Press,
 			Position:  h1pt,
 			PointerID: p1,
 		},
 	)
 	r.Queue(
 		pointer.Event{
-			Type:      pointer.Press,
+			Kind:      pointer.Press,
 			Position:  h2pt,
 			PointerID: p2,
 		},
 	)
 	r.Queue(
 		pointer.Event{
-			Type:      pointer.Release,
+			Kind:      pointer.Release,
 			Position:  h2pt,
 			PointerID: p2,
 		},
@@ -596,7 +629,7 @@ func TestCursor(t *testing.T) {
 
 	_at := func(x, y float32) pointer.Event {
 		return pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Source:   pointer.Mouse,
 			Buttons:  pointer.ButtonPrimary,
 			Position: f32.Pt(x, y),
@@ -696,14 +729,14 @@ func TestPassOp(t *testing.T) {
 	h1, h2, h3, h4 := new(int), new(int), new(int), new(int)
 	area := clip.Rect(image.Rect(0, 0, 100, 100))
 	root := area.Push(&ops)
-	pointer.InputOp{Tag: h1, Types: pointer.Press}.Add(&ops)
+	pointer.InputOp{Tag: h1, Kinds: pointer.Press}.Add(&ops)
 	child1 := area.Push(&ops)
-	pointer.InputOp{Tag: h2, Types: pointer.Press}.Add(&ops)
+	pointer.InputOp{Tag: h2, Kinds: pointer.Press}.Add(&ops)
 	child1.Pop()
 	child2 := area.Push(&ops)
 	pass := pointer.PassOp{}.Push(&ops)
-	pointer.InputOp{Tag: h3, Types: pointer.Press}.Add(&ops)
+	pointer.InputOp{Tag: h3, Kinds: pointer.Press}.Add(&ops)
-	pointer.InputOp{Tag: h4, Types: pointer.Press}.Add(&ops)
+	pointer.InputOp{Tag: h4, Kinds: pointer.Press}.Add(&ops)
 	pass.Pop()
 	child2.Pop()
 	root.Pop()
@@ -712,7 +745,7 @@ func TestPassOp(t *testing.T) {
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type: pointer.Press,
+			Kind: pointer.Press,
 		},
 	)
 	assertEventPointerTypeSequence(t, r.Events(h1), pointer.Cancel, pointer.Press)
@@ -725,13 +758,13 @@ func TestAreaPassthrough(t *testing.T) {
 	var ops op.Ops
 
 	h := new(int)
-	pointer.InputOp{Tag: h, Types: pointer.Press}.Add(&ops)
+	pointer.InputOp{Tag: h, Kinds: pointer.Press}.Add(&ops)
 	clip.Rect(image.Rect(0, 0, 100, 100)).Push(&ops).Pop()
 	var r Router
 	r.Frame(&ops)
 	r.Queue(
 		pointer.Event{
-			Type: pointer.Press,
+			Kind: pointer.Press,
 		},
 	)
 	assertEventPointerTypeSequence(t, r.Events(h), pointer.Cancel, pointer.Press)
@@ -742,7 +775,7 @@ func TestEllipse(t *testing.T) {
 
 	h := new(int)
 	cl := clip.Ellipse(image.Rect(0, 0, 100, 100)).Push(&ops)
-	pointer.InputOp{Tag: h, Types: pointer.Press}.Add(&ops)
+	pointer.InputOp{Tag: h, Kinds: pointer.Press}.Add(&ops)
 	cl.Pop()
 	var r Router
 	r.Frame(&ops)
@@ -750,15 +783,15 @@ func TestEllipse(t *testing.T) {
 		// Outside ellipse.
 		pointer.Event{
 			Position: f32.Pt(10, 10),
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 		},
 		pointer.Event{
-			Type: pointer.Release,
+			Kind: pointer.Release,
 		},
 		// Inside ellipse.
 		pointer.Event{
 			Position: f32.Pt(50, 50),
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 		},
 	)
 	assertEventPointerTypeSequence(t, r.Events(h), pointer.Cancel, pointer.Press)
@@ -787,7 +820,7 @@ func TestTransfer(t *testing.T) {
 		return src, tgt
 	}
 	// Cancel is received when the pointer is first seen.
-	cancel := pointer.Event{Type: pointer.Cancel}
+	cancel := pointer.Event{Kind: pointer.Cancel}
 
 	t.Run("transfer.Offer should panic on nil Data", func(t *testing.T) {
 		defer func() {
@@ -807,11 +840,11 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Press,
+				Kind:     pointer.Press,
 			},
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 		)
 		assertEventSequence(t, r.Events(src), cancel)
@@ -821,11 +854,11 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(30, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 			pointer.Event{
 				Position: f32.Pt(30, 10),
-				Type:     pointer.Release,
+				Kind:     pointer.Release,
 			},
 		)
 		assertEventSequence(t, r.Events(src), transfer.CancelEvent{})
@@ -848,11 +881,11 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Press,
+				Kind:     pointer.Press,
 			},
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 		)
 		assertEventSequence(t, r.Events(src), cancel)
@@ -869,11 +902,11 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Press,
+				Kind:     pointer.Press,
 			},
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 		)
 		assertEventSequence(t, r.Events(src), cancel)
@@ -883,7 +916,7 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(40, 10),
-				Type:     pointer.Release,
+				Kind:     pointer.Release,
 			},
 		)
 		assertEventSequence(t, r.Events(src), transfer.CancelEvent{})
@@ -906,11 +939,11 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Press,
+				Kind:     pointer.Press,
 			},
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 		)
 		assertEventSequence(t, r.Events(src), cancel)
@@ -920,7 +953,7 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(40, 10),
-				Type:     pointer.Release,
+				Kind:     pointer.Release,
 			},
 		)
 		assertEventSequence(t, r.Events(src), transfer.RequestEvent{Type: "file"})
@@ -973,15 +1006,15 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Press,
+				Kind:     pointer.Press,
 			},
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 			pointer.Event{
 				Position: f32.Pt(40, 10),
-				Type:     pointer.Release,
+				Kind:     pointer.Release,
 			},
 		)
 		ofr := &offer{data: "hello"}
@@ -1016,15 +1049,15 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Press,
+				Kind:     pointer.Press,
 			},
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 			pointer.Event{
 				Position: f32.Pt(40, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 		)
 		assertEventPointerTypeSequence(t, r.Events(&hover), pointer.Cancel, pointer.Enter)
@@ -1033,7 +1066,7 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(40, 10),
-				Type:     pointer.Release,
+				Kind:     pointer.Release,
 			},
 		)
 
@@ -1064,15 +1097,15 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Press,
+				Kind:     pointer.Press,
 			},
 			pointer.Event{
 				Position: f32.Pt(10, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 			pointer.Event{
 				Position: f32.Pt(40, 10),
-				Type:     pointer.Move,
+				Kind:     pointer.Move,
 			},
 		)
 		assertEventPointerTypeSequence(t, r.Events(&hover), pointer.Cancel)
@@ -1081,7 +1114,7 @@ func TestTransfer(t *testing.T) {
 		r.Queue(
 			pointer.Event{
 				Position: f32.Pt(40, 10),
-				Type:     pointer.Release,
+				Kind:     pointer.Release,
 			},
 		)
 
@@ -1129,7 +1162,7 @@ func TestPassCursor(t *testing.T) {
 	r.Frame(&ops)
 	r.Queue(pointer.Event{
 		Position: f32.Pt(10, 10),
-		Type:     pointer.Move,
+		Kind:     pointer.Move,
 	})
 	if got := r.Cursor(); want != got {
 		t.Errorf("got cursor %v, want %v", got, want)
@@ -1154,18 +1187,18 @@ func addPointerHandler(ops *op.Ops, tag event.Tag, area image.Rectangle) {
 	defer clip.Rect(area).Push(ops).Pop()
 	pointer.InputOp{
 		Tag:   tag,
-		Types: pointer.Press | pointer.Release | pointer.Move | pointer.Drag | pointer.Enter | pointer.Leave,
+		Kinds: pointer.Press | pointer.Release | pointer.Move | pointer.Drag | pointer.Enter | pointer.Leave,
 	}.Add(ops)
 }
 
 // pointerTypes converts a sequence of event.Event to their pointer.Types. It assumes
 // that all input events are of underlying type pointer.Event, and thus will
 // panic if some are not.
-func pointerTypes(events []event.Event) []pointer.Type {
+func pointerTypes(events []event.Event) []pointer.Kind {
-	var types []pointer.Type
+	var types []pointer.Kind
 	for _, e := range events {
 		if e, ok := e.(pointer.Event); ok {
-			types = append(types, e.Type)
+			types = append(types, e.Kind)
 		}
 	}
 	return types
@@ -1173,7 +1206,7 @@ func pointerTypes(events []event.Event) []pointer.Type {
 
 // assertEventPointerTypeSequence checks that the provided events match the expected pointer event types
 // in the provided order.
-func assertEventPointerTypeSequence(t *testing.T, events []event.Event, expected ...pointer.Type) {
+func assertEventPointerTypeSequence(t *testing.T, events []event.Event, expected ...pointer.Kind) {
 	t.Helper()
 	got := pointerTypes(events)
 	if !reflect.DeepEqual(got, expected) {
@@ -1201,7 +1234,7 @@ func eventsToString(evs []event.Event) string {
 	for _, ev := range evs {
 		switch e := ev.(type) {
 		case pointer.Event:
-			s = append(s, fmt.Sprintf("%T{%s}", e, e.Type.String()))
+			s = append(s, fmt.Sprintf("%T{%s}", e, e.Kind.String()))
 		default:
 			s = append(s, fmt.Sprintf("{%T}", e))
 		}
@@ -1231,6 +1264,17 @@ func assertScrollEvent(t *testing.T, ev event.Event, scroll f32.Point) {
 	}
 }
 
+// assertActionAt checks that the router has a system action of the expected type at point.
+func assertActionAt(t *testing.T, q Router, point f32.Point, expected system.Action) {
+	t.Helper()
+	action, ok := q.ActionAt(point)
+	if !ok {
+		t.Errorf("expected action %v at %v, got no action", expected, point)
+	} else if action != expected {
+		t.Errorf("expected action %v at %v, got %v", expected, point, action)
+	}
+}
+
 func BenchmarkRouterAdd(b *testing.B) {
 	// Set this to the number of overlapping handlers that you want to
 	// evaluate performance for. Typical values for the example applications
@@ -1259,7 +1303,7 @@ func BenchmarkRouterAdd(b *testing.B) {
 					Push(&ops)
 				pointer.InputOp{
 					Tag:   handlers[i],
-					Types: pointer.Move,
+					Kinds: pointer.Move,
 				}.Add(&ops)
 			}
 			var r Router
@@ -1269,7 +1313,7 @@ func BenchmarkRouterAdd(b *testing.B) {
 			for i := 0; i < b.N; i++ {
 				r.Queue(
 					pointer.Event{
-						Type:     pointer.Move,
+						Kind:     pointer.Move,
 						Position: f32.Pt(50, 50),
 					},
 				)

io/router/router.go

@@ -273,7 +273,7 @@ func (q *Router) ScrollFocus(dist image.Point) {
 	}
 	area := q.key.queue.AreaFor(focus)
 	q.pointer.queue.Deliver(area, pointer.Event{
-		Type:   pointer.Scroll,
+		Kind:   pointer.Scroll,
 		Source: pointer.Touch,
 		Scroll: f32internal.FPt(dist),
 	}, &q.handlers)
@@ -317,9 +317,9 @@ func (q *Router) ClickFocus() {
 		Source:   pointer.Touch,
 	}
 	area := q.key.queue.AreaFor(focus)
-	e.Type = pointer.Press
+	e.Kind = pointer.Press
 	q.pointer.queue.Deliver(area, e, &q.handlers)
-	e.Type = pointer.Release
+	e.Kind = pointer.Release
 	q.pointer.queue.Deliver(area, e, &q.handlers)
 }
 
@@ -438,7 +438,7 @@ func (q *Router) collect() {
 			op := pointer.InputOp{
 				Tag:   encOp.Refs[0].(event.Tag),
 				Grab:  encOp.Data[1] != 0,
-				Types: pointer.Type(bo.Uint16(encOp.Data[2:])),
+				Kinds: pointer.Kind(bo.Uint16(encOp.Data[2:])),
 				ScrollBounds: image.Rectangle{
 					Min: image.Point{
 						X: int(int32(bo.Uint32(encOp.Data[4:]))),
@@ -490,11 +490,11 @@ func (q *Router) collect() {
 			}
 			kc.softKeyboard(op.Show)
 		case ops.TypeKeyInput:
-			filter := encOp.Refs[1].(*key.Set)
+			filter := key.Set(*encOp.Refs[1].(*string))
 			op := key.InputOp{
 				Tag:  encOp.Refs[0].(event.Tag),
 				Hint: key.InputHint(encOp.Data[1]),
-				Keys: *filter,
+				Keys: filter,
 			}
 			a := pc.currentArea()
 			b := pc.currentAreaBounds()
@@ -532,10 +532,10 @@ func (q *Router) collect() {
 
 		// Semantic ops.
 		case ops.TypeSemanticLabel:
-			lbl := encOp.Refs[0].(string)
+			lbl := *encOp.Refs[0].(*string)
 			pc.semanticLabel(lbl)
 		case ops.TypeSemanticDesc:
-			desc := encOp.Refs[0].(string)
+			desc := *encOp.Refs[0].(*string)
 			pc.semanticDesc(desc)
 		case ops.TypeSemanticClass:
 			class := semantic.ClassOp(encOp.Data[1])
@@ -546,11 +546,11 @@ func (q *Router) collect() {
 			} else {
 				pc.semanticSelected(false)
 			}
-		case ops.TypeSemanticDisabled:
+		case ops.TypeSemanticEnabled:
 			if encOp.Data[1] != 0 {
-				pc.semanticDisabled(true)
+				pc.semanticEnabled(true)
 			} else {
-				pc.semanticDisabled(false)
+				pc.semanticEnabled(false)
 			}
 		}
 	}
@@ -593,16 +593,6 @@ func (h *handlerEvents) HadEvents() bool {
 func (h *handlerEvents) Events(k event.Tag) []event.Event {
 	if events, ok := h.handlers[k]; ok {
 		h.handlers[k] = h.handlers[k][:0]
-		// Schedule another frame if we delivered events to the user
-		// to flush half-updated state. This is important when an
-		// event changes UI state that has already been laid out. In
-		// the worst case, we waste a frame, increasing power usage.
-		//
-		// Gio is expected to grow the ability to construct
-		// frame-to-frame differences and only render to changed
-		// areas. In that case, the waste of a spurious frame should
-		// be minimal.
-		h.hadEvents = h.hadEvents || len(events) > 0
 		return events
 	}
 	return nil

io/router/semantic_test.go

@@ -74,11 +74,11 @@ func TestSemanticTree(t *testing.T) {
 
 func TestSemanticDescription(t *testing.T) {
 	var ops op.Ops
-	pointer.InputOp{Tag: new(int), Types: pointer.Press | pointer.Release}.Add(&ops)
+	pointer.InputOp{Tag: new(int), Kinds: pointer.Press | pointer.Release}.Add(&ops)
 	semantic.DescriptionOp("description").Add(&ops)
 	semantic.LabelOp("label").Add(&ops)
 	semantic.Button.Add(&ops)
-	semantic.DisabledOp(true).Add(&ops)
+	semantic.EnabledOp(false).Add(&ops)
 	semantic.SelectedOp(true).Add(&ops)
 	var r Router
 	r.Frame(&ops)

io/semantic/semantic.go

@@ -36,16 +36,16 @@ const (
 // boolean state.
 type SelectedOp bool
 
-// DisabledOp describes the disabled state.
+// EnabledOp describes the enabled state.
-type DisabledOp bool
+type EnabledOp bool
 
 func (l LabelOp) Add(o *op.Ops) {
-	data := ops.Write1(&o.Internal, ops.TypeSemanticLabelLen, string(l))
+	data := ops.Write1String(&o.Internal, ops.TypeSemanticLabelLen, string(l))
 	data[0] = byte(ops.TypeSemanticLabel)
 }
 
 func (d DescriptionOp) Add(o *op.Ops) {
-	data := ops.Write1(&o.Internal, ops.TypeSemanticDescLen, string(d))
+	data := ops.Write1String(&o.Internal, ops.TypeSemanticDescLen, string(d))
 	data[0] = byte(ops.TypeSemanticDesc)
 }
 
@@ -63,10 +63,10 @@ func (s SelectedOp) Add(o *op.Ops) {
 	}
 }
 
-func (d DisabledOp) Add(o *op.Ops) {
+func (e EnabledOp) Add(o *op.Ops) {
-	data := ops.Write(&o.Internal, ops.TypeSemanticDisabledLen)
+	data := ops.Write(&o.Internal, ops.TypeSemanticEnabledLen)
-	data[0] = byte(ops.TypeSemanticDisabled)
+	data[0] = byte(ops.TypeSemanticEnabled)
-	if d {
+	if e {
 		data[1] = 1
 	}
 }

layout/example_test.go

@@ -103,6 +103,30 @@ func ExampleStack() {
 	// Expand: {(50,50) (100,100)}
 }
 
+func ExampleBackground() {
+	gtx := layout.Context{
+		Ops: new(op.Ops),
+		Constraints: layout.Constraints{
+			Max: image.Point{X: 100, Y: 100},
+		},
+	}
+
+	layout.Background{}.Layout(gtx,
+		// Force widget to the same size as the second.
+		func(gtx layout.Context) layout.Dimensions {
+			fmt.Printf("Expand: %v\n", gtx.Constraints)
+			return layoutWidget(gtx, 10, 10)
+		},
+		// Rigid 50x50 widget.
+		func(gtx layout.Context) layout.Dimensions {
+			return layoutWidget(gtx, 50, 50)
+		},
+	)
+
+	// Output:
+	// Expand: {(50,50) (100,100)}
+}
+
 func ExampleList() {
 	gtx := layout.Context{
 		Ops: new(op.Ops),

layout/list.go

@@ -144,7 +144,7 @@ func (l *List) Dragging() bool {
 }
 
 func (l *List) update(gtx Context) {
-	d := l.scroll.Scroll(gtx.Metric, gtx, gtx.Now, gesture.Axis(l.Axis))
+	d := l.scroll.Update(gtx.Metric, gtx, gtx.Now, gesture.Axis(l.Axis))
 	l.scrollDelta = d
 	l.Position.Offset += d
 }

layout/list_test.go

@@ -93,18 +93,18 @@ func TestListPosition(t *testing.T) {
 				pointer.Event{
 					Source:   pointer.Mouse,
 					Buttons:  pointer.ButtonPrimary,
-					Type:     pointer.Press,
+					Kind:     pointer.Press,
 					Position: f32.Pt(0, 0),
 				},
 				pointer.Event{
 					Source: pointer.Mouse,
-					Type:   pointer.Scroll,
+					Kind:   pointer.Scroll,
 					Scroll: f32.Pt(5, 0),
 				},
 				pointer.Event{
 					Source:   pointer.Mouse,
 					Buttons:  pointer.ButtonPrimary,
-					Type:     pointer.Release,
+					Kind:     pointer.Release,
 					Position: f32.Pt(5, 0),
 				},
 			)},
@@ -113,18 +113,18 @@ func TestListPosition(t *testing.T) {
 				pointer.Event{
 					Source:   pointer.Mouse,
 					Buttons:  pointer.ButtonPrimary,
-					Type:     pointer.Press,
+					Kind:     pointer.Press,
 					Position: f32.Pt(0, 0),
 				},
 				pointer.Event{
 					Source: pointer.Mouse,
-					Type:   pointer.Scroll,
+					Kind:   pointer.Scroll,
 					Scroll: f32.Pt(3, 0),
 				},
 				pointer.Event{
 					Source:   pointer.Mouse,
 					Buttons:  pointer.ButtonPrimary,
-					Type:     pointer.Release,
+					Kind:     pointer.Release,
 					Position: f32.Pt(5, 0),
 				},
 			)},
@@ -133,18 +133,18 @@ func TestListPosition(t *testing.T) {
 				pointer.Event{
 					Source:   pointer.Mouse,
 					Buttons:  pointer.ButtonPrimary,
-					Type:     pointer.Press,
+					Kind:     pointer.Press,
 					Position: f32.Pt(0, 0),
 				},
 				pointer.Event{
 					Source: pointer.Mouse,
-					Type:   pointer.Scroll,
+					Kind:   pointer.Scroll,
 					Scroll: f32.Pt(10, 0),
 				},
 				pointer.Event{
 					Source:   pointer.Mouse,
 					Buttons:  pointer.ButtonPrimary,
-					Type:     pointer.Release,
+					Kind:     pointer.Release,
 					Position: f32.Pt(15, 0),
 				},
 			)},

layout/stack.go

@@ -118,3 +118,36 @@ func (s Stack) Layout(gtx Context, children ...StackChild) Dimensions {
 		Baseline: baseline,
 	}
 }
+
+// Background lays out single child widget on top of a background,
+// centering, if necessary.
+type Background struct{}
+
+// Layout a widget and then add a background to it.
+func (Background) Layout(gtx Context, background, widget Widget) Dimensions {
+	macro := op.Record(gtx.Ops)
+	wdims := widget(gtx)
+	baseline := wdims.Baseline
+	call := macro.Stop()
+
+	cgtx := gtx
+	cgtx.Constraints.Min = gtx.Constraints.Constrain(wdims.Size)
+	bdims := background(cgtx)
+
+	if bdims.Size != wdims.Size {
+		p := image.Point{
+			X: (bdims.Size.X - wdims.Size.X) / 2,
+			Y: (bdims.Size.Y - wdims.Size.Y) / 2,
+		}
+		baseline += (bdims.Size.Y - wdims.Size.Y) / 2
+		trans := op.Offset(p).Push(gtx.Ops)
+		defer trans.Pop()
+	}
+
+	call.Add(gtx.Ops)
+
+	return Dimensions{
+		Size:     bdims.Size,
+		Baseline: baseline,
+	}
+}

layout/stack_test.go

@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package layout
+
+import (
+	"image"
+	"testing"
+
+	"gioui.org/op"
+)
+
+func BenchmarkStack(b *testing.B) {
+	gtx := Context{
+		Ops: new(op.Ops),
+		Constraints: Constraints{
+			Max: image.Point{X: 100, Y: 100},
+		},
+	}
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		gtx.Ops.Reset()
+
+		Stack{}.Layout(gtx,
+			Expanded(emptyWidget{
+				Size: image.Point{X: 60, Y: 60},
+			}.Layout),
+			Stacked(emptyWidget{
+				Size: image.Point{X: 30, Y: 30},
+			}.Layout),
+		)
+	}
+}
+
+func BenchmarkBackground(b *testing.B) {
+	gtx := Context{
+		Ops: new(op.Ops),
+		Constraints: Constraints{
+			Max: image.Point{X: 100, Y: 100},
+		},
+	}
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		gtx.Ops.Reset()
+
+		Background{}.Layout(gtx,
+			emptyWidget{
+				Size: image.Point{X: 60, Y: 60},
+			}.Layout,
+			emptyWidget{
+				Size: image.Point{X: 30, Y: 30},
+			}.Layout,
+		)
+	}
+}
+
+type emptyWidget struct {
+	Size image.Point
+}
+
+func (w emptyWidget) Layout(gtx Context) Dimensions {
+	return Dimensions{Size: w.Size}
+}

op/clip/clip.go

@@ -29,7 +29,7 @@ type Op struct {
 type Stack struct {
 	ops     *ops.Ops
 	id      ops.StackID
-	macroID int
+	macroID uint32
 }
 
 var pathSeed maphash.Seed
@@ -204,6 +204,9 @@ func (p *Path) Line(delta f32.Point) {
 
 // LineTo moves the pen to the absolute point specified, recording a line.
 func (p *Path) LineTo(to f32.Point) {
+	if to == p.pen {
+		return
+	}
 	data := ops.WriteMulti(p.ops, scene.CommandSize+4)
 	bo := binary.LittleEndian
 	bo.PutUint32(data[0:], uint32(p.contour))
@@ -250,6 +253,9 @@ func (p *Path) Quad(ctrl, to f32.Point) {
 // QuadTo records a quadratic Bézier from the pen to end
 // with the control point ctrl, with absolute coordinates.
 func (p *Path) QuadTo(ctrl, to f32.Point) {
+	if ctrl == p.pen && to == p.pen {
+		return
+	}
 	data := ops.WriteMulti(p.ops, scene.CommandSize+4)
 	bo := binary.LittleEndian
 	bo.PutUint32(data[0:], uint32(p.contour))

op/op.go

@@ -111,7 +111,7 @@ type TransformOp struct {
 // TransformStack represents a TransformOp pushed on the transformation stack.
 type TransformStack struct {
 	id      ops.StackID
-	macroID int
+	macroID uint32
 	ops     *ops.Ops
 }
 

op/paint/paint.go

@@ -15,8 +15,20 @@ import (
 	"gioui.org/op/clip"
 )
 
+// ImageFilter is the scaling filter for images.
+type ImageFilter byte
+
+const (
+	// FilterLinear uses linear interpolation for scaling.
+	FilterLinear ImageFilter = iota
+	// FilterNearest uses nearest neighbor interpolation for scaling.
+	FilterNearest
+)
+
 // ImageOp sets the brush to an image.
 type ImageOp struct {
+	Filter ImageFilter
+
 	uniform bool
 	color   color.NRGBA
 	src     *image.RGBA
@@ -44,6 +56,14 @@ type LinearGradientOp struct {
 type PaintOp struct {
 }
 
+// OpacityStack represents an opacity applied to all painting operations
+// until Pop is called.
+type OpacityStack struct {
+	id      ops.StackID
+	macroID uint32
+	ops     *ops.Ops
+}
+
 // NewImageOp creates an ImageOp backed by src.
 //
 // NewImageOp assumes the backing image is immutable, and may cache a
@@ -95,6 +115,7 @@ func (i ImageOp) Add(o *op.Ops) {
 	}
 	data := ops.Write2(&o.Internal, ops.TypeImageLen, i.src, i.handle)
 	data[0] = byte(ops.TypeImage)
+	data[1] = byte(i.Filter)
 }
 
 func (c ColorOp) Add(o *op.Ops) {
@@ -145,3 +166,31 @@ func Fill(ops *op.Ops, c color.NRGBA) {
 	ColorOp{Color: c}.Add(ops)
 	PaintOp{}.Add(ops)
 }
+
+// PushOpacity creates a drawing layer with an opacity in the range [0;1].
+// The layer includes every subsequent drawing operation until [OpacityStack.Pop]
+// is called.
+//
+// The layer is drawn in two steps. First, the layer operations are
+// drawn to a separate image. Then, the image is blended on top of
+// the frame, with the opacity used as the blending factor.
+func PushOpacity(o *op.Ops, opacity float32) OpacityStack {
+	if opacity > 1 {
+		opacity = 1
+	}
+	if opacity < 0 {
+		opacity = 0
+	}
+	id, macroID := ops.PushOp(&o.Internal, ops.OpacityStack)
+	data := ops.Write(&o.Internal, ops.TypePushOpacityLen)
+	bo := binary.LittleEndian
+	data[0] = byte(ops.TypePushOpacity)
+	bo.PutUint32(data[1:], math.Float32bits(opacity))
+	return OpacityStack{ops: &o.Internal, id: id, macroID: macroID}
+}
+
+func (t OpacityStack) Pop() {
+	ops.PopOp(t.ops, ops.OpacityStack, t.id, t.macroID)
+	data := ops.Write(t.ops, ops.TypePopOpacityLen)
+	data[0] = byte(ops.TypePopOpacity)
+}

text/gotext.go

@@ -36,7 +36,8 @@ type document struct {
 	lines     []line
 	alignment Alignment
 	// alignWidth is the width used when aligning text.
-	alignWidth int
+	alignWidth      int
+	unreadRuneCount int
 }
 
 // append adds the lines of other to the end of l and ensures they
@@ -52,6 +53,7 @@ func (l *document) reset() {
 	l.lines = l.lines[:0]
 	l.alignment = Start
 	l.alignWidth = 0
+	l.unreadRuneCount = 0
 }
 
 func max(a, b int) int {
@@ -93,6 +95,55 @@ type line struct {
 	yOffset int
 }
 
+// insertTrailingSyntheticNewline adds a synthetic newline to the final logical run of the line
+// with the given shaping cluster index.
+func (l *line) insertTrailingSyntheticNewline(newLineClusterIdx int) {
+	// If there was a newline at the end of this paragraph, insert a synthetic glyph representing it.
+	finalContentRun := len(l.runs) - 1
+	// If there was a trailing newline update the rune counts to include
+	// it on the last line of the paragraph.
+	l.runeCount += 1
+	l.runs[finalContentRun].Runes.Count += 1
+
+	syntheticGlyph := glyph{
+		id:           0,
+		clusterIndex: newLineClusterIdx,
+		glyphCount:   0,
+		runeCount:    1,
+		xAdvance:     0,
+		yAdvance:     0,
+		xOffset:      0,
+		yOffset:      0,
+	}
+	// Inset the synthetic newline glyph on the proper end of the run.
+	if l.runs[finalContentRun].Direction.Progression() == system.FromOrigin {
+		l.runs[finalContentRun].Glyphs = append(l.runs[finalContentRun].Glyphs, syntheticGlyph)
+	} else {
+		// Ensure capacity.
+		l.runs[finalContentRun].Glyphs = append(l.runs[finalContentRun].Glyphs, glyph{})
+		copy(l.runs[finalContentRun].Glyphs[1:], l.runs[finalContentRun].Glyphs)
+		l.runs[finalContentRun].Glyphs[0] = syntheticGlyph
+	}
+}
+
+func (l *line) setTruncatedCount(truncatedCount int) {
+	// If we've truncated the text with a truncator, adjust the rune counts within the
+	// truncator to make it represent the truncated text.
+	finalRunIdx := len(l.runs) - 1
+	l.runs[finalRunIdx].truncator = true
+	finalGlyphIdx := len(l.runs[finalRunIdx].Glyphs) - 1
+	// The run represents all of the truncated text.
+	l.runs[finalRunIdx].Runes.Count = truncatedCount
+	// Only the final glyph represents any runes, and it represents all truncated text.
+	for i := range l.runs[finalRunIdx].Glyphs {
+		if i == finalGlyphIdx {
+			l.runs[finalRunIdx].Glyphs[finalGlyphIdx].runeCount = truncatedCount
+		} else {
+			l.runs[finalRunIdx].Glyphs[finalGlyphIdx].runeCount = 0
+		}
+	}
+}
+
 // Range describes the position and quantity of a range of text elements
 // within a larger slice. The unit is usually runes of unicode data or
 // glyphs of shaped font data.
@@ -233,6 +284,7 @@ func (s *shaperImpl) addFace(f font.Face, md giofont.Font) {
 	if _, ok := s.faceToIndex[f.Font]; ok {
 		return
 	}
+	s.logger.Printf("loaded face %s(style:%s, weight:%d)", md.Typeface, md.Style, md.Weight)
 	idx := len(s.faces)
 	s.faceToIndex[f.Font] = idx
 	s.faces = append(s.faces, f)
@@ -528,35 +580,21 @@ func (s *shaperImpl) LayoutRunes(params Parameters, txt []rune) document {
 	if hasNewline {
 		txt = txt[:len(txt)-1]
 	}
-	truncatedNewline := false
+	if params.MaxLines != 0 && hasNewline {
-	if hasNewline && len(txt) == 0 {
+		// If we might end up truncating a trailing newline, we must insert the truncator symbol
-		params.forceTruncate = false
+		// on the final line (if we hit the limit).
-		// If we only have a newline, shape a space to get line metrics.
+		params.forceTruncate = true
-		ls, truncated = s.shapeAndWrapText(params, []rune{' '})
-		if truncated > 0 {
-			// Our space was truncated. Since our space didn't exist in any meaningful
-			// capacity, ensure the truncated count is zeroed out.
-			truncated = 0
-			truncatedNewline = true
-		} else {
-			// We shaped a space to get proper line metrics, but we need to drop
-			// the rune/glyph info since it isn't actually part of the text.
-			ls[0][0].Glyphs = ls[0][0].Glyphs[:0]
-			ls[0][0].Advance = 0
-			ls[0][0].Runes.Count = 0
-		}
-	} else {
-		ls, truncated = s.shapeAndWrapText(params, replaceControlCharacters(txt))
 	}
+	ls, truncated = s.shapeAndWrapText(params, replaceControlCharacters(txt))
 
-	didTruncate := truncated > 0 || truncatedNewline || (params.forceTruncate && params.MaxLines == len(ls))
+	hasTruncator := truncated > 0 || (params.forceTruncate && params.MaxLines == len(ls))
-
+	if hasTruncator && hasNewline {
-	if didTruncate && hasNewline {
+		// We have a truncator at the end of the line, so the newline is logically
-		// We've truncated the newline, since it was at the end and we've truncated some amount of runes
+		// truncated as well.
-		// before it.
 		truncated++
 		hasNewline = false
 	}
+
 	// Convert to Lines.
 	textLines := make([]line, len(ls))
 	maxHeight := fixed.Int26_6(0)
@@ -565,49 +603,12 @@ func (s *shaperImpl) LayoutRunes(params Parameters, txt []rune) document {
 		if otLine.lineHeight > maxHeight {
 			maxHeight = otLine.lineHeight
 		}
-		isFinalLine := i == len(ls)-1
+		if isFinalLine := i == len(ls)-1; isFinalLine {
-		if isFinalLine && hasNewline {
+			if hasNewline {
-			// If there was a trailing newline update the rune counts to include
+				otLine.insertTrailingSyntheticNewline(len(txt))
-			// it on the last line of the paragraph.
-			finalRunIdx := len(otLine.runs) - 1
-			otLine.runeCount += 1
-			otLine.runs[finalRunIdx].Runes.Count += 1
-
-			syntheticGlyph := glyph{
-				id:           0,
-				clusterIndex: len(txt),
-				glyphCount:   0,
-				runeCount:    1,
-				xAdvance:     0,
-				yAdvance:     0,
-				xOffset:      0,
-				yOffset:      0,
 			}
-			// Inset the synthetic newline glyph on the proper end of the run.
+			if hasTruncator {
-			if otLine.runs[finalRunIdx].Direction.Progression() == system.FromOrigin {
+				otLine.setTruncatedCount(truncated)
-				otLine.runs[finalRunIdx].Glyphs = append(otLine.runs[finalRunIdx].Glyphs, syntheticGlyph)
-			} else {
-				// Ensure capacity.
-				otLine.runs[finalRunIdx].Glyphs = append(otLine.runs[finalRunIdx].Glyphs, glyph{})
-				copy(otLine.runs[finalRunIdx].Glyphs[1:], otLine.runs[finalRunIdx].Glyphs)
-				otLine.runs[finalRunIdx].Glyphs[0] = syntheticGlyph
-			}
-		}
-		if isFinalLine && didTruncate {
-			// If we've truncated the text with a truncator, adjust the rune counts within the
-			// truncator to make it represent the truncated text.
-			finalRunIdx := len(otLine.runs) - 1
-			otLine.runs[finalRunIdx].truncator = true
-			finalGlyphIdx := len(otLine.runs[finalRunIdx].Glyphs) - 1
-			// The run represents all of the truncated text.
-			otLine.runs[finalRunIdx].Runes.Count = truncated
-			// Only the final glyph represents any runes, and it represents all truncated text.
-			for i := range otLine.runs[finalRunIdx].Glyphs {
-				if i == finalGlyphIdx {
-					otLine.runs[finalRunIdx].Glyphs[finalGlyphIdx].runeCount = truncated
-				} else {
-					otLine.runs[finalRunIdx].Glyphs[finalGlyphIdx].runeCount = 0
-				}
 			}
 		}
 		textLines[i] = otLine

text/lru.go

@@ -3,9 +3,8 @@
 package text
 
 import (
-	"encoding/binary"
-	"hash/maphash"
 	"image"
+	"sync/atomic"
 
 	giofont "gioui.org/font"
 	"gioui.org/io/system"
@@ -88,32 +87,32 @@ type glyphValue[V any] struct {
 }
 
 type glyphLRU[V any] struct {
-	seed  maphash.Seed
+	seed  uint64
 	cache lru[uint64, glyphValue[V]]
 }
 
+var seed uint32
+
 // hashGlyphs computes a hash key based on the ID and X offset of
 // every glyph in the slice.
 func (c *glyphLRU[V]) hashGlyphs(gs []Glyph) uint64 {
-	if c.seed == (maphash.Seed{}) {
+	if c.seed == 0 {
-		c.seed = maphash.MakeSeed()
+		c.seed = uint64(atomic.AddUint32(&seed, 3900798947))
 	}
-	var h maphash.Hash
+	if len(gs) == 0 {
-	h.SetSeed(c.seed)
+		return 0
-	var b [8]byte
-	firstX := fixed.Int26_6(0)
-	for i, g := range gs {
-		if i == 0 {
-			firstX = g.X
-		}
-		// Cache glyph X offsets relative to the first glyph.
-		binary.LittleEndian.PutUint32(b[:4], uint32(g.X-firstX))
-		h.Write(b[:4])
-		binary.LittleEndian.PutUint64(b[:], uint64(g.ID))
-		h.Write(b[:])
 	}
-	sum := h.Sum64()
+
-	return sum
+	h := c.seed
+	firstX := gs[0].X
+	for _, g := range gs {
+		h += uint64(g.X - firstX)
+		h *= 6585573582091643
+		h += uint64(g.ID)
+		h *= 3650802748644053
+	}
+
+	return h
 }
 
 func (c *glyphLRU[V]) Get(key uint64, gs []Glyph) (V, bool) {

text/shaper.go

@@ -121,7 +121,7 @@ type Glyph struct {
 	// belongs to. If Flags does not contain FlagClusterBreak, this value will
 	// always be zero. The final glyph in the cluster contains the runes count
 	// for the entire cluster.
-	Runes int
+	Runes uint16
 	// Flags encode special properties of this glyph.
 	Flags Flags
 }
@@ -245,8 +245,11 @@ func WithCollection(collection []FontFace) ShaperOption {
 	}
 }
 
-// NewShaper constructs a shaper with the provided collection of font faces
+// NewShaper constructs a shaper with the provided options.
-// available.
+//
+// NewShaper must be called after [app.NewWindow], unless the [NoSystemFonts]
+// option is specified. This is an unfortunate restriction caused by some platforms
+// such as Android.
 func NewShaper(options ...ShaperOption) *Shaper {
 	l := &Shaper{}
 	for _, opt := range options {
@@ -351,11 +354,7 @@ func (l *Shaper) layoutText(params Parameters, txt io.Reader, str string) {
 							unreadRunes++
 						}
 					}
-					lastLineIdx := len(lines.lines) - 1
+					l.txt.unreadRuneCount = unreadRunes
-					lastRunIdx := len(lines.lines[lastLineIdx].runs) - 1
-					lastGlyphIdx := len(lines.lines[lastLineIdx].runs[lastRunIdx].Glyphs) - 1
-					lines.lines[lastLineIdx].runs[lastRunIdx].Runes.Count += unreadRunes
-					lines.lines[lastLineIdx].runs[lastRunIdx].Glyphs[lastGlyphIdx].runeCount += unreadRunes
 				}
 			}
 			l.txt.append(lines)
@@ -470,7 +469,7 @@ func (l *Shaper) NextGlyph() (_ Glyph, ok bool) {
 			Ascent:  line.ascent,
 			Descent: line.descent,
 			Advance: g.xAdvance,
-			Runes:   g.runeCount,
+			Runes:   uint16(g.runeCount),
 			Offset: fixed.Point26_6{
 				X: g.xOffset,
 				Y: g.yOffset,
@@ -505,6 +504,9 @@ func (l *Shaper) NextGlyph() (_ Glyph, ok bool) {
 		}
 		if endOfCluster {
 			glyph.Flags |= FlagClusterBreak
+			if run.truncator {
+				glyph.Runes += uint16(l.txt.unreadRuneCount)
+			}
 		} else {
 			glyph.Runes = 0
 		}

text/shaper_test.go

@@ -51,9 +51,9 @@ func TestWrappingTruncation(t *testing.T) {
 			for g, ok := cache.NextGlyph(); ok; g, ok = cache.NextGlyph() {
 				glyphs = append(glyphs, g)
 				if g.Flags&FlagTruncator != 0 && g.Flags&FlagClusterBreak != 0 {
-					truncatedRunes += g.Runes
+					truncatedRunes += int(g.Runes)
 				} else {
-					untruncatedRunes += g.Runes
+					untruncatedRunes += int(g.Runes)
 				}
 				if g.Flags&FlagLineBreak != 0 {
 					lineCount++
@@ -117,9 +117,9 @@ func TestWrappingForcedTruncation(t *testing.T) {
 			for g, ok := cache.NextGlyph(); ok; g, ok = cache.NextGlyph() {
 				glyphs = append(glyphs, g)
 				if g.Flags&FlagTruncator != 0 && g.Flags&FlagClusterBreak != 0 {
-					truncatedRunes += g.Runes
+					truncatedRunes += int(g.Runes)
 				} else {
-					untruncatedRunes += g.Runes
+					untruncatedRunes += int(g.Runes)
 				}
 				if g.Flags&FlagLineBreak != 0 {
 					lineCount++
@@ -154,9 +154,11 @@ func TestWrappingForcedTruncation(t *testing.T) {
 // consistently and does not create spurious lines of text.
 func TestShapingNewlineHandling(t *testing.T) {
 	type testcase struct {
-		textInput      string
+		textInput         string
-		expectedLines  int
+		expectedLines     int
-		expectedGlyphs int
+		expectedGlyphs    int
+		maxLines          int
+		expectedTruncated int
 	}
 	for _, tc := range []testcase{
 		{textInput: "a\n", expectedLines: 1, expectedGlyphs: 3},
@@ -165,21 +167,41 @@ func TestShapingNewlineHandling(t *testing.T) {
 		{textInput: "\n", expectedLines: 1, expectedGlyphs: 2},
 		{textInput: "\n\n", expectedLines: 2, expectedGlyphs: 3},
 		{textInput: "\n\n\n", expectedLines: 3, expectedGlyphs: 4},
+		{textInput: "\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 1, expectedTruncated: 1},
+		{textInput: "\n\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 1, expectedTruncated: 2},
+		{textInput: "\n\n\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 1, expectedTruncated: 3},
+		{textInput: "a\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 2, expectedTruncated: 1},
+		{textInput: "a\n\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 2, expectedTruncated: 2},
+		{textInput: "a\n\n\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 2, expectedTruncated: 3},
+		{textInput: "\n", expectedLines: 1, maxLines: 2, expectedGlyphs: 2},
+		{textInput: "\n\n", expectedLines: 2, maxLines: 2, expectedGlyphs: 2, expectedTruncated: 1},
+		{textInput: "\n\n\n", expectedLines: 2, maxLines: 2, expectedGlyphs: 2, expectedTruncated: 2},
+		{textInput: "a\n", expectedLines: 1, maxLines: 2, expectedGlyphs: 3},
+		{textInput: "a\n\n", expectedLines: 2, maxLines: 2, expectedGlyphs: 3, expectedTruncated: 1},
+		{textInput: "a\n\n\n", expectedLines: 2, maxLines: 2, expectedGlyphs: 3, expectedTruncated: 2},
 	} {
-		t.Run(fmt.Sprintf("%q", tc.textInput), func(t *testing.T) {
+		t.Run(fmt.Sprintf("%q-maxLines%d", tc.textInput, tc.maxLines), func(t *testing.T) {
 			ltrFace, _ := opentype.Parse(goregular.TTF)
 			collection := []FontFace{{Face: ltrFace}}
 			cache := NewShaper(NoSystemFonts(), WithCollection(collection))
 			checkGlyphs := func() {
 				glyphs := []Glyph{}
 				runes := 0
+				truncated := 0
 				for g, ok := cache.NextGlyph(); ok; g, ok = cache.NextGlyph() {
 					glyphs = append(glyphs, g)
-					runes += g.Runes
+					if g.Flags&FlagTruncator == 0 {
+						runes += int(g.Runes)
+					} else {
+						truncated += int(g.Runes)
+					}
 				}
-				if expected := len([]rune(tc.textInput)); expected != runes {
+				if expected := len([]rune(tc.textInput)) - tc.expectedTruncated; expected != runes {
 					t.Errorf("expected %d runes, got %d", expected, runes)
 				}
+				if truncated != tc.expectedTruncated {
+					t.Errorf("expected %d truncated runes, got %d", tc.expectedTruncated, truncated)
+				}
 				if len(glyphs) != tc.expectedGlyphs {
 					t.Errorf("expected %d glyphs, got %d", tc.expectedGlyphs, len(glyphs))
 				}
@@ -207,29 +229,27 @@ func TestShapingNewlineHandling(t *testing.T) {
 						t.Errorf("expected paragraph start glyph to have cursor y")
 					}
 				}
-				if count := strings.Count(tc.textInput, "\n"); found != count {
+				if count := strings.Count(tc.textInput, "\n"); found != count && tc.maxLines == 0 {
 					t.Errorf("expected %d paragraph breaks, found %d", count, found)
+				} else if tc.maxLines > 0 && found > tc.maxLines {
+					t.Errorf("expected %d paragraph breaks due to truncation, found %d", tc.maxLines, found)
 				}
 			}
-			cache.LayoutString(Parameters{
+			params := Parameters{
 				Alignment: Middle,
 				PxPerEm:   fixed.I(10),
 				MinWidth:  200,
 				MaxWidth:  200,
 				Locale:    english,
-			}, tc.textInput)
+				MaxLines:  tc.maxLines,
+			}
+			cache.LayoutString(params, tc.textInput)
 			if lineCount := len(cache.txt.lines); lineCount > tc.expectedLines {
 				t.Errorf("shaping string %q created %d lines", tc.textInput, lineCount)
 			}
 			checkGlyphs()
 
-			cache.Layout(Parameters{
+			cache.Layout(params, strings.NewReader(tc.textInput))
-				Alignment: Middle,
-				PxPerEm:   fixed.I(10),
-				MinWidth:  200,
-				MaxWidth:  200,
-				Locale:    english,
-			}, strings.NewReader(tc.textInput))
 			if lineCount := len(cache.txt.lines); lineCount > tc.expectedLines {
 				t.Errorf("shaping reader %q created %d lines", tc.textInput, lineCount)
 			}
@@ -551,7 +571,7 @@ func TestShapeStringRuneAccounting(t *testing.T) {
 					}
 					totalRunes := 0
 					for _, g := range glyphs {
-						totalRunes += g.Runes
+						totalRunes += int(g.Runes)
 					}
 					if inputRunes := len([]rune(tc.input)); totalRunes != inputRunes {
 						t.Errorf("input contained %d runes, but glyphs contained %d", inputRunes, totalRunes)

widget/bool.go

@@ -11,15 +11,15 @@ type Bool struct {
 	Value bool
 
 	clk Clickable
-
-	changed bool
 }
 
-// Changed reports whether Value has changed since the last
+// Update the widget state and report whether Value was changed.
-// call to Changed.
+func (b *Bool) Update(gtx layout.Context) bool {
-func (b *Bool) Changed() bool {
+	changed := false
-	changed := b.changed
+	for b.clk.Clicked(gtx) {
-	b.changed = false
+		b.Value = !b.Value
+		changed = true
+	}
 	return changed
 }
 
@@ -43,13 +43,10 @@ func (b *Bool) History() []Press {
 }
 
 func (b *Bool) Layout(gtx layout.Context, w layout.Widget) layout.Dimensions {
+	b.Update(gtx)
 	dims := b.clk.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
-		for b.clk.Clicked() {
-			b.Value = !b.Value
-			b.changed = true
-		}
 		semantic.SelectedOp(b.Value).Add(gtx.Ops)
-		semantic.DisabledOp(gtx.Queue == nil).Add(gtx.Ops)
+		semantic.EnabledOp(gtx.Queue != nil).Add(gtx.Ops)
 		return w(gtx)
 	})
 	return dims

widget/button.go

@@ -17,17 +17,16 @@ import (
 
 // Clickable represents a clickable area.
 type Clickable struct {
-	click  gesture.Click
+	click gesture.Click
-	clicks []Click
+	// clicks is for saved clicks to support Clicked.
-	// prevClicks is the index into clicks that marks the clicks
+	clicks  []Click
-	// from the most recent Layout call. prevClicks is used to keep
+	history []Press
-	// clicks bounded.
-	prevClicks int
-	history    []Press
 
-	keyTag       struct{}
+	keyTag        struct{}
-	requestFocus bool
+	requestFocus  bool
-	focused      bool
+	requestClicks int
+	focused       bool
+	pressedKey    string
 }
 
 // Click represents a click.
@@ -49,26 +48,24 @@ type Press struct {
 	Cancelled bool
 }
 
-// Click executes a simple programmatic click
+// Click executes a simple programmatic click.
 func (b *Clickable) Click() {
-	b.clicks = append(b.clicks, Click{
+	b.requestClicks++
-		Modifiers: 0,
-		NumClicks: 1,
-	})
 }
 
-// Clicked reports whether there are pending clicks as would be
+// Clicked reports whether there are pending clicks. If so, Clicked
-// reported by Clicks. If so, Clicked removes the earliest click.
+// removes the earliest click.
-func (b *Clickable) Clicked() bool {
+func (b *Clickable) Clicked(gtx layout.Context) bool {
-	if len(b.clicks) == 0 {
+	if len(b.clicks) > 0 {
-		return false
+		b.clicks = b.clicks[1:]
+		return true
 	}
-	n := copy(b.clicks, b.clicks[1:])
+	b.clicks = b.Update(gtx)
-	b.clicks = b.clicks[:n]
+	if len(b.clicks) > 0 {
-	if b.prevClicks > 0 {
+		b.clicks = b.clicks[1:]
-		b.prevClicks--
+		return true
 	}
-	return true
+	return false
 }
 
 // Hovered reports whether a pointer is over the element.
@@ -91,44 +88,44 @@ func (b *Clickable) Focused() bool {
 	return b.focused
 }
 
-// Clicks returns and clear the clicks since the last call to Clicks.
-func (b *Clickable) Clicks() []Click {
-	clicks := b.clicks
-	b.clicks = nil
-	b.prevClicks = 0
-	return clicks
-}
-
 // History is the past pointer presses useful for drawing markers.
 // History is retained for a short duration (about a second).
 func (b *Clickable) History() []Press {
 	return b.history
 }
 
-// Layout and update the button state
+// Layout and update the button state.
 func (b *Clickable) Layout(gtx layout.Context, w layout.Widget) layout.Dimensions {
-	b.update(gtx)
+	b.Update(gtx)
 	m := op.Record(gtx.Ops)
 	dims := w(gtx)
 	c := m.Stop()
 	defer clip.Rect(image.Rectangle{Max: dims.Size}).Push(gtx.Ops).Pop()
-	disabled := gtx.Queue == nil
+	enabled := gtx.Queue != nil
-	semantic.DisabledOp(disabled).Add(gtx.Ops)
+	semantic.EnabledOp(enabled).Add(gtx.Ops)
 	b.click.Add(gtx.Ops)
-	if !disabled {
+	if enabled {
 		keys := key.Set("⏎|Space")
 		if !b.focused {
 			keys = ""
 		}
 		key.InputOp{Tag: &b.keyTag, Keys: keys}.Add(gtx.Ops)
-		if b.requestFocus {
-			key.FocusOp{Tag: &b.keyTag}.Add(gtx.Ops)
-			b.requestFocus = false
-		}
-	} else {
-		b.focused = false
 	}
 	c.Add(gtx.Ops)
+	return dims
+}
+
+// Update the button state by processing events, and return the resulting
+// clicks, if any.
+func (b *Clickable) Update(gtx layout.Context) []Click {
+	b.clicks = nil
+	if gtx.Queue == nil {
+		b.focused = false
+	}
+	if b.requestFocus {
+		key.FocusOp{Tag: &b.keyTag}.Add(gtx.Ops)
+		b.requestFocus = false
+	}
 	for len(b.history) > 0 {
 		c := b.history[0]
 		if c.End.IsZero() || gtx.Now.Sub(c.End) < 1*time.Second {
@@ -137,34 +134,31 @@ func (b *Clickable) Layout(gtx layout.Context, w layout.Widget) layout.Dimension
 		n := copy(b.history, b.history[1:])
 		b.history = b.history[:n]
 	}
-	return dims
+	var clicks []Click
-}
+	if c := b.requestClicks; c > 0 {
-
+		b.requestClicks = 0
-// update the button state by processing events.
+		clicks = append(clicks, Click{
-func (b *Clickable) update(gtx layout.Context) {
+			NumClicks: c,
-	// Flush clicks from before the last update.
+		})
-	n := copy(b.clicks, b.clicks[b.prevClicks:])
+	}
-	b.clicks = b.clicks[:n]
+	for _, e := range b.click.Update(gtx) {
-	b.prevClicks = n
+		switch e.Kind {
-
+		case gesture.KindClick:
-	for _, e := range b.click.Events(gtx) {
-		switch e.Type {
-		case gesture.TypeClick:
-			b.clicks = append(b.clicks, Click{
-				Modifiers: e.Modifiers,
-				NumClicks: e.NumClicks,
-			})
 			if l := len(b.history); l > 0 {
 				b.history[l-1].End = gtx.Now
 			}
-		case gesture.TypeCancel:
+			clicks = append(clicks, Click{
+				Modifiers: e.Modifiers,
+				NumClicks: e.NumClicks,
+			})
+		case gesture.KindCancel:
 			for i := range b.history {
 				b.history[i].Cancelled = true
 				if b.history[i].End.IsZero() {
 					b.history[i].End = gtx.Now
 				}
 			}
-		case gesture.TypePress:
+		case gesture.KindPress:
 			if e.Source == pointer.Mouse {
 				key.FocusOp{Tag: &b.keyTag}.Add(gtx.Ops)
 			}
@@ -178,17 +172,31 @@ func (b *Clickable) update(gtx layout.Context) {
 		switch e := e.(type) {
 		case key.FocusEvent:
 			b.focused = e.Focus
+			if !b.focused {
+				b.pressedKey = ""
+			}
 		case key.Event:
-			if !b.focused || e.State != key.Release {
+			if !b.focused {
 				break
 			}
 			if e.Name != key.NameReturn && e.Name != key.NameSpace {
 				break
 			}
-			b.clicks = append(b.clicks, Click{
+			switch e.State {
-				Modifiers: e.Modifiers,
+			case key.Press:
-				NumClicks: 1,
+				b.pressedKey = e.Name
-			})
+			case key.Release:
+				if b.pressedKey != e.Name {
+					break
+				}
+				// only register a key as a click if the key was pressed and released while this button was focused
+				b.pressedKey = ""
+				clicks = append(clicks, Click{
+					Modifiers: e.Modifiers,
+					NumClicks: 1,
+				})
+			}
 		}
 	}
+	return clicks
 }

widget/button_test.go

@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package widget_test
+
+import (
+	"image"
+	"testing"
+
+	"gioui.org/io/key"
+	"gioui.org/io/router"
+	"gioui.org/io/system"
+	"gioui.org/layout"
+	"gioui.org/op"
+	"gioui.org/widget"
+)
+
+func TestClickable(t *testing.T) {
+	var (
+		ops op.Ops
+		r   router.Router
+		b1  widget.Clickable
+		b2  widget.Clickable
+	)
+	gtx := layout.NewContext(&ops, system.FrameEvent{Queue: &r})
+	layout := func() {
+		b1.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+			return layout.Dimensions{Size: image.Pt(100, 100)}
+		})
+		// buttons are on top of each other but we only use focus and keyevents, so this is fine
+		b2.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+			return layout.Dimensions{Size: image.Pt(100, 100)}
+		})
+	}
+	frame := func() {
+		ops.Reset()
+		layout()
+		r.Frame(gtx.Ops)
+	}
+	// frame: request focus for button 1
+	b1.Focus()
+	frame()
+	// frame: gain focus for button 1
+	frame()
+	if !b1.Focused() {
+		t.Error("button 1 did not gain focus")
+	}
+	if b2.Focused() {
+		t.Error("button 2 should not have focus")
+	}
+	// frame: press & release return
+	frame()
+	r.Queue(
+		key.Event{
+			Name:  key.NameReturn,
+			State: key.Press,
+		},
+		key.Event{
+			Name:  key.NameReturn,
+			State: key.Release,
+		},
+	)
+	if !b1.Clicked(gtx) {
+		t.Error("button 1 did not get clicked when it got return press & release")
+	}
+	if b2.Clicked(gtx) {
+		t.Error("button 2 got clicked when it did not have focus")
+	}
+	// frame: press return down
+	r.Queue(
+		key.Event{
+			Name:  key.NameReturn,
+			State: key.Press,
+		},
+	)
+	frame()
+	if b1.Clicked(gtx) {
+		t.Error("button 1 got clicked, even if it only got return press")
+	}
+	// frame: request focus for button 2
+	b2.Focus()
+	frame()
+	// frame: gain focus for button 2
+	frame()
+	if b1.Focused() {
+		t.Error("button 1 should not have focus")
+	}
+	if !b2.Focused() {
+		t.Error("button 2 did not gain focus")
+	}
+	// frame: release return
+	r.Queue(
+		key.Event{
+			Name:  key.NameReturn,
+			State: key.Release,
+		},
+	)
+	frame()
+	if b1.Clicked(gtx) {
+		t.Error("button 1 got clicked, even if it had lost focus")
+	}
+	if b2.Clicked(gtx) {
+		t.Error("button 2 should not have been clicked, as it only got return release")
+	}
+}

widget/decorations.go

@@ -12,12 +12,11 @@ import (
 
 // Decorations handles the states of window decorations.
 type Decorations struct {
-	clicks []Clickable
+	clicks map[int]*Clickable
 	resize [8]struct {
 		gesture.Hover
 		gesture.Drag
 	}
-	actions   system.Action
 	maximized bool
 }
 
@@ -35,22 +34,13 @@ func (d *Decorations) Clickable(action system.Action) *Clickable {
 		panic(fmt.Errorf("not a single action"))
 	}
 	idx := bits.TrailingZeros(uint(action))
-	if n := idx - len(d.clicks); n >= 0 {
+	click, found := d.clicks[idx]
-		d.clicks = append(d.clicks, make([]Clickable, n+1)...)
+	if !found {
-	}
+		click = new(Clickable)
-	click := &d.clicks[idx]
+		if d.clicks == nil {
-	if click.Clicked() {
+			d.clicks = make(map[int]*Clickable)
-		if action == system.ActionMaximize {
-			if d.maximized {
-				d.maximized = false
-				d.actions |= system.ActionUnmaximize
-			} else {
-				d.maximized = true
-				d.actions |= system.ActionMaximize
-			}
-		} else {
-			d.actions |= action
 		}
+		d.clicks[idx] = click
 	}
 	return click
 }
@@ -66,11 +56,27 @@ func (d *Decorations) Perform(actions system.Action) {
 	}
 }
 
-// Actions returns the set of actions activated by the user.
+// Update the state and return the set of actions activated by the user.
-func (d *Decorations) Actions() system.Action {
+func (d *Decorations) Update(gtx layout.Context) system.Action {
-	a := d.actions
+	var actions system.Action
-	d.actions = 0
+	for idx, clk := range d.clicks {
-	return a
+		if !clk.Clicked(gtx) {
+			continue
+		}
+		action := system.Action(1 << idx)
+		switch {
+		case action == system.ActionMaximize && d.maximized:
+			action = system.ActionUnmaximize
+		case action == system.ActionUnmaximize && !d.maximized:
+			action = system.ActionMaximize
+		}
+		switch action {
+		case system.ActionMaximize, system.ActionUnmaximize:
+			d.maximized = !d.maximized
+		}
+		actions |= action
+	}
+	return actions
 }
 
 // Maximized returns whether the window is maximized.

widget/dnd.go

@@ -17,41 +17,16 @@ type Draggable struct {
 	// Type contains the MIME type and matches transfer.SourceOp.
 	Type string
 
-	handle    struct{}
+	handle struct{}
-	drag      gesture.Drag
+	drag   gesture.Drag
-	click     f32.Point
+	click  f32.Point
-	pos       f32.Point
+	pos    f32.Point
-	requested bool
-	request   string
 }
 
 func (d *Draggable) Layout(gtx layout.Context, w, drag layout.Widget) layout.Dimensions {
 	if gtx.Queue == nil {
 		return w(gtx)
 	}
-	pos := d.pos
-	for _, ev := range d.drag.Events(gtx.Metric, gtx.Queue, gesture.Both) {
-		switch ev.Type {
-		case pointer.Press:
-			d.click = ev.Position
-			pos = f32.Point{}
-		case pointer.Drag, pointer.Release:
-			pos = ev.Position.Sub(d.click)
-		}
-	}
-	d.pos = pos
-
-	for _, ev := range gtx.Queue.Events(&d.handle) {
-		switch e := ev.(type) {
-		case transfer.RequestEvent:
-			d.requested = true
-			d.request = e.Type
-		case transfer.CancelEvent:
-			d.requested = false
-			d.request = ""
-		}
-	}
-
 	dims := w(gtx)
 
 	stack := clip.Rect{Max: dims.Size}.Push(gtx.Ops)
@@ -64,7 +39,7 @@ func (d *Draggable) Layout(gtx layout.Context, w, drag layout.Widget) layout.Dim
 
 	if drag != nil && d.drag.Pressed() {
 		rec := op.Record(gtx.Ops)
-		op.Offset(pos.Round()).Add(gtx.Ops)
+		op.Offset(d.pos.Round()).Add(gtx.Ops)
 		drag(gtx)
 		op.Defer(gtx.Ops, rec.Stop())
 	}
@@ -77,13 +52,27 @@ func (d *Draggable) Dragging() bool {
 	return d.drag.Dragging()
 }
 
-// Requested returns the MIME type, if any, for which the Draggable was requested to offer data.
+// Update the draggable and returns the MIME type for which the Draggable was
-func (d *Draggable) Requested() (mime string, requested bool) {
+// requested to offer data, if any
-	mime = d.request
+func (d *Draggable) Update(gtx layout.Context) (mime string, requested bool) {
-	requested = d.requested
+	pos := d.pos
-	d.requested = false
+	for _, ev := range d.drag.Update(gtx.Metric, gtx.Queue, gesture.Both) {
-	d.request = ""
+		switch ev.Kind {
-	return
+		case pointer.Press:
+			d.click = ev.Position
+			pos = f32.Point{}
+		case pointer.Drag, pointer.Release:
+			pos = ev.Position.Sub(d.click)
+		}
+	}
+	d.pos = pos
+
+	for _, ev := range gtx.Queue.Events(&d.handle) {
+		if e, ok := ev.(transfer.RequestEvent); ok {
+			return e.Type, true
+		}
+	}
+	return "", false
 }
 
 // Offer the data ready for a drop. Must be called after being Requested.

widget/dnd_test.go

@@ -39,15 +39,15 @@ func TestDraggable(t *testing.T) {
 	r.Queue(
 		pointer.Event{
 			Position: f32.Pt(10, 10),
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 		},
 		pointer.Event{
 			Position: f32.Pt(20, 10),
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 		},
 		pointer.Event{
 			Position: f32.Pt(20, 10),
-			Type:     pointer.Release,
+			Kind:     pointer.Release,
 		},
 	)
 	ofr := &offer{data: "hello"}

widget/editor.go

@@ -225,7 +225,7 @@ func (e *Editor) processPointer(gtx layout.Context) {
 		axis = gesture.Vertical
 		smin, smax = sbounds.Min.Y, sbounds.Max.Y
 	}
-	sdist := e.scroller.Scroll(gtx.Metric, gtx, gtx.Now, axis)
+	sdist := e.scroller.Update(gtx.Metric, gtx, gtx.Now, axis)
 	var soff int
 	if e.SingleLine {
 		e.text.ScrollRel(sdist, 0)
@@ -238,8 +238,8 @@ func (e *Editor) processPointer(gtx layout.Context) {
 		switch evt := evt.(type) {
 		case gesture.ClickEvent:
 			switch {
-			case evt.Type == gesture.TypePress && evt.Source == pointer.Mouse,
+			case evt.Kind == gesture.KindPress && evt.Source == pointer.Mouse,
-				evt.Type == gesture.TypeClick && evt.Source != pointer.Mouse:
+				evt.Kind == gesture.KindClick && evt.Source != pointer.Mouse:
 				prevCaretPos, _ := e.text.Selection()
 				e.blinkStart = gtx.Now
 				e.text.MoveCoord(image.Point{
@@ -278,10 +278,10 @@ func (e *Editor) processPointer(gtx layout.Context) {
 		case pointer.Event:
 			release := false
 			switch {
-			case evt.Type == pointer.Release && evt.Source == pointer.Mouse:
+			case evt.Kind == pointer.Release && evt.Source == pointer.Mouse:
 				release = true
 				fallthrough
-			case evt.Type == pointer.Drag && evt.Source == pointer.Mouse:
+			case evt.Kind == pointer.Drag && evt.Source == pointer.Mouse:
 				if e.dragging {
 					e.blinkStart = gtx.Now
 					e.text.MoveCoord(image.Point{
@@ -305,10 +305,10 @@ func (e *Editor) processPointer(gtx layout.Context) {
 
 func (e *Editor) clickDragEvents(gtx layout.Context) []event.Event {
 	var combinedEvents []event.Event
-	for _, evt := range e.clicker.Events(gtx) {
+	for _, evt := range e.clicker.Update(gtx) {
 		combinedEvents = append(combinedEvents, evt)
 	}
-	for _, evt := range e.dragger.Events(gtx.Metric, gtx, gesture.Both) {
+	for _, evt := range e.dragger.Update(gtx.Metric, gtx, gesture.Both) {
 		combinedEvents = append(combinedEvents, evt)
 	}
 	return combinedEvents
@@ -517,15 +517,10 @@ func (e *Editor) initBuffer() {
 	e.text.WrapPolicy = e.WrapPolicy
 }
 
-// Layout lays out the editor using the provided textMaterial as the paint material
+// Update the state of the editor in response to input events.
-// for the text glyphs+caret and the selectMaterial as the paint material for the
+func (e *Editor) Update(gtx layout.Context) {
-// selection rectangle.
-func (e *Editor) Layout(gtx layout.Context, lt *text.Shaper, font font.Font, size unit.Sp, textMaterial, selectMaterial op.CallOp) layout.Dimensions {
 	e.initBuffer()
-	e.text.Update(gtx, lt, font, size, e.processEvents)
+	e.processEvents(gtx)
-
-	dims := e.layout(gtx, textMaterial, selectMaterial)
-
 	if e.focused {
 		// Notify IME of selection if it changed.
 		newSel := e.ime.selection
@@ -551,8 +546,16 @@ func (e *Editor) Layout(gtx layout.Context, lt *text.Shaper, font font.Font, siz
 
 		e.updateSnippet(gtx, e.ime.start, e.ime.end)
 	}
+}
 
-	return dims
+// Layout lays out the editor using the provided textMaterial as the paint material
+// for the text glyphs+caret and the selectMaterial as the paint material for the
+// selection rectangle.
+func (e *Editor) Layout(gtx layout.Context, lt *text.Shaper, font font.Font, size unit.Sp, textMaterial, selectMaterial op.CallOp) layout.Dimensions {
+	e.Update(gtx)
+
+	e.text.Layout(gtx, lt, font, size)
+	return e.layout(gtx, textMaterial, selectMaterial)
 }
 
 // updateSnippet adds a key.SnippetOp if the snippet content or position

widget/editor_test.go

@@ -139,7 +139,7 @@ func TestEditorReadOnly(t *testing.T) {
 	// Type some new characters.
 	gtx.Ops.Reset()
 	gtx.Queue = &testQueue{events: []event.Event{key.EditEvent{Range: key.Range{Start: cStart2, End: cEnd2}, Text: "something else"}}}
-	e.Layout(gtx, cache, font, fontSize, op.CallOp{}, op.CallOp{})
+	e.Update(gtx)
 	textContent2 := e.Text()
 	if textContent2 != textContent {
 		t.Errorf("readonly editor modified by key.EditEvent")
@@ -159,22 +159,22 @@ func TestEditorReadOnly(t *testing.T) {
 	gtx.Ops.Reset()
 	gtx.Queue = &testQueue{events: []event.Event{
 		pointer.Event{
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Buttons:  pointer.ButtonPrimary,
 			Position: f32.Pt(float32(dims.Size.X)*.5, 5),
 		},
 		pointer.Event{
-			Type:     pointer.Drag,
+			Kind:     pointer.Drag,
 			Buttons:  pointer.ButtonPrimary,
 			Position: layout.FPt(dims.Size).Mul(.5),
 		},
 		pointer.Event{
-			Type:     pointer.Release,
+			Kind:     pointer.Release,
 			Buttons:  pointer.ButtonPrimary,
 			Position: layout.FPt(dims.Size).Mul(.5),
 		},
 	}}
-	e.Layout(gtx, cache, font, fontSize, op.CallOp{}, op.CallOp{})
+	e.Update(gtx)
 	cStart3, cEnd3 := e.Selection()
 	if cStart3 == cStart2 || cEnd3 == cEnd2 {
 		t.Errorf("expected mouse interaction to change selection.")
@@ -285,44 +285,10 @@ func TestEditor(t *testing.T) {
 	e.MoveCaret(-3, -3)
 	assertCaret(t, e, 1, 1, len("æbc\na"))
 	e.text.Mask = '*'
-	e.Layout(gtx, cache, font, fontSize, op.CallOp{}, op.CallOp{})
+	e.Update(gtx)
 	assertCaret(t, e, 1, 1, len("æbc\na"))
 	e.MoveCaret(-3, -3)
 	assertCaret(t, e, 0, 2, len("æb"))
-	/*
-		    NOTE(whereswaldon): it isn't possible to check the raw glyph data
-		    like this anymore. How should we handle this?
-			e.Mask = '\U0001F92B'
-			e.Layout(gtx, cache, font, fontSize, op.CallOp{},op.CallOp{})
-			e.moveEnd(selectionClear)
-			assertCaret(t, e, 0, 3, len("æbc"))
-
-			// When a password mask is applied, it should replace all visible glyphs
-			spaces := 0
-			for _, r := range textSample {
-				if unicode.IsSpace(r) {
-					spaces++
-				}
-			}
-			nonSpaces := len([]rune(textSample)) - spaces
-			glyphCounts := make(map[int]int)
-			// This loop assumes a single-run text, which we know is safe here.
-			for _, line := range e.lines {
-				for _, glyph := range line.Runs[0].Glyphs {
-					glyphCounts[int(glyph.ID)]++
-				}
-			}
-			if len(glyphCounts) > 2 {
-				t.Errorf("masked text contained glyphs other than mask and whitespace")
-			}
-
-			for gid, count := range glyphCounts {
-				if count != spaces && count != nonSpaces {
-					t.Errorf("glyph with id %d occurred %d times, expected either %d or %d", gid, count, spaces, nonSpaces)
-				}
-			}
-
-	*/
 	// Test that moveLine applies x offsets from previous moves.
 	e.SetText("long line\nshort")
 	e.SetCaret(0, 0)
@@ -680,11 +646,8 @@ func TestEditorMoveWord(t *testing.T) {
 			Constraints: layout.Exact(image.Pt(100, 100)),
 			Locale:      english,
 		}
-		cache := text.NewShaper(text.NoSystemFonts(), text.WithCollection(gofont.Collection()))
-		fontSize := unit.Sp(10)
-		font := font.Font{}
 		e.SetText(t)
-		e.Layout(gtx, cache, font, fontSize, op.CallOp{}, op.CallOp{})
+		e.Update(gtx)
 		return e
 	}
 	for ii, tt := range tests {
@@ -785,11 +748,8 @@ func TestEditorInsert(t *testing.T) {
 			Constraints: layout.Exact(image.Pt(100, 100)),
 			Locale:      english,
 		}
-		cache := text.NewShaper(text.NoSystemFonts(), text.WithCollection(gofont.Collection()))
-		fontSize := unit.Sp(10)
-		font := font.Font{}
 		e.SetText(t)
-		e.Layout(gtx, cache, font, fontSize, op.CallOp{}, op.CallOp{})
+		e.Update(gtx)
 		return e
 	}
 	for ii, tt := range tests {
@@ -875,11 +835,8 @@ func TestEditorDeleteWord(t *testing.T) {
 			Constraints: layout.Exact(image.Pt(100, 100)),
 			Locale:      english,
 		}
-		cache := text.NewShaper(text.NoSystemFonts(), text.WithCollection(gofont.Collection()))
-		fontSize := unit.Sp(10)
-		font := font.Font{}
 		e.SetText(t)
-		e.Layout(gtx, cache, font, fontSize, op.CallOp{}, op.CallOp{})
+		e.Update(gtx)
 		return e
 	}
 	for ii, tt := range tests {
@@ -947,13 +904,13 @@ g 2 4 6 8 g
 			events: []event.Event{
 				pointer.Event{
 					Buttons:  pointer.ButtonPrimary,
-					Type:     pointer.Press,
+					Kind:     pointer.Press,
 					Source:   pointer.Mouse,
 					Time:     tim,
 					Position: f32.Pt(textWidth(e, startPos.lineCol.line, 0, startPos.lineCol.col), textBaseline(e, startPos.lineCol.line)),
 				},
 				pointer.Event{
-					Type:     pointer.Release,
+					Kind:     pointer.Release,
 					Source:   pointer.Mouse,
 					Time:     tim,
 					Position: f32.Pt(textWidth(e, endPos.lineCol.line, 0, endPos.lineCol.col), textBaseline(e, endPos.lineCol.line)),

widget/enum.go

@@ -20,8 +20,6 @@ type Enum struct {
 	focus   string
 	focused bool
 
-	changed bool
-
 	keys []*enumKey
 }
 
@@ -40,11 +38,55 @@ func (e *Enum) index(k string) *enumKey {
 	return nil
 }
 
-// Changed reports whether Value has changed by user interaction since the last
+// Update the state and report whether Value has changed by user interaction.
-// call to Changed.
+func (e *Enum) Update(gtx layout.Context) bool {
-func (e *Enum) Changed() bool {
+	if gtx.Queue == nil {
-	changed := e.changed
+		e.focused = false
-	e.changed = false
+	}
+	e.hovering = false
+	changed := false
+	for _, state := range e.keys {
+		for _, ev := range state.click.Update(gtx) {
+			switch ev.Kind {
+			case gesture.KindPress:
+				if ev.Source == pointer.Mouse {
+					key.FocusOp{Tag: &state.tag}.Add(gtx.Ops)
+				}
+			case gesture.KindClick:
+				if state.key != e.Value {
+					e.Value = state.key
+					changed = true
+				}
+			}
+		}
+		for _, ev := range gtx.Events(&state.tag) {
+			switch ev := ev.(type) {
+			case key.FocusEvent:
+				if ev.Focus {
+					e.focused = true
+					e.focus = state.key
+				} else if state.key == e.focus {
+					e.focused = false
+				}
+			case key.Event:
+				if !e.focused || ev.State != key.Release {
+					break
+				}
+				if ev.Name != key.NameReturn && ev.Name != key.NameSpace {
+					break
+				}
+				if state.key != e.Value {
+					e.Value = state.key
+					changed = true
+				}
+			}
+		}
+		if state.click.Hovered() {
+			e.hovered = state.key
+			e.hovering = true
+		}
+	}
+
 	return changed
 }
 
@@ -60,6 +102,7 @@ func (e *Enum) Focused() (string, bool) {
 
 // Layout adds the event handler for the key k.
 func (e *Enum) Layout(gtx layout.Context, k string, content layout.Widget) layout.Dimensions {
+	e.Update(gtx)
 	m := op.Record(gtx.Ops)
 	dims := content(gtx)
 	c := m.Stop()
@@ -73,57 +116,13 @@ func (e *Enum) Layout(gtx layout.Context, k string, content layout.Widget) layou
 		e.keys = append(e.keys, state)
 	}
 	clk := &state.click
-	for _, ev := range clk.Events(gtx) {
-		switch ev.Type {
-		case gesture.TypePress:
-			if ev.Source == pointer.Mouse {
-				key.FocusOp{Tag: &state.tag}.Add(gtx.Ops)
-			}
-		case gesture.TypeClick:
-			if state.key != e.Value {
-				e.Value = state.key
-				e.changed = true
-			}
-		}
-	}
-	for _, ev := range gtx.Events(&state.tag) {
-		switch ev := ev.(type) {
-		case key.FocusEvent:
-			if ev.Focus {
-				e.focused = true
-				e.focus = state.key
-			} else if state.key == e.focus {
-				e.focused = false
-			}
-		case key.Event:
-			if !e.focused || ev.State != key.Release {
-				break
-			}
-			if ev.Name != key.NameReturn && ev.Name != key.NameSpace {
-				break
-			}
-			if state.key != e.Value {
-				e.Value = state.key
-				e.changed = true
-			}
-		}
-	}
-	if clk.Hovered() {
-		e.hovered = k
-		e.hovering = true
-	} else if e.hovered == k {
-		e.hovering = false
-	}
-
 	clk.Add(gtx.Ops)
-	disabled := gtx.Queue == nil
+	enabled := gtx.Queue != nil
-	if !disabled {
+	if enabled {
 		key.InputOp{Tag: &state.tag, Keys: "⏎|Space"}.Add(gtx.Ops)
-	} else if e.focus == k {
-		e.focused = false
 	}
 	semantic.SelectedOp(k == e.Value).Add(gtx.Ops)
-	semantic.DisabledOp(disabled).Add(gtx.Ops)
+	semantic.EnabledOp(enabled).Add(gtx.Ops)
 	c.Add(gtx.Ops)
 
 	return dims

widget/example_test.go

@@ -47,23 +47,21 @@ func ExampleClickable_passthrough() {
 		pointer.Event{
 			Source:   pointer.Mouse,
 			Buttons:  pointer.ButtonPrimary,
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(50, 50),
 		},
 		pointer.Event{
 			Source:   pointer.Mouse,
 			Buttons:  pointer.ButtonPrimary,
-			Type:     pointer.Release,
+			Kind:     pointer.Release,
 			Position: f32.Pt(50, 50),
 		},
 	)
-	// The second layout ensures that the click event is registered by the buttons.
-	widget()
 
-	if button1.Clicked() {
+	if button1.Clicked(gtx) {
 		fmt.Println("button1 clicked!")
 	}
-	if button2.Clicked() {
+	if button2.Clicked(gtx) {
 		fmt.Println("button2 clicked!")
 	}
 
@@ -95,7 +93,7 @@ func ExampleDraggable_Layout() {
 		drag.Layout(gtx, w, w)
 		// drag must respond with an Offer event when requested.
 		// Use the drag method for this.
-		if m, ok := drag.Requested(); ok {
+		if m, ok := drag.Update(gtx); ok {
 			drag.Offer(gtx.Ops, m, offer{Data: "hello world"})
 		}
 
@@ -125,15 +123,15 @@ func ExampleDraggable_Layout() {
 	// Send drag and drop gesture events.
 	r.Queue(
 		pointer.Event{
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(5, 5), // in the drag area
 		},
 		pointer.Event{
-			Type:     pointer.Move,
+			Kind:     pointer.Move,
 			Position: f32.Pt(5, 5), // in the drop area
 		},
 		pointer.Event{
-			Type:     pointer.Release,
+			Kind:     pointer.Release,
 			Position: f32.Pt(30, 30), // in the drop area
 		},
 	)

widget/float.go

@@ -9,59 +9,29 @@ import (
 	"gioui.org/io/pointer"
 	"gioui.org/layout"
 	"gioui.org/op/clip"
+	"gioui.org/unit"
 )
 
 // Float is for selecting a value in a range.
 type Float struct {
+	// Value is the value of the Float, in the [0; 1] range.
 	Value float32
 
-	drag    gesture.Drag
+	drag   gesture.Drag
-	pos     float32 // position normalized to [0, 1]
+	axis   layout.Axis
-	length  float32
+	length float32
-	changed bool
 }
 
 // Dragging returns whether the value is being interacted with.
 func (f *Float) Dragging() bool { return f.drag.Dragging() }
 
-// Layout updates the value according to drag events along the f's main axis.
+func (f *Float) Layout(gtx layout.Context, axis layout.Axis, pointerMargin unit.Dp) layout.Dimensions {
-//
+	f.Update(gtx)
-// The range of f is set by the minimum constraints main axis value.
-func (f *Float) Layout(gtx layout.Context, axis layout.Axis, min, max float32, invert bool, pointerMargin int) layout.Dimensions {
 	size := gtx.Constraints.Min
 	f.length = float32(axis.Convert(size).X)
+	f.axis = axis
 
-	var de *pointer.Event
+	margin := axis.Convert(image.Pt(gtx.Dp(pointerMargin), 0))
-	for _, e := range f.drag.Events(gtx.Metric, gtx, gesture.Axis(axis)) {
-		if e.Type == pointer.Press || e.Type == pointer.Drag {
-			de = &e
-		}
-	}
-
-	value := f.Value
-	if de != nil {
-		xy := de.Position.X
-		if axis == layout.Vertical {
-			xy = f.length - de.Position.Y
-		}
-		if invert {
-			xy = f.length - xy
-		}
-		f.pos = xy / f.length
-		value = min + (max-min)*f.pos
-	} else if min != max {
-		f.pos = (value - min) / (max - min)
-	}
-	// Unconditionally call setValue in case min, max, or value changed.
-	f.setValue(value, min, max)
-
-	if f.pos < 0 {
-		f.pos = 0
-	} else if f.pos > 1 {
-		f.pos = 1
-	}
-
-	margin := axis.Convert(image.Pt(pointerMargin, 0))
 	rect := image.Rectangle{
 		Min: margin.Mul(-1),
 		Max: size.Add(margin),
@@ -72,30 +42,26 @@ func (f *Float) Layout(gtx layout.Context, axis layout.Axis, min, max float32, i
 	return layout.Dimensions{Size: size}
 }
 
-func (f *Float) setValue(value, min, max float32) {
+// Update the Value according to drag events along the f's main axis.
-	if min > max {
+// The return value reports whether the value was changed.
-		min, max = max, min
+//
+// The range of f is set by the minimum constraints main axis value.
+func (f *Float) Update(gtx layout.Context) bool {
+	changed := false
+	for _, e := range f.drag.Update(gtx.Metric, gtx, gesture.Axis(f.axis)) {
+		if f.length > 0 && (e.Kind == pointer.Press || e.Kind == pointer.Drag) {
+			pos := e.Position.X
+			if f.axis == layout.Vertical {
+				pos = f.length - e.Position.Y
+			}
+			f.Value = pos / f.length
+			if f.Value < 0 {
+				f.Value = 0
+			} else if f.Value > 1 {
+				f.Value = 1
+			}
+			changed = true
+		}
 	}
-	if value < min {
-		value = min
-	} else if value > max {
-		value = max
-	}
-	if f.Value != value {
-		f.Value = value
-		f.changed = true
-	}
-}
-
-// Pos reports the selected position.
-func (f *Float) Pos() float32 {
-	return f.pos * f.length
-}
-
-// Changed reports whether the value has changed since
-// the last call to Changed.
-func (f *Float) Changed() bool {
-	changed := f.changed
-	f.changed = false
 	return changed
 }

widget/label.go

@@ -134,17 +134,17 @@ type textIterator struct {
 
 // processGlyph checks whether the glyph is visible within the iterator's configured
 // viewport and (if so) updates the iterator's text dimensions to include the glyph.
-func (it *textIterator) processGlyph(g text.Glyph, ok bool) (_ text.Glyph, visibleOrBefore bool) {
+func (it *textIterator) processGlyph(g text.Glyph, ok bool) (visibleOrBefore bool) {
 	if it.maxLines > 0 {
 		if g.Flags&text.FlagTruncator != 0 && g.Flags&text.FlagClusterBreak != 0 {
 			// A glyph carrying both of these flags provides the count of truncated runes.
-			it.truncated = g.Runes
+			it.truncated = int(g.Runes)
 		}
 		if g.Flags&text.FlagLineBreak != 0 {
 			it.linesSeen++
 		}
 		if it.linesSeen == it.maxLines && g.Flags&text.FlagParagraphBreak != 0 {
-			return g, false
+			return false
 		}
 	}
 	// Compute the maximum extent to which glyphs overhang on the horizontal
@@ -191,7 +191,7 @@ func (it *textIterator) processGlyph(g text.Glyph, ok bool) (_ text.Glyph, visib
 		it.bounds.Max.X = max(it.bounds.Max.X, logicalBounds.Max.X)
 		it.bounds.Max.Y = max(it.bounds.Max.Y, logicalBounds.Max.Y)
 	}
-	return g, ok && !below
+	return ok && !below
 }
 
 func fixedToFloat(i fixed.Int26_6) float32 {
@@ -206,7 +206,7 @@ func fixedToFloat(i fixed.Int26_6) float32 {
 // This design is awkward, but prevents the line slice from escaping
 // to the heap.
 func (it *textIterator) paintGlyph(gtx layout.Context, shaper *text.Shaper, glyph text.Glyph, line []text.Glyph) ([]text.Glyph, bool) {
-	_, visibleOrBefore := it.processGlyph(glyph, true)
+	visibleOrBefore := it.processGlyph(glyph, true)
 	if it.visible {
 		if len(line) == 0 {
 			it.lineOff = f32.Point{X: fixedToFloat(glyph.X), Y: float32(glyph.Y)}.Sub(layout.FPt(it.viewport.Min))

widget/label_test.go

@@ -146,10 +146,7 @@ func TestGlyphIterator(t *testing.T) {
 			glyphs := getGlyphs(16, 0, maxWidth, text.Start, tc.str)
 			it := textIterator{viewport: tc.viewport, maxLines: tc.maxLines}
 			for i, g := range glyphs {
-				gOut, ok := it.processGlyph(g, true)
+				ok := it.processGlyph(g, true)
-				if gOut != g {
-					t.Errorf("textIterator modified glyphs[%d], original:\n%#+v, modified:\n%#+v", i, g, gOut)
-				}
 				if !ok && i != tc.stopAtGlyph {
 					t.Errorf("expected iterator to stop at glyph %d, stopped at %d", tc.stopAtGlyph, i)
 				}

widget/list.go

@@ -61,8 +61,8 @@ func (s *Scrollbar) Layout(gtx layout.Context, axis layout.Axis, viewportStart,
 	}
 
 	// Jump to a click in the track.
-	for _, event := range s.track.Events(gtx) {
+	for _, event := range s.track.Update(gtx) {
-		if event.Type != gesture.TypeClick ||
+		if event.Kind != gesture.KindClick ||
 			event.Modifiers != key.Modifiers(0) ||
 			event.NumClicks > 1 {
 			continue
@@ -80,8 +80,8 @@ func (s *Scrollbar) Layout(gtx layout.Context, axis layout.Axis, viewportStart,
 	}
 
 	// Offset to account for any drags.
-	for _, event := range s.drag.Events(gtx.Metric, gtx, gesture.Axis(axis)) {
+	for _, event := range s.drag.Update(gtx.Metric, gtx, gesture.Axis(axis)) {
-		switch event.Type {
+		switch event.Kind {
 		case pointer.Drag:
 		case pointer.Release, pointer.Cancel:
 			s.dragging = false
@@ -136,7 +136,7 @@ func (s *Scrollbar) Layout(gtx layout.Context, axis layout.Axis, viewportStart,
 
 	// Process events from the indicator so that hover is
 	// detected properly.
-	_ = s.indicator.Events(gtx)
+	_ = s.indicator.Update(gtx)
 
 	return layout.Dimensions{}
 }

widget/material/button.go

@@ -93,9 +93,8 @@ func IconButton(th *Theme, button *widget.Clickable, icon *widget.Icon, descript
 func Clickable(gtx layout.Context, button *widget.Clickable, w layout.Widget) layout.Dimensions {
 	return button.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
 		semantic.Button.Add(gtx.Ops)
-		constraints := gtx.Constraints
+		return layout.Background{}.Layout(gtx,
-		return layout.Stack{}.Layout(gtx,
+			func(gtx layout.Context) layout.Dimensions {
-			layout.Expanded(func(gtx layout.Context) layout.Dimensions {
 				defer clip.Rect{Max: gtx.Constraints.Min}.Push(gtx.Ops).Pop()
 				if button.Hovered() || button.Focused() {
 					paint.Fill(gtx.Ops, f32color.Hovered(color.NRGBA{}))
@@ -104,11 +103,8 @@ func Clickable(gtx layout.Context, button *widget.Clickable, w layout.Widget) la
 					drawInk(gtx, c)
 				}
 				return layout.Dimensions{Size: gtx.Constraints.Min}
-			}),
+			},
-			layout.Stacked(func(gtx layout.Context) layout.Dimensions {
+			w,
-				gtx.Constraints = constraints
-				return w(gtx)
-			}),
 		)
 	})
 }
@@ -131,8 +127,8 @@ func (b ButtonLayoutStyle) Layout(gtx layout.Context, w layout.Widget) layout.Di
 	min := gtx.Constraints.Min
 	return b.Button.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
 		semantic.Button.Add(gtx.Ops)
-		return layout.Stack{Alignment: layout.Center}.Layout(gtx,
+		return layout.Background{}.Layout(gtx,
-			layout.Expanded(func(gtx layout.Context) layout.Dimensions {
+			func(gtx layout.Context) layout.Dimensions {
 				rr := gtx.Dp(b.CornerRadius)
 				defer clip.UniformRRect(image.Rectangle{Max: gtx.Constraints.Min}, rr).Push(gtx.Ops).Pop()
 				background := b.Background
@@ -147,11 +143,11 @@ func (b ButtonLayoutStyle) Layout(gtx layout.Context, w layout.Widget) layout.Di
 					drawInk(gtx, c)
 				}
 				return layout.Dimensions{Size: gtx.Constraints.Min}
-			}),
+			},
-			layout.Stacked(func(gtx layout.Context) layout.Dimensions {
+			func(gtx layout.Context) layout.Dimensions {
 				gtx.Constraints.Min = min
 				return layout.Center.Layout(gtx, w)
-			}),
+			},
 		)
 	})
 }
@@ -163,8 +159,8 @@ func (b IconButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
 		if d := b.Description; d != "" {
 			semantic.DescriptionOp(b.Description).Add(gtx.Ops)
 		}
-		return layout.Stack{Alignment: layout.Center}.Layout(gtx,
+		return layout.Background{}.Layout(gtx,
-			layout.Expanded(func(gtx layout.Context) layout.Dimensions {
+			func(gtx layout.Context) layout.Dimensions {
 				rr := (gtx.Constraints.Min.X + gtx.Constraints.Min.Y) / 4
 				defer clip.UniformRRect(image.Rectangle{Max: gtx.Constraints.Min}, rr).Push(gtx.Ops).Pop()
 				background := b.Background
@@ -179,8 +175,8 @@ func (b IconButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
 					drawInk(gtx, c)
 				}
 				return layout.Dimensions{Size: gtx.Constraints.Min}
-			}),
+			},
-			layout.Stacked(func(gtx layout.Context) layout.Dimensions {
+			func(gtx layout.Context) layout.Dimensions {
 				return b.Inset.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
 					size := gtx.Dp(b.Size)
 					if b.Icon != nil {
@@ -191,7 +187,7 @@ func (b IconButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
 						Size: image.Point{X: size, Y: size},
 					}
 				})
-			}),
+			},
 		)
 	})
 	c := m.Stop()

widget/material/decorations.go

@@ -88,18 +88,18 @@ func (d DecorationsStyle) layoutDecorations(gtx layout.Context) layout.Dimension
 				cl := d.Decorations.Clickable(a)
 				dims := cl.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
 					semantic.Button.Add(gtx.Ops)
-					return layout.Stack{Alignment: layout.Center}.Layout(gtx,
+					return layout.Background{}.Layout(gtx,
-						layout.Expanded(func(gtx layout.Context) layout.Dimensions {
+						func(gtx layout.Context) layout.Dimensions {
 							defer clip.Rect{Max: gtx.Constraints.Min}.Push(gtx.Ops).Pop()
 							for _, c := range cl.History() {
 								drawInk(gtx, c)
 							}
 							return layout.Dimensions{Size: gtx.Constraints.Min}
-						}),
+						},
-						layout.Stacked(func(gtx layout.Context) layout.Dimensions {
+						func(gtx layout.Context) layout.Dimensions {
 							paint.ColorOp{Color: d.Foreground}.Add(gtx.Ops)
 							return inset.Layout(gtx, w)
-						}),
+						},
 					)
 				})
 				size.X += dims.Size.X

widget/material/list.go

@@ -165,12 +165,9 @@ func (s ScrollbarStyle) layout(gtx layout.Context, axis layout.Axis, viewportSta
 	if axis == layout.Horizontal {
 		inset.Top, inset.Bottom, inset.Left, inset.Right = inset.Left, inset.Right, inset.Top, inset.Bottom
 	}
-	// Capture the outer constraints because layout.Stack will reset
-	// the minimum to zero.
-	outerConstraints := gtx.Constraints
 
-	return layout.Stack{}.Layout(gtx,
+	return layout.Background{}.Layout(gtx,
-		layout.Expanded(func(gtx layout.Context) layout.Dimensions {
+		func(gtx layout.Context) layout.Dimensions {
 			// Lay out the draggable track underneath the scroll indicator.
 			area := image.Rectangle{
 				Max: gtx.Constraints.Min,
@@ -186,10 +183,9 @@ func (s ScrollbarStyle) layout(gtx layout.Context, axis layout.Axis, viewportSta
 			s.Scrollbar.AddTrack(gtx.Ops)
 
 			paint.FillShape(gtx.Ops, s.Track.Color, clip.Rect(area).Op())
-			return layout.Dimensions{}
+			return layout.Dimensions{Size: gtx.Constraints.Min}
-		}),
+		},
-		layout.Stacked(func(gtx layout.Context) layout.Dimensions {
+		func(gtx layout.Context) layout.Dimensions {
-			gtx.Constraints = outerConstraints
 			return inset.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
 				// Use axis-independent constraints.
 				gtx.Constraints.Min = axis.Convert(gtx.Constraints.Min)
@@ -231,7 +227,7 @@ func (s ScrollbarStyle) layout(gtx layout.Context, axis layout.Axis, viewportSta
 
 				return layout.Dimensions{Size: axis.Convert(gtx.Constraints.Min)}
 			})
-		}),
+		},
 	)
 }
 

widget/material/radiobutton.go

@@ -38,6 +38,7 @@ func RadioButton(th *Theme, group *widget.Enum, key, label string) RadioButtonSt
 
 // Layout updates enum and displays the radio button.
 func (r RadioButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
+	r.Group.Update(gtx)
 	hovered, hovering := r.Group.Hovered()
 	focus, focused := r.Group.Focused()
 	return r.Group.Layout(gtx, r.Key, func(gtx layout.Context) layout.Dimensions {

widget/material/slider.go

@@ -16,10 +16,8 @@ import (
 )
 
 // Slider is for selecting a value in a range.
-func Slider(th *Theme, float *widget.Float, min, max float32) SliderStyle {
+func Slider(th *Theme, float *widget.Float) SliderStyle {
 	return SliderStyle{
-		Min:        min,
-		Max:        max,
 		Color:      th.Palette.ContrastBg,
 		Float:      float,
 		FingerSize: th.FingerSize,
@@ -27,35 +25,34 @@ func Slider(th *Theme, float *widget.Float, min, max float32) SliderStyle {
 }
 
 type SliderStyle struct {
-	Axis     layout.Axis
+	Axis  layout.Axis
-	Min, Max float32
+	Color color.NRGBA
-	Invert   bool
+	Float *widget.Float
-	Color    color.NRGBA
-	Float    *widget.Float
 
 	FingerSize unit.Dp
 }
 
 func (s SliderStyle) Layout(gtx layout.Context) layout.Dimensions {
-	thumbRadius := gtx.Dp(6)
+	const thumbRadius unit.Dp = 6
+	tr := gtx.Dp(thumbRadius)
 	trackWidth := gtx.Dp(2)
 
 	axis := s.Axis
 	// Keep a minimum length so that the track is always visible.
-	minLength := thumbRadius + 3*thumbRadius + thumbRadius
+	minLength := tr + 3*tr + tr
 	// Try to expand to finger size, but only if the constraints
 	// allow for it.
 	touchSizePx := min(gtx.Dp(s.FingerSize), axis.Convert(gtx.Constraints.Max).Y)
 	sizeMain := max(axis.Convert(gtx.Constraints.Min).X, minLength)
-	sizeCross := max(2*thumbRadius, touchSizePx)
+	sizeCross := max(2*tr, touchSizePx)
 	size := axis.Convert(image.Pt(sizeMain, sizeCross))
 
-	o := axis.Convert(image.Pt(thumbRadius, 0))
+	o := axis.Convert(image.Pt(tr, 0))
 	trans := op.Offset(o).Push(gtx.Ops)
-	gtx.Constraints.Min = axis.Convert(image.Pt(sizeMain-2*thumbRadius, sizeCross))
+	gtx.Constraints.Min = axis.Convert(image.Pt(sizeMain-2*tr, sizeCross))
-	s.Float.Layout(gtx, axis, s.Min, s.Max, s.Invert, thumbRadius)
+	dims := s.Float.Layout(gtx, axis, thumbRadius)
 	gtx.Constraints.Min = gtx.Constraints.Min.Add(axis.Convert(image.Pt(0, sizeCross)))
-	thumbPos := thumbRadius + int(s.Float.Pos())
+	thumbPos := tr + int(s.Float.Value*float32(axis.Convert(dims.Size).X))
 	trans.Pop()
 
 	color := s.Color
@@ -65,7 +62,7 @@ func (s SliderStyle) Layout(gtx layout.Context) layout.Dimensions {
 
 	rect := func(minx, miny, maxx, maxy int) image.Rectangle {
 		r := image.Rect(minx, miny, maxx, maxy)
-		if s.Invert != (axis == layout.Vertical) {
+		if axis == layout.Vertical {
 			r.Max.X, r.Min.X = sizeMain-r.Min.X, sizeMain-r.Max.X
 		}
 		r.Min = axis.Convert(r.Min)
@@ -75,7 +72,7 @@ func (s SliderStyle) Layout(gtx layout.Context) layout.Dimensions {
 
 	// Draw track before thumb.
 	track := rect(
-		thumbRadius, sizeCross/2-trackWidth/2,
+		tr, sizeCross/2-trackWidth/2,
 		thumbPos, sizeCross/2+trackWidth/2,
 	)
 	paint.FillShape(gtx.Ops, color, clip.Rect(track).Op())
@@ -83,15 +80,15 @@ func (s SliderStyle) Layout(gtx layout.Context) layout.Dimensions {
 	// Draw track after thumb.
 	track = rect(
 		thumbPos, axis.Convert(track.Min).Y,
-		sizeMain-thumbRadius, axis.Convert(track.Max).Y,
+		sizeMain-tr, axis.Convert(track.Max).Y,
 	)
 	paint.FillShape(gtx.Ops, f32color.MulAlpha(color, 96), clip.Rect(track).Op())
 
 	// Draw thumb.
 	pt := image.Pt(thumbPos, sizeCross/2)
 	thumb := rect(
-		pt.X-thumbRadius, pt.Y-thumbRadius,
+		pt.X-tr, pt.Y-tr,
-		pt.X+thumbRadius, pt.Y+thumbRadius,
+		pt.X+tr, pt.Y+tr,
 	)
 	paint.FillShape(gtx.Ops, color, clip.Ellipse(thumb).Op(gtx.Ops))
 

widget/material/switch.go

@@ -39,6 +39,7 @@ func Switch(th *Theme, swtch *widget.Bool, description string) SwitchStyle {
 
 // Layout updates the switch and displays it.
 func (s SwitchStyle) Layout(gtx layout.Context) layout.Dimensions {
+	s.Switch.Update(gtx)
 	trackWidth := gtx.Dp(36)
 	trackHeight := gtx.Dp(16)
 	thumbSize := gtx.Dp(20)

widget/selectable.go

@@ -182,25 +182,31 @@ func (l *Selectable) Truncated() bool {
 	return l.text.Truncated()
 }
 
+// Update the state of the selectable in response to input events.
+func (l *Selectable) Update(gtx layout.Context) {
+	l.initialize()
+	l.handleEvents(gtx)
+}
+
 // Layout clips to the dimensions of the selectable, updates the shaped text, configures input handling, and paints
 // the text and selection rectangles. The provided textMaterial and selectionMaterial ops are used to set the
 // paint material for the text and selection rectangles, respectively.
 func (l *Selectable) Layout(gtx layout.Context, lt *text.Shaper, font font.Font, size unit.Sp, textMaterial, selectionMaterial op.CallOp) layout.Dimensions {
-	l.initialize()
+	l.Update(gtx)
 	l.text.LineHeight = l.LineHeight
 	l.text.LineHeightScale = l.LineHeightScale
 	l.text.Alignment = l.Alignment
 	l.text.MaxLines = l.MaxLines
 	l.text.Truncator = l.Truncator
 	l.text.WrapPolicy = l.WrapPolicy
-	l.text.Update(gtx, lt, font, size, l.handleEvents)
+	l.text.Layout(gtx, lt, font, size)
 	dims := l.text.Dimensions()
 	defer clip.Rect(image.Rectangle{Max: dims.Size}).Push(gtx.Ops).Pop()
 	pointer.CursorText.Add(gtx.Ops)
 	var keys key.Set
 	if l.focused {
-		const keyFilterAllArrows = "(ShortAlt)-(Shift)-[←,→,↑,↓]|(Shift)-[⏎,⌤]|(ShortAlt)-(Shift)-[⌫,⌦]|(Shift)-[⇞,⇟,⇱,⇲]|Short-[C,V,X,A]|Short-(Shift)-Z"
+		const keyFilter = "(ShortAlt)-(Shift)-[←,→,↑,↓]|(Shift)-[⇞,⇟,⇱,⇲]|Short-[C,X,A]"
-		keys = keyFilterAllArrows
+		keys = keyFilter
 	}
 	key.InputOp{Tag: l, Keys: keys}.Add(gtx.Ops)
 	if l.requestFocus {
@@ -236,8 +242,8 @@ func (e *Selectable) processPointer(gtx layout.Context) {
 		switch evt := evt.(type) {
 		case gesture.ClickEvent:
 			switch {
-			case evt.Type == gesture.TypePress && evt.Source == pointer.Mouse,
+			case evt.Kind == gesture.KindPress && evt.Source == pointer.Mouse,
-				evt.Type == gesture.TypeClick && evt.Source != pointer.Mouse:
+				evt.Kind == gesture.KindClick && evt.Source != pointer.Mouse:
 				prevCaretPos, _ := e.text.Selection()
 				e.text.MoveCoord(image.Point{
 					X: int(math.Round(float64(evt.Position.X))),
@@ -271,10 +277,10 @@ func (e *Selectable) processPointer(gtx layout.Context) {
 		case pointer.Event:
 			release := false
 			switch {
-			case evt.Type == pointer.Release && evt.Source == pointer.Mouse:
+			case evt.Kind == pointer.Release && evt.Source == pointer.Mouse:
 				release = true
 				fallthrough
-			case evt.Type == pointer.Drag && evt.Source == pointer.Mouse:
+			case evt.Kind == pointer.Drag && evt.Source == pointer.Mouse:
 				if e.dragging {
 					e.text.MoveCoord(image.Point{
 						X: int(math.Round(float64(evt.Position.X))),
@@ -292,10 +298,10 @@ func (e *Selectable) processPointer(gtx layout.Context) {
 
 func (e *Selectable) clickDragEvents(gtx layout.Context) []event.Event {
 	var combinedEvents []event.Event
-	for _, evt := range e.clicker.Events(gtx) {
+	for _, evt := range e.clicker.Update(gtx) {
 		combinedEvents = append(combinedEvents, evt)
 	}
-	for _, evt := range e.dragger.Events(gtx.Metric, gtx, gesture.Both) {
+	for _, evt := range e.dragger.Update(gtx.Metric, gtx, gesture.Both) {
 		combinedEvents = append(combinedEvents, evt)
 	}
 	return combinedEvents

widget/text.go

@@ -228,10 +228,8 @@ func (e *textView) calculateViewSize(gtx layout.Context) image.Point {
 	return gtx.Constraints.Constrain(base)
 }
 
-// Update the text, reshaping it as necessary. If not nil, eventHandling will be invoked after reshaping the text to
+// Layout the text, reshaping it as necessary.
-// allow parent widgets to adapt to any changes in text content or positioning. If eventHandling modifies the contents
+func (e *textView) Layout(gtx layout.Context, lt *text.Shaper, font font.Font, size unit.Sp) {
-// of the textView, it is guaranteed to be reshaped (and ready for painting) before Update returns.
-func (e *textView) Update(gtx layout.Context, lt *text.Shaper, font font.Font, size unit.Sp, eventHandling func(gtx layout.Context)) {
 	if e.params.Locale != gtx.Locale {
 		e.params.Locale = gtx.Locale
 		e.invalidate()
@@ -289,10 +287,6 @@ func (e *textView) Update(gtx layout.Context, lt *text.Shaper, font font.Font, s
 	}
 
 	e.makeValid()
-	if eventHandling != nil {
-		eventHandling(gtx)
-		e.makeValid()
-	}
 
 	if viewSize := e.calculateViewSize(gtx); viewSize != e.viewSize {
 		e.viewSize = viewSize
@@ -492,14 +486,19 @@ func (e *textView) layoutText(lt *text.Shaper) {
 	it := textIterator{viewport: image.Rectangle{Max: image.Point{X: math.MaxInt, Y: math.MaxInt}}}
 	if lt != nil {
 		lt.Layout(e.params, r)
-		for glyph, ok := it.processGlyph(lt.NextGlyph()); ok; glyph, ok = it.processGlyph(lt.NextGlyph()) {
+		for {
-			e.index.Glyph(glyph)
+			g, ok := lt.NextGlyph()
+			if !it.processGlyph(g, ok) {
+				break
+			}
+			e.index.Glyph(g)
 		}
 	} else {
 		// Make a fake glyph for every rune in the reader.
 		b := bufio.NewReader(r)
 		for _, _, err := b.ReadRune(); err != io.EOF; _, _, err = b.ReadRune() {
-			g, _ := it.processGlyph(text.Glyph{Runes: 1, Flags: text.FlagClusterBreak}, true)
+			g := text.Glyph{Runes: 1, Flags: text.FlagClusterBreak}
+			_ = it.processGlyph(g, true)
 			e.index.Glyph(g)
 		}
 	}

widget/text_bench_test.go

@@ -7,7 +7,6 @@ import (
 	"os"
 	"sort"
 	"testing"
-	"time"
 
 	colEmoji "eliasnaur.com/font/noto/emoji/color"
 	"gioui.org/font"
@@ -48,10 +47,6 @@ var (
 	}()
 )
 
-func init() {
-	rand.Seed(int64(time.Now().Nanosecond()))
-}
-
 func runBenchmarkPermutations(b *testing.B, benchmark func(b *testing.B, runes int, locale system.Locale, document string)) {
 	docKeys := maps.Keys(documents)
 	sort.Strings(docKeys)
@@ -127,11 +122,12 @@ func BenchmarkLabelDynamic(b *testing.B) {
 		font := font.Font{}
 		runes := []rune(txt)[:runeCount]
 		l := Label{}
+		r := rand.New(rand.NewSource(42))
 		b.ResetTimer()
 		for i := 0; i < b.N; i++ {
 			// simulate a constantly changing string
-			a := rand.Intn(len(runes))
+			a := r.Intn(len(runes))
-			b := rand.Intn(len(runes))
+			b := r.Intn(len(runes))
 			runes[a], runes[b] = runes[b], runes[a]
 			l.Layout(gtx, cache, font, fontSize, string(runes), op.CallOp{})
 			if render {
@@ -196,11 +192,12 @@ func BenchmarkEditorDynamic(b *testing.B) {
 		runes := []rune(txt)[:runeCount]
 		e := Editor{}
 		e.SetText(string(runes))
+		r := rand.New(rand.NewSource(42))
 		b.ResetTimer()
 		for i := 0; i < b.N; i++ {
 			// simulate a constantly changing string
-			a := rand.Intn(e.Len())
+			a := r.Intn(e.Len())
-			b := rand.Intn(e.Len())
+			b := r.Intn(e.Len())
 			e.SetCaret(a, a+1)
 			takeStr := e.SelectedText()
 			e.Insert("")

widget/widget_test.go

@@ -35,12 +35,12 @@ func TestBool(t *testing.T) {
 	r.Queue(
 		pointer.Event{
 			Source:   pointer.Touch,
-			Type:     pointer.Press,
+			Kind:     pointer.Press,
 			Position: f32.Pt(50, 50),
 		},
 		pointer.Event{
 			Source:   pointer.Touch,
-			Type:     pointer.Release,
+			Kind:     pointer.Release,
 			Position: f32.Pt(50, 50),
 		},
 	)