app: [macOS] handle mouse dragging with buttons other than the left one

Signed-off-by: Dominik Honnef <dominik@honnef.co>

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
@@ -245,6 +252,7 @@ const (
 	WM_MOUSEHWHEEL          = 0x020E
 	WM_NCACTIVATE           = 0x0086
 	WM_NCHITTEST            = 0x0084
+	WM_NCCALCSIZE           = 0x0083
 	WM_PAINT                = 0x000F
 	WM_QUIT                 = 0x0012
 	WM_SETCURSOR            = 0x0020
@@ -379,6 +387,9 @@ 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 +441,14 @@ 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 {

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.
@@ -128,18 +131,18 @@ func NewDisplayLink(callback func()) (*displayLink, error) {
 		states:   make(chan bool),
 		dids:     make(chan uint64),
 	}
-	h := cgo.NewHandle(d)
-	dl := C.gio_createDisplayLink(C.uintptr_t(h))
+	dl := C.gio_createDisplayLink()
 	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) {
-	d := cgo.Handle(handle).Value().(*displayLink)
-	if atomic.LoadUint32(&d.running) != 0 {
-		d.callback()
+func gio_onFrameCallback(ref C.CFTypeRef) {
+	d, exists := displayLinks.Load(ref)
+	if !exists {
+		return
+	}
+	dl := d.(*displayLink)
+	if atomic.LoadUint32(&dl.running) != 0 {
+		dl.callback()
 	}
 }
 

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 {
-}
-@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:)];
+CFTypeRef gio_createDisplayLink(void) {
+	CADisplayLink *dl = [CADisplayLink displayLinkWithTarget:[GioView class] selector:@selector(onFrameCallback:)];
 	dl.paused = YES;
 	NSRunLoop *runLoop = [NSRunLoop mainRunLoop];
 	[dl addToRunLoop:runLoop forMode:[runLoop currentMode]];

app/os_macos.go

@@ -523,6 +523,8 @@ 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
 	switch cdir {
@@ -788,13 +790,13 @@ 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

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

@@ -94,7 +94,10 @@ type wlDisplay struct {
 
 	// Notification pipe fds.
 	notify struct {
-		read, write int
+		read int
+
+		mu    sync.Mutex
+		write int
 	}
 
 	repeat repeatState
@@ -1442,6 +1445,11 @@ func (w *window) SetAnimating(anim bool) {
 // Wakeup wakes up the event loop through the notification pipe.
 func (d *wlDisplay) wakeup() {
 	oneByte := make([]byte, 1)
+	d.notify.mu.Lock()
+	defer d.notify.mu.Unlock()
+	if d.notify.write == 0 {
+		return
+	}
 	if _, err := syscall.Write(d.notify.write, oneByte); err != nil && err != syscall.EAGAIN {
 		panic(fmt.Errorf("failed to write to pipe: %v", err))
 	}
@@ -1820,10 +1828,12 @@ func newWLDisplay() (*wlDisplay, error) {
 }
 
 func (d *wlDisplay) destroy() {
+	d.notify.mu.Lock()
 	if d.notify.write != 0 {
 		syscall.Close(d.notify.write)
 		d.notify.write = 0
 	}
+	d.notify.mu.Unlock()
 	if d.notify.read != 0 {
 		syscall.Close(d.notify.read)
 		d.notify.read = 0

app/os_windows.go

@@ -325,6 +325,11 @@ 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 {
+			// No client areas; we draw decorations ourselves.
+			return 0
+		}
 	case windows.WM_PAINT:
 		w.draw(true)
 	case windows.WM_SIZE:
@@ -446,23 +451,18 @@ 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 +480,11 @@ 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) {
@@ -669,9 +674,6 @@ 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
@@ -695,9 +697,12 @@ func (w *window) Configure(options []Option) {
 		// Set desired window size.
 		wr.Right = wr.Left + width
 		wr.Bottom = wr.Top + height
-		// Convert from client size to window size.
+		// Compute client size and position. Note that the client size is
+		// equal to the window size when we are in control of decorations.
 		r := wr
-		windows.AdjustWindowRectEx(&r, uint32(style), 0, dwExStyle)
+		if w.config.Decorated {
+			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
@@ -706,6 +711,10 @@ func (w *window) Configure(options []Option) {
 		y = wr.Top
 		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:
 		mi := windows.GetMonitorInfo(w.hwnd)

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
 }
 

io/router/pointer.go

@@ -432,39 +432,42 @@ func (q *pointerQueue) semanticIDFor(content semanticContent) SemanticID {
 	return id.id
 }
 
-func (q *pointerQueue) ActionAt(pos f32.Point) (system.Action, bool) {
-	for i := len(q.hitTree) - 1; i >= 0; i-- {
-		n := &q.hitTree[i]
-		hit, _ := q.hit(n.area, pos)
-		if !hit {
-			continue
-		}
+func (q *pointerQueue) ActionAt(pos f32.Point) (action system.Action, hasAction bool) {
+	q.hitTest(pos, func(n *hitNode) bool {
 		area := q.areas[n.area]
-		return area.action, area.action != 0
-	}
-	return 0, false
+		if area.action != 0 {
+			action = area.action
+			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-- {
-		n := &q.hitTree[i]
-		hit, _ := q.hit(n.area, pos)
-		if !hit {
-			continue
-		}
+	q.hitTest(pos, func(n *hitNode) bool {
 		area := q.areas[n.area]
 		if area.semantic.id != 0 {
-			return area.semantic.id, true
+			semID = area.semantic.id
+			hasSemID = true
+			return false
 		}
-	}
-	return 0, false
+		return true
+	})
+	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
 }

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"
@@ -221,6 +222,43 @@ func TestPointerTypes(t *testing.T) {
 	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)
@@ -1231,6 +1269,17 @@ 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

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.
@@ -528,35 +579,21 @@ func (s *shaperImpl) LayoutRunes(params Parameters, txt []rune) document {
 	if hasNewline {
 		txt = txt[:len(txt)-1]
 	}
-	truncatedNewline := false
-	if hasNewline && len(txt) == 0 {
-		params.forceTruncate = false
-		// If we only have a newline, shape a space to get line metrics.
-		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))
+	if params.MaxLines != 0 && hasNewline {
+		// If we might end up truncating a trailing newline, we must insert the truncator symbol
+		// on the final line (if we hit the limit).
+		params.forceTruncate = true
 	}
+	ls, truncated = s.shapeAndWrapText(params, replaceControlCharacters(txt))
 
-	didTruncate := truncated > 0 || truncatedNewline || (params.forceTruncate && params.MaxLines == len(ls))
-
-	if didTruncate && hasNewline {
-		// We've truncated the newline, since it was at the end and we've truncated some amount of runes
-		// before it.
+	hasTruncator := truncated > 0 || (params.forceTruncate && params.MaxLines == len(ls))
+	if hasTruncator && hasNewline {
+		// We have a truncator at the end of the line, so the newline is logically
+		// truncated as well.
 		truncated++
 		hasNewline = false
 	}
+
 	// Convert to Lines.
 	textLines := make([]line, len(ls))
 	maxHeight := fixed.Int26_6(0)
@@ -565,49 +602,12 @@ func (s *shaperImpl) LayoutRunes(params Parameters, txt []rune) document {
 		if otLine.lineHeight > maxHeight {
 			maxHeight = otLine.lineHeight
 		}
-		isFinalLine := i == len(ls)-1
-		if isFinalLine && hasNewline {
-			// If there was a trailing newline update the rune counts to include
-			// 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,
+		if isFinalLine := i == len(ls)-1; isFinalLine {
+			if hasNewline {
+				otLine.insertTrailingSyntheticNewline(len(txt))
 			}
-			// Inset the synthetic newline glyph on the proper end of the run.
-			if otLine.runs[finalRunIdx].Direction.Progression() == system.FromOrigin {
-				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
-				}
+			if hasTruncator {
+				otLine.setTruncatedCount(truncated)
 			}
 		}
 		textLines[i] = otLine

text/shaper.go

@@ -245,8 +245,11 @@ func WithCollection(collection []FontFace) ShaperOption {
 	}
 }
 
-// NewShaper constructs a shaper with the provided collection of font faces
-// available.
+// NewShaper constructs a shaper with the provided options.
+//
+// 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
-					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.unreadRuneCount = unreadRunes
 				}
 			}
 			l.txt.append(lines)
@@ -505,6 +504,9 @@ func (l *Shaper) NextGlyph() (_ Glyph, ok bool) {
 		}
 		if endOfCluster {
 			glyph.Flags |= FlagClusterBreak
+			if run.truncator {
+				glyph.Runes += l.txt.unreadRuneCount
+			}
 		} else {
 			glyph.Runes = 0
 		}

text/shaper_test.go

@@ -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
-		expectedLines  int
-		expectedGlyphs int
+		textInput         string
+		expectedLines     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 += g.Runes
+					} else {
+						truncated += 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{
-				Alignment: Middle,
-				PxPerEm:   fixed.I(10),
-				MinWidth:  200,
-				MaxWidth:  200,
-				Locale:    english,
-			}, strings.NewReader(tc.textInput))
+			cache.Layout(params, strings.NewReader(tc.textInput))
 			if lineCount := len(cache.txt.lines); lineCount > tc.expectedLines {
 				t.Errorf("shaping reader %q created %d lines", tc.textInput, lineCount)
 			}

widget/button.go

@@ -28,6 +28,7 @@ type Clickable struct {
 	keyTag       struct{}
 	requestFocus bool
 	focused      bool
+	pressedKey   string
 }
 
 // Click represents a click.
@@ -178,17 +179,30 @@ 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{
-				Modifiers: e.Modifiers,
-				NumClicks: 1,
-			})
+			switch e.State {
+			case key.Press:
+				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 = ""
+				b.clicks = append(b.clicks, Click{
+					Modifiers: e.Modifiers,
+					NumClicks: 1,
+				})
+			}
 		}
 	}
 }

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
+	r.Queue(
+		key.Event{
+			Name:  key.NameReturn,
+			State: key.Press,
+		},
+		key.Event{
+			Name:  key.NameReturn,
+			State: key.Release,
+		},
+	)
+	frame()
+	if !b1.Clicked() {
+		t.Error("button 1 did not get clicked when it got return press & release")
+	}
+	if b2.Clicked() {
+		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() {
+		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() {
+		t.Error("button 1 got clicked, even if it had lost focus")
+	}
+	if b2.Clicked() {
+		t.Error("button 2 should not have been clicked, as it only got return release")
+	}
+}