app: use material.Decorations on undecorated platforms

This patch implements a mechanism for customizing window
decorations.
If a window is configured with app.Decorated(true), then
the widget/material.Decorations are applied. On Wayland,
the option is automatically set when the server does not
provide window decorations.

Server side decorations are no longer requested.
The Decorated flag is set according to the
server's requests.

Wayland is now the default driver for UNIX platforms.

References: https://todo.sr.ht/~eliasnaur/gio/318
Signed-off-by: Pierre Curto <pierre.curto@gmail.com>

app/os.go

@@ -43,6 +43,8 @@ type Config struct {
 	CustomRenderer bool
 	// center is a flag used to center the window. Set by option.
 	center bool
+	// Decorated reports whether window decorations are provided automatically.
+	Decorated bool
 }
 
 // ConfigEvent is sent whenever the configuration of a Window changes.
@@ -177,6 +179,9 @@ type driver interface {
 
 	// Wakeup wakes up the event loop and sends a WakeupEvent.
 	Wakeup()
+
+	// Perform actions on the window.
+	Perform(system.Action)
 }
 
 type windowRendezvous struct {
@@ -218,3 +223,12 @@ func newWindowRendezvous() *windowRendezvous {
 
 func (wakeupEvent) ImplementsEvent() {}
 func (ConfigEvent) ImplementsEvent() {}
+
+func walkActions(actions system.Action, do func(system.Action)) {
+	for a := system.Action(1); actions != 0; a <<= 1 {
+		if actions&a != 0 {
+			actions &^= a
+			do(a)
+		}
+	}
+}

app/os_android.go

@@ -1166,6 +1166,9 @@ func (w *window) Configure(options []Option) {
 		prev := w.config
 		cnf := w.config
 		cnf.apply(unit.Metric{}, options)
+		// Decorations are never disabled.
+		cnf.Decorated = true
+
 		if prev.Orientation != cnf.Orientation {
 			w.config.Orientation = cnf.Orientation
 			setOrientation(env, w.view, cnf.Orientation)
@@ -1188,12 +1191,17 @@ func (w *window) Configure(options []Option) {
 				w.config.Mode = Windowed
 			}
 		}
+		if cnf.Decorated != prev.Decorated {
+			w.config.Decorated = cnf.Decorated
+		}
 		if w.config != prev {
 			w.callbacks.Event(ConfigEvent{Config: w.config})
 		}
 	})
 }
 
+func (w *window) Perform(system.Action) {}
+
 func (w *window) Raise() {}
 
 func (w *window) SetCursor(name pointer.CursorName) {

app/os_ios.go

@@ -98,6 +98,7 @@ type window struct {
 
 	visible bool
 	cursor  pointer.CursorName
+	config  Config
 
 	pointerMap []C.CFTypeRef
 }
@@ -273,7 +274,16 @@ func (w *window) WriteClipboard(s string) {
 	C.writeClipboard(chars, C.NSUInteger(len(u16)))
 }
 
-func (w *window) Configure([]Option) {}
+func (w *window) Configure([]Option) {
+	prev := w.config
+	// Decorations are never disabled.
+	w.config.Decorated = true
+	if w.config != prev {
+		w.w.Event(ConfigEvent{Config: w.config})
+	}
+}
+
+func (w *window) Perform(system.Action) {}
 
 func (w *window) Raise() {}
 

app/os_js.go

@@ -513,6 +513,9 @@ func (w *window) Configure(options []Option) {
 	prev := w.config
 	cnf := w.config
 	cnf.apply(unit.Metric{}, options)
+	// Decorations are never disabled.
+	cnf.Decorated = true
+
 	if prev.Title != cnf.Title {
 		w.config.Title = cnf.Title
 		w.document.Set("title", cnf.Title)
@@ -528,11 +531,16 @@ func (w *window) Configure(options []Option) {
 		w.config.Orientation = cnf.Orientation
 		w.orientation(cnf.Orientation)
 	}
+	if cnf.Decorated != prev.Decorated {
+		w.config.Decorated = cnf.Decorated
+	}
 	if w.config != prev {
 		w.w.Event(ConfigEvent{Config: w.config})
 	}
 }
 
+func (w *window) Perform(system.Action) {}
+
 func (w *window) Raise() {}
 
 func (w *window) SetCursor(name pointer.CursorName) {

app/os_macos.go

@@ -261,6 +261,8 @@ func (w *window) Configure(options []Option) {
 	cnf.Size = cnf.Size.Div(int(screenScale))
 	cnf.MinSize = cnf.MinSize.Div(int(screenScale))
 	cnf.MaxSize = cnf.MaxSize.Div(int(screenScale))
+	// Decorations are never disabled.
+	cnf.Decorated = true
 
 	switch cnf.Mode {
 	case Fullscreen:
@@ -325,6 +327,9 @@ func (w *window) Configure(options []Option) {
 			C.setScreenFrame(w.window, C.CGFloat(x), C.CGFloat(y), C.CGFloat(sz.X), C.CGFloat(sz.Y))
 		}
 	}
+	if cnf.Decorated != prev.Decorated {
+		w.config.Decorated = cnf.Decorated
+	}
 	if w.config != prev {
 		w.w.Event(ConfigEvent{Config: w.config})
 	}
@@ -339,6 +344,8 @@ func (w *window) setTitle(prev, cnf Config) {
 	}
 }
 
+func (w *window) Perform(system.Action) {}
+
 func (w *window) SetCursor(name pointer.CursorName) {
 	w.cursor = windowSetCursor(w.cursor, name)
 }

app/os_unix.go

@@ -29,7 +29,7 @@ var wlDriver, x11Driver windowDriver
 
 func newWindow(window *callbacks, options []Option) error {
 	var errFirst error
-	for _, d := range []windowDriver{x11Driver, wlDriver} {
+	for _, d := range []windowDriver{wlDriver, x11Driver} {
 		if d == nil {
 			continue
 		}

app/os_wayland.c

@@ -6,6 +6,7 @@
 
 #include <wayland-client.h>
 #include "wayland_xdg_shell.h"
+#include "wayland_xdg_decoration.h"
 #include "wayland_text_input.h"
 #include "_cgo_export.h"
 
@@ -29,6 +30,10 @@ const struct xdg_toplevel_listener gio_xdg_toplevel_listener = {
 	.close = gio_onToplevelClose,
 };
 
+const struct zxdg_toplevel_decoration_v1_listener gio_zxdg_toplevel_decoration_v1_listener = {
+	.configure = gio_onToplevelDecorationConfigure,
+};
+
 static void xdg_wm_base_handle_ping(void *data, struct xdg_wm_base *wm, uint32_t serial) {
 	xdg_wm_base_pong(wm, serial);
 }

app/os_wayland.go

@@ -64,6 +64,7 @@ extern const struct wl_registry_listener gio_registry_listener;
 extern const struct wl_surface_listener gio_surface_listener;
 extern const struct xdg_surface_listener gio_xdg_surface_listener;
 extern const struct xdg_toplevel_listener gio_xdg_toplevel_listener;
+extern const struct zxdg_toplevel_decoration_v1_listener gio_zxdg_toplevel_decoration_v1_listener;
 extern const struct xdg_wm_base_listener gio_xdg_wm_base_listener;
 extern const struct wl_callback_listener gio_callback_listener;
 extern const struct wl_output_listener gio_output_listener;
@@ -149,6 +150,7 @@ type repeatState struct {
 type window struct {
 	w          *callbacks
 	disp       *wlDisplay
+	seat       *wlSeat
 	surf       *C.struct_wl_surface
 	wmSurf     *C.struct_xdg_surface
 	topLvl     *C.struct_xdg_toplevel
@@ -190,7 +192,8 @@ type window struct {
 	// size is the unscaled window size (unlike config.Size which is scaled).
 	size         image.Point
 	config       Config
-	wsize  image.Point // window config size before going fullscreen
+	wsize        image.Point // window config size before going fullscreen or maximized
+	inCompositor bool        // window is moving or being resized
 
 	wakeups chan struct{}
 }
@@ -212,7 +215,7 @@ type wlOutput struct {
 }
 
 // callbackMap maps Wayland native handles to corresponding Go
-// references. It is necessary because the the Wayland client API
+// references. It is necessary because the Wayland client API
 // forces the use of callbacks and storing pointers to Go values
 // in C is forbidden.
 var callbackMap sync.Map
@@ -369,9 +372,8 @@ func (d *wlDisplay) createNativeWindow(options []Option) (*window, error) {
 	C.xdg_toplevel_add_listener(w.topLvl, &C.gio_xdg_toplevel_listener, unsafe.Pointer(w.surf))
 
 	if d.decor != nil {
-		// Request server side decorations.
 		w.decor = C.zxdg_decoration_manager_v1_get_toplevel_decoration(d.decor, w.topLvl)
-		C.zxdg_toplevel_decoration_v1_set_mode(w.decor, C.ZXDG_TOPLEVEL_DECORATION_V1_MODE_SERVER_SIDE)
+		C.zxdg_toplevel_decoration_v1_add_listener(w.decor, &C.gio_zxdg_toplevel_decoration_v1_listener, unsafe.Pointer(w.surf))
 	}
 	w.updateOpaqueRegion()
 	return w, nil
@@ -499,6 +501,24 @@ func gio_onToplevelConfigure(data unsafe.Pointer, topLvl *C.struct_xdg_toplevel,
 		w.size = image.Pt(int(width), int(height))
 		w.updateOpaqueRegion()
 	}
+	w.needAck = true
+}
+
+//export gio_onToplevelDecorationConfigure
+func gio_onToplevelDecorationConfigure(data unsafe.Pointer, deco *C.struct_zxdg_toplevel_decoration_v1, mode C.uint32_t) {
+	w := callbackLoad(data).(*window)
+	decorated := w.config.Decorated
+	switch mode {
+	case C.ZXDG_TOPLEVEL_DECORATION_V1_MODE_CLIENT_SIDE:
+		w.config.Decorated = false
+	case C.ZXDG_TOPLEVEL_DECORATION_V1_MODE_SERVER_SIDE:
+		w.config.Decorated = true
+	}
+	if decorated != w.config.Decorated {
+		w.w.Event(ConfigEvent{Config: w.config})
+	}
+	w.needAck = true
+	w.draw(true)
 }
 
 //export gio_onOutputMode
@@ -772,15 +792,22 @@ func gio_onPointerEnter(data unsafe.Pointer, pointer *C.struct_wl_pointer, seria
 	s := callbackLoad(data).(*wlSeat)
 	s.serial = serial
 	w := callbackLoad(unsafe.Pointer(surf)).(*window)
+	w.seat = s
 	s.pointerFocus = w
 	w.setCursor(pointer, serial)
 	w.lastPos = f32.Point{X: fromFixed(x), Y: fromFixed(y)}
 }
 
 //export gio_onPointerLeave
-func gio_onPointerLeave(data unsafe.Pointer, p *C.struct_wl_pointer, serial C.uint32_t, surface *C.struct_wl_surface) {
+func gio_onPointerLeave(data unsafe.Pointer, p *C.struct_wl_pointer, serial C.uint32_t, surf *C.struct_wl_surface) {
+	w := callbackLoad(unsafe.Pointer(surf)).(*window)
+	w.seat = nil
 	s := callbackLoad(data).(*wlSeat)
 	s.serial = serial
+	if w.inCompositor {
+		w.inCompositor = false
+		w.w.Event(pointer.Event{Type: pointer.Cancel})
+	}
 }
 
 //export gio_onPointerMotion
@@ -818,6 +845,8 @@ func gio_onPointerButton(data unsafe.Pointer, p *C.struct_wl_pointer, serial, t,
 	case 0:
 		w.pointerBtns &^= btn
 		typ = pointer.Release
+		// Move or resize gestures no longer applies.
+		w.inCompositor = false
 	case 1:
 		w.pointerBtns |= btn
 		typ = pointer.Press
@@ -978,6 +1007,9 @@ func (w *window) Configure(options []Option) {
 			C.xdg_toplevel_set_max_size(w.topLvl, C.int32_t(cnf.MaxSize.X), C.int32_t(cnf.MaxSize.Y))
 		}
 	}
+	if cnf.Decorated != prev.Decorated {
+		w.config.Decorated = cnf.Decorated
+	}
 	if w.config != prev {
 		w.w.Event(ConfigEvent{Config: w.config})
 	}
@@ -992,6 +1024,63 @@ func (w *window) setTitle(prev, cnf Config) {
 	}
 }
 
+func (w *window) Perform(actions system.Action) {
+	walkActions(actions, func(action system.Action) {
+		switch action {
+		case system.ActionMinimize:
+			w.Configure([]Option{Minimized.Option()})
+		case system.ActionMaximize:
+			w.Configure([]Option{Maximized.Option()})
+		case system.ActionUnmaximize:
+			w.Configure([]Option{Windowed.Option()})
+		case system.ActionClose:
+			w.Close()
+		case system.ActionMove:
+			w.move()
+		default:
+			w.resize(action)
+		}
+	})
+}
+
+func (w *window) move() {
+	if !w.inCompositor && w.seat != nil {
+		w.inCompositor = true
+		s := w.seat
+		C.xdg_toplevel_move(w.topLvl, s.seat, s.serial)
+	}
+}
+
+func (w *window) resize(a system.Action) {
+	if w.inCompositor || w.seat == nil {
+		return
+	}
+	var edge int
+	switch a {
+	case system.ActionResizeNorth:
+		edge = C.XDG_TOPLEVEL_RESIZE_EDGE_TOP
+	case system.ActionResizeSouth:
+		edge = C.XDG_TOPLEVEL_RESIZE_EDGE_BOTTOM
+	case system.ActionResizeEast:
+		edge = C.XDG_TOPLEVEL_RESIZE_EDGE_LEFT
+	case system.ActionResizeWest:
+		edge = C.XDG_TOPLEVEL_RESIZE_EDGE_RIGHT
+	case system.ActionResizeNorthWest:
+		edge = C.XDG_TOPLEVEL_RESIZE_EDGE_TOP_LEFT
+	case system.ActionResizeNorthEast:
+		edge = C.XDG_TOPLEVEL_RESIZE_EDGE_BOTTOM_LEFT
+	case system.ActionResizeSouthEast:
+		edge = C.XDG_TOPLEVEL_RESIZE_EDGE_BOTTOM_RIGHT
+	case system.ActionResizeSouthWest:
+		edge = C.XDG_TOPLEVEL_RESIZE_EDGE_TOP_RIGHT
+	default:
+		return
+	}
+	w.inCompositor = true
+	s := w.seat
+	C.xdg_toplevel_resize(w.topLvl, s.seat, s.serial, C.uint32_t(edge))
+}
+
 func (w *window) Raise() {
 	// NB. there is no way for a minimized window to be unminimized.
 	// https://wayland.app/protocols/xdg-shell#xdg_toplevel:request:set_minimized

app/os_windows.go

@@ -531,6 +531,8 @@ func (w *window) Configure(options []Option) {
 	metric := configForDPI(dpi)
 	w.config.apply(metric, options)
 	windows.SetWindowText(w.hwnd, w.config.Title)
+	// Decorations are never disabled.
+	w.config.Decorated = true
 
 	switch w.config.Mode {
 	case Minimized:
@@ -691,6 +693,8 @@ func (w *window) Close() {
 	windows.PostMessage(w.hwnd, windows.WM_CLOSE, 0, 0)
 }
 
+func (w *window) Perform(system.Action) {}
+
 func (w *window) Raise() {
 	windows.SetForegroundWindow(w.hwnd)
 	windows.SetWindowPos(w.hwnd, windows.HWND_TOPMOST, 0, 0, 0, 0,

app/os_x11.go

@@ -164,6 +164,8 @@ func (w *x11Window) Configure(options []Option) {
 	prev := w.config
 	cnf := w.config
 	cnf.apply(w.metric, options)
+	// Decorations are never disabled.
+	cnf.Decorated = true
 
 	switch cnf.Mode {
 	case Fullscreen:
@@ -245,6 +247,9 @@ func (w *x11Window) Configure(options []Option) {
 			C.XMoveResizeWindow(w.x, w.xw, C.int(x), C.int(y), C.uint(sz.X), C.uint(sz.Y))
 		}
 	}
+	if cnf.Decorated != prev.Decorated {
+		w.config.Decorated = cnf.Decorated
+	}
 	if w.config != prev {
 		w.w.Event(ConfigEvent{Config: w.config})
 	}
@@ -268,6 +273,8 @@ func (w *x11Window) setTitle(prev, cnf Config) {
 	}
 }
 
+func (w *x11Window) Perform(system.Action) {}
+
 func (w *x11Window) Raise() {
 	var xev C.XEvent
 	ev := (*C.XClientMessageEvent)(unsafe.Pointer(&xev))

app/window.go

@@ -11,14 +11,18 @@ import (
 	"time"
 
 	"gioui.org/f32"
+	"gioui.org/font/gofont"
 	"gioui.org/gpu"
+	"gioui.org/internal/ops"
 	"gioui.org/io/event"
 	"gioui.org/io/pointer"
 	"gioui.org/io/profile"
 	"gioui.org/io/router"
 	"gioui.org/io/system"
+	"gioui.org/layout"
 	"gioui.org/op"
 	"gioui.org/unit"
+	"gioui.org/widget/material"
 
 	_ "gioui.org/app/internal/log"
 )
@@ -61,6 +65,11 @@ type Window struct {
 
 	queue       queue
 	cursor      pointer.CursorName
+	decorations struct {
+		op.Ops
+		Config
+		*material.Decorations
+	}
 
 	callbacks callbacks
 
@@ -578,9 +587,16 @@ func (w *Window) processEvent(d driver, e event.Event) {
 		w.hasNextFrame = false
 		e2.Frame = w.update
 		e2.Queue = &w.queue
+
+		// Prepare the decorations and update the frame insets.
+		wrapper := &w.decorations.Ops
+		wrapper.Reset()
+		size := e2.Size // save the initial window size as the decorations will change it.
+		e2.FrameEvent.Size = w.decorate(d, e2.FrameEvent, wrapper)
 		w.out <- e2.FrameEvent
 		frame, gotFrame := w.waitFrame()
-		err := w.validateAndProcess(d, e2.Size, e2.Sync, frame)
+		ops.AddCall(&wrapper.Internal, &frame.Internal, ops.PC{}, ops.PCFor(&frame.Internal))
+		err := w.validateAndProcess(d, size, e2.Sync, wrapper)
 		if gotFrame {
 			// We're done with frame, let the client continue.
 			w.frameAck <- struct{}{}
@@ -606,6 +622,9 @@ func (w *Window) processEvent(d driver, e event.Event) {
 		w.out <- e2
 		w.waitAck()
 	case wakeupEvent:
+	case ConfigEvent:
+		w.decorations.Config = e2.Config
+		w.out <- e
 	case event.Event:
 		if w.queue.q.Queue(e2) {
 			w.setNextFrame(time.Time{})
@@ -664,6 +683,59 @@ func (w *Window) updateCursor(d driver) {
 	}
 }
 
+// decorate the window if enabled and returns the corresponding Insets.
+func (w *Window) decorate(d driver, e system.FrameEvent, o *op.Ops) image.Point {
+	if w.decorations.Config.Decorated || w.decorations.Config.Mode == Fullscreen {
+		return e.Size
+	}
+	deco := w.decorations.Decorations
+	if deco == nil {
+		theme := material.NewTheme(gofont.Collection())
+		allActions := system.ActionMinimize | system.ActionMaximize | system.ActionUnmaximize |
+			system.ActionClose | system.ActionMove |
+			system.ActionResizeNorth | system.ActionResizeSouth |
+			system.ActionResizeWest | system.ActionResizeEast |
+			system.ActionResizeNorthWest | system.ActionResizeSouthWest |
+			system.ActionResizeNorthEast | system.ActionResizeSouthEast
+		deco = &material.Decorations{
+			DecorationsStyle: material.Decorate(theme, allActions),
+		}
+		w.decorations.Decorations = deco
+	}
+	// Update the decorations based on the current window mode.
+	var actions system.Action
+	switch m := w.decorations.Config.Mode; m {
+	case Windowed:
+		actions |= system.ActionUnmaximize
+	case Minimized:
+		actions |= system.ActionMinimize
+	case Maximized:
+		actions |= system.ActionMaximize
+	case Fullscreen:
+		actions |= system.ActionFullscreen
+	default:
+		panic(fmt.Errorf("unknown WindowMode %v", m))
+	}
+	deco.Perform(actions)
+	// Update the window based on the actions on the decorations.
+	d.Perform(deco.Actions())
+
+	gtx := layout.Context{
+		Ops:         o,
+		Now:         e.Now,
+		Queue:       e.Queue,
+		Metric:      e.Metric,
+		Constraints: layout.Exact(e.Size),
+	}
+	rec := op.Record(o)
+	dims := deco.Decorate(gtx, w.decorations.Config.Title)
+	op.Defer(o, rec.Stop())
+	// Offset to place the frame content below the decorations.
+	size := image.Point{Y: dims.Size.Y}
+	op.Offset(f32.Point{Y: float32(size.Y)}).Add(o)
+	return e.Size.Sub(size)
+}
+
 // Raise requests that the platform bring this window to the top of all open windows.
 // Some platforms do not allow this except under certain circumstances, such as when
 // a window from the same application already has focus. If the platform does not
@@ -764,3 +836,11 @@ func CustomRenderer(custom bool) Option {
 		cnf.CustomRenderer = custom
 	}
 }
+
+// Decorated controls whether automatic window decorations
+// are enabled.
+func Decorated(enabled bool) Option {
+	return func(_ unit.Metric, cnf *Config) {
+		cnf.Decorated = enabled
+	}
+}

widget/material/decorations.go

@@ -57,7 +57,7 @@ type Decorations struct {
 // Decorate a window with the title and actions defined in DecorationsStyle.
 // The space used by the decorations is returned as an inset for the window
 // content.
-func (d *Decorations) Decorate(gtx layout.Context, title string) layout.Inset {
+func (d *Decorations) Decorate(gtx layout.Context, title string) layout.Dimensions {
 	rec := op.Record(gtx.Ops)
 	dims := d.layoutDecorations(gtx, title)
 	decos := rec.Stop()
@@ -65,9 +65,7 @@ func (d *Decorations) Decorate(gtx layout.Context, title string) layout.Inset {
 	paint.FillShape(gtx.Ops, d.DecorationsStyle.Background, r.Op())
 	decos.Add(gtx.Ops)
 	d.layoutResizing(gtx)
-	return layout.Inset{
-		Top: unit.Px(float32(dims.Size.Y)),
-	}
+	return dims
 }
 
 func (d *Decorations) layoutResizing(gtx layout.Context) {