app,app/internal/wm: introduce app.Window.Run and use it internally

app.Window implements a method for safely running functions against the
underlying native window through the driverFuncs channel. However, the
functions still run in a different goroutine than the one driving the
native event loop, which forces the implementations in package wm to do
complicated synchronization.

A previous change added a mechanism to run functions in the native event
loop thread. The macOS port needed this functionality, but with some
care it can be generalized. That's what this change does through the
new Run method.

The advantage is that the thread switch dance is now confined to
app.Window, with the help of a generic wm.Driver.Wakeup method. All
other Driver methods can then assume they run on their event loop
threads.

Run is exported because it is also needed for programs that use
Windows configured with CustomRenderer to control their own rendering.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/internal/wm/os_js.go

@@ -7,7 +7,6 @@ import (
 	"image"
 	"image/color"
 	"strings"
-	"sync"
 	"syscall/js"
 	"time"
 	"unicode"
@@ -47,7 +46,6 @@ type window struct {
 	chanAnimation chan struct{}
 	chanRedraw    chan struct{}
 
-	mu        sync.Mutex
 	size      f32.Point
 	inset     f32.Point
 	scale     float32
@@ -55,6 +53,7 @@ type window struct {
 	// animRequested tracks whether a requestAnimationFrame callback
 	// is pending.
 	animRequested bool
+	wakeups       chan struct{}
 }
 
 func NewWindow(win Callbacks, opts *Options) error {
@@ -71,6 +70,7 @@ func NewWindow(win Callbacks, opts *Options) error {
 		window:    js.Global().Get("window"),
 		head:      doc.Get("head"),
 		clipboard: js.Global().Get("navigator").Get("clipboard"),
+		wakeups:   make(chan struct{}, 1),
 	}
 	w.requestAnimationFrame = w.window.Get("requestAnimationFrame")
 	w.browserHistory = w.window.Get("history")
@@ -89,7 +89,7 @@ func NewWindow(win Callbacks, opts *Options) error {
 	})
 	w.clipboardCallback = w.funcOf(func(this js.Value, args []js.Value) interface{} {
 		content := args[0].String()
-		win.Event(clipboard.Event{Text: content})
+		go win.Event(clipboard.Event{Text: content})
 		return nil
 	})
 	w.addEventListeners()
@@ -106,6 +106,8 @@ func NewWindow(win Callbacks, opts *Options) error {
 		w.draw(true)
 		for {
 			select {
+			case <-w.wakeups:
+				w.w.Event(WakeupEvent{})
 			case <-w.chanAnimation:
 				w.animCallback()
 			case <-w.chanRedraw:
@@ -349,9 +351,7 @@ func (w *window) touchEvent(typ pointer.Type, e js.Value) {
 	changedTouches := e.Get("changedTouches")
 	n := changedTouches.Length()
 	rect := w.cnv.Call("getBoundingClientRect")
-	w.mu.Lock()
 	scale := w.scale
-	w.mu.Unlock()
 	var mods key.Modifiers
 	if e.Get("shiftKey").Bool() {
 		mods |= key.ModShift
@@ -401,9 +401,7 @@ func (w *window) pointerEvent(typ pointer.Type, dx, dy float32, e js.Value) {
 	rect := w.cnv.Call("getBoundingClientRect")
 	x -= rect.Get("left").Float()
 	y -= rect.Get("top").Float()
-	w.mu.Lock()
 	scale := w.scale
-	w.mu.Unlock()
 	pos := f32.Point{
 		X: float32(x) * scale,
 		Y: float32(y) * scale,
@@ -452,21 +450,17 @@ func (w *window) funcOf(f func(this js.Value, args []js.Value) interface{}) js.F
 }
 
 func (w *window) animCallback() {
-	w.mu.Lock()
 	anim := w.animating
 	w.animRequested = anim
 	if anim {
 		w.requestAnimationFrame.Invoke(w.redraw)
 	}
-	w.mu.Unlock()
 	if anim {
 		w.draw(false)
 	}
 }
 
 func (w *window) SetAnimating(anim bool) {
-	w.mu.Lock()
-	defer w.mu.Unlock()
 	w.animating = anim
 	if anim && !w.animRequested {
 		w.animRequested = true
@@ -511,6 +505,13 @@ func (w *window) SetCursor(name pointer.CursorName) {
 	style.Set("cursor", string(name))
 }
 
+func (w *window) Wakeup() {
+	select {
+	case w.wakeups <- struct{}{}:
+	default:
+	}
+}
+
 func (w *window) ShowTextInput(show bool) {
 	// Run in a goroutine to avoid a deadlock if the
 	// focus change result in an event.
@@ -527,9 +528,6 @@ func (w *window) ShowTextInput(show bool) {
 func (w *window) Close() {}
 
 func (w *window) resize() {
-	w.mu.Lock()
-	defer w.mu.Unlock()
-
 	w.scale = float32(w.window.Get("devicePixelRatio").Float())
 
 	rect := w.cnv.Call("getBoundingClientRect")
@@ -570,9 +568,6 @@ func (w *window) draw(sync bool) {
 }
 
 func (w *window) config() (int, int, system.Insets, unit.Metric) {
-	w.mu.Lock()
-	defer w.mu.Unlock()
-
 	return int(w.size.X + .5), int(w.size.Y + .5), system.Insets{
 			Bottom: unit.Px(w.inset.Y),
 			Right:  unit.Px(w.inset.X),