app: use driver defer mechanism for changing animation flag

Now that Window.driverDefer can be run in any context, the special case
of setting the animation flag can use that mechanism instead of a
special purpose channel.

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

app/window.go

@@ -47,8 +47,7 @@ type Window struct {
 	frames      chan *op.Ops
 	frameAck    chan struct{}
 	// dead is closed when the window is destroyed.
-	dead          chan struct{}
-	notifyAnimate chan struct{}
+	dead chan struct{}
 
 	stage        system.Stage
 	animating    bool
@@ -104,18 +103,17 @@ func NewWindow(options ...Option) *Window {
 	}
 
 	w := &Window{
-		in:            make(chan event.Event),
-		out:           make(chan event.Event),
-		ack:           make(chan struct{}),
-		invalidates:   make(chan struct{}, 1),
-		frames:        make(chan *op.Ops),
-		frameAck:      make(chan struct{}),
-		driverFuncs:   make(chan func(d driver), 1),
-		driverDefers:  make(chan func(d driver), 1),
-		wakeups:       make(chan struct{}, 1),
-		dead:          make(chan struct{}),
-		notifyAnimate: make(chan struct{}, 1),
-		nocontext:     cnf.CustomRenderer,
+		in:           make(chan event.Event),
+		out:          make(chan event.Event),
+		ack:          make(chan struct{}),
+		invalidates:  make(chan struct{}, 1),
+		frames:       make(chan *op.Ops),
+		frameAck:     make(chan struct{}),
+		driverFuncs:  make(chan func(d driver), 1),
+		driverDefers: make(chan func(d driver), 1),
+		wakeups:      make(chan struct{}, 1),
+		dead:         make(chan struct{}),
+		nocontext:    cnf.CustomRenderer,
 	}
 	w.callbacks.w = w
 	go w.run(cnf)
@@ -362,14 +360,22 @@ func (w *Window) updateAnimation() {
 	}
 	if animate != w.animating {
 		w.animating = animate
-		select {
-		case w.notifyAnimate <- struct{}{}:
-			w.wakeup()
-		default:
+		if animate {
+			w.driverDefer(enableAnim)
+		} else {
+			w.driverDefer(disableAnim)
 		}
 	}
 }
 
+func enableAnim(d driver) {
+	d.SetAnimating(true)
+}
+
+func disableAnim(d driver) {
+	d.SetAnimating(false)
+}
+
 func (w *Window) wakeup() {
 	select {
 	case w.wakeups <- struct{}{}:
@@ -421,8 +427,6 @@ func (w *Window) runFuncs(d driver) {
 	// Wait for ack while running incoming runnables.
 	for {
 		select {
-		case <-w.notifyAnimate:
-			d.SetAnimating(w.animating)
 		case f := <-w.driverFuncs:
 			f(d)
 		case f := <-w.driverDefers: