app/internal/wm: [macOS] use NSView+NSOpenGLContext, not NSOpenGLContextView

NSOpenGLContextView couples the window manager logic tightly with
OpenGL. Use generic NSViews, and attach NSOpenGLContext just like the
other platforms.

This change prepares for supporting GPU contexts created by clients as
well as a future Metal port.

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

app/window.go

@@ -56,7 +56,8 @@ type Window struct {
 }
 
 type callbacks struct {
-	w *Window
+	w     *Window
+	funcs chan func()
 }
 
 // queue is an event.Queue implementation that distributes system events
@@ -104,6 +105,7 @@ func NewWindow(options ...Option) *Window {
 		driverFuncs: make(chan func()),
 		dead:        make(chan struct{}),
 	}
+	w.callbacks.funcs = make(chan func())
 	w.callbacks.w = w
 	go w.run(opts)
 	return w
@@ -299,11 +301,22 @@ func (c *callbacks) SetDriver(d wm.Driver) {
 func (c *callbacks) Event(e event.Event) {
 	select {
 	case c.w.in <- e:
-		<-c.w.ack
+		for {
+			select {
+			case <-c.w.ack:
+				return
+			case f := <-c.funcs:
+				f()
+			}
+		}
 	case <-c.w.dead:
 	}
 }
 
+func (c *callbacks) Func(f func()) {
+	c.funcs <- f
+}
+
 func (w *Window) waitAck() {
 	// Send a dummy event; when it gets through we
 	// know the application has processed the previous event.