app: [macOS] ensure the Window is initalized before Run functions

Don't call eventLoop.FlushEvents which in turn applies Options and
executes Run functions before the window is fully initialized.

References: https://todo.sr.ht/~eliasnaur/gio/575
Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/os_macos.go

@@ -326,6 +326,7 @@ type window struct {
 	cursor      pointer.Cursor
 	pointerBtns pointer.Buttons
 	loop        *eventLoop
+	initialized bool
 
 	scale  float32
 	config Config
@@ -833,7 +834,9 @@ func (w *window) draw() {
 
 func (w *window) ProcessEvent(e event.Event) {
 	w.w.ProcessEvent(e)
-	w.loop.FlushEvents()
+	if w.initialized {
+		w.loop.FlushEvents()
+	}
 }
 
 func (w *window) Event() event.Event {
@@ -924,7 +927,6 @@ func newWindow(win *callbacks, options []Option) {
 		}
 		w.loop = newEventLoop(w.w, w.wakeup)
 		win.SetDriver(w)
-		res <- struct{}{}
 		if err := w.init(); err != nil {
 			w.ProcessEvent(DestroyEvent{Err: err})
 			return
@@ -942,6 +944,9 @@ func newWindow(win *callbacks, options []Option) {
 		nextTopLeft = C.cascadeTopLeftFromPoint(window, nextTopLeft)
 		// makeKeyAndOrderFront assumes ownership of our window reference.
 		C.makeKeyAndOrderFront(window)
+		w.initialized = true
+		res <- struct{}{}
+		w.loop.FlushEvents()
 	})
 	<-res
 }