app/internal/wm: [macOS] avoid deadlock in Window.Close

Native window callbacks now run in the same context as the event loop.
However, a call to Close immediately calls onClose which in turn wants
to send events. Break the deadlock by deferring the Close call.

Fixes gio#227

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

app/internal/wm/os_macos.go

@@ -206,7 +206,13 @@ func (w *window) runOnMain(f func()) {
 }
 
 func (w *window) Close() {
-	C.gio_close(w.window)
+	// gio_close immediately calls gio_onClose which sends events
+	// causing a deadlock because Close is called during an event.
+	// Break the deadlock by deferring the close, making Close more
+	// akin to a message like the other platforms.
+	go runOnMain(func() {
+		C.gio_close(w.window)
+	})
 }
 
 func (w *window) setStage(stage system.Stage) {