app/internal/app: introduce runOnMain for main thread callbacks

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

app/internal/window/os_darwin.go

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package window
+
+/*
+#include "os_darwin.h"
+*/
+import "C"
+
+var mainFuncs = make(chan func(), 1)
+
+// runOnMain runs the function on the main thread.
+func runOnMain(f func()) {
+	go func() {
+		mainFuncs <- f
+		C.gio_wakeupMainThread()
+	}()
+}
+
+//export gio_dispatchMainFuncs
+func gio_dispatchMainFuncs() {
+	for {
+		select {
+		case f := <-mainFuncs:
+			f()
+		default:
+			return
+		}
+	}
+}