From f997a5f8f6e51db47ca6ecfc11923847ed464094 Mon Sep 17 00:00:00 2001
From: bruvzg <7645683+bruvzg@users.noreply.github.com>
Date: Mon, 8 Nov 2021 12:34:14 +0200
Subject: [PATCH] [macOS] Use pre-wait observer to keep main run loop running
 and redraw window during the window resize and displaying modal popups.

---
 platform/osx/os_osx.h  |  2 ++
 platform/osx/os_osx.mm | 33 ++++++++++++++++++++-------------
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/platform/osx/os_osx.h b/platform/osx/os_osx.h
index fd317b6df604..51f24af25840 100644
--- a/platform/osx/os_osx.h
+++ b/platform/osx/os_osx.h
@@ -175,6 +175,8 @@ class OS_OSX : public OS_Unix {
 
 	void _update_global_menu();
 
+	static void pre_wait_observer_cb(CFRunLoopObserverRef p_observer, CFRunLoopActivity p_activiy, void *p_context);
+
 protected:
 	virtual void initialize_core();
 	virtual Error initialize(const VideoMode &p_desired, int p_video_driver, int p_audio_driver);
diff --git a/platform/osx/os_osx.mm b/platform/osx/os_osx.mm
index 6517549283ae..27baebee8b09 100644
--- a/platform/osx/os_osx.mm
+++ b/platform/osx/os_osx.mm
@@ -389,14 +389,6 @@ - (void)windowDidResize:(NSNotification *)notification {
 		CGLEnable((CGLContextObj)[OS_OSX::singleton->context CGLContextObj], kCGLCESurfaceBackingSize);
 	}
 
-	if (OS_OSX::singleton->main_loop) {
-		Main::force_redraw();
-		//Event retrieval blocks until resize is over. Call Main::iteration() directly.
-		if (!Main::is_iterating()) { //avoid cyclic loop
-			Main::iteration();
-		}
-	}
-
 	/*
 	_GodotInputFramebufferSize(window, fbRect.size.width, fbRect.size.height);
 	_GodotInputWindowSize(window, contentRect.size.width, contentRect.size.height);
@@ -3295,11 +3287,25 @@ void _update_keyboard_layouts() {
 	joypad_osx->process_joypads();
 }
 
+void OS_OSX::pre_wait_observer_cb(CFRunLoopObserverRef p_observer, CFRunLoopActivity p_activiy, void *p_context) {
+	// Prevent main loop from sleeping and redraw window during resize / modal popups.
+
+	if (get_singleton()->get_main_loop()) {
+		Main::force_redraw();
+		if (!Main::is_iterating()) { // Avoid cyclic loop.
+			Main::iteration();
+		}
+	}
+
+	CFRunLoopWakeUp(CFRunLoopGetCurrent()); // Prevent main loop from sleeping.
+}
+
 void OS_OSX::run() {
 	force_quit = false;
 
-	if (!main_loop)
+	if (!main_loop) {
 		return;
+	}
 
 	main_loop->init();
 
@@ -3308,10 +3314,8 @@ void _update_keyboard_layouts() {
 		set_window_fullscreen(true);
 	}
 
-	//uint64_t last_ticks=get_ticks_usec();
-
-	//int frames=0;
-	//uint64_t frame=0;
+	CFRunLoopObserverRef pre_wait_observer = CFRunLoopObserverCreate(kCFAllocatorDefault, kCFRunLoopBeforeWaiting, true, 0, &pre_wait_observer_cb, nullptr);
+	CFRunLoopAddObserver(CFRunLoopGetCurrent(), pre_wait_observer, kCFRunLoopCommonModes);
 
 	bool quit = false;
 
@@ -3328,6 +3332,9 @@ void _update_keyboard_layouts() {
 		}
 	};
 
+	CFRunLoopRemoveObserver(CFRunLoopGetCurrent(), pre_wait_observer, kCFRunLoopCommonModes);
+	CFRelease(pre_wait_observer);
+
 	main_loop->finish();
 }