app: [macOS] synchronize rendering with Core Animation for smooth resizes

Magic incantations lifted from

https://thume.ca/2019/06/19/glitchless-metal-window-resizing/

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

app/metal_darwin.go

@@ -60,8 +60,9 @@ static void presentDrawable(CFTypeRef queueRef, CFTypeRef drawableRef) {
 		id<MTLDrawable> drawable = (__bridge id<MTLDrawable>)drawableRef;
 		id<MTLCommandQueue> queue = (__bridge id<MTLCommandQueue>)queueRef;
 		id<MTLCommandBuffer> cmdBuffer = [queue commandBuffer];
-		[cmdBuffer presentDrawable:drawable];
 		[cmdBuffer commit];
+		[cmdBuffer waitUntilScheduled];
+		[drawable present];
 	}
 }
 

app/metal_ios.go

@@ -21,7 +21,10 @@ Class gio_layerClass(void) {
 static CFTypeRef getMetalLayer(CFTypeRef viewRef) {
 	@autoreleasepool {
 		UIView *view = (__bridge UIView *)viewRef;
-		return CFBridgingRetain(view.layer);
+		CAMetalLayer *l = (CAMetalLayer *)view.layer;
+		l.needsDisplayOnBoundsChange = YES;
+		l.presentsWithTransaction = YES;
+		return CFBridgingRetain(l);
 	}
 }
 

app/metal_macos.go

@@ -14,7 +14,11 @@ package app
 
 CALayer *gio_layerFactory(void) {
 	@autoreleasepool {
-		return [CAMetalLayer layer];
+		CAMetalLayer *l = [CAMetalLayer layer];
+		l.autoresizingMask = kCALayerHeightSizable|kCALayerWidthSizable;
+		l.needsDisplayOnBoundsChange = YES;
+		l.presentsWithTransaction = YES;
+		return l;
 	}
 }
 

app/os_macos.go

@@ -195,6 +195,14 @@ static void setScreenFrame(CFTypeRef windowRef, CGFloat x, CGFloat y, CGFloat w,
 	}
 }
 
+static void resetLayerFrame(CFTypeRef viewRef) {
+	@autoreleasepool {
+		NSView* view = (__bridge NSView *)viewRef;
+		NSRect r = view.frame;
+		view.layer.frame = r;
+	}
+}
+
 static void hideWindow(CFTypeRef windowRef) {
 	@autoreleasepool {
 		NSWindow* window = (__bridge NSWindow *)windowRef;
@@ -456,6 +464,9 @@ func (w *window) Configure(options []Option) {
 		C.setWindowStandardButtonHidden(window, C.NSWindowCloseButton, barTrans)
 		C.setWindowStandardButtonHidden(window, C.NSWindowMiniaturizeButton, barTrans)
 		C.setWindowStandardButtonHidden(window, C.NSWindowZoomButton, barTrans)
+		// When toggling the titlebar, the layer doesn't update its frame
+		// until the next resize. Force it.
+		C.resetLayerFrame(w.view)
 	}
 	w.ProcessEvent(ConfigEvent{Config: w.config})
 }