commit e995a0c101863688d5f14649ae3de45a7c43789c
from: Xiao-Yong <xjin@anl.gov>
via: Russ Cox <rsc@swtch.com>
date: Wed Jun 19 18:32:57 2019 UTC

devdraw: cocoa metal screen adds a delayed update (#270)

The immediate display of the screen sometimes miss the update from
the CPU side memory.  No obvious synchronization mechanism is available.
In order to make sure the screen updates properly, we set needsDisplay
again after 16ms delay to ensure a second screen update.

commit - d4e16c838ab2cccd97ad6e24fc290239666eaaac
commit + e995a0c101863688d5f14649ae3de45a7c43789c
blob - 959df59bf7832d0baef883599ac36162b99b1c37
blob + 984ede03385731021a5e00263c5ffec54a7f1341
--- src/cmd/devdraw/cocoa-screen-metal.m
+++ src/cmd/devdraw/cocoa-screen-metal.m
@@ -212,12 +212,19 @@ threadmain(int argc, char **argv)
 + (void)callsetNeedsDisplayInRect:(NSValue *)v
 {
 	NSRect r;
+	dispatch_time_t time;
 
 	r = [v rectValue];
 	LOG(@"callsetNeedsDisplayInRect(%g, %g, %g, %g)", r.origin.x, r.origin.y, r.size.width, r.size.height);
 	r = [win convertRectFromBacking:r];
 	LOG(@"setNeedsDisplayInRect(%g, %g, %g, %g)", r.origin.x, r.origin.y, r.size.width, r.size.height);
 	[layer setNeedsDisplayInRect:r];
+
+	time = dispatch_time(DISPATCH_TIME_NOW, 16 * NSEC_PER_MSEC);
+	dispatch_after(time, dispatch_get_main_queue(), ^(void){
+		[layer setNeedsDisplayInRect:r];
+	});
+
 	[myContent enlargeLastInputRect:r];
 }