devdraw: cocoa metal screen adds a delayed update

[jxy]

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 a minimal delay to ensure a second screen update.

Fix #268 for the time being and I will see if I can fix it properly.

[jacobvosmaer]

I don't know why but with this patch applied I can still get missed screen updates.

[jxy]

Can you try adding a qlock as in #268 (comment) ?

[jacobvosmaer]

Added this, does not help.

diff --git a/src/cmd/devdraw/cocoa-screen-metal.m b/src/cmd/devdraw/cocoa-screen-metal.m
index 1588992f..6ef95af7 100644
--- a/src/cmd/devdraw/cocoa-screen-metal.m
+++ b/src/cmd/devdraw/cocoa-screen-metal.m
@@ -67,6 +67,7 @@ static DrawLayer *layer;
 static id<MTLDevice> device;
 static id<MTLCommandQueue> commandQueue;
 static id<MTLTexture> texture;
+static QLock texturel;
 
 static Memimage *img = NULL;
 
@@ -795,6 +796,7 @@ struct Cursors {
 
 	LOG(@"display got drawable");
 
+	qlock(&texturel);
 	blit = [cbuf blitCommandEncoder];
 	[blit copyFromTexture:texture
 		sourceSlice:0
@@ -811,6 +813,7 @@ struct Cursors {
 	drawable = nil;
 }
 	[cbuf addCompletedHandler:^(id<MTLCommandBuffer> cmdBuff){
+		qunlock(&texturel);
 		if(cmdBuff.error){
 			NSLog(@"command buffer finished with error: %@",
 				cmdBuff.error.localizedDescription);
@@ -953,7 +956,9 @@ initimg(void)
 	textureDesc.allowGPUOptimizedContents = YES;
 	textureDesc.usage = MTLTextureUsageShaderRead;
 	textureDesc.cpuCacheMode = MTLCPUCacheModeWriteCombined;
+	qlock(&texturel);
 	texture = [device newTextureWithDescriptor:textureDesc];
+	qunlock(&texturel);
 
 	scale = [win backingScaleFactor];
 	[layer setDrawableSize:size];
@@ -981,11 +986,13 @@ _flushmemscreen(Rectangle r)
 	}
 
 	@autoreleasepool{
+		qlock(&texturel);
 		[texture
 			replaceRegion:MTLRegionMake2D(r.min.x, r.min.y, Dx(r), Dy(r))
 			mipmapLevel:0
 			withBytes:byteaddr(img, Pt(r.min.x, r.min.y))
 			bytesPerRow:img->width*sizeof(u32int)];
+		qunlock(&texturel);
 		[AppDelegate
 			performSelectorOnMainThread:@selector(callsetNeedsDisplayInRect:)
 			withObject:[NSValue valueWithRect:NSMakeRect(r.min.x, r.min.y, Dx(r), Dy(r))]

[jxy]

How about increasing the dispatch time?

[jacobvosmaer]

16ms dispatch + qlock: OK.

16ms dispatch without qlock: OK

[rsc]

I changed the code to 16ms and merged this commit. Thank you.