From 23be799a67e15e0a35b385fb53c9b928b23c84c2 Mon Sep 17 00:00:00 2001
From: rogerman <rogerman@users.noreply.github.com>
Date: Sat, 3 Feb 2018 21:21:54 -0800
Subject: [PATCH] Cocoa Port: Metal display views no longer lose visible frames
 when running multiple display views.

---
 .../cocoa/userinterface/MacMetalDisplayView.h |  1 +
 .../userinterface/MacMetalDisplayView.mm      | 35 ++++++++++++++-----
 2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/desmume/src/frontend/cocoa/userinterface/MacMetalDisplayView.h b/desmume/src/frontend/cocoa/userinterface/MacMetalDisplayView.h
index bf5a64fe0..865258710 100644
--- a/desmume/src/frontend/cocoa/userinterface/MacMetalDisplayView.h
+++ b/desmume/src/frontend/cocoa/userinterface/MacMetalDisplayView.h
@@ -259,6 +259,7 @@ typedef DisplayViewShaderProperties DisplayViewShaderProperties;
 {
 	MacDisplayLayeredView *_cdv;
 	MacMetalDisplayPresenterObject *presenterObject;
+	dispatch_semaphore_t _semDrawable;
 }
 
 @property (readonly, nonatomic) MacMetalDisplayPresenterObject *presenterObject;
diff --git a/desmume/src/frontend/cocoa/userinterface/MacMetalDisplayView.mm b/desmume/src/frontend/cocoa/userinterface/MacMetalDisplayView.mm
index c858aef59..51742cfb5 100644
--- a/desmume/src/frontend/cocoa/userinterface/MacMetalDisplayView.mm
+++ b/desmume/src/frontend/cocoa/userinterface/MacMetalDisplayView.mm
@@ -2147,6 +2147,7 @@
 	}
 	
 	_cdv = NULL;
+	_semDrawable = dispatch_semaphore_create(3);
 	
 	presenterObject = thePresenterObject;
 	if (thePresenterObject != nil)
@@ -2160,6 +2161,13 @@
 	return self;
 }
 
+- (void)dealloc
+{
+	dispatch_release(_semDrawable);
+	
+	[super dealloc];
+}
+
 - (void) setupLayer
 {
 	if ([self device] == nil)
@@ -2174,33 +2182,44 @@
 	@autoreleasepool
 	{
 		// Now that everything is set up, go ahead and draw everything.
-		id<CAMetalDrawable> layerDrawable = [self nextDrawable];
+		dispatch_semaphore_wait(_semDrawable, DISPATCH_TIME_FOREVER);
+		id<CAMetalDrawable> layerDrawable = [[self nextDrawable] retain];
 		
 		if (layerDrawable != nil)
 		{
 			[[presenterObject colorAttachment0Desc] setTexture:[layerDrawable texture]];
-			id<MTLCommandBuffer> cb = [presenterObject newCommandBuffer];
+			id<MTLCommandBuffer> cbRender = [presenterObject newCommandBuffer];
+			id<MTLCommandBuffer> cbPresent = [presenterObject newCommandBuffer];
 			
 			const MetalTexturePair texProcess = [presenterObject texPairProcess];
 			const MetalRenderFrameInfo mrfi = [presenterObject renderFrameInfo];
 			
-			[presenterObject renderForCommandBuffer:cb
+			[presenterObject renderForCommandBuffer:cbRender
 								outputPipelineState:[presenterObject outputDrawablePipeline]
 								   hudPipelineState:[[presenterObject sharedData] hudPipeline]
 										texDisplays:texProcess
 											   mrfi:mrfi];
 			
-			[cb presentDrawable:layerDrawable];
-			
-			[cb addScheduledHandler:^(id<MTLCommandBuffer> block) {
+			[cbRender addScheduledHandler:^(id<MTLCommandBuffer> block) {
 				[presenterObject setRenderBufferState:ClientDisplayBufferState_Reading index:mrfi.renderIndex];
 			}];
 			
-			[cb addCompletedHandler:^(id<MTLCommandBuffer> block) {
+			[cbRender addCompletedHandler:^(id<MTLCommandBuffer> block) {
 				[presenterObject renderFinishAtIndex:mrfi.renderIndex];
 			}];
 			
-			[cb commit];
+			[cbPresent presentDrawable:layerDrawable];
+			[cbPresent addCompletedHandler:^(id<MTLCommandBuffer> block) {
+				[layerDrawable release];
+				dispatch_semaphore_signal(_semDrawable);
+			}];
+			
+			[cbRender commit];
+			[cbPresent commit];
+		}
+		else
+		{
+			dispatch_semaphore_signal(_semDrawable);
 		}
 	}
 }