renderer: fix screen tearing issues

Fixes #2569
utmapp · Jul 10, 2021 · 9977a79 · 9977a79
1 parent b186c14
commit 9977a79
Showing 1 changed file with 15 additions and 5 deletions.
diff --git a/Renderer/UTMRenderer.m b/Renderer/UTMRenderer.m
@@ -168,10 +168,6 @@ - (void)drawInMTKView:(nonnull MTKView *)view
         [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
         renderEncoder.label = @"MyRenderEncoder";
 
-        // Lock screen updates
-        dispatch_semaphore_t drawLock = source.drawLock;
-        dispatch_semaphore_wait(drawLock, DISPATCH_TIME_FOREVER);
-
         // Render the screen first
 
         bool hasAlpha = NO;
@@ -245,11 +241,25 @@ - (void)drawInMTKView:(nonnull MTKView *)view
         // Schedule a present once the framebuffer is complete using the current drawable
         [commandBuffer presentDrawable:view.currentDrawable];
 
+        // Lock screen updates
+        __weak dispatch_semaphore_t drawLock = source.drawLock;
+
+        // Acquire lock before GPU schedules rendering
+        [commandBuffer addScheduledHandler:^(id<MTLCommandBuffer> commandBuffer) {
+            dispatch_semaphore_t _drawLock = drawLock;
+            if (_drawLock) {
+                dispatch_semaphore_wait(drawLock, DISPATCH_TIME_FOREVER);
+            }
+        }];
+
         // Release lock after GPU is done
         [commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> commandBuffer) {
             // GPU work is complete
             // Signal the semaphore to start the CPU work
-            dispatch_semaphore_signal(drawLock);
+            dispatch_semaphore_t _drawLock = drawLock;
+            if (_drawLock) {
+                dispatch_semaphore_signal(_drawLock);
+            }
         }];
     }