Uses DisplayMetrics to disable supersampling when too slow.

OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme

@@ -67,7 +67,7 @@
       </Testables>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Release"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       enableASanStackUseAfterReturn = "YES"

OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm

@@ -276,6 +276,7 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 	// Additional pipeline information.
 	size_t _lumaKernelSize;
 	size_t _chromaKernelSize;
+	std::atomic<bool> _isUsingSupersampling;
 
 	// The output view.
 	__weak MTKView *_view;
@@ -359,14 +360,22 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 	[self setAspectRatio];
 
 	@synchronized(self) {
+		// Always [re]try multisampling upon a resize.
+		_scanTarget.display_metrics_.announce_did_resize();
+		_isUsingSupersampling = true;
 		[self updateSizeBuffersToSize:size];
 	}
 }
 
+- (void)updateSizeBuffers {
+	@synchronized(self) {
+		[self updateSizeBuffersToSize:_view.drawableSize];
+	}
+}
+
 - (void)updateSizeBuffersToSize:(CGSize)size {
-	// TODO: above what size threshold is supersampling no longer desired?
+	const NSUInteger frameBufferWidth = NSUInteger(size.width * _view.layer.contentsScale) * (_isUsingSupersampling ? 2 : 1);
-	const NSUInteger frameBufferWidth = NSUInteger(size.width * _view.layer.contentsScale) * 2;
+	const NSUInteger frameBufferHeight = NSUInteger(size.height * _view.layer.contentsScale) * (_isUsingSupersampling ? 2 : 1);
-	const NSUInteger frameBufferHeight = NSUInteger(size.height * _view.layer.contentsScale) * 2;
 
 	// Generate a framebuffer and a stencil.
 	MTLTextureDescriptor *const textureDescriptor = [MTLTextureDescriptor
@@ -1075,9 +1084,16 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
  */
 - (void)drawInMTKView:(nonnull MTKView *)view {
 	if(_isDrawing.test_and_set()) {
+		_scanTarget.display_metrics_.announce_draw_status(false);
 		return;
 	}
 
+	// Disable supersampling if performance requires it.
+	if(_isUsingSupersampling && _scanTarget.display_metrics_.should_lower_resolution()) {
+		_isUsingSupersampling = false;
+		[self updateSizeBuffers];
+	}
+
 	// Schedule a copy from the current framebuffer to the view; blitting is unavailable as the target is a framebuffer texture.
 	id<MTLCommandBuffer> commandBuffer = [_commandQueue commandBuffer];
 
@@ -1085,7 +1101,7 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 	view.currentRenderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionDontCare;
 	id<MTLRenderCommandEncoder> encoder = [commandBuffer renderCommandEncoderWithDescriptor:view.currentRenderPassDescriptor];
 
-	[encoder setRenderPipelineState:_supersamplePipeline];
+	[encoder setRenderPipelineState:_isUsingSupersampling ? _supersamplePipeline : _copyPipeline];
 	[encoder setVertexTexture:_frameBuffer atIndex:0];
 	[encoder setFragmentTexture:_frameBuffer atIndex:0];
 
@@ -1095,6 +1111,7 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 	[commandBuffer presentDrawable:view.currentDrawable];
 	[commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> _Nonnull) {
 		self->_isDrawing.clear();
+		self->_scanTarget.display_metrics_.announce_draw_status(true);
 	}];
 	[commandBuffer commit];
 }

Outputs/DisplayMetrics.cpp

@@ -50,7 +50,7 @@ void Metrics::announce_did_resize() {
 	frames_missed_ = frames_hit_ = 0;
 }
 
-void Metrics::announce_draw_status(size_t, std::chrono::high_resolution_clock::duration, bool complete) {
+void Metrics::announce_draw_status(bool complete) {
 	if(!complete) {
 		++frames_missed_;
 	} else {
@@ -79,6 +79,10 @@ void Metrics::announce_draw_status(size_t, std::chrono::high_resolution_clock::d
 	}
 }
 
+void Metrics::announce_draw_status(size_t, std::chrono::high_resolution_clock::duration, bool complete) {
+	announce_draw_status(complete);
+}
+
 bool Metrics::should_lower_resolution() const {
 	// If less than 100 frames are on record, return no opinion; otherwise
 	// suggest a lower resolution if more than 10 frames in the last 100-200

Outputs/DisplayMetrics.hpp

@@ -33,6 +33,9 @@ class Metrics {
 		/// Provides Metrics with a new data point for output speed estimation.
 		void announce_draw_status(size_t lines, std::chrono::high_resolution_clock::duration duration, bool complete);
 
+		/// Provides Metrics with a new data point for output speed estimation, albeit without line-specific information.
+		void announce_draw_status(bool complete);
+
 		/// @returns @c true if Metrics thinks a lower output buffer resolution is desirable in the abstract; @c false otherwise.
 		bool should_lower_resolution() const;