diff --git a/OSBindings/Mac/Clock Signal/Documents/ElectronDocument.swift b/OSBindings/Mac/Clock Signal/Documents/ElectronDocument.swift
index 43cb38475..4568d6982 100644
--- a/OSBindings/Mac/Clock Signal/Documents/ElectronDocument.swift	
+++ b/OSBindings/Mac/Clock Signal/Documents/ElectronDocument.swift	
@@ -61,8 +61,8 @@ class ElectronDocument: MachineDocument {
 		electron.runForNumberOfCycles(numberOfCycles)
 	}
 
-	override func openGLViewDrawView(view: CSCathodeRayView) {
-		electron.drawViewForPixelSize(view.backingSize)
+	override func openGLView(view: CSCathodeRayView, drawViewOnlyIfDirty onlyIfDirty: Bool) {
+		electron.drawViewForPixelSize(view.backingSize, onlyIfDirty: onlyIfDirty)
 	}
 
 	// MARK: CSOpenGLViewResponderDelegate
diff --git a/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift b/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift
index 126eb2a9d..e1f14f833 100644
--- a/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift	
+++ b/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift	
@@ -46,7 +46,7 @@ class MachineDocument: NSDocument, CSCathodeRayViewDelegate, CSCathodeRayViewRes
 		lastCycleCount = cycleCount
 	}
 
-	func openGLViewDrawView(view: CSCathodeRayView) {}
+	func openGLView(view: CSCathodeRayView, drawViewOnlyIfDirty onlyIfDirty: Bool) {}
 	func runForNumberOfCycles(numberOfCycles: Int32) {}
 
 	// MARK: CSOpenGLViewResponderDelegate
diff --git a/OSBindings/Mac/Clock Signal/Views/CSCathodeRayView.h b/OSBindings/Mac/Clock Signal/Views/CSCathodeRayView.h
index abecc655b..a463953d5 100644
--- a/OSBindings/Mac/Clock Signal/Views/CSCathodeRayView.h	
+++ b/OSBindings/Mac/Clock Signal/Views/CSCathodeRayView.h	
@@ -13,7 +13,7 @@
 
 @protocol CSCathodeRayViewDelegate
 - (void)openGLView:(nonnull CSCathodeRayView *)view didUpdateToTime:(CVTimeStamp)time;
-- (void)openGLViewDrawView:(nonnull CSCathodeRayView *)view;
+- (void)openGLView:(nonnull CSCathodeRayView *)view drawViewOnlyIfDirty:(BOOL)onlyIfDirty;
 @end
 
 @protocol CSCathodeRayViewResponderDelegate <NSObject>
diff --git a/OSBindings/Mac/Clock Signal/Views/CSCathodeRayView.m b/OSBindings/Mac/Clock Signal/Views/CSCathodeRayView.m
index 069f10dd0..1dc801978 100644
--- a/OSBindings/Mac/Clock Signal/Views/CSCathodeRayView.m	
+++ b/OSBindings/Mac/Clock Signal/Views/CSCathodeRayView.m	
@@ -76,6 +76,7 @@ static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeSt
 {
 	CSCathodeRayView *view = (__bridge CSCathodeRayView *)displayLinkContext;
 	[view.delegate openGLView:view didUpdateToTime:*now];
+	[view drawViewOnlyIfDirty:YES];
 	return kCVReturnSuccess;
 }
 
@@ -291,15 +292,15 @@ static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeSt
 
 - (void)drawRect:(NSRect)dirtyRect
 {
-	[self drawView];
+	[self drawViewOnlyIfDirty:NO];
 }
 
-- (void)drawView
+- (void)drawViewOnlyIfDirty:(BOOL)onlyIfDirty
 {
 	[self.openGLContext makeCurrentContext];
 	CGLLockContext([[self openGLContext] CGLContextObj]);
 
-	[self.delegate openGLViewDrawView:self];
+	[self.delegate openGLView:self drawViewOnlyIfDirty:onlyIfDirty];
 
 	CGLFlushDrawable([[self openGLContext] CGLContextObj]);
 	CGLUnlockContext([[self openGLContext] CGLContextObj]);
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.h b/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.h
index a58cf49cc..7902fee52 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.h	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.h	
@@ -18,6 +18,6 @@
 
 - (void)setKey:(uint16_t)key isPressed:(BOOL)isPressed;
 
-- (void)drawViewForPixelSize:(CGSize)pixelSize;
+- (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty;
 
 @end
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm b/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm
index 11957973b..a48cde887 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm	
@@ -32,8 +32,8 @@
 	_electron.set_rom((Electron::ROMSlot)slot, rom.length, (const uint8_t *)rom.bytes);
 }
 
-- (void)drawViewForPixelSize:(CGSize)pixelSize {
-	_electron.get_crt()->draw_frame((int)pixelSize.width, (int)pixelSize.height, false);
+- (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty {
+	_electron.get_crt()->draw_frame((int)pixelSize.width, (int)pixelSize.height, onlyIfDirty ? true : false);
 }
 
 - (BOOL)openUEFAtURL:(NSURL *)URL {
diff --git a/Outputs/CRT/CRTOpenGL.cpp b/Outputs/CRT/CRTOpenGL.cpp
index 5c815a904..83ed3a0b9 100644
--- a/Outputs/CRT/CRTOpenGL.cpp
+++ b/Outputs/CRT/CRTOpenGL.cpp
@@ -37,7 +37,7 @@ static GLenum formatForDepth(unsigned int depth)
 {
 	switch(depth)
 	{
-		default: return -1;
+		default: return GL_FALSE;
 		case 1: return GL_RED;
 		case 2: return GL_RG;
 		case 3: return GL_RGB;
@@ -64,50 +64,44 @@ void CRT::draw_frame(int output_width, int output_height, bool only_if_dirty)
 {
 	_current_frame_mutex->lock();
 
-	if(!_current_frame)
+	if(!_current_frame || !only_if_dirty)
 	{
 		glClear(GL_COLOR_BUFFER_BIT);
 	}
-	else
+
+	if(_current_frame && _current_frame != _last_drawn_frame)
 	{
-		if(_current_frame != _last_drawn_frame)
+		if(!_openGL_state)
 		{
-			if(!_openGL_state)
-			{
-				_openGL_state = new OpenGLState;
-
-				glGenTextures(1, &_openGL_state->textureName);
-				glBindTexture(GL_TEXTURE_2D, _openGL_state->textureName);
-				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
-				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
-
-				glGenVertexArrays(1, &_openGL_state->vertexArray);
-				glBindVertexArray(_openGL_state->vertexArray);
-				glGenBuffers(1, &_openGL_state->arrayBuffer);
-				glBindBuffer(GL_ARRAY_BUFFER, _openGL_state->arrayBuffer);
-			}
-
-			glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)(_current_frame->number_of_vertices * _current_frame->size_per_vertex), _current_frame->vertices, GL_DYNAMIC_DRAW);
+			_openGL_state = new OpenGLState;
 
+			glGenTextures(1, &_openGL_state->textureName);
 			glBindTexture(GL_TEXTURE_2D, _openGL_state->textureName);
-			if(_openGL_state->textureSize.width != _current_frame->size.width || _openGL_state->textureSize.height != _current_frame->size.height)
-			{
-				GLenum format = formatForDepth(_current_frame->buffers[0].depth);
-				glTexImage2D(GL_TEXTURE_2D, 0, (GLint)format, _current_frame->size.width, _current_frame->size.height, 0, format, GL_UNSIGNED_BYTE, _current_frame->buffers[0].data);
-				_openGL_state->textureSize = _current_frame->size;
+			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 
-				if(_openGL_state->textureSizeUniform >= 0) glUniform2f(_openGL_state->textureSizeUniform, _current_frame->size.width, _current_frame->size.height);
-			}
-			else
-				glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, _current_frame->dirty_size.width, _current_frame->dirty_size.height, formatForDepth(_current_frame->buffers[0].depth), GL_UNSIGNED_BYTE, _current_frame->buffers[0].data);
+			glGenVertexArrays(1, &_openGL_state->vertexArray);
+			glBindVertexArray(_openGL_state->vertexArray);
+			glGenBuffers(1, &_openGL_state->arrayBuffer);
+			glBindBuffer(GL_ARRAY_BUFFER, _openGL_state->arrayBuffer);
 		}
-	}
 
-	if(_current_frame != _last_drawn_frame || only_if_dirty)
-	{
-		glClear(GL_COLOR_BUFFER_BIT);
+		glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)(_current_frame->number_of_vertices * _current_frame->size_per_vertex), _current_frame->vertices, GL_DYNAMIC_DRAW);
+
+		glBindTexture(GL_TEXTURE_2D, _openGL_state->textureName);
+		if(_openGL_state->textureSize.width != _current_frame->size.width || _openGL_state->textureSize.height != _current_frame->size.height)
+		{
+			GLenum format = formatForDepth(_current_frame->buffers[0].depth);
+			glTexImage2D(GL_TEXTURE_2D, 0, (GLint)format, _current_frame->size.width, _current_frame->size.height, 0, format, GL_UNSIGNED_BYTE, _current_frame->buffers[0].data);
+			_openGL_state->textureSize = _current_frame->size;
+
+			if(_openGL_state->textureSizeUniform >= 0) glUniform2f(_openGL_state->textureSizeUniform, _current_frame->size.width, _current_frame->size.height);
+		}
+		else
+			glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, _current_frame->dirty_size.width, _current_frame->dirty_size.height, formatForDepth(_current_frame->buffers[0].depth), GL_UNSIGNED_BYTE, _current_frame->buffers[0].data);
+
 		glDrawArrays(GL_TRIANGLES, 0, (GLsizei)_current_frame->number_of_vertices);
 	}