From 4496493e85df55936fbfc432ec181c82748e10c7 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 16 Jul 2015 21:16:21 -0400
Subject: [PATCH] Performed the bare necessary steps to get my little OpenGL
 view to create a CVDisplayLink and then repaint itself in time with the
 display.

---
 .../Base.lproj/Atari2600Document.xib          | 13 ++++++-
 OSBindings/Mac/Clock Signal/OpenGLView.m      | 35 +++++++++++++++----
 2 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/OSBindings/Mac/Clock Signal/Base.lproj/Atari2600Document.xib b/OSBindings/Mac/Clock Signal/Base.lproj/Atari2600Document.xib
index 7b26bd57f..8effec6d7 100644
--- a/OSBindings/Mac/Clock Signal/Base.lproj/Atari2600Document.xib	
+++ b/OSBindings/Mac/Clock Signal/Base.lproj/Atari2600Document.xib	
@@ -17,9 +17,20 @@
             <rect key="contentRect" x="133" y="235" width="507" height="413"/>
             <rect key="screenRect" x="0.0" y="0.0" width="2560" height="1417"/>
             <value key="minSize" type="size" width="94" height="86"/>
-            <view key="contentView" id="gIp-Ho-8D9" customClass="CSOpenGLView">
+            <view key="contentView" id="gIp-Ho-8D9">
                 <rect key="frame" x="0.0" y="0.0" width="507" height="413"/>
                 <autoresizingMask key="autoresizingMask"/>
+                <subviews>
+                    <openGLView useAuxiliaryDepthBufferStencil="NO" allowOffline="YES" wantsBestResolutionOpenGLSurface="YES" translatesAutoresizingMaskIntoConstraints="NO" id="DEG-fq-cjd" customClass="CSOpenGLView">
+                        <rect key="frame" x="0.0" y="0.0" width="507" height="413"/>
+                    </openGLView>
+                </subviews>
+                <constraints>
+                    <constraint firstItem="DEG-fq-cjd" firstAttribute="centerX" secondItem="gIp-Ho-8D9" secondAttribute="centerX" id="ES5-nL-N3h"/>
+                    <constraint firstItem="DEG-fq-cjd" firstAttribute="height" secondItem="gIp-Ho-8D9" secondAttribute="height" id="YoB-qI-LFX"/>
+                    <constraint firstItem="DEG-fq-cjd" firstAttribute="centerY" secondItem="gIp-Ho-8D9" secondAttribute="centerY" id="d5Y-3a-CEI"/>
+                    <constraint firstItem="DEG-fq-cjd" firstAttribute="width" secondItem="gIp-Ho-8D9" secondAttribute="width" id="mYS-bH-DST"/>
+                </constraints>
             </view>
             <connections>
                 <outlet property="delegate" destination="-2" id="0bl-1N-x8E"/>
diff --git a/OSBindings/Mac/Clock Signal/OpenGLView.m b/OSBindings/Mac/Clock Signal/OpenGLView.m
index e4475dee1..023353c6f 100644
--- a/OSBindings/Mac/Clock Signal/OpenGLView.m	
+++ b/OSBindings/Mac/Clock Signal/OpenGLView.m	
@@ -13,15 +13,38 @@
 	CVDisplayLinkRef displayLink;
 }
 
-- (instancetype)initWithCoder:(nonnull NSCoder *)coder
+- (void)prepareOpenGL
 {
-	self = [super initWithCoder:coder];
+	// Synchronize buffer swaps with vertical refresh rate
+	GLint swapInt = 1;
+	[[self openGLContext] setValues:&swapInt forParameter:NSOpenGLCPSwapInterval];
 
-	if(self)
-	{
-	}
+	// Create a display link capable of being used with all active displays
+	CVDisplayLinkCreateWithActiveCGDisplays(&displayLink);
+ 
+	// Set the renderer output callback function
+	CVDisplayLinkSetOutputCallback(displayLink, &MyDisplayLinkCallback, (__bridge void * __nullable)(self));
+ 
+	// Set the display link for the current renderer
+	CGLContextObj cglContext = [[self openGLContext] CGLContextObj];
+	CGLPixelFormatObj cglPixelFormat = [[self pixelFormat] CGLPixelFormatObj];
+	CVDisplayLinkSetCurrentCGDisplayFromOpenGLContext(displayLink, cglContext, cglPixelFormat);
+ 
+	// Activate the display link
+	CVDisplayLinkStart(displayLink);
+}
 
-	return self;
+// This is the renderer output callback function
+static CVReturn MyDisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeStamp* now, const CVTimeStamp* outputTime, CVOptionFlags flagsIn, CVOptionFlags* flagsOut, void* displayLinkContext)
+{
+	[(__bridge CSOpenGLView *)displayLinkContext setNeedsDisplay:YES];
+	return kCVReturnSuccess;
+}
+ 
+- (void)dealloc
+{
+	// Release the display link
+	CVDisplayLinkRelease(displayLink);
 }
 
 @end