box-car-2d/GLEssentials/OSX/GLView.m

//
//
//  OSX GLEssentials
//
//  Copied from the Apple GLEssentials
//
//

#import "GLView.h"
#import "Game.h"

@import GLKit;
@import QuartzCore;

@interface GLView (){
   	CVDisplayLinkRef displayLink;
    Game* game;
}
- (void) initGL;
@end

@implementation GLView

- (CVReturn) getFrameForTime:(const CVTimeStamp*)outputTime{
	// There is no autorelease pool when this method is called
	// because it will be called from a background thread.
	// It's important to create one or app can leak objects.
	@autoreleasepool {
		[self drawView];
		return kCVReturnSuccess;
	}
}

// This is the renderer output callback function
static CVReturn MyDisplayLinkCallback(CVDisplayLinkRef displayLink,
									  const CVTimeStamp* now,
									  const CVTimeStamp* outputTime,
									  CVOptionFlags flagsIn,
									  CVOptionFlags* flagsOut, 
									  void* displayLinkContext)
{
    CVReturn result = [(__bridge GLView*)displayLinkContext getFrameForTime:outputTime];
    return result;
}

- (void) awakeFromNib{
    NSOpenGLPixelFormatAttribute attrs[] = {
		NSOpenGLPFADoubleBuffer,
		NSOpenGLPFADepthSize, 24,
		NSOpenGLPFAOpenGLProfile,
		NSOpenGLProfileVersion3_2Core,
		0
	};
	
	NSOpenGLPixelFormat *pf = [[NSOpenGLPixelFormat alloc] initWithAttributes:attrs];
	assert(pf);
	   
    NSOpenGLContext* context = [[NSOpenGLContext alloc] initWithFormat:pf shareContext:nil];
    assert(context);
    
#ifdef DEBUG
	// When we're using a CoreProfile context, crash if we call a legacy OpenGL function
	// This will make it much more obvious where and when such a function call is made so
	// that we can remove such calls.
	// Without this we'd simply get GL_INVALID_OPERATION error for calling legacy functions
	// but it would be more difficult to see where that function was called.
	CGLEnable([context CGLContextObj], kCGLCECrashOnRemovedFunctions);
#endif
	
    self.pixelFormat = pf;
    self.openGLContext = context;
    
    // Opt-In to Retina resolution
    self.wantsBestResolutionOpenGLSurface = YES;
}

- (void) prepareOpenGL{
	[super prepareOpenGL];
	
	// Make all the OpenGL calls to setup rendering  
	//  and build the necessary rendering objects
	[self initGL];
	
	// 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 *)(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);
	
	// Register to be notified when the window closes so we can stop the displaylink
	[[NSNotificationCenter defaultCenter] addObserver:self
											 selector:@selector(windowWillClose:)
												 name:NSWindowWillCloseNotification
											   object:[self window]];
}

- (void) windowWillClose:(NSNotification*)notification{
	// Stop the display link when the window is closing because default
	// OpenGL render buffers will be destroyed.  If display link continues to
	// fire without renderbuffers, OpenGL draw calls will set errors.
	
	CVDisplayLinkStop(displayLink);
}

- (void) initGL{
	// The reshape function may have changed the thread to which our OpenGL
	// context is attached before prepareOpenGL and initGL are called.  So call
	// makeCurrentContext to ensure that our OpenGL context current to this 
	// thread (i.e. makeCurrentContext directs all OpenGL calls on this thread
	// to [self openGLContext])
	[[self openGLContext] makeCurrentContext];
	
	// Synchronize buffer swaps with vertical refresh rate
	GLint swapInt = 1;
	[[self openGLContext] setValues:&swapInt forParameter:NSOpenGLCPSwapInterval];
	
	game = [[Game alloc] init];
}

- (void) reshape{
	[super reshape];
	
	// We draw on a secondary thread through the display link. However, when
	// resizing the view, -drawRect is called on the main thread.
	// Add a mutex around to avoid the threads accessing the context
	// simultaneously when resizing.
	CGLLockContext([self.openGLContext CGLContextObj]);

	NSRect viewRectPoints = self.bounds;
    
    // [NSView convertRectToBacking] converts point sizes to pixel sizes.
    // viewRectPixels will be larger (2x) than viewRectPoints for retina displays.
    // viewRectPixels will be the same as viewRectPoints for non-retina displays
    NSRect viewRectPixels = [self convertRectToBacking:viewRectPoints];
    game.windowSize = viewRectPixels.size;
	
	CGLUnlockContext([self.openGLContext CGLContextObj]);
}


- (void)renewGState{
	// Called whenever graphics state updated (such as window resize)
	
	// OpenGL rendering is not synchronous with other rendering on the OSX.
	// Therefore, call disableScreenUpdatesUntilFlush so the window server
	// doesn't render non-OpenGL content in the window asynchronously from
	// OpenGL content, which could cause flickering.  (non-OpenGL content
	// includes the title bar and drawing done by the app with other APIs)
	[[self window] disableScreenUpdatesUntilFlush];

	[super renewGState];
}

- (void) drawRect: (NSRect) theRect{
	// Called during resize operations
	// Avoid flickering during resize by drawiing	
	[self drawView];
}

- (void) drawView{
	[[self openGLContext] makeCurrentContext];

	// We draw on a secondary thread through the display link
	// When resizing the view, -reshape is called automatically on the main
	// thread. Add a mutex around to avoid the threads accessing the context
	// simultaneously when resizing
	CGLLockContext([[self openGLContext] CGLContextObj]);
    
    NSRect viewRectPoints = self.bounds;
    NSRect viewRectPixels = [self convertRectToBacking:viewRectPoints];
    
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
	glViewport(0, 0, (int)viewRectPixels.size.width, (int)viewRectPixels.size.height);

    [game update:1/60.0f];
	[game draw];

	CGLFlushDrawable([[self openGLContext] CGLContextObj]);
	CGLUnlockContext([[self openGLContext] CGLContextObj]);
}

- (void) dealloc{
	// Stop the display link BEFORE releasing anything in the view
    // otherwise the display link thread may call into the view and crash
    // when it encounters something that has been release
	CVDisplayLinkStop(displayLink);
	CVDisplayLinkRelease(displayLink);

	// Release the display link AFTER display link has been released
	
}
@end