ExampleCAOpenGLLayer.m

//
// File:       ExampleCAOpenGLLayer.m
//
// Abstract:   A sample CAOpenGLLayer subclass that demonstrates how to use
//             a CAOpenGLLayer to provide content.
//
// Version:    1.0
//
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#import <OpenGL/OpenGL.h>
#import "ExampleCAOpenGLLayer.h"
 
@implementation ExampleCAOpenGLLayer
 
// Numbers (and file layout) is in the typical order that these messages will be sent.
 
// 1)   [Optional] This message is sent prior to get a description of the pixel format that you need to render your content.
//      This pixel format should use the given display mask for the kCGLPFADisplayMask format attribute for optimal performance.
-(CGLPixelFormatObj)copyCGLPixelFormatForDisplayMask:(uint32_t)mask
{
    // The default is fine for this demonstration.
    return [super copyCGLPixelFormatForDisplayMask:mask];
}
 
// 2)   [Optional] This message is sent prior to rendering to create a context to render to.
//      You would typically override this method if you needed to specify a share context to share OpenGL resources.
//      This is also an ideal location to do any initialization that is necessary for the context returned
-(CGLContextObj)copyCGLContextForPixelFormat:(CGLPixelFormatObj)pixelFormat
{
    // Default handling is fine for this demonstration.
    return [super copyCGLContextForPixelFormat:pixelFormat];
}
 
// 3)   [Optional] This message is sent prior to rendering a frame to determine if the layer has new content.
//      If this layer is asynchronous and has internal knowledge of when the content has changed
//      then you would want to implement this message in order to inform Core Animation when you have new content.
//      If the layer is not asynchronous, or you always have new content you do not need to implement this message.
-(BOOL)canDrawInCGLContext:(CGLContextObj)glContext pixelFormat:(CGLPixelFormatObj)pixelFormat forLayerTime:(CFTimeInterval)timeInterval displayTime:(const CVTimeStamp *)timeStamp
{
    // Just like the default, we'll just always return YES and always refresh.
    // You normally would not override this method to do this.
    return YES;
}
 
// 4)   [Required] Implement this message in order to actually draw anything.
//      Typically you will do the following when you recieve this message:
//      1. Draw your OpenGL content! (the current context has already been set)
//      2. call [super drawInContext:pixelFormat:forLayerTime:displayTime:] to finalize the layer content, or call glFlush().
//      NOTE: The viewport has already been set correctly by the time this message is sent, so you do not need to set it yourself.
//      The viewport is automatically updated whenever the layer is displayed (that is, when the -display message is sent).
//      This is arranged for when you send the -setNeedsDisplay message, or when the needsDisplayOnBoundsChange property is set to YES
//      and the layer's size changes.
-(void)drawInCGLContext:(CGLContextObj)glContext pixelFormat:(CGLPixelFormatObj)pixelFormat forLayerTime:(CFTimeInterval)timeInterval displayTime:(const CVTimeStamp *)timeStamp
{
    // Set the current context to the one given to us.
    CGLSetCurrentContext(glContext);
 
    // We're just going to draw a single red quad spinning around based on the current time. Nothing particularly fancy.
    GLfloat rotate = timeInterval * 60.0; // 60 degrees per second!
    glClear(GL_COLOR_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glRotatef(rotate, 0.0, 0.0, 1.0);
    glBegin(GL_QUADS);
        glColor3f(1.0, 0.0, 0.0);
        glVertex2f(-0.5, -0.5);
        glVertex2f(-0.5,  0.5);
        glVertex2f( 0.5,  0.5);
        glVertex2f( 0.5, -0.5);
    glEnd();
    glPopMatrix();
    
    // Call super to finalize the drawing. By default all it does is call glFlush().
    [super drawInCGLContext:glContext pixelFormat:pixelFormat forLayerTime:timeInterval displayTime:timeStamp];
}
 
// 5)   [Optional] Called when the context given is no longer needed.
//      This is a good place to cleaup any context specific initializations that are necessary (which is usually none).
//      It is not typical to override this method.
-(void)releaseCGLContext:(CGLContextObj)glContext
{
    [super releaseCGLContext:glContext];
}
 
// 6)   [Optional] Called when the given pixel format is no longer needed.
//      It is not typical to override this method.
-(void)releaseCGLPixelFormat:(CGLPixelFormatObj)pixelFormat
{
    [super releaseCGLPixelFormat:pixelFormat];
}
 
@end