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 |
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