//

// 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