EAGLView.h

//
//  EAGLView.h
//  OpenGLES_iPhone
//
//  Created by mmalc Crawford on 11/18/10.
//  Copyright 2010 Apple Inc. All rights reserved.
//

#import <UIKit/UIKit.h>

#import <OpenGLES/ES1/gl.h>
#import <OpenGLES/ES1/glext.h>
#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/ES2/glext.h>

#define HAS_EAGLVIEW_DEPTH_BUFFER 1

@class EAGLContext;

// This class wraps the CAEAGLLayer from CoreAnimation into a convenient UIView subclass.
// The view content is basically an EAGL surface you render your OpenGL scene into.
// Note that setting the view non-opaque will only work if the EAGL surface has an alpha channel.
@interface EAGLView : UIView {
@private
    // The pixel dimensions of the CAEAGLLayer.
    GLint framebufferWidth;
    GLint framebufferHeight;
    
    // The OpenGL ES names for the framebuffer and renderbuffer used to render to this view.
    GLuint defaultFramebuffer, colorRenderbuffer;
	
#if HAS_EAGLVIEW_DEPTH_BUFFER
	GLuint depthRenderbuffer;
#endif
}

@property (nonatomic, retain) EAGLContext *context;

- (void)setFramebuffer;
- (BOOL)presentFramebuffer;

@end

EAGLView.m

//
//  EAGLView.m
//  OpenGLES_iPhone
//
//  Created by mmalc Crawford on 11/18/10.
//  Copyright 2010 Apple Inc. All rights reserved.
//

#import <QuartzCore/QuartzCore.h>

#import "EAGLView.h"

@interface EAGLView (PrivateMethods)
- (void)createFramebuffer;
- (void)deleteFramebuffer;
@end

@implementation EAGLView

@synthesize context;

// You must implement this method
+ (Class)layerClass
{
    return [CAEAGLLayer class];
}

//The EAGL view is stored in the nib file. When it's unarchived it's sent -initWithCoder:.
- (id)initWithCoder:(NSCoder*)coder
{
    self = [super initWithCoder:coder];
	if (self) {
        CAEAGLLayer *eaglLayer = (CAEAGLLayer *)self.layer;
        
        eaglLayer.opaque = TRUE;
        eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:
                                        [NSNumber numberWithBool:FALSE], kEAGLDrawablePropertyRetainedBacking,
                                        kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat,
                                        nil];
    }
    
    return self;
}

- (void)dealloc
{
    [self deleteFramebuffer];    
    [context release];
    
    [super dealloc];
}

- (void)setContext:(EAGLContext *)newContext
{
    if (context != newContext) {
        [self deleteFramebuffer];
        
        [context release];
        context = [newContext retain];
        
        [EAGLContext setCurrentContext:nil];
    }
}

- (void)createFramebuffer
{
    if (context && !defaultFramebuffer) {
        [EAGLContext setCurrentContext:context];
        
        // Create default framebuffer object.
        glGenFramebuffers(1, &defaultFramebuffer);
        glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);
        
        // Create color render buffer and allocate backing store.
        glGenRenderbuffers(1, &colorRenderbuffer);
        glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);
        [context renderbufferStorage:GL_RENDERBUFFER fromDrawable:(CAEAGLLayer *)self.layer];
        glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &framebufferWidth);
        glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &framebufferHeight);
        
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorRenderbuffer);
        
#if HAS_EAGLVIEW_DEPTH_BUFFER
		glGenRenderbuffers(1, &depthRenderbuffer);
		glBindRenderbuffer(GL_RENDERBUFFER, depthRenderbuffer);
		glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthRenderbuffer);
		glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, framebufferWidth, framebufferHeight);
#endif
		
        if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
            NSLog(@"Failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
    }
}

- (void)deleteFramebuffer
{
    if (context) {
        [EAGLContext setCurrentContext:context];
        
        if (defaultFramebuffer) {
            glDeleteFramebuffers(1, &defaultFramebuffer);
            defaultFramebuffer = 0;
        }
        
        if (colorRenderbuffer) {
            glDeleteRenderbuffers(1, &colorRenderbuffer);
            colorRenderbuffer = 0;
        }
		
#if HAS_EAGLVIEW_DEPTH_BUFFER
		if (depthRenderbuffer)
        {
            glDeleteRenderbuffers(1, &depthRenderbuffer);
            depthRenderbuffer = 0;
        }
#endif
    }
}

- (void)setFramebuffer
{
    if (context) {
        [EAGLContext setCurrentContext:context];
        
        if (!defaultFramebuffer)
            [self createFramebuffer];
        
        glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);
        
        glViewport(0, 0, framebufferWidth, framebufferHeight);
    }
}

- (BOOL)presentFramebuffer
{
    BOOL success = FALSE;
    
    if (context) {
        [EAGLContext setCurrentContext:context];
        
        glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);
        
        success = [context presentRenderbuffer:GL_RENDERBUFFER];
    }
    
    return success;
}

- (void)layoutSubviews
{
    // The framebuffer will be re-created at the beginning of the next setFramebuffer method call.
    [self deleteFramebuffer];
}

@end