Classes/EAGLView.m

/*
     File: EAGLView.m
 Abstract: 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.
 
  Version: 1.9
 
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 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
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*/
 
#import <QuartzCore/QuartzCore.h>
#import <OpenGLES/EAGLDrawable.h>
 
#import "EAGLView.h"
 
@interface EAGLView (EAGLViewPrivate)
 
- (BOOL)createFramebuffer;
- (void)destroyFramebuffer;
 
@end
 
@interface EAGLView (EAGLViewSprite)
 
- (void)setupView;
 
@end
 
@implementation EAGLView
 
@synthesize animating;
@dynamic animationFrameInterval;
 
// You must implement this
+ (Class) layerClass
{
    return [CAEAGLLayer class];
}
 
 
//The GL view is stored in the nib file. When it's unarchived it's sent -initWithCoder:
- (id)initWithCoder:(NSCoder*)coder
{
    if((self = [super initWithCoder:coder])) {
        // Get the layer
        CAEAGLLayer *eaglLayer = (CAEAGLLayer*) self.layer;
        
        eaglLayer.opaque = YES;
        eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:
                                        [NSNumber numberWithBool:FALSE], kEAGLDrawablePropertyRetainedBacking, kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat, nil];
        
        context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];
        
        if(!context || ![EAGLContext setCurrentContext:context] || ![self createFramebuffer]) {
            [self release];
            return nil;
        }
        
        animating = FALSE;
        displayLinkSupported = FALSE;
        animationFrameInterval = 1;
        displayLink = nil;
        animationTimer = nil;
        
        // A system version of 3.1 or greater is required to use CADisplayLink. The NSTimer
        // class is used as fallback when it isn't available.
        NSString *reqSysVer = @"3.1";
        NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
        if ([currSysVer compare:reqSysVer options:NSNumericSearch] != NSOrderedAscending)
            displayLinkSupported = TRUE;
        
        [self setupView];
        [self drawView];
    }
    
    return self;
}
 
 
- (void)layoutSubviews
{
    [EAGLContext setCurrentContext:context];
    [self destroyFramebuffer];
    [self createFramebuffer];
    [self drawView];
}
 
 
- (BOOL)createFramebuffer
{
    glGenFramebuffersOES(1, &viewFramebuffer);
    glGenRenderbuffersOES(1, &viewRenderbuffer);
    
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);
    glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
    [context renderbufferStorage:GL_RENDERBUFFER_OES fromDrawable:(id<EAGLDrawable>)self.layer];
    glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, viewRenderbuffer);
    
    glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth);
    glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight);
    
    if(glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES) != GL_FRAMEBUFFER_COMPLETE_OES) {
        NSLog(@"failed to make complete framebuffer object %x", glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES));
        return NO;
    }
    
    return YES;
}
 
 
- (void)destroyFramebuffer
{
    glDeleteFramebuffersOES(1, &viewFramebuffer);
    viewFramebuffer = 0;
    glDeleteRenderbuffersOES(1, &viewRenderbuffer);
    viewRenderbuffer = 0;
    
    if(depthRenderbuffer) {
        glDeleteRenderbuffersOES(1, &depthRenderbuffer);
        depthRenderbuffer = 0;
    }
}
 
 
- (NSInteger) animationFrameInterval
{
    return animationFrameInterval;
}
 
- (void) setAnimationFrameInterval:(NSInteger)frameInterval
{
    // Frame interval defines how many display frames must pass between each time the
    // display link fires. The display link will only fire 30 times a second when the
    // frame internal is two on a display that refreshes 60 times a second. The default
    // frame interval setting of one will fire 60 times a second when the display refreshes
    // at 60 times a second. A frame interval setting of less than one results in undefined
    // behavior.
    if (frameInterval >= 1)
    {
        animationFrameInterval = frameInterval;
        
        if (animating)
        {
            [self stopAnimation];
            [self startAnimation];
        }
    }
}
 
- (void) startAnimation
{
    if (!animating)
    {
        if (displayLinkSupported)
        {
            // CADisplayLink is API new to iPhone SDK 3.1. Compiling against earlier versions will result in a warning, but can be dismissed
            // if the system version runtime check for CADisplayLink exists in -initWithCoder:. The runtime check ensures this code will
            // not be called in system versions earlier than 3.1.
            
            displayLink = [NSClassFromString(@"CADisplayLink") displayLinkWithTarget:self selector:@selector(drawView)];
            [displayLink setFrameInterval:animationFrameInterval];
            [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
        }
        else
            animationTimer = [NSTimer scheduledTimerWithTimeInterval:(NSTimeInterval)((1.0 / 60.0) * animationFrameInterval) target:self selector:@selector(drawView) userInfo:nil repeats:TRUE];
        
        animating = TRUE;
    }
}
 
- (void)stopAnimation
{
    if (animating)
    {
        if (displayLinkSupported)
        {
            [displayLink invalidate];
            displayLink = nil;
        }
        else
        {
            [animationTimer invalidate];
            animationTimer = nil;
        }
        
        animating = FALSE;
    }
}
 
 
// Sets up an array of values to use as the sprite vertices.
const GLfloat spriteVertices[] = {
-0.5f, -0.5f,
0.5f, -0.5f,
-0.5f,  0.5f,
0.5f,  0.5f,
};
 
// Sets up an array of values for the texture coordinates.
const GLshort spriteTexcoords[] = {
0, 0,
1, 0,
0, 1,
1, 1,
};
 
- (void)setupView
{
    CGImageRef spriteImage;
    CGContextRef spriteContext;
    GLubyte *spriteData;
    size_t  width, height;
    
    // Sets up matrices and transforms for OpenGL ES
    glViewport(0, 0, backingWidth, backingHeight);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrthof(-1.0f, 1.0f, -1.5f, 1.5f, -1.0f, 1.0f);
    glMatrixMode(GL_MODELVIEW);
    
    // Clears the view with black
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    
    // Sets up pointers and enables states needed for using vertex arrays and textures
    glVertexPointer(2, GL_FLOAT, 0, spriteVertices);
    glEnableClientState(GL_VERTEX_ARRAY);
    glTexCoordPointer(2, GL_SHORT, 0, spriteTexcoords);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    
    // Creates a Core Graphics image from an image file
    spriteImage = [UIImage imageNamed:@"Sprite.png"].CGImage;
    // Get the width and height of the image
    width = CGImageGetWidth(spriteImage);
    height = CGImageGetHeight(spriteImage);
    // Texture dimensions must be a power of 2. If you write an application that allows users to supply an image,
    // you'll want to add code that checks the dimensions and takes appropriate action if they are not a power of 2.
 
    if(spriteImage) {
        // Allocated memory needed for the bitmap context
        spriteData = (GLubyte *) calloc(width * height * 4, sizeof(GLubyte));
        // Uses the bitmap creation function provided by the Core Graphics framework. 
        spriteContext = CGBitmapContextCreate(spriteData, width, height, 8, width * 4, CGImageGetColorSpace(spriteImage), kCGImageAlphaPremultipliedLast);
        // After you create the context, you can draw the sprite image to the context.
        CGContextDrawImage(spriteContext, CGRectMake(0.0, 0.0, (CGFloat)width, (CGFloat)height), spriteImage);
        // You don't need the context at this point, so you need to release it to avoid memory leaks.
        CGContextRelease(spriteContext);
        
        // Use OpenGL ES to generate a name for the texture.
        glGenTextures(1, &spriteTexture);
        // Bind the texture name. 
        glBindTexture(GL_TEXTURE_2D, spriteTexture);
        // Set the texture parameters to use a minifying filter and a linear filer (weighted average)
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        // Specify a 2D texture image, providing the a pointer to the image data in memory
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData);
        // Release the image data
        free(spriteData);
        
        // Enable use of the texture
        glEnable(GL_TEXTURE_2D);
        // Set a blending function to use
        glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
        // Enable blending
        glEnable(GL_BLEND);
    }
}
 
// Updates the OpenGL view when the timer fires
- (void)drawView
{
    // Make sure that you are drawing to the current context
    [EAGLContext setCurrentContext:context];
    
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);
    glRotatef(3.0f, 0.0f, 0.0f, 1.0f);
    
    glClear(GL_COLOR_BUFFER_BIT);
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    
    glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
    [context presentRenderbuffer:GL_RENDERBUFFER_OES];
}
 
// Release resources when they are no longer needed.
- (void)dealloc
{
    if([EAGLContext currentContext] == context) {
        [EAGLContext setCurrentContext:nil];
    }
    
    [context release];
    context = nil;
    
    [super dealloc];
}
 
@end