SpriteLayer, a CALayer subclass for spritesheet-based animation

SpriteLayer.h

//
//  SpriteLayer.h
//
//  Created by Joseph C Osborn on 2011.01.12.
//  Copyright 2011 Universal Happy-Maker. All rights reserved.
//  This code is made available under the 3-clause BSD license:
//  http://www.opensource.org/licenses/BSD-3-Clause
//

#import <Foundation/Foundation.h>
#import <QuartzCore/QuartzCore.h>

extern const int SpriteAnimEnd;

@interface SpriteLayer : CALayer {
    CGSize frameSize;
    NSString *currentAnimation;
    int currentFrame;
    NSMutableDictionary *animations;
}
@property (readwrite, assign, nonatomic) CGSize frameSize;
@property (readonly, copy, nonatomic) NSString *currentAnimation;
@property (readonly, assign, nonatomic) float framesWide, framesHigh;

- (void)addSpriteAnimationNamed:(NSString *)n atFramerate:(float)fps looping:(BOOL)loop withFrames:(int)frame1, ...;

- (void)play:(NSString *)anim;
- (void)play:(NSString *)anim restart:(BOOL)restart;
- (CAAnimation *)CAAnimationNamed:(NSString *)n;

@end

SpriteLayer.m

//
//  SpriteLayer.m
//
//  Created by Joseph C Osborn on 2011.01.12.
//  Copyright 2011 Universal Happy-Maker. All rights reserved.
//  This code is made available under the 3-clause BSD license:
//  http://www.opensource.org/licenses/BSD-3-Clause
// 
#import "SpriteLayer.h"

const int SpriteAnimEnd = -1;

@interface SpriteAnim : NSObject {
  BOOL loop;
  float framerate;
  NSArray *frames;
  NSMutableArray *times;
}
@property (readonly, assign, nonatomic) BOOL loop;
@property (readonly, assign, nonatomic) float framerate;
@property (readonly, copy, nonatomic) NSArray *frames;
- (id)initWithFramerate:(float)fps looping:(BOOL)loop frames:(NSArray *)frames;
- (CAAnimation *)animation;
@end
@implementation SpriteAnim
@synthesize loop, framerate, frames;

- (id)initWithFramerate:(float)fps looping:(BOOL)looping frames:(NSArray *)frameArray {
  if((self = [super init])) {
    framerate = fps;
    loop = looping;
    frames = [frameArray copy];
    times = [[NSMutableArray alloc] initWithCapacity:frames.count];
    for(int i = 0; i < frames.count; i++) {
      [times addObject:[NSNumber numberWithFloat:i / (float)frames.count]];
    }
    [times addObject:[NSNumber numberWithFloat:1.0]];
  }
  return self;
}
- (void)dealloc {
  [frames release];
  [times release];
  [super dealloc];
}
- (CAAnimation *)animation {
  CAKeyframeAnimation *a = [CAKeyframeAnimation animationWithKeyPath:@"contentsRect"];
  a.values = frames;
  a.keyTimes = times;
  if(loop) {
    a.repeatCount = HUGE_VALF;
  }
  a.fillMode = kCAFillModeForwards;
  a.removedOnCompletion = NO;
  a.duration = frames.count / framerate;
  a.calculationMode = kCAAnimationDiscrete;
  return a;
}

@end

@interface SpriteLayer()
@property (readwrite, nonatomic, copy) NSString *currentAnimation;
@end

@implementation SpriteLayer
@synthesize frameSize, currentAnimation;
@dynamic framesWide, framesHigh;

- (id)init {
  if((self = [super init])) {
    animations = [[NSMutableDictionary alloc] initWithCapacity:8];
    currentAnimation = nil;
    frameSize = CGSizeZero;
    NSMutableDictionary *actions = [NSMutableDictionary dictionaryWithDictionary:self.actions];
    [actions setObject:[NSNull null] forKey:@"position"];
    [actions setObject:[NSNull null] forKey:@"contentsRect"];
    self.actions = actions;
    self.magnificationFilter = kCAFilterNearest;
    self.minificationFilter = kCAFilterNearest;
  }
  return self;
}

- (void)dealloc {
  [currentAnimation release];
  [animations release];
  [super dealloc];
}

- (void)addSpriteAnimationNamed:(NSString *)n atFramerate:(float)fps looping:(BOOL)loop withFrames:(int)frame1, ... {
  NSMutableArray *frameArray = [NSMutableArray arrayWithCapacity:8];
  
  int framesWide = (int)ceilf(self.framesWide);
  //int framesHigh = (int)ceilf(self.framesHigh);
  
  double fw = self.frameSize.width/CGImageGetWidth((CGImageRef)self.contents);
  double fh = self.frameSize.height/CGImageGetHeight((CGImageRef)self.contents);
  
  va_list args;
  va_start(args, frame1);    
  int f = frame1;
  while(f != SpriteAnimEnd) {
    int col = f % framesWide;
    int row = f / framesWide;
    CGRect cBounds = CGRectMake(fw*col, fh*row, fw, fh);
    [frameArray addObject:[NSValue valueWithCGRect:cBounds]];
    
    f = va_arg(args, int);
  }
  va_end(args);
  
  SpriteAnim *anim = [[[SpriteAnim alloc] initWithFramerate:fps looping:loop frames:frameArray] autorelease];
  [animations setObject:anim forKey:n];
}

- (void)play:(NSString *)anim {
  [self play:anim restart:NO];
}
- (void)play:(NSString *)anim restart:(BOOL)restart {
  if(!restart && [self.currentAnimation isEqualToString:anim]) { return; }
  CAAnimation *caAnim = [self CAAnimationNamed:anim];
  if(!caAnim) { return; }
  if([self animationForKey:@"sprite-animation"]) {
    [self removeAnimationForKey:@"sprite-animation"];
  }
  self.currentAnimation = anim;
  caAnim.delegate = self;
  [self addAnimation:caAnim forKey:@"sprite-animation"];
}

- (CAAnimation *)CAAnimationNamed:(NSString *)n {
  return [[animations objectForKey:n] animation];
}

//- (void)animationDidStart:(CAAnimation *)anim {
//    
//}
- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag {
  if([self animationForKey:@"sprite-animation"] == anim) {
    self.currentAnimation = nil;
  }
}

- (float)framesWide {
  return CGImageGetWidth((CGImageRef)self.contents)/frameSize.width;
}
- (float)framesHigh {
  return CGImageGetHeight((CGImageRef)self.contents)/frameSize.height;
}

@end