A simple clipped sprite extension for Sparrow

SHClippedSprite.h

//
//  SHClippedSprite.h
//  Sparrow
//
//  Created by Shilo White on 5/30/11.
//  Copyright 2011 Shilocity Productions. All rights reserved.
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the Simplified BSD License.
//

#import <Foundation/Foundation.h>
#import "SPSprite.h"
@class SPStage;
@class SPQuad;

@interface SHClippedSprite : SPSprite {
    SPQuad *mClip;
    SPStage *mStage;
    BOOL mClipping;
}

@property (nonatomic, readonly) SPQuad *clip;
@property (nonatomic, assign) BOOL clipping;

+ (SHClippedSprite *)clippedSprite;
@end

SHClippedSprite.m

//
//  SHClippedSprite.m
//  Sparrow
//
//  Created by Shilo White on 5/30/11.
//  Copyright 2011 Shilocity Productions. All rights reserved.
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the Simplified BSD License.
//

#import "SHClippedSprite.h"
#import "SPEvent.h"
#import "SPQuad.h"
#import "SPStage.h"
#import "SPDisplayObject.h"

@interface SHClippedSprite ()
- (void)onAddedToStage:(SPEvent *)event;
@end

@implementation SHClippedSprite

@synthesize clip = mClip;
@synthesize clipping = mClipping;

+ (SHClippedSprite *)clippedSprite {
    return [[[SHClippedSprite alloc] init] autorelease];
}

- (SHClippedSprite *)init {
    if ((self = [super init])) {
        mClip = [[SPQuad alloc] init];
        mClip.visible = NO;
        mClip.width = 0;
        mClip.height = 0;
        [self addChild:mClip];
        mClipping = NO;
        [self addEventListener:@selector(onAddedToStage:) atObject:self forType:SP_EVENT_TYPE_ADDED_TO_STAGE];
    }
    return self;
}

- (void)onAddedToStage:(SPEvent *)event {
	[self removeEventListener:@selector(onAddedToStage:) atObject:self forType:SP_EVENT_TYPE_ADDED_TO_STAGE];
	mStage = (SPStage *)self.stage;
}

- (void)render:(SPRenderSupport *)support {
    if (mClipping) {
        glEnable(GL_SCISSOR_TEST);
        SPRectangle *clip = [[mClip boundsInSpace:mStage] intersectionWithRectangle:[self.parent boundsInSpace:mStage]];
        glScissor((clip.x*[SPStage contentScaleFactor]), (mStage.height*[SPStage contentScaleFactor])-(clip.y*[SPStage contentScaleFactor])-(clip.height*[SPStage contentScaleFactor]), (clip.width*[SPStage contentScaleFactor]), (clip.height*[SPStage contentScaleFactor]));
        [super render:support];
        glDisable(GL_SCISSOR_TEST);
    } else {
        [super render:support];
    }
}

- (SPRectangle *)boundsInSpace:(SPDisplayObject *)targetCoordinateSpace {    
    if (mClipping) {
        return [mClip boundsInSpace:targetCoordinateSpace];
    } else {
        return [super boundsInSpace:targetCoordinateSpace];
    }
}

- (void)dealloc {
    [self removeEventListener:@selector(onAddedToStage:) atObject:self forType:SP_EVENT_TYPE_ADDED_TO_STAGE];
    [mClip release];
    [super dealloc];
}
@end

@implementation SPDisplayObject (ClippedHitTest)
- (SPDisplayObject*)hitTestPoint:(SPPoint*)localPoint forTouch:(BOOL)isTouch
{
    if (isTouch && (!mVisible || !mTouchable)) return nil;
    
    SPDisplayObject *parent = self.parent;
    while (parent) {
        if ([parent isKindOfClass:[SHClippedSprite class]] && ![[parent boundsInSpace:parent] containsPoint:localPoint])
            return nil;
        parent = parent.parent;
    }
    
    if ([[self boundsInSpace:self] containsPoint:localPoint]) return self; 
    else return nil;
}
@end