cocos2d Viewport class which provides clipping for all nodes added to the Viewport

Viewport.h

//
//  Viewport.h
//
//  Created by Benjamin Broll on 21.01.10.
//  Copyright 2010 NEXT Munich. All rights reserved.
//

#import "cocos2d.h"


/**
 * Implements a viewport which will only render the content that lies within its
 * rectangle.
 */
@interface Viewport : CCNode {

	// the clipping rectangle
	CGRect rect;
	
}

@property (assign) CGRect rect;

+ (Viewport*) viewportWithRect:(CGRect)rect;
- (id) initWithRect:(CGRect)rect;

@end

Viewport.m

//
//  Viewport.m
//  Think
//
//  Created by Benjamin Broll on 21.01.10.
//  Copyright 2010 NEXT Munich. All rights reserved.
//

#import "Viewport.h"


@implementation Viewport

@synthesize rect;

#pragma mark Clipping logic

- (void) visit {
	if (!self.visible)
		return;
	
	glPushMatrix();
	
	glEnable(GL_SCISSOR_TEST);
	
	// convert from node space to world space
	CGPoint bottomLeft = [self convertToWorldSpace:self.position];
	CGPoint topRight = ccpAdd(self.position, ccp(self.contentSize.width, self.contentSize.height));
	topRight = [self convertToWorldSpace:topRight];
	
	// calculate scissor rect in world space
	CGSize size = [[CCDirector sharedDirector] winSize];
	CGRect scissorRect = CGRectMake(bottomLeft.x, bottomLeft.y, topRight.x-bottomLeft.x, topRight.y-bottomLeft.y);
	
	// transform the clipping rectangle to adjust to the current screen
	// orientation: the rectangle that has to be passed into glScissor is
	// always based on the coordinate system as if the device was held with the
	// home button at the bottom. the transformations account for different
	// device orientations and adjust the clipping rectangle to what the user
	// expects to happen.
	ccDeviceOrientation orientation = [[CCDirector sharedDirector] deviceOrientation];
	switch (orientation) {
		case kCCDeviceOrientationPortrait:
			break;
		case kCCDeviceOrientationPortraitUpsideDown:
			scissorRect.origin.x = size.width-scissorRect.size.width-scissorRect.origin.x;
			scissorRect.origin.y = size.height-scissorRect.size.height-scissorRect.origin.y;
			break;
		case kCCDeviceOrientationLandscapeLeft:
		{
			float tmp = scissorRect.origin.x;
			scissorRect.origin.x = scissorRect.origin.y;
			scissorRect.origin.y = size.width-scissorRect.size.width-tmp;
			tmp = scissorRect.size.width;
			scissorRect.size.width = scissorRect.size.height;
			scissorRect.size.height = tmp;
		}
			break;
		case kCCDeviceOrientationLandscapeRight:
		{
			float tmp = scissorRect.origin.y;
			scissorRect.origin.y = scissorRect.origin.x;
			scissorRect.origin.x = size.height-scissorRect.size.height-tmp;
			tmp = scissorRect.size.width;
			scissorRect.size.width = scissorRect.size.height;
			scissorRect.size.height = tmp;
		}
			break;
	}
	
	glScissor(scissorRect.origin.x, scissorRect.origin.y,
			  scissorRect.size.width, scissorRect.size.height);
	
	[super visit];
	
	glDisable(GL_SCISSOR_TEST);
	glPopMatrix();
}


#pragma mark Init & Dealloc

+ (Viewport*) viewportWithRect:(CGRect)rect {
	return [[[self alloc] initWithRect:rect] autorelease];
}

- (id) initWithRect:(CGRect)r {
	if ((self = [super init])) {
		self.position = r.origin;
		self.contentSize = r.size;
	}
	
	return self;
}

@end