CCLayerPanZoomTestLayer.m

- (void) layerPanZoom: (CCLayerPanZoom *) sender
       clickedAtPoint: (CGPoint) point
             tapCount: (NSUInteger) tapCount
{
    NSLog(@"CCLayerPanZoomTestLayer#layerPanZoom: %@ clickedAtPoint: { %f, %f }", sender, point.x, point.y);
    
    if (tapCount == 2) {
        // Toggle zooming all the way in and all the way out.
        
        float midScale = (sender.minScale + sender.maxScale) / 2.0;
        float newScale = (sender.scale <= midScale) ? sender.maxScale : sender.minScale;
        
        // Zoom towards the tap point.  Note that scaling is performed "around" the anchor point.
        // Thus, we need to account for how far the layer should be translated after its scaling
        // change is performed.
        
        CGPoint anchorPointNodeSpace = ccp(sender.anchorPoint.x * sender.contentSize.width,
                                           sender.anchorPoint.y * sender.contentSize.height);       
        
        CGFloat deltaScale = newScale - sender.scale;

        CGPoint deltaPos = ccpMult(ccpSub(point, anchorPointNodeSpace), deltaScale);
        
        // Scale and translate in parallel.  We negate the direction since to zoom to the point
        // we want to move the layer in the opposite direction.
        
        [sender runAction:[CCSpawn actions:
                           [CCScaleTo actionWithDuration:0.4 scale:newScale],
                           [CCMoveBy actionWithDuration:0.4 position:ccpNeg(deltaPos)],
                           nil]];
    }
}