CALayer - Shadow causes a performance hit?

Question

So I am doing some custom animations on my navigationcontroller and the way it pushes and pops the viewControllers.

Everything runs smooth. As soon as I add the foll

Answer 1

Using shadowPath instead of shadowOffset.

theView.layer.shadowPath = [UIBezierPath bezierPathWithRect:theView.bounds].CGPath;

Check this post: iphone - Animation's performance is very poor when view's shadow is on

Answer 2

You should expect a slowdown from adding a shadow. A shadowRadius of 20 is very high and will be especially slow.

The other key to improve shadow rendering speed: set the shadowPath property. It can help dramatically.

Answer 3

Swift 5.3. add this code.

myView -> UIView, collectionViewCell or tableViewCell can be.

myview.layer.shadowPath = UIBezierPath(rect: cell.bounds).cgPath
myview.layer.shouldRasterize = true
myview.layer.rasterizationScale = UIScreen.main.scale

Answer 4

Yes, shadow's are very expensive (especially a shadow that big -- play with the radius and you'll notice it makes a huge difference in the degree of slowdown you experience). One way to improve performance is to render it once to a CGImageContext and just display that image instead of having the layer re-render the shadow every time it redraws (but this doesn't work if the shadow needs to animate or something).

Answer 5

self.view.layer.shouldRasterize = YES;
self.view.layer.rasterizationScale = UIScreen.mainScreen.scale;

I was recently having some issues with slow CALayer shadows, and that simple line of code fixed up everything for me!