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 following code (In a subclass of UINavigationController), I face a huge performance hit. After adding a shadow all animations become very laggy. Is this expected or am I doing something wrong in the code?

// This code gets called once during NavigationController initialization. [self.view setClipsToBounds:NO]; [self.view.layer setCornerRadius:5]; [self.view.layer setShadowOffset:CGSizeMake(0, 20)]; [self.view.layer setShadowColor:[[UIColor yellowColor] CGColor]]; [self.view.layer setShadowRadius:20.0]; [self.view.layer setShadowOpacity:1]; 

EDIT:

Changed my shadow radius to 1 and it's still slow

Answer 1

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!

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.