Why would a borderless full-screen window stutter occasionally?

Question

I want to be able to allow players to switch between full-screen, windowed, and full-screen-with-a-borderless-window rendering modes. The last mode, borderless is an important one lots of players, myself included.

I have noticed that my game will stutter a little bit in borderless windowed mode. It's not terrible, but choppy gameplay can get slightly annoying and I want to it to be as smooth as it is in full-screen. I know other games have always had some issue with being borderless. I just figured since my game isn't that intensive I shouldn't see much of problem.

I am using David Amador's "XNA 2D Independent Resolution Rendering" code. The trouble comes when I create my gameplay screen and use the following code to create a borderless window:

Form gameForm = (Form)Form.FromHandle(curGame.control.Handle);
gameForm.FormBorderStyle = FormBorderStyle.None;

If I have it set to fullscreen through Amador's Resolution class then this borderless code doesn't seem to do anything at all. If I have it set to windowed it does work as expected and creates a borderless window. The only problem is that strange choppy behavior.

In full screen it doesn't lag one bit so I'm wondering if there's some issue with how the borderless code works. Is how I'm doing a borderless window correct? Am I just going to have to deal with a little bit of stuttering in that mode?

Answer 1

You are seeing a performance difference due to the fact that in actual full-screen mode, you get exclusive access to the GPU for that adapter, so you won't have to content with any other process for that particular resource.

This may be slightly faster, but mostly it is just more predictable (and thus smoother), since nothing else will be allowed to make requests of the GPU that would cause it to hold any kind of lock on any resource or any kind of pipeline stall.

Those sorts of unpredictable, out-of-your-control demands are the cause for your occasional stutters when in full-screen windowed mode. It's akin to how loading all your game data from your disk will take longer if there is also another program (like a virus scanner) poking around at all those same files at the same time.