Prevent WPF stutter / dropped frames

Question

I've written a simple game-like app in WPF. The number of objects drawn is well within WPF capabilities - something like a few hundred ellipses and lines with simple fills. I have a DispatcherTimer to adjust the positions of the objects from time to time (1/60th of a second).

The code to compute the new positions can be quite intensive when there are lots of objects, and can fully load a processor. Whenever this occurs, WPF starts skipping frames, presumably trying to compensate for the "slowness" of my application.

What I would much rather happen is for all the frames to be drawn anyway, only slower. The dropped frames do not add any speed - because visual updates were pretty quick anyway.

Can I somehow force WPF to have my changes to the visuals be reflected on the screen regardless of whether WPF thinks it's a good idea?

Answer 1

Unfortunately I don't think there's anything you can do about this, although I will happily be corrected! WPF is designed to be an application creation framework, not a games library, so it priortises application performance and "usability" over framerate. This actually works very well when producing applications as it allows you to use quite rich animations and effects while maintaining perceived performance on lower end systems.

The only thing I think you might be able to try is push your movement code's Dispatcher priority down slightly to below Render (Loaded is the next one down) using something like:

this.Dispatcher.BeginInvoke(DispatcherPriority.Loaded, MoveMyStuff);

I don't have any kind of test harness to verify if that will help though.

Answer 2

This issue was fixed by using a Canvas with an OnRender override instead of creating and moving UIElements. This does mean that everything needs to be drawn by hand in OnRender, but it can now run at any FPS consistently, without skipping any frames.