Why is Frame Rate in WPF Irregular and Not Limited To Monitor Refresh?

Question

I\'m measuring the time between frames in a simple WPF animation. Perforator says the app performs at ~60fps, so I expected the time between frames to be ~16.6ms with little

Answer 1

First - 'Christopher Bennage's-Answer has a good explanation and provides a hint to a solution:

"Only do “per-frame” work when the reported frame time changes"

This is a little bit hard, since the RenderingEventArgs are hidden as a normal EventArgs and a cast has to be done.

To make this a little bit easyer, a convinient solution can be found in "EVAN'S CODE CLUNKERS" http://evanl.wordpress.com/2009/12/06/efficient-optimal-per-frame-eventing-in-wpf/

I took his code and modified it a bit. Now just take my snipped, add the class to your Project, use CompositionTargetEx were you used CompositionTarget and you are fine :)

public static class CompositionTargetEx { 
    private static TimeSpan _last = TimeSpan.Zero; 
    private static event EventHandler _FrameUpdating; 
    public static event EventHandler Rendering { 
        add { 
            if (_FrameUpdating == null)                 
                CompositionTarget.Rendering += CompositionTarget_Rendering;
            _FrameUpdating += value; 
        } 
        remove { 
            _FrameUpdating -= value; 
            if (_FrameUpdating == null)                
                CompositionTarget.Rendering -= CompositionTarget_Rendering; 
        } 
    } 
    static void CompositionTarget_Rendering(object sender, EventArgs e) { 
        RenderingEventArgs args = (RenderingEventArgs)e;
        if (args.RenderingTime == _last) 
            return;
        _last = args.RenderingTime; _FrameUpdating(sender, args); 
    } 
}