Window drag stutter when using Direct X

[Gavin-Williams]

Is anyone aware of an issue with dragging windows while rendering direct-x content? I don't know if we are not meant to use CompositionTarget_Rendering. But if I do this...

  private void CompositionTarget_Rendering(object? sender, object e)
  {
      Gpu.DrawFrame(triangle.Render);
  }

The window can't be dragged around properly, it's really bad. And I'm pretty sure the application crashed one time while I was dragging it around.

[castorix]

I always use CompositionTarget_Rendering to render Direct2D and I did not meet this problem (I had uploaded some test samples in my GitHub directory)
The only recent problem is this one on my Windows 10 OS : #10092
(I did not test with Windows App SDK 1.7)

[Gavin-Williams]

Interesting. My app starts at 144fps, the rate of my display, but after I move the window around, it drops to 32, the fps discussed in that issue. If I leave the window alone, after a while it returns to normal rendering speed. This behavior is not always apparent though, sometimes, the fps just slows down while dragging, to about 40-50 fps and then returns to normal as soon as I stop dragging.

[Gavin-Williams]

I've only just switched from D3d11 to D3d12 so it's possible that my synchronization code is wrong and causing the stutter. I'm currently rendering on the UI thread. When I was using D3d11 with WinUI years ago, I think I would put the swap-chain rendering and also the swap-chain input on background threads. There are instructions for UWP in the docs regarding the use of 'independent input source' concept with the UWP swap-chain.

As for putting the rendering on a background thread. I can't quite remember what I did, I think the case is that the swap-chain must be created on the UI thread, but after that, rendering can be done from a background thread. If that's how it should be done, that's almost fine, but the one thing I don't like about that is that the UI is then out of sync with the swap-chain. It's quite noticeable when you drag something, and the object is not under the mouse. Almost by definition, the UI and content must be rendered on the same thread.

[Gavin-Williams]

I have now got Dx12 working via CsWin32 and I'm not seeing the same behavior. I guess I will have to take a look at independent input.