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[Preview 5] Constant FrameMessages being sent in previewer

See original GitHub issue

Describe the bug In Preview 5, when a xaml file is open in the designer the previewer process is sending constant FrameMessages for no reason (VS is just sitting open while I type this and we’re already at sequence id 17 000+).

I’ve traced this back to nightly CI build 11.0.999-cibuild0029216-beta which was built on Jan 29. I think that corresponds to #10120 as the package is the second nightly package on the 29th and that was the second PR merged, and the PR changes show some changes with the previewer. See comment for update

This also leads to VS using a constant 20-ish% CPU and leads to a lag in visual studio if the preview window is left open long enough.

Issue Analytics

State:
Created 8 months ago
Reactions:1
Comments:7 (4 by maintainers)

Top GitHub Comments

1reaction

grokyscommented, Apr 18, 2023

Actually, maybe the problem is that Compositor.AfterCommit gets raised twice:

Once synchronously via:
- CompositingRenderer.Paint
- CompositionTarget.ImmediateUIThreadRender
- Compositor.Commit
Once asynchronously via:
- CompositingRenderer.Paint
- CompositingRenderer.QueueUpdate
- Compositor.RequestCompositionUpdate
- Compositor.RequestCommitAsync

1reaction

grokyscommented, Apr 18, 2023

Seems to be caused because although the compositor is being run on the main thread, the commit message is raised using Dispatcher.UIThread.Post:

https://github.com/AvaloniaUI/Avalonia/blob/master/src/Avalonia.Base/Rendering/Composition/Compositor.cs#L74

This causes it to arrive after RemoteServerTopLevelImpl.RenderIfNeeded exits.

This means that when RemoteServerTopLevelImpl.QueueNextRender is called, _inRender has been set to false, causing the top level impl to think that a new render has completed due to an invalidation.