Fix an issue that DirtyRects are full region every frame.

[walterlv]

What does the pull request do?

This PR #14924 add a field _fullRedrawRequested to force the dirty rects to be ignored and redraw the whole window. After that, the rendering performance becomes poor. By the test on my machine, the fps drops from 45 to 30.

I can't figure out why this field is introduced. There is no description about this field in the PR !14924 nor in the comments. So I'm trying to remove the assignment and fix the dirty rects.

The previous PR:

• Don't create a layer if the previous frame is retained by the render target #14924

What is the current behavior?

See this video below to view the dirty rect changes before and after this PR.

What is the updated/expected behavior with this PR?

DirtyRectsAlwaysFull.mp4

How was the solution implemented (if it's not obvious)?

Remove the assignment of the _fullRedrawRequested field.

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

To be discussed.

Obsoletions / Deprecations

Fixed issues

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0051545-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[walterlv]

We have tested the changes in this PR for a period of time, and in some cases, the window content does not render at all. The issue only resolves after resizing the window or opening a new window. It has been confirmed that this PR is causing the issue, so I am currently investigating the root cause.

In any case, I hope to enhance rendering performance as much as possible without introducing rendering defects.