[Bug]: WCO using colors with transparency while animating causes visual glitches

[martijnhartlief]

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a bug report that matches the one I want to file, without success.

Electron Version

20.1.3

What operating system are you using?

Windows

Operating System Version

Windows 10, Windows 11

What arch are you using?

x64

Last Known Working Electron version

No response

Expected Behavior

Changing the background color of a document, while setting transparency on WCO buttons, should not cause side effects.

Actual Behavior

While the background color of the document changes, transparency causes various rendering glitches.

• Always applies black line under all buttons when transparency on the WCO buttons is used
• Using transparency when setting a color does not use actual transparency on the button, but seems to make a snapshot of the current document color and merges it with the transparent color.
• Hover background color is wrong
• Hover background color persists after hovering (Does not revert to background color)

Testcase Gist URL

https://gist.github.com/f7abdc25039e5cfbaa868bae73d043ec

Additional Information

Use case: De-emphasize WCO buttons when a modal is open, but modal backdrop animation causes WCO buttons to have inconsistent behavior.

The test case is emulating opening and closing of a modal while attempting to update the WCO button colors.

[codebytere]

This is not currently supported - see #33567 for updates.