fixed transparent windows

[Icekey]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Docs
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

Checklist

• This PR will resolve #___
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.
• I have added a convincing reason for adding this feature, if necessary
• It can be built on all targets and pass CI/CD.

Other information

This fix was found in a old unmerged winit pullrequest. This fix removes the buggy inital white background from transparent windows and fixes transparent fullscreen windows too. I tested it on Win10.

[dklassic]

Does seem to work, thanks for your contribution!

[amrbashir]

This PR shouldn't have been merged and should be reverted asap, Layered Windows is complex and has special attributes, in cases, it might be even invisible and cannot be embedded as a child window, so setting this style is not the fix for transparency in this crate. Also Layered Windows delegates the alpha blending to the compositor which is more performant but might conflict with crates like egui, wgpu and so on.

Note that the window is actually transparent, but the surface has not been cleared so you see a white artifact, and to fix this, if you're using a drawing crate like wgpu or egui, you can just clear the surface.

The main problem is that when adding wry to a tao window, you will still see a white background and I think it is the responsibility of wry to clear the surface and I am working on that so the next release of wry should have this fixed and transitively tauri.

[amrbashir]

Also one of the reasons that transparent example might have artifacts until you resize, is because we enable shadows by default for undecorated window, you can disable that when creating the window and then enabling it back up later and the surface should be clear.

[dklassic]

@amrbashir sorry about that I'll submit a revert immediately.

[Icekey]

@amrbashir good to know that you working on a proper fix. I hope that it will also solve the issue with the buggy tao title, as that is currently main problem when creating an overlay with tauri.