Transparent windows are completely broken on Windows 11

[parasyte]

Running the transparent example on Windows 11 (version 21H2, build 22000.348) appears to completely crash something in the OS. My screens flash black for a moment, and all windows appear as just the decoration with empty contents for a second until things settle down. This looks pretty similar to what happens when you update the display drivers, except window positions are not reset (because the driver update temporarily changes the desktop resolution).

Whatever crashes also disables Night Light; I have to re-enable it manually in Settings > System > Display. Working on this bug in the middle of the night is really unkind to my eyesight.

git bisect points at #1933 as causing the crash.

The transparent window itself is completely invisible, but it still receives events. I am not sure if this example is supposed to behave this way. It acts the same with 0.25.0 on Windows 11. I don't think it's supposed to do this, considering #1933 (comment) shows a video with this example creating an actual window. Something I don't get at all.

[parasyte]

Here's some more info with screenshots to help illustrate the issues.

0.26.0 and 0.25.0 both show the same completely invisible window behavior. Here's what it looks like with 0.25.0 specifically. I'm hovering over the window in the taskbar to bring up the little invisible window preview:

And if I run the same example in 0.24.0, I do see something resembling a transparent window:

🤷

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One more datapoint: egui_demo_app (which uses winit 0.25.0) properly shows a transparent background on Windows 11. In the linked egui PR, I commented with_transparent(true) to work around the crash. When that is enabled, I get the crash and the window background is not transparent, suggesting that transparent windows are in fact not at all working in 0.26.0 on Windows 11.

[msiglreith]

Thanks for the report - checked on Windows 10 and seems to work fine there. Unfortunately, I don't have a Win11 compatible system so I currently can't looks further into this.

[msiglreith]

Should be fixed by #2121

[parasyte]

Confirmed!