Layered Window issues on Windows and Linux

[rombust]

It has been a while since I tried the Examples/Display/LayeredWindow on Windows.

On Windows 11, it crashes the application inside a Nvidia library.

Looking at: Win32Window::update_layered_worker_thread_process_dwm() (In Sources/Display/Platform/Win32/win32_windows.cpp)

This is used when system is enabled for "DwmFunctions::is_composition_enabled()"

Nearly 4000 Rectangles are produced for the example to pass to ::SetWindowRgn(). This is excessive and would have a significant performance impact (except is crashes the application).

When composition is not enabled, we use the shadow_window technique (using ::UpdateLayeredWindow() ). That I assume is still working.

Both techniques have advantages and disadvantages, but at the moment we cannot choose the desired code path. Maybe a switch in the display window description.

In addition, this example doesn't work on X11 with the cinnamon desktop. You cannot interact with the application.

I am not going to fix it, since I don't need it :)

[dpjudas]

The nvidia drivers of late have been rather broken. Maybe they'll fix it again. Or it may be that we used multithreaded OpenGL? I can't remember. Multithreaded OpenGL barely ever worked - if it no longer works I wouldn't be surprised.

It is a lot of rectangles, but it isn't worse than that we ran it just fine on 15 year old hardware and honestly this isn't much worse than of regions have always been. If you take the classic clock or xeyes applications, they drew a circle and, if you think about it, the only way to convert such a circle into rectangles is to create one per line.

If I understand the region clipping algorithm correctly, the list is sorted top/left to bottom/right and then as hardware draws the scanlines it moves the pointer for which rectangle is used for clipping, so it doesn't have the performance impact one might think.

In any case, I agree there's no reason to put work into this. As cool as it was, there's no actual functional need for what its doing. :)