COcoldpie·Nov 10, 2020
First, sure, if games didn't do complex things, it would be easier to support. But they do. So it is hard.
Also, it's much more complicated than that. When running in exclusive fullscreen mode (which almost all fullscreen games did before about 5 years ago), they have to do stuff like restore the original display resolution, tear down their graphics stack, and restore all of that when bringing the window back up. Many games depend on a very particular sequence of window messages during that process, including D3D handling some of those messages on their behalf in certain ways. In the case of non-exclusive or windowed mode games, they may choose to stop reading controller input, stop rendering, stop sending audio, etc. All of that requires correct window notifications in the correct order, and support in Wine for correctly tearing down and
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restoring all of those things.
And all that is just on the Windows side of the equation, you also need to tear down the Linux graphics stack and manage how X thinks about the windows in a way that the window manager will do the right thing for the user, without doing the /wrong/ thing for the app from the Windows perspective. For example if the WM chooses to resize the window when it requests fullscreen mode, at a time when Windows does not, then we have to ignore those messages, or the game will suddenly be rendering at the wrong size (or worse, infinite loop as the WM and the game fight over the window sizes... yeah, that happened[1]).
It's a nightmare. I've spent months and months on this stuff, and other devs have spent even more. If it was easy to fix, it would be fixed, I promise you :)
[1] https://github.com/ValveSoftware/wine/commit/4f590327ab2028a...