Did you read this thread? What would be possible if the WM would handle it instead of the app (without nasty hacks):
- Guaranteed multi-monitor compatibility.
- Fake resolution (scale up/down).
- Reset resolution back if the application crash.
And maybe more. The WM could even decide to paint the fullscreen window as desktop background image (up/downscaled if needed).
If you can't set a non-native resolution (either because your display isn't very capable, or has an awful scaler), you can also use the overlays to do the scaling, which will provide you much better image quality at much lower power.
Actually I was just playing Left 4 Dead 2 through Wine(steam made it free to play for 2 days) and my resolution got changed. I run KDE 4.9.2 under Ubuntu 12.10. While it wasn't correct when I exited(not the same as before the game, although it may have to do with an error that occurred during gameplay too), both with the incorrect one and after resetting it myself, all my widgets were pretty much how they should be( I just have a a few to monitor CPU, RAM and temperature on the desktop) . Is that certainly a problem with KDE as of now?(widgets getting messed up with resolution changes)
The general concensus there was that games shouldn't be changing resolution, but instead, if the game requests a fullscreen resolution - the WM should provide the game a surface of the size it requested but then upscale that to fullscreen, perhaps even with sensible black-barring if the aspect ratio doesn't match the native resolution.
Why isn't this the standard? I mean, there is several advantages:
-Because its a window, it actually behaves properly on a multi monitor setup
-Don't dick the desktop if it crashes
-Possibly allowing the WM to select the used up/down scaling algorithm, which would be really nice for legacy applications
-Allowing a free setup of Super Sampling by setting the rendered resolution higher than the monitor
-Allows alt+tabbing smoothly without 2-3 second reblacking of the screen
-Allows WM to override the fullscreen, so it can be changed into a window too, seamless
Of course, it still don't change the fact that you need a sane scheme of locking the mouse inside the window, and various other goodies.
I'm with the people that wants it like it was done in AmigaOS. Why should a games resoultion have any impact on the desktop at all? If a game was to open a 640x480 fullscreen then a alt-tab to the desktop should change back to 1920x1080 or what the desktop now was running, or is there something fundamentally wrong with X11 in this regard so that this isn't possible?
I rather doubt it. The performance of games in windowed modeus and fullscreen is identical on Windows, so if we wrote a sane scheme, why would it degrade?
Maybe unscaled... for scaling, Rasterman suggests somewhere between 5%-50% performance hit, since you need to add a minimum of about 3 buffer-swaps (up from 0) for the entire screen. And as I said earlier - the only time you legitimately want to change resolutions for gaming is when your hardware isn't powerful enough to run at native, so adding that performance hit couldn't come at a worse time.