[PATCH] SDL2: Can't set resolution in fullscreen mode

[historic_bruno]

With SDL1, we could set the fullscreen resolution, but not with SDL2, because we create the window with ​SDL_WINDOW_FULLSCREEN_DESKTOP to work around some issues with true fullscreen mode. Fullscreen desktop is a "fake" fullscreen which is only a borderless window that fills the screen, so it runs at native resolution.

Currently I know of issues on Windows and OS X using SDL_WINDOW_FULLSCREEN (see #2041). Once they are fixed, we can change the flag and fix this regression.

[historic_bruno]

I think we should add a config option to toggle between SDL_WINDOW_FULLSCREEN and ​SDL_WINDOW_FULLSCREEN_DESKTOP. SDL_WINDOW_FULLSCREEN would always be preferable but it's still too buggy to be the default, and sometimes SDL_WINDOW_FULLSCREEN_DESKTOP could be preferred for those who want the desktop resolution in fullscreen mode.

[historic_bruno]

Tested the latest SDL Hg version on Windows 7 and the fullscreen transitions are much improved, I didn't find any obvious bugs on my system.

[SuperTux95]

I'd like to be able to use the super key or alt+tab to temporarily minimize 0ad on Debian. Currently it is only possible in windowed mode with the added performance impact. Other games like Xonotic allow to be minimized with super/alt+tab in fullscreen when paused.

[fcxSanya]

Added a patch according to Ben's suggestion here:

I think we should add a config option to toggle between SDL_WINDOW_FULLSCREEN and ​SDL_WINDOW_FULLSCREEN_DESKTOP.

By default it preserves the current implementation (SDL_WINDOW_FULLSCREEN_DESKTOP).

Tested on Linux, looks working.

To test: change xres/yres to something different from the current screen resolution, set windowed = false and make sure that:

1. with fakefullscreen = true (default) the game window is created with the desktop resolution
2. with fakefullscreen = false the game window is created with xres/yres

[fcxSanya]

I suddenly realized that it doesn't make sense to pass fakeFullscreen around as method arguments like fullscreen as I do in fake_fullscreen_option.diff​, so I made the second version of the patch (fake_fullscreen_option_v2.diff​) which doesn't add fakeFullscreen params to methods.

[wraitii]

Patch does what it says, but that doesn't play nice with OSX. Also seems to fail with #2349: hold the screen gets mangled (probably an SDL issue)

If the point is to allow running at a reduced resolution in fullscreen to speed up the game, I would advise instead, as I did on #2349, to decouple the renderer resolution from the real resolution.

Removing rfc in the meantime.

[elexis]

Moving to the Work In Progress milestone, since there is a patch asking for feedback, but since it is not strictly bound to a specific release.

[wraitii]

Perhaps after ​https://code.wildfiregames.com/D1925 we could add support for SDL_WINDOW_FULLSCREEN.