g_nOutput* stored two different values: preferred values taken from
the CLI at init-time, then current values after init. This results
in some tricky logic because depending on when code is executed it'd
access one or the other.
Introduce two separate sets of variables instead. DRM reads from the
preferred values, decides which DRM mode to enable, then writes to
the current values. SDL reads from the preferred values and makes
them current immediately.
This changes gamescope's behaviour so that native DRM modes are
picked when -w/-h isn't specified on the command line. When -w/-h are
specified, the DRM logic will try to pick a mode which matches.
When nested, the default output size still defaults to 720p, but
changes when the user resizes the window.
Closes: https://github.com/Plagman/gamescope/issues/258
1d528be605