If obs was shutting down in very early in initialization like when the
X11 display is missing this context parameter might still be NULL.
Return early to allow shutdown to complete without crashing.
This is a Unix-specific code. The only available platforms
at this point are the X11/GLX and X11/EGL platforms.
The concept of a platform display is also introduced. Again,
the only display that is set right now is the X11 display.
Currently, obs-nix.c is highly tied to the X11 display
server. It includes X11 headers directly, and make use
of X11 functions. Most of the code inside obs-nix.c that
is X11-specific is related to hotkeys handling.
Introduce a new vtable for hotkeys callbacks, that will
used by X11 and Wayland to expose their specific routines.
In this commit, only the X11 hotkeys vtable is implemented.
Move all the X11-specific code to obs-nix-x11.c, and add
a new function to retrieve the X11 hotkeys vtable.
