In find_onscreen_for_xid() we want to loop over the framebuffers
and skip any that is not onscreen.
The code today does this by negating the framebuffer type variable
and skipping if that equals COGL_FRAMEBUFFER_TYPE_ONSCREEN. This
actually works as the enum used will function as a boolean:
typedef enum _CoglFramebufferType {
COGL_FRAMEBUFFER_TYPE_ONSCREEN,
COGL_FRAMEBUFFER_TYPE_OFFSCREEN
} CoglFramebufferType;
But it is a bit weird logic and fragile if more types are added.
(not that I can think of any different type...)
To simplify this, and to silence a warning in clang this patch just
changes it to a != test.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/905
7c036c5896