Compositors now are expected to wait for an initial commit by checking
wlr_xdg_surface.initial_commit on every surface commit and send
(schedule) configure events manually.
Since we only use the backend capabilities here we can simply pass
them in directly. This allows other locations to create an allocator
even if they don't have a backend. They can simply specify the caps
they want instead.
Some opaque pixel formats (nv12, p010) require per-plane bytes_per_block
info. However, it doesn't make sense to store them in
wlr_pixel_format_info, as they will never be useful (currently, this
info is used for shm, which doesn't have a concept of multi-planar
buffers.)
Let's define a separate array and function for determining whether a
pixel format has alpha.
This makes it easy for compositors to handle situations where the
DRM or libinput backend becomes unavailable. Compositors can listen
the destroy event of the multi backend returned by
wlr_backend_autocreate() and decide what to do.
Some users might want to destroy the multi backend when a child
backend is being destroyed. However, they can't destroy the multi
backend if it's already in the process of being destroyed.
The destroy signal was changed to be emitted after destroying child
backends in babdd6ccf7 ("backend: fix use-after-free when destroying
backends"). However, this was done to accomodate for an old
"output_remove" event on backends, which has long been dropped in
favor of wlr_output.events.destroy.
This patch follows the same principle as 5d639394f3
("types/output: emit destroy event before destroying global").
A motivating example of such problem - Zoom's popups that open on button presses.
Before this fix the popup would flicker and immediately disappear - because the PID is not yet
available for the verification (as the surface has not been associated yet), wlroots would refuse to
focus the popup and instead focus the previous window. This leads QT to interpret this as a sign to
close the popup.
This change moves the PID aqcuisition to an earlier phase - just where the window is created.