Pekka Paalanen authored Jul 22, 2022 and Pekka Paalanen committed Sep 23, 2022

Previously renderers were not told when the output (framebuffer they
need to draw) size changed. Renderers just pulled that information out
from weston_output::current_mode when they happened to need it. This
makes some things awkward, like resizing the shadow or intermediate
buffers. In fact, Pixman-renderer does not even support resizing its
shadow buffer, nor does GL-renderer. DRM-backend has to destroy and
re-create the renderer output state anyway, but rdp, x11 and wayland
backends would be natural users of resizing API.

This commit adds an API for resizing with empty implementations. Actual
implementations will be added in following patches for each renderer
while moving parts of resizing code from backends into the renderers.
No-op renderer needs no implementation.

Only wayland-backend has actual resizing code already, and that is made
to call the new API. Unfortunately, Pixman and GL renderers differ: one
does not blit them while the other does. In order to assert the
functionality of each renderer to keep the API consistent,
wayland-backend needs to lie to pixman-renderer. That's not new, it
already does so in wayland_output_get_shm_buffer() where the 'pm_image'
addresses only the interior area instead of the whole buffer.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>