ui: add egl_fb_read_rect()

Similar to egl_fb_read(), same limitations, but with extra arguments to
read a subset of the framebuffer. Used in following commits.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20230606115658.677673-15-marcandre.lureau@redhat.com>
2 files changed