This function is useful for testing the window contents in certain cases. In addition,
this means that we can now have reliable tests for softbuffer's actual functionality.
Signed-off-by: John Nunley <jtnunley01@gmail.com>
Co-authored-by: dAxpeDDa <daxpedda@gmail.com>
This is based on the API that will be used for no-copy presentation. But
wraps it in `set_buffer`.
This also fixes the Wayland buffer code to set `self.width` and
`self.height` on resize, and set the length of the shared memory file
when the buffer is created.
Co-authored-by: jtnunley <jtnunley01@gmail.com>
