The wlr_drm_surface_init function is called (upon others) when the drm
mode is changed.
When the surface was used previously this replaced the gbm_surface, but
did not replace the gbm buffers (front/back).
With this, wlr_drm_surface_get_from never set up the new buffers with
the new glViewport because surf->front existed.
This frees the buffers to get new buffers on the new surface with the
new viewport.
emersion
Markus Ongyerth
Scott Anderson