As per 5643aa584051bde2069b056f85177a875e351fb4, weston no longer repaints just the damaged area of a surface but always the entire surface. How to reproduce: run simple-shm and enable repaint debugging. simple-shm does not post damage for the white border, but from the debug you can see weston repainting the entire surface.
commit 5df8ecac5d31467122a9d8bda6241d5957ae6848 Author: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com> Date: Tue Oct 30 17:44:01 2012 +0200 compositor: Fix partial repaints Partial repaints have been broken since the introduction of the atomic surface updates. The problem was that surface_commit would set the geometry dirty flag unconditionally, causing transform updates on every frame which would in turn cause weston_surface_damage_below() to damage the whole surface area. This patch changes this so that flag is only set if the pending buffer has a different size, the location of the surface changed or the opaque region changed. Note that changing the opaque region will cause a full repaint of the affected surface, because of the transform update. https://bugs.freedesktop.org/show_bug.cgi?id=56538
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.