Robert Mader authored Aug 18, 2018 and Jonas Ådahl committed Aug 20, 2018

Currently xdg-shell applies a geometry set with set_window_geometry
unconditionally. But the specification requires:

> When applied, the effective window geometry will be
> the set window geometry clamped to the bounding rectangle of the
> combined geometry of the surface of the xdg_surface and the
> associated subsurfaces.

This is especially important to implement viewporter and
transformation.