Wayland is sometimes at-odds with clients that want to enforce an aspect ratio or min/max window size, as certain window states have dimensions that either must be obeyed (maximized), or will give terrible results if they aren't (tiled). Use a viewport and a masking subsurface to handle cases where surfaces are unable to match the exact window size.
The changes made to accommodate this also catches some additional windowing related edge-cases, simplifies synchronization, and prevents commits before a buffer has been attached to the surface.
