mouse_warping container sets cursor to (0,0) for newly created windows (on drm backend)

[Emantor]

The focus is set during view_map, however the window size is not set at this point and the pointer warps to (0,0).
The proper fix would be to warp the pointer to the correct position in the new window, however that is only set after view_update_size is called, which is done on surface commit, not on surface map.

Easy fix but partially broken fix (see fix-mouse-warping-container in my repo):
check if x and y are > 0 before warping the cursor, however that effectively disables focus warping for new windows.

From IRC:

ryan-au: Emantor: The size is set when calling the arrange_* function                                                                                                                           
         That might be done from each shell's handle_map function                                                                                                                               
         Maybe you could move that into view_map, then set the focus after calling arrange