The old model was implemented based on a misunderstanding of NotifyVirtual and
NotifyNonlinearVirtual events. It became complicated and was broken in some
places [1]. This patch wipes this model completely.
A much simplified implementation is provided instead. Rather than a top-down
approach ("we have a tree of windows, which ones need to get which event")
this one uses a step-by-step approach. For each window W between A and B
determine the pointer window P as perceived by this window and determine the
event type based on this information. This is in-line with the model described
by Owen Taylor [2].
[1] http://lists.freedesktop.org/archives/xorg/2008-December/041559.html
[2] http://lists.freedesktop.org/archives/xorg/2008-August/037606.html