There was a race condition when mapping a window and not setting the event mask
before. Therefore, the ReparentNotify and (more important) the UnmapNotify generated
by reparenting were not received, thus leaving the awaiting_useless_unmap variable
of the client "true". To just make it work, in previous commits the DestroyNotify
handler was introduced. Fortunately, with fixing this race condition by first
setting the event mask and mapping the window afterwards, we can remove this handler.
As for the dock windows, there were quite some occurences were client->container
was used without checking if the client is inside a container at all.
Furthermore, the client’s strut containing the space to reserve at the screen edge
is now checked and the desired height is set to the window’s height if the strut
contains 0 or if no strut was specified at all.
By specifying XCB_EVENT_MASK_SUBSTRUCTURE_REDIRECT, the window manager
will get map request events instead of map notify events, and therefore
can act sooner (the window won’t be positioned on the screen and moved
afterwards).
Furthermore, this fixes some problems with GIMP/VLC (and probably others)
which caused endless loops.
Also, events which should be ignored are now saved in a queue rather than
saving just the last event. This should eliminate race conditions.
Note that there is a new FIXME in src/handlers.c. Some windows generate
unmap notify events when reparenting while others don’t. We need to
understand, document and implement a more correct way to handle this.
