This improves the way the output numbers are handled for the x11
backend. Instead of using the number of active outputs plus one, the
last used number is stored and new outputs will increment it. This
fixes the situation where you start with one output, create a second,
close the first, and create a third. Without this, both outputs will be
X11-2, which causes an issue since the identifier will also be
identical. With this, the last output is X11-3 and the outputs can be
distinguished.
Set the default "wlroots - " title when the title argument to the
set_title functions is NULL. Otherwise, for at least the Wayland
backend, we'd crash because xdg_toplevel_set_title doesn't handle a NULL
pointer.
Before this commit, the x11 server would fill any exposed area with
white before the wlroots x11 backend got a chance to do anything. This
was e.g. visible when running rootston and resizing the window: When the
window becomes larger, the new area is filled with black.
By just not setting a back pixel value, this commit gets rid of this
behaviour.
Signed-off-by: Uli Schlachter <psychon@znc.in>
