When querying for an adjacent output we now need an absolute position in
order to know which adjacent output that matches. (The position is
either the current mouse position or the center of the currently focused
container, depending on context.)
If two outputs have one edge each that at least partially align with
each other they now count as adjacent.
Seamless mouse is affected by this and now properly moves and positions
itself between outputs with "uneven" placement (as long as they have at
least some part of the edge adjacent to each other).
When focusing or moving a container in a specified direction the center
of the current focused container decides where to look for an adjacent
output. So if e.g. an output has two adjacent outputs to the right and a
"focus right" command is issued then it's the placement of the currently
focused container that decides which output actually gets focused.
Also, if an output has at least one output adjacent in some direction
but the entire edge is not covered (ie. it has "holes" with no outputs),
then the algorithm will choose the output that is closest to the
currently focused container (this does not apply to seamless mouse, the
pointer will just stop at the edge in that case).
After adding pid to the socket path the `--get-socketpath` command broke
because it doesn't know the pid of the running instance. Fix this by
setting and querying `SWAYSOCK`.
Also ignore `SWAYSOCK` upon normal startup if a socket exists at that
location (ie. from another sway instance), and don't overwrite `I3SOCK`
if it exists either.
This will let users set their background to something other than that
cringy demoscene thing wlc has now. It's also going to be the first
wayland client written for sway, so I picked an easy thing to work on.
We'll have to figure out how to indicate that it's a special view.
Socket now includes pid in the filename (fixes nested sway sessions or
old sockets causing problems).
Fixed warnings on strict aliasing and cleaned up relevant code in
general.
