The `dimension_t` struct was used in many different places and even held
on the geometry info at some point which is counter-intuitive as it's
best to have each struct serve a single purpose.
Change the value of geometry in settings from an unparsed string to a
struct containing the properly parsed geometry info. Since we depend on
X11 for geometry parsing this (unfortunately) introduces an X11
dependency on the settings module, this can only be resolved if we
implement our own parsing.
Since after the release a lot of downstream users will not be building
from source, it makes a lot more sense to have an option to fall back to
the Xinerama extension for those that are still on systems that do not
support RandR.
Previously, we were getting screen info every time we tried to move the
window. To improve the situation, information about the available
screens is initialised once when dunst starts and further behaviour
depends on the compile-time options used.
If Xrandr is enabled, screen information is updated when an
XRRScreenChangeNotify event is received, meaning only when the screen
layout changes.
If Xinerama is enabled, screen information is only updated on startup.
This behaviour might be changed later.
If none are enabled, then dunst assumes only one screen and ignores all
multi-monitor options.
Since we are adding Xrandr support to allow for automatic dpi detection,
split screen handling code into a new file as part of the effort to
simplify x.c
