meta_monitor_config_match_current() only matches the number of outputs
and if the output connector, vendor, product and serial match.
In the X backend, this means that we can't use it to bypass doing any
work because it won't detect cases where we actually want to update
ourselves like e.g. an output being turned off either by us or by
another X client (e.g. xrandr).
In the native backend, unlike the xrandr backend, we only get called
on real hotplug events and thus should always trigger the common
hotplug code to (possibly) apply a new mode so the check is pointless
anyway.
https://bugzilla.gnome.org/show_bug.cgi?id=738630
In randr events, configTimestamp can be considered the hotplug time,
i.e. whenever the server notices hardware changes, this value will be
updated.
Having that in mind, we can re-work the logic to make it clearer.
There are no semantic changes.
The code here was a bit messy with the addition of
hotplug_mode_update, and the comments were a bit confusing and
inaccurate. Clean it up and comment it a bit better to make the flow and
intention more clear.
RandR's QueryOutputProperty request makes the incredible decision of
throwing a BadName if you pass a property that doesn't exist, which
means that trying to check if a property exists is a royal pain when
using Xlib.
XCB's interface is much more friendly about errors and not having global
state and things like that, so use that instead to query our backlight
property.
If the property doesn't exist, a BadName error will be generated. This
is a terrible API, but it's what we're stuck with. Use
RRGetOutputProperty instead.
The output_id is more of an opaque identifier for the monitor, based on
its underlying ID from the windowing system. Since we also use the term
"output_id" for the output's index, rename our use of the opaque cookie
"output_id" to "winsys_id".
