DRM objects like connectors and encoders might change at any time, in
particular they might become invalid between drmModeGetResources() and
getting the actual objects in which case they'll be NULL. Be defensive
against that.
Note that, if this happens, we should get another udev event soon
which will cause us to update our state.
https://bugzilla.gnome.org/show_bug.cgi?id=745476
EDID parsing has been refactored to a common meta_output_parse_edid()
function, which ensures the extracted information is the same on both KMS
and X11 backend, so it can be used consistently on eg. settings values.
https://bugzilla.gnome.org/show_bug.cgi?id=742882
In recent versions of the QXL driver, it may set "suggested X|Y" connector
properties. These properties are used to indicate the position at which
multiple displays should be aligned. If all outputs have a suggested position,
the displays are arranged according to these positions, otherwise we fall back
to the default configuration.
At the moment, we trust that the driver has chosen sane values for the
suggested position.
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
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".
