On startup, save the kernel brightness switch setting and restore it
on exit. If xfce4-power-manager has crashed, restore it on the next
run.

On most machines, especially those using the video module backlight, the kernel
will already have hooked up the brightness keys. If the user wants to use
xfce4-power-manager to control the keys, then we need to disable this module
setting to avoid conflicts like brightness lowered or raised twice on key
presses.

Of course, it would be nice if the power manager restored the original setting
when it gives control back to the kernel or on exit. To be able to do this,
it needs to remember the value.

It is best to do this in a xfconf setting so it survives crashes. This way,
power manager has a chance of restoring the original setting even after a
crash, so that the user will not have to fix it manually.

There are three possible settings, read from
/sys/module/video/parameters/brightness_switch_enabled:

 1 = kernel brightness switch setting is enabled (value 'Y')
 0 = kernel brightness switch setting is disabled (value 'N')
-1 = kernel brightness switch unavailable or could not be read

Similar to xfpm-power we set this up in xfpm-backlight.

This adds the necessary utility functions to read and write the kernel
brightness switch setting.

207 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).

207 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).

207 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).

190 translated messages, 17 untranslated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).

207 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).

207 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).

133 translated messages, 76 untranslated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).

Users can still control the sleep mode via the hidden option dpms-sleep-mode ("Standby" or "Suspend")
The default value is "Suspend" (implicitely set in xfpm-dpms.c)

209 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).

When the GTK theme changes, resize the panel button and its icon.

... and fix hiding battery stuff on the brightness tab if the laptop
has no battery.

216 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).

The exact intent of this feature is unclear, its implementation
unfinished.

Finally, let's remove the low-level code and remaining definitions.

Remove all related GUI widgets from the settings dialog.

The spin down feature does not work and would need a rewrite
to work with udisks-2. What's more, it is probably functionality
best handled by other tools or scripts, so let's remove it from
the power manager.

As a first step, this commit removes all interfacing code between
GUI and low-level udisks functions.

If xfpm isn't running when the power manager settings application
is launched it will ask if you want to start the xfpm then quit.
This patch changes it to launch xfpm, wait 2 seconds, then check
if xfpm loaded properly before continuing to show the settings
dialog.

216 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).