Xrandr loop with gnome-settings-daemon [WAS: Re: Intel GM45: Loop of continuously triggered output detections]

[Alberto Milone]

On Saturday 17 January 2009 15:10:58 Peter Clifton wrote:
> Ok, it looks like I was off-base on my diagnosis of an infinite loop.
>
> It seems that gnome-power-manager may have been emitting a series of
> very small changes in backlight brightness to cause a fading effect. The
> fact that each triggered one (or more!) output probes meant that the
> process took a very long time indeed!
>
> Each change caused a notification from Xrandr, which all GDK using
> applications then translated to a "monitors-changed" signal.
>
> Interestingly, some people seeing the looping behaviour have reported it
> as only occurring after an upgrade from libXrandr 1.2.3 to 1.2.99.2.
> I've not had a lot of luck figuring out why this might be, but wonder if
> the bug fixed during that period relating to a corrupt / unset "window"
> property on the wire for some events, might have caused GTK to drop some
> of those events in the past without handling them. (Just an untested
> idea).
>
> gnome-power-manager handles the "monitors-changed" signal by retrieving
> information from Xrandr, causing a re-probe of outputs.
>
> Patching GDK not to emit "monitors-changed" for output property
> notifications causes the problem to go away as far as I can tell.
>
> Now Xrandr 1.3 is available, on systems which have it,
> gnome-power-manager should probably be calling
> XRRGetScreenResourcesCurrent () in retaliation to notified events - at
> the very least. (Not XRRGetScreenResources () as it currently uses)
>
> Arguably, GDK shouldn't be generating a "monitors-changed" signal for an
> output property change. The description of that signal states:
>
> "The ::monitors-changed signal is emitted when the number, size or
> position of the monitors attached to the screen change."
>
> I presume output properties don't reflect any of the above changes?

Using XRRGetScreenResourcesCurrent instead of XRRGetScreenResources in both 
gnome-desktop and gnome-power-manager solves the problem here (without having 
to patch GDK).

Regards,

Alberto Milone
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