Re: Moving DPMS to gnome-power-manager

[William Jon McCann <mccann jhu edu>]

Hey Richard,

Richard Hughes wrote:
> On Thu, 2006-01-05 at 12:27 -0500, William Jon McCann wrote:
> > I'm thinking that we make the following changes:
> >
> > 1. Move the GConf keys and policy management to gnome-power-manager
>
> Sure, good for me. I guess you mean the dpms_* keys currently in g-s.

Yup.

> > 2. Instead of activating display power management when the screensaver 
> > starts, gnome-power-manager can activate it when the session goes idle 
> > (in response to SessionIdleChanged).  This will allow it to work even 
> > when the screensaver is disabled.
>
> Yup, also okay.
>
> > 3. Probably still need to do manually turn on the display when we get 
> > "poked".  Or alternately, we can use a g-p-m D-Bus method to turn the 
> > display power on.
>
> DBUS method is good for me.
>
> > 4. Maybe the best thing is for g-p-m to emit a signal when the display 
> > power is changed.  g-s could then just watch for that.
>
> So, we need a DPMS API for g-p-m:
>
> typedef enum {
>         POWER_MODE_ON,
>         POWER_MODE_STANDBY,
>         POWER_MODE_SUSPEND,
>         POWER_MODE_OFF
> } PowerMode;
>
> void DpmsPowerSet (int PowerMode)
> int DpmsPowerGet (void)
>
> Or should we break out these individually like:
>
> void DpmsPowerSetModeOn (bool);
> bool DpmsPowerGetModeOn (void);
>
> And presumably emit:
>
> DbusStateChanged

I'm not a D-Bus expert/insider so there may be a better convention, but 
how about:

Methods:
void  setDpmsMode (const char *mode_string)
char *getDpmsMode (void)

Signals:
DpmsModeChanged (const char *mode_string)

where mode_string is one of: "on", "standby", "suspend", "off".

> Incidentally, what is the practical difference between
> GS_POWER_MODE_STANDBY and GS_POWER_MODE_SUSPEND? 

This says there is a difference:
http://en.wikipedia.org/wiki/VESA_Display_Power_Management_Signaling

In practice I'm not sure most hardware follows that but we should 
probably respect the standard.

> Sure -- do you feel confident hacking on the g-p-m codebase, or do you
> want me to implement this? I definitely need help with the API design.

I think we can copy and paste a good deal of this.  I'll take a stab at it.

Jon