[argyllcms] Re: Dispwin vs. xscreensaver

  • From: Geoff Kuenning <geoff@xxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 03 Mar 2015 00:14:46 -0800

Thanks, Graeme!  That does indeed help.

(Now all I have to do is find time to write an xscreensaver patch, since
I probably can't talk Jamie Z into doing it.)

> Geoff Kuenning wrote:
> Hi,
>> It appears that on modern RandR setups, dispwin uses XRRSetCrtcGamma to
>> set the gamma curve.  However, xscreensaver uses XF86VidModeGetGammaRamp
>> to read the current gamma, and the XF86VidModeSetGammaRamp to perform a
>> fadeout.  Unfortunately, it seems that GetGammaRamp doesn't return the
>> ramp set by SetCrtcGamma.  So the SetGammaRamp works like "dispwin -c".
> Right.
>> My feeling is that this is either an X server bug (on the theory that
>> the two interfaces should be compatible) or an xscreensaver bug (on the
>> theory that it should use SetCrtcGamme if it's available.  But I also
>> think that I'm more likely to find the necessary expertise on this list,
>> so I'm starting here.
> Both theories have merit. In practice though, XRandR is pretty fundamental
> to a modern X11 server, while XF86VidModeSetGammaRamp is part of the
> XVidMode extension. So to make these two be consistent implies
> making the XVidMode extension XRandR aware. I would guess that
> the XVidMode extension is tweaked with each HW implementation,
> and is in a "legacy maintanence" mode with the arrival of XRandR,
> so getting this updated would seem to be hard.
> xscreensaver on the other hand, is a stand alone application
> that (presumably) is still being maintained, so I think that
> making it XRandR aware would be the appropriate and practical
> fix.
> Hope that helps,
> Graeme Gill.

    Geoff Kuenning   geoff@xxxxxxxxxx   http://www.cs.hmc.edu/~geoff/

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