RandR version 1.2 revisited

[Graeme Gill]

Keith Packard wrote:

> 10.1 XFree86-VidModeExtension
> 
> XFree86-VidModeExtension changes the configuration of a single monitor
> attached to the screen without changing the configuration of the screen
> itself. It provides the ability to specify new mode lines for the server to
> use along with selecting among existing mode lines. As it uses screen
> numbers instead of window identifiers, it can be used to affect multiple
> monitors in a single-screen Xinerama configuration. However, the association
> between screen numbers and root windows in a multi-Screen environment is not
> defined by the extension. Version 2.0 of this extension added the ability to
> adjust the DAC values in a TrueColor server to modify the brightness curves
> of the display.

Hello Keith,

Just to harp upon my favourite topic:

 > Most of the utility of this extension is subsumed by RandR version 1.2,
 > except for the gamma adjustments. If this features continue to be useful,
 > either some relationship between the screen indices used in the
 > XFree86-VidModeExtension and the screen/monitor pairs used int RandR or an
 > incorporation of this functionality into RandR might be needed.

The latter is in fact essential if color calibration, and consequently
high quality color profiling, is to be supported. To not support this
disqualifies RandR/X11 systems from consideration for color quality
critical work.

Might a way of incorporating the output LUT adjustment into RandR be
a set of LUT read/write functions that identify the target by the
CRTC ID ? [The CRTC being where I assume the underlying RAMDAC hardware is].

Graeme Gill.