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Color: Properly handle calibration profiles and CTM

Sebastian Wick requested to merge swick/gnome-settings-daemon:ctm into master

System calibration profiles contain a VCGT tag and a colorimetric transform. When they are both applied the display is effectively has a calibrated sRGB color space. Currently there are two problems with this:

  1. The profile exposed to clients is created from EDID primaries and thus not sRGB
  2. The transform may only be applied for profiles which are specifically crafted for calibration purposes. Doing so for any other profile which is exposed to clients results in invalid conversions for clients.

Additionally the EDID created profiles are often not correct so even if clients ignore the profile the whole output can look incorrect.

This fixes all the issues by exposing sRGB profiles to clients if there is a system calibration profile and only setting the CTM transform for outputs which are calibrated that way.

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