[Bug 92977] Display artifacts when using MST

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=92977

--- Comment #4 from Dan Doel <dan.doel at gmail.com> ---
I've conducted some tests with respect to the color oddities on the
left-most/main monitor.

First, colorizing a blank image in gimp gives a way of seeing the color
disparity in a decent manner. When changing the hue step by step, it's possible
to see the colors becoming closer and farther apart from one another, which
would make sense if the color depths are different, I think. I was never able
to make the colors match exactly. I'm unsure if it's ever possible to get a
color to display the same when approximated to 24 bit and 16 bit color.

Next, it occurred to me that the issue may be gamma or brightness, because even
white on the right half of the monitor was 'more white' (or, brighter) than
white on the left. However, regardless of what I set these to on the left half
of the monitor using xrandr, the white was not as bright as on the right half.
I'm unsure if color depth is a sensible explanation for this, as I wouldn't
expect 16-bit white to be 'less white' than 24-bit white.

Finally, some other issues have led me to cause mode resets in which the main
monitor gets laid out logically backwards, so that the right half of the
monitor is the left half of the desktop. When this happens, the right half of
the monitor then gets put in the 'low' color mode, and is stuck there until a
reboot. So it seems that the color oddity is somehow related to _ever_ being
laid out with a positive x offset (since the entire right monitor is in this
mode from the start).

I don't know if any of this is helpful, but I thought I'd document it for
whoever eventually looks into this stuff.

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