Bug 110677

Summary: Can't invert screen colors by adjusting the gamma ramp
Product: DRI Reporter: Vlad Zagorodniy <vladzzag>
Component: DRM/AMDgpuAssignee: Default DRI bug account <dri-devel>
Status: RESOLVED MOVED QA Contact:
Severity: normal    
Priority: medium CC: nicholas.kazlauskas
Version: XOrg git   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
observed
none
expected
none
Screen without inverted colors
none
dmesg output
none
Xorg log file none

Description Vlad Zagorodniy 2019-05-14 16:37:30 UTC 
On X11, there are several ways KWin can invert screen colors: either by using an OpenGL-based effect, or by adjusting the gamma ramp. While the former approach works well on most hardware, we experience some issues with the latter approach on AMD hardware.

After adjusting the gamma ramp, the screen is filled with mostly white color.
 
Steps to reproduce:
* Open System Settings, go to Shortcuts, select KWin component under Global Shortcuts tab, assign custom shortcut to "Invert Screen Colors";
* Press the shortcut.

(or just use xcalib -i)

Observed results:
The screen is filled with mostly white color.

Expected results:
Inverted screen.

Hardware: Radeon RX 580
Mesa: 19.0.3
Linux: 5.0.13
xorg: 1.20.4
Comment 1 Vlad Zagorodniy 2019-05-14 16:38:24 UTC 
Created attachment 144265 [details]
observed
Comment 2 Vlad Zagorodniy 2019-05-14 16:38:45 UTC 
Created attachment 144266 [details]
expected
Comment 3 Vlad Zagorodniy 2019-05-14 16:40:37 UTC 
Created attachment 144267 [details]
Screen without inverted colors
Comment 4 Michel Dänzer 2019-05-14 16:59:59 UTC 
Please attach the corresponding dmesg output and Xorg log file.
Comment 5 Vlad Zagorodniy 2019-05-14 17:18:36 UTC 
Created attachment 144268 [details]
dmesg output
Comment 6 Vlad Zagorodniy 2019-05-14 17:19:03 UTC 
Created attachment 144269 [details]
Xorg log file
Comment 7 Nicholas Kazlauskas 2019-05-14 17:29:02 UTC 
The issue is in the display driver.

The driver does an sRGB degamma, CTM, then sRGB regamma + user regamma - which explains why the screen is mostly white (since the curve is inverse).

If the the degamma block was put into linear bypass and the user regamma was applied directly to the regamma block that should give the correct result.

Not sure if mapping the legacy gamma to the full LUT would break any IGT color or standard X11 gamma operations.

I do have some changes that fix this kind of operation for atomic userspace but I'd have to take a look at the legacy one again to know if this is easy to support or not.
Comment 8 Martin Peres 2019-11-19 09:27:54 UTC 
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