Hi,

I was studying color theory this evening, and I wanted to experiment again with the Artistic Color Selector. But , after don't understanding it at all , I thought this one might be broken ( 2.8.3 testing, compiled source ). After a bit of research about it, I saw that indeed the feature is broken.
I know it's not a feature used by a lot of testers, it's probably broken since long time. The bug concerns the Luminance/Value/Lightness cells/slot who can't appear ; and so makes the whole selector obsolete. 

To reproduce :
* Open Krita, and display the docker :  ( Setting > Docker > Artistic Color Selector )
* Reset preferences of the docker  ( on the 'Pref' drop down button, press 'reset to default', and on  Reset, 'Reset Everything' ). The default is a HSY wheel, with : 9 light pieces, 12 hue pieces, 7 saturation rings. 

Problem :
* the 9 light piece promised are not displayed. Setting the Light Piece to 4 or 20 doesn't change anything, and HLS, HSV etc... got similar issue.  
To see how it should look , I had to find on internet ( Animtim blog ! thx ) a screenshot from 2.4 : 
http://timotheegiet.com/images/krita/15-ArtColorDock.png
Same on Wolthera's blog : https://lh6.googleusercontent.com/7nh7N_rEw8logstqrdCPzkKceK_VpEr0eyh4fXijlZ7CBLWIpuI0sDI27BE-WuV6AzPBmiwN8BJy75ryBdNMn0SEs6Wq2ksXu0Rjw5_DFCbUH8Uph2Dk9DIgIg

Observations :
* If you resize and look closely, on the top-left corner, a red outline of 1px width is here. 
* If you set in Pref the LightPiece to 1 , you can see a horizontal top bar slider, tinted with red to black gradient ( not usable ).