Enhance better Theme Support for better-tool-library

[Ventusfahrer]

When running Freecad with the UI-Theme FreeCAD Dark the visibility of certain information (mainly the one from UI-Elements using embedded images/pixmaps) is very poor. This makes the library close to not usable with this new UI-Theme.

I attached two example screenshots made with the currently weekly developers build of FreeCAD to show the problem.

It would be very great, if this could be enhanced. Changing the Theme in FreeCAD to have a better experience in an addon is little suboptimal

[knipknap]

Probably in your theme the style of subtitles in list views is not correctly defined, likely because this is not a common scenario in FreeCAD.

However, theme colors are completely defined in FreeCAD and cannot be changed in BTL. So you would have to open a theme issue with FreeCAD for a fix.

[luzpaz]

@Ventusfahrer did you open an upstream ticket yet ?