Follow-up to bug 89841: Using a dark system theme, the blue text color for text when the autofilter is active is hard to read.

Possible solutions: 
* different hard-coded value; con: not customizable and potentially not appropriate too
* attaching the color to some application color, eg. hidden col/row; con: using the normal application colors wont work well

Current code tries to merge the system text color with light blue more or less depending on dark themes.

    bool bDark = rStyleSettings.GetFaceColor().IsDark();
    Color aAFilterTextColor = rStyleSettings.GetButtonTextColor();
    aAFilterTextColor.Merge(COL_LIGHTBLUE, bDark ? 150 : 10); // color of filtered row numbers

It works when I recompile/debug returning RGB = 9494fe (kf5/gtk3 -> dark) and 0000f5 (gen -> bright) but obviously not with Version: 7.3.5.2 (the patch was for 7.2) and probably not reliably (first test with master returned blue text color). I suspect COLOR.merge() to be buggy.


We could alternatively do something like aAFilterTextColor = SC_MOD()->GetColorConfig().GetColorValue(svtools::CALCHIDDENROWCOL).nColor; but it mixes system theme color with application colors and is not appropriate too in many scenarios.