🚀 go-pugleaf

Where do I find the names of those glyphs whose properties may be
manipulated through an .Xdefaults file?

For example, this works

            MyApp*HScrollBar*flat: red

but this  doesn't

           MyApp*HScrollBar*Thumb*flat: red

So "HScrollBar", "flat" are recognized, but "Thumb" is not.

Is there some way -- perhaps even cruising throught the iv source --
that I can use to learn which glyphs, with what names, can be
manipulated this way?

Thanks.

 - Paul