Esoteric GTK Question

I’ve finally gotten around to tinkering with Xojo on the Raspberry Pi, and it’s extremely impressive. The anomalies I’ve run into so far have been trivial. However, there is one I might be able to deal with given some more information. I’ve had a halfway decent OSX theme for XFCE for some time now. In the attached picture, note the list header in Thunar. Not bad, right? Now note the list header in my quickie “Activity Monitor” application. If I had a hint as to what GTK widgets to theme over, I might be able to make my Xojo apps look right. Anyone have any idea what the Xojo Listbox header is in GTK-speak?

Hello Daniel! Very nice!
Could I ask you how did you install it?
Does it work on RASPBIAN JESSIE?
Thanks Rob

Daniel what do you mean with “Anyone have any idea what the Xojo Listbox header is in GTK-speak?”
I don’t think that Listbox header can change and look like the theme ….

The picture above was Wheezy. Since my original post, I’ve tried this on Jessie and it works fine.

I assumed that Xojo was using standard GTK elements for its listbox headers, and therefore I could theme them. Still no luck.

Apparently I missed this when it was first posted, sorry. It uses gtk_paint_box with “box” as the detail.