Adjusting the look and feel of the separator in a treeview/combobox

[Jef Driesen <jefdriesen hotmail com>]

Both the treeview and the combobox widgets have a set_row_separator_func 
function to turn a row into a separator. When I use them, the separator 
is drawn as a simple line. Is it possible to change the appearance of 
the separator? Or does depend entirely on the chosen theme?

I would like to have a separator that looks more like a real row, but 
with different colors,... An example of this can be found in the 
metadata view of the KDE application digiKam (see screenshot [1]).

I also noticed the normal line separator is broken into multiple pieces 
when the treeview contains multiple columns (I have a CellRendererToggle 
and a CellRendererText column). And that doesn't look very nice to me.

[1] http://www.digikam.org/?q=system/files&file=images/ss016.preview.png