Rotating a pathbar

[Tristian Celestin <tristian celestin outlook com>]

What is the best solution to display a vertical set of linked buttons in GTK 3.10? For instance, suppose I 
wanted to create a vertically oriented pathbar.

I have a vertical gtk_box with 3 buttons. The gtk_box has the "linked" style class set. While the borders of 
these buttons become connected when the style class is set, the "linked" effect is lost because the gradient 
for each button is only appropriate for a horizontally oriented pathbar, not a vertically oriented one.

Here are screenshots of the phenomenon:
horizontal pathbar:
https://drive.google.com/file/d/0B05KpXoNVpBeQ0hhZ3ZUWU1iTWM/edit?usp=sharing

vertical pathbar:
https://drive.google.com/file/d/0B05KpXoNVpBea3NuaU1OdldiYTA/edit?usp=sharing


I think one solution is to use .css to change the gradient for buttons in the vertical pathbar widget's case. 
My concern is that this solution isn't independent of the system theme. Currently, I don't understand the 
details of this solution to know how much this concern matters.

My ideal solution would involve having the ability to rotate a widget. It doesn't look like GTK3 currently 
offers this out-of-the-box for arbitrary widgets. How much of a pain would it be to try to implement this 
myself for a particular widget, and where would I start? I think I would start at trying to figure out how to 
rotate the GdkRectangle the widget draws into.