So, I just committed FS#8799 which adds the UI viewport. With this, you can make nice themes like this:
I.e.: Put a (invisible) viewport border around lists and stuff.
We possible want to use that feature not only for pretty themes, but also to have some sort of background wps updating (but later, if at all).
How to use?
You add the lines to your themes.cfg, there's no setting for it in any menu.
ui viewport: X, Y, [width], [height], [font], [foreground pattern], [background pattern] (the patterns are dependant on the depth of your display.
The same for the remote, just that it's "remote ui viewport: ..."
width through background pattern might be omitted, X and Y not. Omit them by inserting a "-".
As you can see, nearly the same syntax as for WPS viewports, the way the optional values is also the same. In fact, it's the same except for the comma separator!
An example: "ui viewport: 15,15,100,150,1,-,-". That will give you a ui viewport starting at 15|15, 100px wide, 150px high, using the user font and using the colors from the global settings.
PS: You might want to report bugs here if you find some (but our flyspray tracker is still preferred).
PS2: If you have themes that do not have the above lines in are going to look weird if you have a theme with ui viewport before (the viewport isn't reset). You then need to add "ui viewport: -" and "remote ui viewport: -" (without the quotes) to the thems to have them resetting the viewport properly.