In Plasma 4 (and, according to techbase.kde.org/Development/Tutorials/Plasma5/ThemeDetails, in Plasma 5 as well) there is a feature that allows theme designers to define different theme elements to be used for panels based on the side of the screen they are on. This seems to be quite buggy at the moment.

First of all, elements prefixed with north-mini, south-mini, east-mini and west-mini are completely ignored, whether or not there are analogous elements without -mini.

Secondly, north-bottom (and west-bottomleft and west-bottomright), west-right (and west-topright and west-bottom-right) elements are recognized and the workspace allocates room for them but doesn't paint them, leaving transparent borders in the panels (see screenshot).

The same theme renders perfectly under Plasma 4 so the theme isn't the problem. I assume this was not found before because Breeze (like most themes) doesn't use that feature.

Reproducible: Always

Steps to Reproduce:
1. Use a theme with prefixed panel elements
2. Use north or west panels or mini panels on any side of the screen

Actual Results:  
The bottom elements from the north panels and the right elements from the west panels are not displayed but still take up space.

Expected Results:  
All elements should be painted.

Screenshots:

Svg file with coloured parts to tell them apart: http://i.imgur.com/FY80LGC.png
Result: http://i.imgur.com/skZIp7n.png

As you can see, none of the north-mini or west-mini elements are actually painted. Instead, the north-center element is picked. The empty space underneath it might be for north-bottom, or, as it should, north-mini-bottom, or possibly center-bottom. Either way, it isn't painted.

For testing purposes, my theme can be found here: https://github.com/obnosim/velours/tree/plasma5