How to make Krusader run under different icon theme

I use Kubuntu with KDE5 Plasma. I didn't want to migrate from KDE3 to KDE4. The environment was providing me everything I required for programming, use, ..etc. Same happened with the "upgrade" from KDE4 to KDE5. KDE5 to me is some new (but unneeded) visual changes, complete rewrite of the underlying code, a lot of new bugs to fight with.. :( I am going to document overcoming several issues with KDE5 and it's apps. This post is dedicated to best file manager under Linux - Krusader (guess I am staying under KDE for just a few of those apps: Krusader, Kmail (sadly no longer usable under KDE5, so had to switch to Claws Mail), Kate (as programming IDE) and Konsole as terminal).

After recent upgrade of Krusader and Paper icon theme, Krusader`s settings somehow were reset (krusaderrc seems to have been overwriten with a stock version). Moreover, it lost many of it's icons and started to display text strings instead, which seriously affected the GUI.

Package: paper-icon-theme
Version: 1.4+r679~daily~ubuntu16.04.1

Package: krusader
Version: 2:2.6.0-0ubuntu1~ubuntu16.04~ppa1

Paper icon theme is nice, but it's lacking some icons (fair to note, that it's under active development and this is changing for the better).

Nevertheless, I had to add missing icons to Krusader.

Krusader is built under KDE Frameworks and QT 5.

First of all, I googled if it's possible to change QT themes on a per app basis. I couldn't find anything of a value. Apparently - it's not.

Then I started to look under strace to where Krusader is looking for icons, as I needed to add a missing icon for bookmarks and folder history list. The following attempt to load a file caught my attention:


Krusader is looking for a binary icon theme file! Which means all it's icons can be supplemented in that file and this icon set can be different from the system theme.

In Kubuntu repositories I was able to find Breeze (default Plasma theme) icons in binary rcc format:

Breeze Icons

Downloading these icons, renaming .rcc file to icontheme.rcc and placing it under Krusader path made the application to use this set. Problem fixed!

PS: Useful command to clear system's icon cache when experimenting: $ cd /var/tmp/kdecache-$USER $ rm icon-cache.kcache