Breeze icon theme wrong icons

I could not find this specific issue on Google. After I updated from Ubuntu 15.04 to 16.04 LTS, next to xfce4 and unity not working correctly, also the icons from the Breeze icon theme are behaving in an unexpected manner. I have tried to reconfigure and reinstall these packages, however the problem remains.

• Icons such as the Firefox icon are missing
• Instead of the blue folder icon I am seeing a simple flat white icon, this happens as well for icons of files with extensions of images, text, jars, etc.

.

Thanks for your help.

This problem was caused by some application from Ubuntu/Unity. In my inspection, it was appmenu-qt5 which was setting an environment variable QT_QPA_PLATFORMTHEME incorrectly, trying to unify look and feel in GTK and QT. To solve this, we have two options

Option 1: Remove package appmenu-qt5

Just remove the offending package appmenu-qt5

sudo apt remove appmenu-qt5

But, I don't recommend it, if important packages for Unity tries to go away with it. Though, In my case, no other packages was depending on it and simply went away.

Option 2: Unset the environment variable

You can also unset the environment variable QT_QPA_PLATFORMTHEME to solve this. I recommend this solution.

Put these lines at the end of your ~/.profile file.

## Fixing QT problems caused by `appmenu-qt5` in KDE environement
if [ "x$XDG_SESSION_DESKTOP" == "xplasma" ] || [ "x$XDG_SESSION_DESKTOP" == "xKDE" ]; then
    unset QT_STYLE_OVERRIDE
    unset QT_QPA_PLATFORMTHEME
fi