Geany 1.32 on Kubuntu 18.04 (open GL 2.0); Breeze desktop theme. I have a strange situation. Running Geany in user mode (not as root), the toolbar icons are simply missing, with only the system place holders showing. However, if I run Geany as root to access system files the icons show. 
as root:
Geany is supposed to use the system theme, as your user version does, so that one is correct.
Why the root user isn't supplied with a theme is a Kubuntu issue. Maybe a Kubuntu user might be able to help.
Also Geany devs do not support running Geany as root, is a complicated application and your security isn't guaranteed. [required disclaimer]
You have it backwards --running as root the icons show properly.
You have labelled the second image "as root" and it shows the default GTK/Geany fallback icons, not the theme icons.
To be clear, the top screenshot is using the Breeze theme from your KDE, while the bottom one is using what appears the be the default Ubuntu Humanity theme.
I don't think this is a Geany issue at all, just that you're using two different user accounts which have different icon themes configured.
I'm going to let it go at that. I think you're right, it is a problem with Kubuntu or KDE. Also, since I posted this I've observed the same issue even with KDE apps. The old Mint I had with KDE was near perfect but it is now obsolete and I haven't found an OS I like as well.
Closed #2375.
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