I'm unsure if this relates to #1002 in any way. The bug is being reported here first as Geany is the only application with the behaviour so far.
For the past year or more, geany's scrollbars haven't repainted properly, as I've observed in a few versions of Lubuntu (Ubuntu with the alternate LXDE desktop environment). This happens on my desktop and numerous Lubuntu VMs. I'm using ```apt``` installed geany. I haven't tried building it from source, or normal Ubuntu to see if is happens there.
To reproduce: 1. Start geany 2. Make a new document 3. Copy & paste text into the new document, enough to make the document bigger than the available view. 4. Switch to another desktop (I'm using LXDE's desktop pager) 5. Switch back to the desktop with Geany 6. Note the scrollbars have not been repainted, so they show whatever was previously on the screen in the scroll area.
This happened in a fresh Lubuntu 18.04 VM I built earlier today.
Geany info (this is geany installed with ```apt```): ``` $ geany -V geany 1.32 (built on 2018-01-08 with GTK 3.22.26, GLib 2.54.1) ``` System info: ``` $ lsb_release -a Distributor ID: Ubuntu Description: Ubuntu 18.04.3 LTS Release: 18.04 Codename: bionic
$ uname -sr Linux 4.15.0-58-generic ``` Here's the before/Geany freshly started view on a new VM: 
After switching away, then back, the scrollbars have the desktop colour: 