Created attachment 534 [details]
I'm getting rendering bugs with Xfce on Ubuntu 14.04. If you press F5 on the desktop, it will render the text without the surrounding box (see attached screen shot). It seems to be a problem with tracking changes though, as grabbing a screen shot in the session shows that the frame buffer is properly updated.
I dug around and it turns out that there are a bunch of render operations that we don't hook in to properly. In this case it seems to be "Trapezoids", but there are a few others.
Fixed in upstream commit 2922e74970 and brought to CTC with vendor drop commit r33562
I could reproduce this problem on Fedora 28 usinf latest Xfce without compositing, creating a shortcut / folder on desktop using ThinLinc 4.9.0.
Problem is solved when using nightly build.