If an app has an owner-drawn ListView, rendering of menus and dialog windows can be reduced to drawing semi-transparent rectangles.

I created a small executable that demonstrates the problem. Build and run the "DisappearingMenus" app from https://github.com/fadden/MonoBugs/ . See the README for that project for additional details and repro steps.

Sample image after clicking on the "Edit" menu:

The problem was observed in Mono 5.18.0.240, on Ubuntu 18.04.2 LTS. It was also present in Mono 5.16.0.179 on Ubuntu 16.04.