Chat panel text flickers when radar/panel opacity set to 100%

[blast007]

A user reported this on the forums with their Intel HD 630 on Linux. So far I have replicated the text flicker with the latest 2.4 on Debian 10 with Intel HD 4000 graphics and Debian 11 with an AMD Radeon RX 570. I haven't yet tried it on Windows or macOS.

The issue is more noticeable at lower frame rates, so enabling the FPS limit set to 30 makes it very visible. I also noticed that opening and closing the menu leaves a ghost image of menu items that were over the chat panel area. Our panel rendering code has some old optimizations for software rendering so it won't re-draw if nothing has changed. This may be related. I think it worked better once I removed that. I still noticed some weird noise on the far right of the panel, perhaps a pixel wide.