Composer: Keyboard input lag
When using the composer on a 4K screen, there is keyboard input lag. Although difficult to illustrate, see the following gif: In the above recording, the two characters were typed in quick succession, then a moment later deleted in quick succession. However, the record shows that there is sometimes a significant lag between the two characters, both when inserting and when deleting. Obviously, this gets rather annoying when editing emails.
The problem only seems to occur at a 4K resolution, and indeed only when the composer window itself is large enough. I have tried a number of other text input fields in different applications (Firefox, Chromium, terminals, emacs, gedit, others), and curiously, the only other place where I have found this behaviour is the editor in Geary. So I'm stuck with using an external editor.
I'm using 3.38.1-1.fc33, and the same problem also occurred in the Flatpak version. I'm running Fedora 33, and using a Quadro RTX 4000 graphics card with the Nvidia drivers from RMPFusion. Let me know if any more information is needed.