Seemingly random uncontrolled key repeats
Over at the GNOME MPV repository a bug was found that the video player reacts unexpectedly to jumping in the video with keyboard shortcuts. Instead of following the 10 seconds forward/backward jump norm, the video would sometimes skip a bigger span of time.
To illustrate this I downloaded a 10 minute timer video (https://www.youtube.com/watch?v=4ASKMcdCc3g) and played it while repeatedly pressing the right arrow, which normally skips 10 seconds. As you can see the video is over after a few seconds. I did not spam the key, only pressed it around once or twice per second). Screencast_from_10.01.2019_00_24_22
I am reporting this against GTK, because I also have seen unexpected key repeats in other programs, such as Firefox and Inkscape, which to my knowledge both use GTK. These repeats sometimes lead to crashes there too, but I never really could reproduce the issue.
The crash seems very likely not application related, because it is not reproducible under Xorg (and in fact I never witnessed uncontrolled key repeats there either).
I tested this in GNOME Shell 3.30.2 and Weston 5.0.0-1, so it seems not to be a DE/WM error either.
System: Archlinux, Linux 4.20.0-arch1-1-ARCH, libinput 1.12.5-1