I just spent ages debugging the fact that my Ctrl-Shift-T key stopped working in Ubuntu. This is my attempt to write a blog post that search engines will find if anyone else has the same problem. Ctrl-Shift-T is “new tab” in Terminal, and “reopen last closed tab” in Firefox, so it’s rather useful, and annoying when not working.
After lots of research and debugging, it turned out to be the following. I recently installed a bunch of VoIP apps, including Jitsi. Jitsi decided to run on startup, in a way which was invisible in the UI, and override a bunch of my keybindings, in a way which didn’t make it clear that it was the app capturing them. :-( So if anyone ever finds Ctrl-Shift keybindings stop working (seems like Jitsi takes A, H, P, L, M and T), and sees output like this in xev:
FocusOut event, serial 37, synthetic NO, window 0x5400001, mode NotifyGrab, detail NotifyAncestor FocusIn event, serial 37, synthetic NO, window 0x5400001, mode NotifyUngrab, detail NotifyAncestor KeymapNotify event, serial 37, synthetic NO, window 0x0, keys: 34 0 0 0 32 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
instead of the expected KeyPress / KeyRelease events, then look for some app which has pinched your keys. I spent ages looking through the Compiz config settings, finding nothing, but then started killing processes until I found my keys were working again.