M-= shortcut suddenly stops working in Emacs in KDE

Question

I'm trying to run M-= on a region of text, but nothing happens. I think the shortcut is registered (I don't get a message like "M-= is undefined") but the execution stops for some reason and there is no output.

If I run the command that the shortcut is bound to manually, count-words-region, it works fine. It also works if I type Esc =.

I added (global-set-key (kbd "M-=") 'count-words-region) to my initialization file, just to be sure that it is bound, but no effect. In fact, even if I bind some other function to M-=, pressing it has no effect.

I suspected that a recent update of the desktop environment might have redefined M-= (I'm using KDE), but currently nothing seems to be bound to that key.

How to debug this?

Update. If I run M-= through xev, I get the following output:

Alt pressed:

KeyPress event, serial 40, synthetic NO, window 0x5800001,
    root 0x1c9, subw 0x0, time 3737607, (61,104), root:(1461,133),
    state 0x0, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

= pressed:

FocusOut event, serial 40, synthetic NO, window 0x5800001,
    mode NotifyGrab, detail NotifyAncestor

FocusOut event, serial 40, synthetic NO, window 0x5800001,
    mode NotifyUngrab, detail NotifyPointer

FocusIn event, serial 40, synthetic NO, window 0x5800001,
    mode NotifyUngrab, detail NotifyAncestor

KeymapNotify event, serial 40, synthetic NO, window 0x0,
    keys:  4294967241 0   32  0   0   0   0   0   1   0   0   0   0   0   0   0   
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   

= released:

KeyRelease event, serial 40, synthetic NO, window 0x5800001,
    root 0x1c9, subw 0x0, time 3738919, (61,104), root:(1461,133),
    state 0x8, keycode 21 (keysym 0x3d, equal), same_screen YES,
    XLookupString gives 1 bytes: (3d) "="
    XFilterEvent returns: False

Alt released:

KeyRelease event, serial 40, synthetic NO, window 0x5800001,
    root 0x1c9, subw 0x0, time 3739829, (61,104), root:(1461,133),
    state 0x8, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

Does this mean the shortcut is handled by another process and how to find out which one?

Answer 1

What worked for me was to bind M-= to a command under KDE settings and then unbind that command. By first binding it to something it automatically unbinds whatever it was bound to before. This way you can reset the shortcut even if you don't know what it originally bound to. Now M-= works again in Emacs and is not captured by another process.

UPDATE

Unfortunately, this is not a permanent solution for me. The shortcut resets every time the computer restarts or, more specifically, when Kwin restarts. You can test by issuing killall kwin_x11 and kwin_x11 &. See related bug report here.