How to reverse-engineer a keyboard sequence?

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#1

OpenSUSE 13.2/KDE 4.14.8 with fglrx graphics

n attempting to toggle Compositing (Desktop Effects) from the keyboard, I entered the combination ctl+alt+F12 by mistake and crashed my system.

Alt+shift+F12 does work as intended.

If possible, I would like to decouple alt+ctl+F12 from whatever it is doing/starting.

I don’t see that combination in systemSettings-ShortcutsandGestures.
Is there somewhere else to look?

#2

ctrl-alt-F12 changes to an apparent uninitiated terminal thus the blank screen ctrl-alt-F7 should bring you back to the GUI

#3

Add the this to your xorg.conf, in the “ServerFlags” section:

Option "DontVTSwitch"  "true"

From “man xorg.conf”:

       Option "DontVTSwitch"  "boolean"
              This disallows the use of the  Ctrl+Alt+Fn  sequence  (where  Fn
              refers  to one of the numbered function keys).  That sequence is
              normally used to switch to another "virtual terminal" on operat-
              ing  systems  that  have  this  feature.   When  this  option is
              enabled, that key sequence has no special meaning and is  passed
              to clients.  Default: off.

As you probably don’t have an xorg.conf, better create a file in /etc/X11/xorg.conf.d/ named 10-myserverflags.conf (the exact name doesn’t matter, but it should end in .conf) with this content:

Section "ServerFlags"
  Option "DontVTSwitch"  "true"
EndSection

As gogalthorp already indicated, you didn’t “crash” your system. You just switched to console#12 (also called “virtual terminal #12” or “VT12”). You can switch back to the graphical system (which normally runs on console#7) with Ctrl+Alt+F7, or to a text mode console via Ctrl+Alt+F1 to Ctrl+Alt+F6.

#4

Ah so, a couple other things are starting to make sense.

Again, my system is 13.2/KDE 4.14.8 +fglrx.

IF I have Desktop Effects enabled (Compositing), then alt+ctl+F12 does in fact go to neverland and will not return to F7 or F1.

IF I toggle compositing off, it works as you describe.

I have also determined that this system will not Sleep (STR) if Desktop Effects are enabled.
Seems likely an fglrx issue, based on other discussions.

I do have an /etc/X11/xorg.conf, but it has no Server Flags section.

I now, more or less, know what is happening and how to avoid it; thanks

#5

Yeah, sounds like a graphics driver issue.
Have you updated to the latest fglrx version yet?
https://forums.opensuse.org/showthread.php/508077-AMD-Catalyst-15-5-for-openSUSE-–-new-makerpm-amd-script-is-available
Will take a while until it’s in the “official” repos, but not too long I suppose.

I do have an /etc/X11/xorg.conf, but it has no Server Flags section.

You could add it, if you wanted to disable those keyboard shortcuts.
Basically, just add the 3 lines I posted (as 10-myserverflags.conf) to the existing xorg.conf.

If you’re in doubt, please ask, and probably post the whole xorg.conf so I could tell you what changes are needed in particular.

#6

Nope, I had not seen the 15-5 post , may give it a go.

I understand the Xorg tweak, but am good with vt switching so don’t want to disable.
I just need to be more careful with the keyboard :wink: