View Full Version : [all variants] ALT-1, ALT-2, etc. don't work in VNC client

December 7th, 2009, 05:46 PM
When I run my VNC viewer (xtightvncviewer), ALT-1, ALT-2, etc. do not get passed to the VNC server. This is annoying when using Emacs and switching between tabs in various apps (Firefox, gnome-terminal, and mrxvt).

Is there a configuration or switch which can fix this?


December 7th, 2009, 06:22 PM
Go to Preferences->Keyboard Shortcuts, find what is set to use those alt combos, and set them disabled (use backspace).

Compiz sets some hotkeys too.

December 8th, 2009, 05:38 PM
I don't see any shortcuts which specifically capture ALT-1, etc.

But! When connecting to the VNC server from Windows, I discovered that it too didn't work. Which makes me thing it's a server-side thing.

I think my xrdp uses xtightvncserver. Are there any tweaks to allow these sequences to be passed through?

December 25th, 2009, 09:27 PM
I made some new (or a couple of weeks ago :)) discoveries:
Fluxbox was capturing some ALT-1, etc. I commented out the relevant lines in ~/.fluxbox/keys .
X Windows wasn't dealing with the ALT key properly; I did the xmodmap trick (on the xmodmap man page) to map ALT to META.
starting TightVNC Viewer on Windows with the Scroll Lock (ScrlLk) key seems to make things (all ALT key operations) work perfectly.
However, I still am unable to make xtightvncviewer pass the ALT key for (ALT-1) through.

ALT-1, ALT-2, etc. works perfectly outside of xtightvncviewer (e.g., works in mrxvt with multiple tabs). xev correctly shows Alt_L and "1" when pressing ALT-1. Because it works with Windows but not Linux, this makes me think this is a bug with xtightvncviewer.

December 29th, 2009, 04:47 PM
I made one more discovery.

If I run xev locally (the client machine running the VNC viewer), the ALT key emits ALT_L. If I run xev on the host machine (running the VNC server), the ALT key emits Meta_L. I.e.,
local -> Alt_L
remote -> Meta_L
So, it seems that xtightvncviewer remaps the ALT key somehow. I cannot find out how to suppress this remapping. (The ScrollLk trick doesn't seem to work with xtightvncviewer unlike the Windows VNCViewer.)

December 30th, 2009, 04:30 AM
It appears that through the proper manipulation of xmodmap (xmodmap -e 'add mod4 = Alt_L'), the ScrollLk key trick seems unnecessary.

And, in fact, everything works, including both Windows VNCViewer and xtightvncviewer. Everything, that is, except Firefox. I just could not get ALT-Left to go back a page. There seems to be a strange bug where if both mod1 and mod4 include an Alt key, it rejects both. As a workaround, I only add Alt_L to mod4 (so it appears in both mod1 and mod4) and leave Alt_R only in mod1. So, I can do Alt_R-Left to go back a page. (I could not figure out a way to manipulate Firefox to accept the Alt key in the way I want it.)