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Make Shift-Tab work

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created 2003 · complexity intermediate · author Geoff Hubbard · version 5.7


Shift-Tab is a useful key combination to be able to use.

I wanted to use it for tab completion: Smart mapping for tab completion. Many people also use it for unindenting: Shifting blocks visually.

But Shift-Tab seemed not to work on my system (Slackware 8.1) but I managed to find a solution, and a workaround.

Diagnosis:

Make sure you are getting something from the keypress.
Go into insert mode and press <control-v> then <tab>
You should get a tab.
and press <control-v> then <shift-tab>
You should get ^[[Z

If this happens, it is good, you can skip the next part of the diagnosis.

Diagnosis Part 2:

If you get nothing when you do <control-v> then <shift-tab> go to a command line prompt (#) and type:

# xmodmap -pke | grep 'Tab'

It should either show:

keycode 23 = Tab
or
keycode 23 = Tab ISO_Left_Tab

Now, which one is the 'right' one seems to depend on what terminal program you are using its various settings. (I need to use the 'ISO_Left_Tab' one with 'xterm' but the 'Tab' one with Eterm) I suggest you try changing to the mapping to the other one and test what you get from the keypresses again. If it doesn't work, you can just change it back.

To change the mapping:

# xmodmap -e 'keycode 23 = Tab ISO_Left_Tab'
or
# xmodmap -e 'keycode 23 = Tab'

If changing the xmodmap setting worked, you'll probably need to put it somewhere where it will load on X startup or login. (.xinitrc or .bashrc or somewhere else depending on your system config.) If it didn't work see the other things to try below.

Interpreting shift-tab correctly:

Once you have the shift-tab key combo generating the correct string ^[[Z you just need to make sure that is then interpreted by Vim as <s-tab>

As of version 6.2 Vim does this, so upgrading to 6.2 would be good. If you cannot upgrade for whatever reason try this workaround:

:map <Esc>[Z <s-tab>
:ounmap <Esc>[Z

This will map the key you get when you press shift tab to <s-tab> which you can then use in other maps/scripts I suggest adding these lines (minus the leading : of course) to your .vimrc

A more robust version of the above is to directly tell Vim what escape sequence is used for <S-Tab>. This can be done by setting the t_kB option appropriately:

 :exe 'set t_kB=' . nr2char(27) . '[Z'

Other things to try:

If none of the above worked, here are some other things to investigate.

Make sure your window manager is not eating the keystrokes. You don't have it mapped there to change desktop, or switch between windows or something do you? Use 'xev' to check that shift-tab is registering as a keypress and what it is returning.

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