Fixing terminfo so that terminal applications like vi(1) restore the screen
By PeteH on Jun 14, 2007
Ever noticed in Solaris that when you finish using vi(1) the terminal screen is not restored? Similarly true for applications like screen(1) and prstat(1M).
This was irritating me somewhat a few months ago but I've only now just logged bug 6569261 (xterm, xtermc, xterm-color: smcup/rmcup definitions are incorrect/missing) on it.
Essentially the problem is that the smcup and rmcup definitions don't work with our gnome-terminal and xterm implementations.
terminfo(4) defines smcup and rmcup as follows:
exit_ca_mode rmcup te String to end programs that use cup enter_ca_mode smcup ti String to begin programs that use cup
These sequences are typically used by terminal applications that control the cursor (eg vi). smcup switches to an alternate screen buffer, rmcup switches back.
The practical effect of this is that the scrolling screen buffer is replaced by a non-scrolling screen buffer when running vi and restored when vi exits.
The rmcup/smcup terminfo descriptions fail to work on Solaris xterm and gnome-terminal implementations. The scolling buffer is not restored and, in some cases, strange escape sequences are seen (eg mysterious '0' characters).
The Solaris xtermc and xterm-color terminfo defines:
These escape sequences don't make much sense for xterm. The xterm terminfo has nothing for rmcup/smcup.
The Sun Freeware terminfo definitions are more as expected:
xterm-color rmcup=\\E[2J\\E[?47l\\E8, smcup=\\E7\\E[?47h
For 'standard' xterm: smcup saves the cursor and switches to the alternate screen buffer; rmcup clears the screen, returns to the normal screen buffer and restores the cursor position.
xterm rmcup=\\E[?1049l smcup=\\E[?1049h
The 1049 sequence is a XFree addition which our xterm doesn't appear to support. Our current gnome-terminal (snv_65) does support this sequence.
xtermc rmcup=\\E@0\\E[?4r smcup=\\E@0\\E[?4s\\E[?4h\\E@1
This is as broken as our definition.
The workaround is to define smcup and rmcup appropriately. Here's one way to fix it:
- mkdir $HOME/terminfo
- TERM=xterm infocmp > xterm.src
- Edit xterm.src and add/change rmcup and smcup:
every entry must be terminated in a comma (,).
- TERMINFO=$HOME/terminfo tic xterm.src
- TERMINFO=$HOME/terminfo TERM=xterm xterm
You should now find that your scrolling terminal window is retored after 'fixed' window terminal applications finish.