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Re: endwin, and temporarily leaving curses mode

From: Thomas Dickey
Subject: Re: endwin, and temporarily leaving curses mode
Date: Fri, 21 Apr 2006 12:49:35 -0400 (EDT)

On Fri, 21 Apr 2006, Mike Mueller wrote:

I'm working on a program which spends all its time in
curses/raw/noecho mode.  Recently I started working on a feature that
lets users drop out to a shell temporarily.  This seems to be a common
thing to do, and the answer in the docs is endwin() before the shell,
and refresh() after, as seen here:


However, I run endwin(), then invoke the shell (via system()) and the
result is somewhat correct, but not completely.  The shell displays a
normal prompt, but typed characters are not echoed back to the
terminal.  'ls' displays things in neat columns, so it seems like

I don't see this (checking with ncurses' test program - menu 'a', 's' to shell-out).

we're in a semi-cooked mode.  Finally, when the user exits the shell,
I prompt "press enter to continue" and call fgets() to wait for that
'enter' before anything else happens.  Unfortunately, hitting enter
(or ^M) doesn't do anything at this prompt.  Hitting ^J, on the other
hand, does work.

When I call refresh(), curses is back to normal and my app is working
fine.  So the problem is only in the endwin-shell part of the process.

That part is expected behavior: refresh() checks to see if there was an endwin() which reset the terminal modes. I don't recall(*) a bug in this area - but it is possible to confuse things by saving the ncurses terminal modes as the default, e.g.,

       The def_prog_mode and def_shell_mode routines save the current terminal
       modes as the "program" (in curses) or "shell" (not in curses) state for
       use by the reset_prog_mode and reset_shell_mode routines.  This is done
       automatically  by initscr.  There is one such save area for each screen
       context allocated by newterm().

(*) but if I knew the version of ncurses and the platform, something might
    come to mind.

Thomas E. Dickey

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