Re: Problem with keys

[Thomas Dickey]

On Mon, 5 May 2008, galapogos wrote:

> Thomas Dickey-2 wrote:
> > On Fri, May 02, 2008 at 01:42:01AM -0700, galapogos wrote:
> > > Hi
> > > I'm building a simple application using ncurses in Mandriva 2008. I have
> > > a
> > > simple text user interface asking the user to enter an ASCII string, and
> > > then I'm using wgetch() to parse the string, checking if each character
> > > is
> > > an ASCII character using isascii(). I'm also checking for special
> > > characters
> > > such as enter and backspace.
> > >
> > > I'm using KEY_BACKSPACE to detect for backspace. It's ASCII value seems
> > > to
> > > be 263, but when I test my app using Mandriva (Konsole), backspace seems
> > > to
> > > be ASCII value 127 instead, so the backspace is never detected. Why is
> > > there
> > > a discrepancy between the 2?
> >
> > ncurses will only return KEY_BACKSPACE if the character(s) happen to
> > match the string kbs in your terminal's description.  It's likely
> > that is ^H (8) instead.  For some platforms, kbs is normally ^H,
> > and for others it is normally ^? (127).
> I've used infocmp to check. kbs is mapped to ^H, but somehow it's still
> being translated to ^? or ASCII 127. When I use stty to  change it to ^H
> with the command "stty erase ^H", in the Linux console a "^?" shows up
> whenever I press the backspace key, and the ncurses application still shows
> backspace as ASCII 127.

If kbs is ^H, then ncurses looks for control/H.
But if your terminal sends ^?, then ncurses will not know it is backspace.

Most of the Linux distributions make changes as needed to make the
terminal emulators send ^? for "backspace", while almost everyone else 
uses ^H.  They should also modify the terminfo entries in ncurses, but
not all of the Linux distributions do _that_.

--
Thomas E. Dickey
http://invisible-island.net
ftp://invisible-island.net