Re: inconsistent bindings of backspace and delete between X and xterm

[Andreas Schwab]

Dale Hagglund <rdh@yottayotta.com> writes:

> [I read bug-gnu-emacs via the gatewayed newsgroup.  Please cc me on
> any followups, if possible. --rdh]
>
> I was experimenting with emacs 21.3 running under X and then inside
> xterm, and I observe the following behaviour.  In all cases, I started
> emacs with the -q flag.
>
> 1. Under X, the backspace and delete keys generate the respective
>    window-system events, each of which is mapped to DEL via the
>    function-key-map, which is then bound to
>    `delete-previous-character'.
>
> 2. Under xterm version 4.2.99.903(174), backspace sends DEL and delete
>    sends `ESC [ 3 ~'.  Emacs treats DEL, of course, as
>    `delete-previous-character', but `ESC [ 3 ~' is mapped to the event
>    <deletechar>, which is bound to `delete-char'.
>
> This behaviour is inconsistent.  In each case, emacs can distinguish
> between the Delete and Backspace keys, but in one environment they
> behave, and in the other, differently.  Also, is there any reason why
> `ESC [ 3 ~' shouldn't be mapped to <delete> instead of <deletechar>.

This is a property of the terminal description.  For xterm it contains
`kdch1=\E[3~' (terminfo) or `kD=\E[3~' (termcap), thus `ESC [ 3 ~' is
mapped to <deletechar>.

Andreas.

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Andreas Schwab, SuSE Labs, schwab@suse.de
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