Chapter 9. The Operating System

74

<  

generates

KB_BackSpace

in X.

Delete

generates

KB_Delete

in X.

  X translations are set up to make

KB_Backspace

generate ASCII DEL, and to make

KB_Delete

generate

ESC [ 3 ~

(this is the vt220 escape code for the  delete character 

key). This must be done by loading the X resources using

xrdb

on all local X displays,

not using the application defaults, so that the translation resources used correspond to

the

xmodmap

settings.

  The Linux console is configured to make

<  

generate DEL, and

Delete

generate

ESC

[ 3 ~

.

  X applications are configured so that

<

deletes left, and

Delete

deletes right. Motif

applications already work like this.

  Terminals should have

stty erase ^?

.

  The

xterm

terminfo entry should have

ESC [ 3 ~

for

kdch1

, just as for

TERM=linux

and

TERM=vt220

.

  Emacs is programmed to map

KB_Backspace

or the

stty erase

character to

delete backward char

, and

KB_Delete

or

kdch1

to

delete forward char

, and

^H

to

help

as always.

  Other applications use the

stty erase

character and

kdch1

for the two delete keys,

with ASCII DEL being  delete previous character  and

kdch1

being  delete character

under cursor .

This will solve the problem except for the following cases:

  Some terminals have a

<  

key that cannot be made to produce anything except

^H

. On

these terminals Emacs help will be unavailable on

^H

(assuming that the

stty erase

character takes precedence in Emacs, and has been set correctly).

M x help

or

F1

(if

available) can be used instead.

  Some operating systems use

^H

for

stty erase

. However, modern telnet versions and

all rlogin versions propagate

stty

settings, and almost all UNIX versions honour

stty

erase

. Where the

stty

settings are not propagated correctly, things can be made to

work by using

stty

manually.

  Some systems (including previous Debian versions) use

xmodmap

to arrange for both

<  

and

Delete

to generate

KB_Delete

. We can change the behavior of their X clients

using the same X resources that we use to do it for our own clients, or configure our

clients using their resources when things are the other way around. On displays config 

ured like this

Delete

will not work, but

<  

will.

  Some operating systems have different

kdch1

settings in their

terminfo

database for

xterm

and others. On these systems the

Delete

key will not work correctly when you

log in from a system conforming to our policy, but

<  

will.