Improve responsiveness while in 'replace-buffer-contents'

[emacs.git] / doc / misc / edt.texi

\input texinfo
@setfilename ../../info/edt.info
@settitle EDT Emulation for Emacs
@include docstyle.texi

@copying
This file documents the EDT emulation package for Emacs.

Copyright @copyright{} 1986, 1992, 1994--1995, 1999--2018
Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover Texts being ``A GNU Manual,''
and with the Back-Cover Texts as in (a) below.  A copy of the license
is included in the section entitled ``GNU Free Documentation License''.

(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
modify this GNU manual.''
@end quotation
@end copying

@dircategory Emacs misc features
@direntry
* EDT: (edt).                   An Emacs emulation of the EDT editor.
@end direntry

@titlepage
@title EDT Emulation User's Manual
@author Kevin Gallagher
@author @email{kevin.gal@@verizon.net}
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@ifnottex
@node Top
@top Emacs EDT emulation
This manual describes the Emacs EDT package, which provides emulation
of DEC's EDT editor.

@insertcopying
@end ifnottex

@menu
* Overview::                Overview of the EDT package.
* Supported terminals::     Terminals/keyboards that are supported.
* Starting emulation::      How to get started.
* Platform-specific notes:: Notes specific to certain platforms.
* Differences::             How does this EDT emulation differ from real EDT?
* Highlights::              Some highlights, and comparisons to the
                              original Emacs EDT emulation.
* Customizing::             Customizing emulation.
* GNU Free Documentation License::  The license for this manual.
@end menu

@node Overview
@chapter Overview of the EDT Package

This manual describes version 4.0 of the EDT Emulation for Emacs.
It comes with special functions which replicate nearly all of
EDT's keypad mode behavior.  It sets up default keypad and function key
bindings which closely match those found in EDT@.  Support is provided so
that users may reconfigure most keypad and function key bindings to
their own liking.

Version 4.0 contains several enhancements (@pxref{Changes}).

@menu
* Quick start::             How to begin using EDT.
* Changes::                 What's new in version 4.0.
* Goals::                   The aims of this package.
@end menu

@node Quick start
@section How to Begin Using EDT

To start the EDT Emulation, first start Emacs and then enter @kbd{M-x
edt-emulation-on} to begin the emulation.  After initialization is
complete, the following message will appear below the status line
informing you that the emulation has been enabled: ``Default EDT keymap
active''.

   You can have the EDT Emulation start up automatically, each time you
initiate an Emacs session, by adding the following line to your
@file{.emacs} file:

@example
(add-hook 'emacs-startup-hook 'edt-emulation-on)
@end example

@noindent @strong{Important:} Be sure to read the rest of this manual.
It contains very useful information on how the EDT Emulation behaves and
how to customize it to your liking.

@noindent The EDT emulation consists of the following files:

@itemize

@item
@file{edt.texi}---This manual.

@item
@file{edt-user.el}---An example customization file (located in the
Emacs distribution etc directory).

@item
@file{edt.el}---EDT emulation functions and default configuration.

@item
@file{edt-lk201.el}---Built-in support for DEC LK-201 keyboards.

@item
@file{edt-vt100.el}---Built-in support for DEC VT-100 (and above) terminals.

@item
@file{edt-pc.el}---Built-in support for PC 101 Keyboards under MS-DOS.

@item
@file{edt-mapper.el}---Create an EDT LK-201 map file for keyboards
without built-in support.

@end itemize

@node Changes
@section What's New in Version 4.0

Version 4.0 contains the following enhancements:

@enumerate

@item
Scroll margins at the top and bottom of the window are now supported.
(The design was copied from @file{tpu-extras.el}.)  By default, this
feature is enabled with the top margin set to 10% of the window and the
bottom margin set to 15% of the window.  To change these settings, you
can invoke the function @code{edt-set-scroll-margins} in your
@file{.emacs} file.  For example, the following line

@example
(edt-set-scroll-margins "20%" "25%")
@end example

@noindent sets the top margin to 20% of the window and the bottom margin
to 25% of the window.  To disable this feature, set each margin to 0%.
You can also invoke @code{edt-set-scroll-margins} interactively while
EDT Emulation is active to change the settings for that session.

@strong{Please note:} Another way to set the scroll margins is to use
the Emacs customization feature to set the following two variables
directly: @code{edt-top-scroll-margin} and @code{edt-bottom-scroll-margin}.

Enter the Emacs @code{customize} command.  First select the
@samp{Editing} group and then select the @samp{Emulations} group.
Finally, select the @samp{Edt} group and follow the directions.

@item
The @samp{SUBS} command is now supported and bound to @kbd{GOLD-Enter}
by default.  (This design was copied from @file{tpu-edt.el}.)  Note, in
earlier versions of EDT Emulation, @kbd{GOLD-Enter} was assigned to the
Emacs function @code{query-replace}.  The binding of
@code{query-replace} has been moved to @kbd{GOLD-/}.  If you prefer to
restore @code{query-replace} to @kbd{GOLD-Enter}, then use an EDT user
customization file, @file{edt-user.el}, to do this
(@pxref{Customizing}).

@item
EDT Emulation now also works in XEmacs, including the highlighting of
selected text.

@item
If you access a workstation using an X Server, observe that the
initialization file generated by @file{edt-mapper.el} will now contain
the name of the X Server vendor.  This is a convenience for those who
have access to their Unix account from more than one type of X Server.
Since different X Servers typically require different EDT emulation
initialization files, @file{edt-mapper.el} will now generate these
different initialization files and save them with different names.
Then, the correct initialization file for the particular X server in use
is loaded correctly automatically.

@item
Also, @file{edt-mapper.el} is now capable of binding an @acronym{ASCII}
key sequence, providing the @acronym{ASCII} key sequence prefix is
already known by Emacs to be a prefix.  As a result of providing this
support, some terminal/keyboard/window system configurations, which
don't have a complete set of sensible function key bindings built into
Emacs in @code{function-key-map}, can still be configured for use with
EDT Emulation.  (Note: In a few rare circumstances this does not work
properly.  In particular, it does not work if a subset of the leading
@acronym{ASCII} characters in a key sequence are recognized by Emacs as
having an existing binding.  For example, if the keypad 7 (@key{KP7})
key generates the sequence @samp{@key{ESC}Ow} and @samp{@key{ESC}O} is already
bound to a function, pressing @key{KP7} when told to do so by
@file{edt-mapper.el} will result in @file{edt-mapper.el} incorrectly
mapping @samp{@key{ESC}O} to @key{KP7} and @samp{w} to @key{KP8}.  If
something like this happens to you, it is probably a bug in the support
for your keyboard within Emacs @strong{or} a bug in the Unix
termcap/terminfo support for your terminal @strong{or} a bug in the
terminal emulation software you are using.)

@item
The @code{edt-quit} function (bound to @kbd{GOLD-q} by default) has been
modified to warn the user when file-related buffer modifications exist.
It now cautions the user that those modifications will be lost if the
user quits without saving those buffers.

@end enumerate

@node Goals
@section The Aims of this Package

@enumerate

@item
Emulate EDT Keypad Mode commands closely so that current EDT users will
find that it easy and comfortable to use Emacs with a small learning
curve.

@item
Make it easy for a user to customize EDT emulation key bindings without
knowing much about Emacs Lisp.

@item
Make it easy to switch between the original EDT default bindings and the
user's customized EDT bindings, without having to exit Emacs.

@item
Provide support for some TPU/EVE functions not supported in EDT.

@item
Provide an easy way to restore @strong{all} original Emacs key bindings,
just as they existed before the EDT emulation was first invoked.

@item
Support Emacs and XEmacs 19 and higher.

@item
Supports highlighting of marked text within the EDT emulation on all
platforms on which Emacs supports highlighting of marked text.

@item
Handle terminal configuration interactively for most terminal
configurations, when the emulation is invoked for the first time.

@item
Support a PC AT keyboard under MS-DOS.

@end enumerate

@node Supported terminals
@chapter Terminals/Keyboards that are Supported

Keyboards used under a Window System are supported via the
@code{edt-mapper} function.  The first time you invoke the emulation
under a window system, the @code{edt-mapper} function is run
automatically and the user is prompted to identify which keys the
emulation is to use for the standard keypad and function keys EDT
expects (e.g., @key{PF1}, @key{PF2}, @key{KP0}, @key{KP1}, @key{F1},
@key{F2}, etc.).  This configuration is saved to disk read each time the
emulation is invoked.

In character oriented connections not running a window manager, built-in
support for the following terminals/keyboards is provided:

@enumerate

@item
DEC VT-100 series and higher.  This includes well behaved VT clones and
emulators.  If you are using a VT series terminal, be sure that the
@env{TERM} environment variable is set properly before invoking emacs.

@item
PC AT keyboard under MS-DOS.

@end enumerate

Be sure to read @ref{Platform-specific notes} to see if those notes
apply to you.

@node Starting emulation
@chapter How to Get Started

Start up Emacs and enter @kbd{M-x edt-emulation-on} to begin the
emulation.  After initialization is complete, the following message will
appear below the status line informing you that the emulation has been
enabled: ``Default EDT keymap active''.

You can have the EDT Emulation start up automatically, each time you
initiate an Emacs session, by adding the following line to your
@file{.emacs} file:

@example
(add-hook 'emacs-startup-hook 'edt-emulation-on)
@end example

A reference sheet is included (later on) listing the default EDT
Emulation key bindings.  This sheet is also accessible on line from
within Emacs by pressing @key{PF2}, @kbd{GOLD-H}, or @samp{HELP} (when
in the EDT Default Mode).

It is easy to customize key bindings in the EDT Emulation
(@pxref{Customizing}).  Customizations are placed in a file called
@file{edt-user.el}.  The Emacs @file{etc/} directory contains an
example.  If @file{edt-user.el} is found in your Emacs load path
during EDT Emulation initialization, then the following message will
appear below the status line indicating that the emulation has been
enabled, enhanced by your own customizations: ``User EDT custom keymap
active''.

Once enabled, it is easy to switch back and forth between your
customized EDT Emulation key bindings and the default EDT Emulation key
bindings.  (Look at the binding to @kbd{GOLD-Z} in the sample
@file{edt-user.el} file.)  It is also easy to turn off the emulation
(via the command @code{edt-emulation-off}).  Doing so completely
restores the original key bindings in effect just prior to invoking the
emulation.

Emacs binds keys to @acronym{ASCII} control characters and so does the
real EDT@.  Where EDT key bindings and Emacs key bindings conflict,
the default Emacs key bindings are retained by the EDT emulation by
default.  If you are a diehard EDT user you may not like this.  The
@ref{Control keys} section explains how to change this so that the EDT
bindings to @acronym{ASCII} control characters override the default
Emacs bindings.

@node Platform-specific notes
@chapter Notes Specific to Certain Platforms

@menu
* Sun workstations::  Sun workstations running X.
* MS-DOS::            PC users running MS-DOS.
* GNU/Linux::         PC users running GNU/Linux.
* Unix::              Using @key{NumLock} for the @key{PF1} key on Unix systems.
@end menu

@node Sun workstations
@section Sun Workstations Running X

Some earlier Sun keyboards do not have arrow keys separate from the
keypad keys.  It is difficult to emulate the full EDT keypad and still
retain use of the arrow keys on such keyboards.

The Sun Type 5 and other more recent Sun keyboards, however, do have
separate arrow keys.  This makes them candidates for setting up a
reasonable EDT keypad emulation.

Depending upon the configuration of the version of X installed on your
system, you may find the default X keynames for the keypad keys don't
permit Emacs to interpret some or all the keypad keys as something other
than arrow keys, numeric keys, @key{Home}, @key{PageUp}, etc.  Both Sun
and HP have been particularly guilty of making bizarre keysym
assignments to the keypad keys.

In most cases, the X Windows command, @code{xmodmap}, can be used to
correct the problem.  Here's a sample @file{.xmodmaprc} file which
corrects this problem on one Sun workstation configuration using an
older SunOS release configured with a Sun Type 5 keyboard:

@example
! File:  .xmodmaprc
!
! Set up Sun Type 5 keypad for use with the Emacs EDT Emulation
!
keycode  53 = KP_Divide
keycode  54 = KP_Multiply
keycode  57 = KP_Decimal
keycode  75 = KP_7
keycode  76 = KP_8
keycode  77 = KP_9
keycode  78 = KP_Subtract
keycode  97 = KP_Enter
keycode  98 = KP_4
keycode  99 = KP_5
keycode 100 = KP_6
keycode 101 = KP_0
keycode 105 = F24
keycode 119 = KP_1
keycode 120 = KP_2
keycode 121 = KP_3
keycode 132 = KP_Add
@end example

If @file{edt-mapper.el} does not recognize your keypad keys as unique
keys, use the command @samp{xmodmap -pke} to get a listing of the actual
key codes and the keysyms mapped to them and then generate you own
custom @file{.xmodmaprc} similar to the one above.

Next, feed @file{.xmodmaprc} to the @code{xmodmap} command and all the
Sun Type 5 keypad keys will now be configurable for the emulation of an
LK-201 keypad (less the @key{,} key).  In this example, the line

@example
keycode 105 = F24
@end example

@noindent changes the X Windows name of the keypad @key{NumLock} key to
be known internally as the @key{F24} key.  Doing so permits it to be
configured to behave as the @key{PF1} (@key{GOLD}) key.

The side effect of this change is that you will no longer have a
@key{NumLock} key.  If you are using other software under X which
requires a @key{NumLock} key, then examine your keyboard and look for
one you don't use and redefine it to be the @key{NumLock} key.
Basically, you need to clear the @key{NumLock} key from being assigned
as a modifier, assign it to the key of your choice, and then add it back
as a modifier.  (@ref{Unix} for further help on how to do this.)

@node MS-DOS
@section PC Users Running MS-DOS

By default, F1 is configured to emulate the @key{PF1} (@key{GOLD}) key.
But @key{NumLock} can be used instead if you load a freeware TSR
distributed with MS-Kermit, call @samp{gold.com}.  This was once
distributed in a file called @file{gold22.zip} and came with the source
code as well as a loadable binary image.  (See @file{edt-pc.el} in the
Emacs @file{lisp/emulation} directory for more information.)

@node GNU/Linux
@section PC Users Running GNU/Linux

The default X server configuration varies from distribution to
distribution and release to release of GNU/Linux.  If your system fails
to recognize the keypad keys as distinct keys, change the NumLock state,
turning it on or off, as the case may be, then try again.  If this
doesn't solve your problem, you may have to modify the X keysym mappings
with @code{xmodmap}.

On one distribution on an Intel PC, the following @file{.xmodmaprc} set
things up nicely.

@example
! File:  .xmodmaprc
!
! Set up PC keypad under GNU/Linux for the Emacs EDT Emulation
!
clear  mod2
keycode  77 = F12
keycode  96 = Num_Lock Pointer_EnableKeys
add mod2 = Num_Lock
@end example

In this example, after feeding the file to the @code{xmodmap} command,
the PC @key{NumLock} keypad key will be configurable for the emulation
of the @key{PF1} key.  The PC keypad can now emulate an LK-201 keypad
(less the comma key), the standard keyboard supplied with DEC terminals
VT-200 and above.  This @file{.xmodmaprc} file switches the role of the
@key{F12} and @key{NumLock} keys.  It has been tested on RedHat
GNU/Linux 5.2.  Other versions of GNU/Linux may require different
keycodes.  (@ref{Unix} for further help on how to do this.)

@strong{Please note:} Remember, it may be necessary to have @key{NumLock} in
one position (ON) or the other (OFF) for the PC keypad to emulate the
LK-201 keypad properly.

@node Unix
@section General Notes on Using @key{NumLock} for the @key{PF1} Key on Unix Systems

Making the physical @key{NumLock} key available for use in the EDT Emulation
requires some modification to the default X Window settings.  Since the
keycode assignments vary from system to system, some investigation is
needed to see how to do this on a particular system.

You will need to look at the output generated by @code{xmodmap} invoked
with the "-pm" switch.  For example, on RedHat GNU/Linux 5.2 on a PC, we
get the following output when running @samp{xmodmap -pm}:

@example
xmodmap:  up to 2 keys per modifier, (keycodes in parentheses):

shift       Shift_L (0x32),  Shift_R (0x3e)
lock        Caps_Lock (0x42)
control     Control_L (0x25),  Control_R (0x6d)
mod1        Alt_L (0x40),  Alt_R (0x71)
mod2        Num_Lock (0x4d)
mod3
mod4
mod5        Scroll_Lock (0x4e)
@end example

@noindent Note that Num_Lock is assigned to the modifier @samp{mod2}.  This is
what hides Num_Lock from being seen by Emacs.

Now, @samp{xmodmap -pke} yields:

@example
   .
   .
   .
keycode  77 = Num_Lock Pointer_EnableKeys
   .
   .
   .
keycode  96 = F12
   .
   .
   .
@end example

@noindent So, in RedHat GNU/Linux 5.2 on a PC, Num_Lock generates keycode 77.
The following steps are taken:

@enumerate
@item
clear the assignment of Num_Lock to mod2;
@item
swap the keycodes assigned to F12 and Num_Lock;
@item
assign Num_Lock back to mod2.
@end enumerate

@noindent The @file{.xmodmaprc} file looks like this:

@example
! File:  .xmodmaprc
!
! Set up PC keypad under GNU/Linux for the Emacs EDT Emulation
!
clear  mod2
keycode  77 = F12
keycode  96 = Num_Lock Pointer_EnableKeys
add mod2 = Num_Lock
@end example

So, after executing @samp{xmodmap .xmodmaprc}, a press of the physical
@key{F12} key looks like a Num_Lock keypress to X@.  Also, a press of the
physical @key{NumLock} key looks like a press of the @key{F12} key to X.

Now, @file{edt-mapper.el} will see @samp{f12} when the physical
@key{NumLock} key is pressed, allowing the @key{NumLock} key to be used
as the EDT @key{PF1} (@key{GOLD}) key.

@node Differences
@chapter How Does this EDT Emulation Differ from Real EDT?

In general, you will find that this emulation of EDT replicates most,
but not all, of EDT's most used Keypad Mode editing functions and
behavior.  It is not perfect, but most EDT users who have tried the
emulation agree that it is quite good enough to make it easy for
die-hard EDT users to move over to using Emacs.

Here's a list of the most important differences between EDT and this GNU
Emacs EDT Emulation.  The list is short but you must be aware of these
differences if you are to use the EDT Emulation effectively.

@enumerate

@item
Entering repeat counts works a little differently than in EDT.

EDT allows users to enter a repeat count before entering a command that
accepts repeat counts.  For example, when using the real EDT, pressing
these three keys in sequence, @kbd{GOLD 5 KP1}, will move the cursor in
the current direction 5 words.  This does @strong{not} work in Emacs!

Emacs provides two ways to enter repeat counts and neither involves
using the @key{GOLD} key.  First, repeat counts can be entered in Emacs
by using the @key{ESC} key.  For example, pressing these keys in
sequence, @kbd{ESC 1 0 KP1}, will move the cursor in the current
direction 10 words.  Second, Emacs provides another command called
@code{universal-argument} that can be used to do the same thing.
Normally, in Emacs has this bound to @kbd{C-u}.

@item
EDT's line mode commands and nokeypad mode commands are @strong{not}
supported (with one important exception; see item 8 in
@ref{Highlights}).  Although, at first, this may seem like a big
omission, the set of built-in Emacs commands provides a much richer set
of capabilities which more than make up for this omission.

To enter Emacs commands not bound to keys, you can press @kbd{GOLD KP7}
or the @key{DO} key.  Emacs will display its own command prompt "M-x".
This stands for the keypress @kbd{Meta-x}, where @key{Meta} is a special
shift key.  The @key{Alt} key is often mapped to behave as a @key{Meta}
key.  So, you can also invoke this prompt by pressing @kbd{Meta-x}.
Typing the sequence @kbd{ESC x} will also invoke the prompt.

@item
Selected text is highlighted @strong{only} on systems where Emacs
supports the highlighting of text.

@item
Just like in TPU/EVE, the @key{ENTER} key is @strong{not} used to
terminate input when the editor prompts you for input.  The @key{RETURN}
key is used, instead.  (@key{KP4} and @key{KP5} (the direction keys) do
terminate input for the @samp{FIND} command, just like in EDT, however.)

@end enumerate

@node Highlights
@chapter Some Highlights, and Comparisons to the Original Emacs EDT Emulation

@enumerate

@item
The EDT define key command is supported (@code{edt-define-key}) and is
bound to @kbd{C-k} in the default EDT mode when EDT control sequence
bindings are enabled, or when the sample @file{edt-user.el}
customization file is used.  The TPU/EVE learn command is supported but
not bound to a key in the default EDT mode but is bound in the sample
@file{edt-user.el} file.

Unlike the TPU/EVE learn command, which uses one key to begin the learn
sequence, @kbd{C-l}, and another command to remember the sequence,
@kbd{C-r}, this version of the learn command (@code{edt-learn}) serves
as a toggle to both begin and to remember the learn sequence.

Many users who change the meaning of a key with the define key and the
learn commands, would like to be able to restore the original key
binding without having to quit and restart emacs.  So a restore key
command is provided to do just that.  When invoked, it prompts you to
press the key to which you wish the last replaced key definition
restored.  It is bound to @kbd{GOLD C-k} in the default EDT mode when
EDT control sequence bindings are enabled or the sample
@file{edt-user.el} customization file is used.

@item
Direction support is fully supported.

@item
All original Emacs bindings are fully restored when EDT emulation is
turned off.  So, if a fellow worker comes over to your terminal to help
you with a software problem, for example, and is completely confused by
your EDT emulation bindings, just enter the command,
@code{edt-emulation-off}, at the @samp{M-x} prompt and the original
Emacs bindings will be restored.  To resume the EDT emulation, just
enter @code{edt-emulation-on}.

@item
User custom EDT bindings are kept separate from the default EDT
bindings.  One can toggle back and forth between the custom EDT bindings
and default EDT bindings.

@item
The Emacs functions in @file{edt.el} attempt to emulate, where
practical, the exact behavior of the corresponding EDT keypad mode
commands.  In a few cases, the emulation is not exact, but we hope you
will agree it is close enough.  In a very few cases, we chose to use the
Emacs way of handling things.  As mentioned earlier, we do not emulate
the EDT @samp{SUBS} command.  Instead, we chose to use the Emacs
@code{query-replace} function, which we find to be easier to use.

@item
Emacs uses the regexp assigned to @code{page-delimiter} to determine
what marks a page break.  This is normally @samp{^\f}, which causes the
@code{edt-page} command to ignore form feeds not located at the
beginning of a line.  To emulate the EDT @samp{PAGE} command exactly,
page-delimiter is set to @samp{\f} when EDT emulation is turned on, and
restored to @samp{^\f} when EDT emulation is turned off.  But, since
some users prefer the Emacs definition of a page break, or may wish to
preserve a customized definition of page break, one can override the EDT
definition by placing

@example
(setq edt-keep-current-page-delimiter t)
@end example

@noindent in your @file{.emacs} file.  Or, you can used the Emacs customize
command to change its setting.

@item
The EDT definition of a section of a terminal window is hardwired to be
16 lines of its one-and-only 24-line window (the EDT @samp{SECT} command
bound to @key{KP8}).  That's two-thirds of the window at a time.  Since
Emacs, like TPU/EVE, can handle multiple windows of sizes of other than
24 lines, the definition of section used here has been modified to
two-thirds of the current window.  (There is also an
@code{edt-scroll-window} function which you may prefer over the
@samp{SECT} emulation.)

@item
Cursor movement and deletion involving word entities is identical to
EDT@.  This, above all else, gives the die-hard EDT user a sense of being
at home.  Also, an emulation of EDT's @samp{SET ENTITY WORD} command is
provided, for those users who like to customize movement by a word at a
time to their own liking.

@item
EDT's @samp{FIND} and @samp{FNDNXT} are supported.

@item
EDT's @samp{APPEND}, @samp{REPLACE}, and @samp{SUBS} commands are supported.

@item
@samp{CHNGCASE} is supported.  It works on individual characters or
selected text, if @samp{SELECT} is active.  In addition, two new
commands are provided: @code{edt-lowercase} and @code{edt-uppercase}.
They work on individual @strong{words} or selected text, if
@samp{SELECT} is active.

@item
Form feed and tab insert commands are supported.

@item
A new command, @code{edt-duplicate-word}, is provided.  If you
experiment with it, you might find it to be surprisingly useful and may
wonder how you ever got along without it!  It is assigned to @kbd{C-j}
in the sample @file{edt-user.el} customization file.

@item
TPU/EVE's Rectangular Cut and Paste functions (originally from the
EVE-Plus package) are supported.  But unlike the TPU/EVE versions, these
here support both insert and overwrite modes.  The seven rectangular
functions are bound to @key{F7}, @key{F8}, @kbd{GOLD-F8}, @key{F9},
@kbd{GOLD-F9}, @key{F10}, and @kbd{GOLD-F10} in the default EDT mode.

@item
The original EDT emulation package set up many default regular and GOLD
bindings.  We tried to preserve most (but not all!)@: of these, so users
of the original emulation package will feel more at home.

Nevertheless, there are still many GOLD key sequences which are not
bound to any functions.  These are prime candidates to use for your own
customizations.

Also, there are several commands in @file{edt.el} not bound to any key.
So, you will find it worthwhile to look through @file{edt.el} for
functions you may wish to add to your personal customized bindings.

@item
The VT200/VT300 series terminals steal the function keys @key{F1} to
@key{F5} for their own use.  These do not generate signals which are
sent to the host.  So, @file{edt.el} does not assign any default
bindings to @key{F1} through @key{F5}.

In addition, our VT220 terminals generate an interrupt when the @key{F6}
key is pressed (@samp{^C} or @samp{^Y}, can't remember which) and not
the character sequence documented in the manual.  So, binding Emacs
commands to @key{F6} will not work if your terminal behaves the same
way.

@item
The VT220 terminal has no @key{ESC}, @key{BS}, nor @key{LF} keys, as
does a VT100.  So the default EDT bindings adopt the standard DEC
convention of having the @key{F11}, @key{F12}, and @key{F13} keys, on a
VT200 series (and above) terminal, assigned to the same EDT functions
that are bound to @key{ESC}, @key{BS}, and @key{LF} on a VT100 terminal.

@item
Each user, through the use of a private @file{edt-user.el} file, can
customize, very easily, personal EDT emulation bindings.

@item
The EDT @samp{SELECT} and @samp{RESET} functions are supported.
However, unlike EDT, pressing @samp{RESET} to cancel text selection does
@strong{not} reset the existing setting of the current direction.

We also provide a TPU/EVE like version of the single @samp{SELECT/RESET}
function, called @code{edt-toggle-select}, which makes the EDT
@samp{SELECT} function into a toggle on/off switch.  That is, if
selection is on, pressing @samp{SELECT} again turns selection off
(cancels selection).  This function is used in the sample
@file{edt-user.el} customization file.

@item
EDT scroll margins are supported, but are disabled by default.
(@ref{Scroll margins} for instructions on how to enable them.)

@end enumerate

@node Customizing
@chapter Customizing Emulation

Most EDT users, at one time or another, make some custom key bindings,
or use someone else's custom key bindings, which they come to depend
upon just as if they were built-in bindings.  This EDT Emulation for GNU
Emacs is designed to make it easy to customize bindings.

If you wish to customize the EDT Emulation to use some of your own key
bindings, you need to make a private version of @file{edt-user.el} in
your own private lisp directory.  The Emacs @file{etc/} directory
contains an example for you to use as a template and for ideas.
@c This seems to be untrue.
@ignore
There are two sample files @file{edt-user.el1} and @file{edt-user.el2}
for you to use as templates and for ideas.  Look at @file{edt-user.el1}
first.  Unless you will be using two or more very different types of
terminals on the same system, you need not look at @file{edt-user.el2}.
@end ignore

First, you need to have your own private lisp directory, say
@file{~/lisp}, and you should add it to the Emacs load path.

@strong{Please note:} A few sites have different load-path requirements,
so the above directions may need some modification if your site has such
special needs.

@menu
* Init file::            Creating your own @file{edt-user.el} file.
* Words::                Specifying word entities.
* Control keys::         Enabling EDT control key sequence bindings.
* Scroll margins::       Setting scroll margins.
@end menu

@node Init file
@section Creating your own @file{edt-user.el} File

A sample @file{edt-user.el} file is provided in the Emacs @file{etc/}
directory.  You should use it as a guide to learn how you can customize
EDT emulation bindings to your own liking.  Names used to identify the
set of LK-201 keypad and function keys are:

@example
Keypad Keys:
                PF1 PF2 PF3 PF4
                KP7 KP8 KP9 KP-
                KP4 KP5 KP6 KP,
                KP1 KP2 KP3
                KP0     KPP KPE
@end example

@example
Arrow Keys:
                LEFT RIGHT DOWN UP
@end example

@example
Function Keys:
                F1 F2 F3 F4 F5  F6 F7 F8 F9 F10  F11 F12 F13 F14
                HELP DO  F17 F18 F19 F20

                FIND   INSERT   REMOVE
                SELECT PREVIOUS NEXT
@end example

Note: Many VT-200 terminals, and above, steal function keys @key{F1}
through @key{F5} for terminal setup control and don't send anything to
the host if pressed.  So customizing bindings to these keys may not work
for you.

There are three basic functions that do the EDT emulation custom
bindings: @code{edt-bind-key}, @code{edt-bind-gold-key}, and
@code{edt-bind-function-key}.

The first two are for binding functions to keys which are standard
across most keyboards.  This makes them keyboard independent, making it
possible to define these key bindings for all terminals in the file
@file{edt.el}.

The first, @code{edt-bind-key}, is used typically to bind emacs commands
to control keys, although some people use it to bind commands to other
keys, as well.  (For example, some people use it to bind the VT200
seldom used back-tick key (@samp{`}) to the function @samp{ESC-prefix}
so it will behave like an @key{ESC} key.)  The second function,
@code{edt-bind-gold-key}, is used to bind emacs commands to gold key
sequences involving alpha-numeric keys, special character keys, and
control keys.

The third function, @code{edt-bind-function-key}, is terminal dependent
and is defined in a terminal specific file (see @file{edt-vt100.el} for
example).  It is used to bind emacs commands to LK-201 function keys, to
keypad keys, and to gold sequences of those keys.

@node Words
@section Specifying Word Entities

The variable @code{edt-word-entities} is used to emulate EDT's @samp{SET
ENTITY WORD} command.  It contains a list of characters to be treated as
words in themselves.  If the user does not define
@code{edt-word-entities} in his/her @file{.emacs} file, then it is set
up with the EDT default containing only @key{TAB}.

The characters are stored in the list by their numerical values, not as
strings.  Emacs supports several ways to specify the numerical value of
a character.  One method is to use the question mark: @samp{?A} means
the numerical value for @samp{A}, @samp{?/} means the numerical value
for @samp{/}, and so on.  Several unprintable characters have special
representations:

@example
?\b  specifies  BS, C-h
?\t  specifies  TAB, C-i
?\n  specifies  LFD, C-j
?\v  specifies  VTAB, C-k
?\f  specifies  FF, C-l
?\r  specifies  CR, C-m
?\e  specifies  ESC, C-[
?\\  specifies  \
@end example

Here are some examples:

@example
(setq edt-word-entities '(?\t ?- ?/)) ; specifies TAB, - , and /
(setq edt-word-entities '(?\t)        ; specifies TAB, the default
@end example

@noindent You can also specify characters by their decimal ascii values:

@example
(setq edt-word-entities '(9 45 47))   ; specifies TAB, - , and /
@end example

@node Control keys
@section Enabling EDT Control Key Sequence Bindings

Where EDT key bindings and Emacs key bindings conflict, the default
Emacs key bindings are retained by default.  Some diehard EDT users
may not like this.  So, if the variable
@code{edt-use-EDT-control-key-bindings} is set to true in a user's
@file{.emacs} file, then the default EDT Emulation mode will enable most
of the original EDT control key sequence bindings.  If you wish to do
this, add the following line to your @file{.emacs} file:

@example
(setq edt-use-EDT-control-key-bindings t)
@end example

@node Scroll margins
@section Setting Scroll Margins

Scroll margins at the top and bottom of the window are now supported.
(The design was copied from @file{tpu-extras.el}.)  By default, this
feature is enabled with the top margin set to 10% of the window and the
bottom margin set to 15% of the window.  To change these settings, you
can invoke the function @code{edt-set-scroll-margins} in your
@file{.emacs} file.  For example, the following line

@example
(edt-set-scroll-margins "20%" "25%")
@end example

@noindent sets the top margin to 20% of the window and the bottom margin
to 25% of the window.  To disable this feature, set each margin to 0%.
You can also invoke @code{edt-set-scroll-margins} interactively while
EDT Emulation is active to change the settings for that session.

@strong{Please note:} Another way to set the scroll margins is to use
the Emacs customization feature to set the following two variables
directly: @code{edt-top-scroll-margin} and @code{edt-bottom-scroll-margin}.

Enter the Emacs @code{customize} command.  First select the
@samp{Editing} group and then select the @samp{Emulations} group.
Finally, select the @samp{Edt} group and follow the directions.

@node GNU Free Documentation License
@appendix GNU Free Documentation License
@include doclicense.texi

@bye