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XEmacs / man / new-users-guide / custom2.texi

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@comment  node-name,  next,  previous,  up
@node Other Customizations, Select and Move, Files, Top
@chapter Other Customizations
@cindex customize
@cindex hook
@cindex font-lock-mode

You can modify the behavior of Emacs in minor ways permanently by
putting your changes in your @file{init.el} file. This file contains Lisp
function call expressions. Each of these expressions will consist of a
function name followed by arguments, all surrounded by parentheses. For
example, to turn on the auto-fill-mode (i.e. break lines automatically
when they become too long) , put the following  line in your
@file{init.el} file: 

@example
(add-hook 'text-mode-hook 
        '(lambda() (auto-fill-mode 1)))
@end example

@noindent
Emacs has a function named "turn-on-auto-fill" which is defined as
"(lambda() (auto-fill-mode 1))". Therefore you can also write the above
as: 

@example
(add-hook 'text-mode-hook 'turn-on-auto-fill)
@end example

@noindent
Emacs provides a number of hooks for the sake of customization. The hook
variables contain list of functions to be called with no arguments. To
turn on the auto-fill-mode, add the appropriate hook as shown in the
example above.

Similarly, to enable the "font-lock mode" which displays your program in
different fonts and colors(@pxref{Modes}), put the following in your
@file{init.el} file. The comments above the statement explain what the
statements do.

@example
;;; enables the font-lock-mode in Lisp Mode
(add-hook 'lisp-mode-hook    'turn-on-font-lock)

;;; enables the font-lock-mode in Texinfo Mode
(add-hook 'texinfo-mode-hook    'turn-on-font-lock)

;;; enables the font-lock mode in C Mode
(add-hook 'c-mode-hook          'turn-on-font-lock)
@end example

To turn on the font-lock mode in other Major Modes like emacs-lisp, just
put the name of the mode with "-hook" appended to it as the middle
parameter in the above examples. You can also select the color that the
functions, comments or other keywords  should be displayed in :

@example
;;; the function names will now be displayed in blue color
(set-face-foreground 'font-lock-function-name-face "blue")

;;; the comments will be displayed in forest green 
 (set-face-foreground 'font-lock-comment-face "forest green")
@end example

@noindent
For other customizations regarding the font-lock face, look at the file
@file{/usr/local/lib/xemacs-VERSION/etc/sample.init.el}. 



@comment  node-name,  next,  previous,  up
@menu
* Setting Variables::           Customizing Emacs variables
* Init File::                   Some examples of Lisp expressions in
                                init.el file
@end menu

@node Setting Variables, Init File, Other Customizations, Other Customizations
@section Other Customizations
@cindex setting variables
@findex describe-variable

In XEmacs, @dfn{variables} are used for internal record-keeping and
customizations. There are some variables called "options" which you can
use for customizations. To examine a variable use:

@example
;;; print the value and documentation of the variable, use either of the
;;; following commands
C-h v
M-x describe variable
@end example

After you type any of the above commands, you will be prompted for a
variable name in the @dfn{echo area}. Type in the name of the variable,
for example, type  @code{case-fold-search} @key{RET}
Your window will split into two and you will see the following message
in that window:

@example
case-fold-search's value is t
This value is specific to the current buffer.

Documentation:
*Non-nil if searches should ignore case.
Automatically becomes buffer-local when set in any fashion.

@end example

@noindent
Since this variable's value is 't' searches will ignore case. If you
want case-sensitive-search (i.e. if you are searching for "Foo" and you do
not want "foo" to be included in the search, you need to set this
variable to "nil". In order to do that, use:

@findex set-variable
@example
M-x set-variable
@end example

@noindent
Emacs will prompt you for the variable which you wish to set. Type in
"case-fold-search" and hit @key{RET}. You will see the following
message:

@example
Set case-fold-search to value:
@end example

@noindent
Type "nil" and hit @key{RET}.  Now if you again use @kbd{M-x describe
variable} , you will see that the new value of case-fold-search will be
"nil" and your searches will be case-sensitive. This will be effective
only for that Emacs session. If you want to change the value of a
variable permanently put the following statement in your @file{init.el}
file :

@example
(setq case-fold-search nil)
@end example

@noindent
This statement will make searches case-sensitive only in the current
buffer which is the @file{init.el} file. This will not be very useful. To
make searches case-sensitive globally in all buffers, use:

@example
(setq-default case-fold-search nil)
@end example

If you want to change the value of any other variable, use :

@example
(setq <variable-name> <new value>)
@end example

@noindent
"setq" will assign the "new value" to the "variable-name" .  


If you want a list of the "options" i.e. the variables available for
customization type:

@findex list-options
@findex edit-options
@example

;;; displays a buffer listing names, values and documentation of options
M-x list-options

;;; displays options and allows you to edit those list of options
M-x edit-options

@end example

@noindent
Try these options. If you are using edit-options to edit a variable,
just point at the variable you wish to edit and use one of the following
commands:

@table @b
@item 1
Set the value of the variable to t (non-nil).
@item 0
Set the value of the variable to nil.
@item n
Move to the next variable.
@item p
Move to the previous variable.
@end table


There are some other options available to make the value of a variable
local to a buffer and then to switch to its global value. You can also
have a @dfn{local variables list} in a file which specifies the values
to use for certain Emacs variables when you edit that
file. @xref{Variables,,,xemacs,XEmacs User's Manual}, for information on
these options.


@comment  node-name,  next,  previous,  up
@node Init File,  , Setting Variables, Other Customizations
@section Init File Examples
@cindex init file examples

   For customizing Emacs, you need to put Lisp expressions in your
@file{init.el} file. The following are some useful Lisp expressions. If
you find any of them useful, just type them in your @file{init.el} file:

@itemize @bullet
@item 
The following expression will make @key{TAB} in C mode insert a real tab
character if the cursor or point is in the middle of the line. Now
hitting the @key{TAB} key will indent a line only if the cursor is at
the left margin or in the line's indentation:

@example
(setq c-tab-always-indent nil)
@end example

@noindent
The value of the variable @code{c-tab-always-indent} is usually @samp{t}
for @samp{true}. When this variable is true, then hitting the @key{TAB}
key always indents the current line. 

@item
This expression will turn on the @var{auto-fill-mode} when you are in
text mode:

@example
(setq text-mode-hook 'turn-on-auto-fill)
@end example

This mode will automatically break lines when you type a space so that
the lines don't become too long. The length of the lines is controlled
by the variable @code{fill-column}. You can set this variable to a value
you wish. Look at the documentation for this variable to see its default
value. To change the value to 75 for example, use:

@vindex fill-column
@example
(setq-default fill-column 75)
@end example

@noindent
This will change the value of this variable globally. 

@item
@findex eval-expression
The following expression will enable the use of @var{eval-expression}
without confirmation:

@example
(put 'eval-expression 'disabled nil)
@end example

@noindent
Now when you use @var{eval-expression}, it will print the value of the
expression you specify in the @dfn{echo area} without confirming with
you. 

@item
This expression will remove the binding of @kbd{C-x C-c}, because its
easy to hit this key by mistake and you will exit Emacs
unintentionally. You can use the @b{Exit Emacs} option from the @b{File}
menu to exit Emacs.

@example
(global-set-key "\C-x\C-c" nil)
@end example

@noindent
Now if you type @kbd{C-x C-c}, you won't exit Emacs.

@item
The following expression will make the @key{BACKSPACE} and the @key{DEL}
key work in the same manner:

@example
(global-set-key 'backspace [delete])
@end example

@item
This expression will make searches case sensitive:

@example
(setq-default case-fold-search nil)
@end example

@noindent
If we use "setq" instead of "setq-default" then searches will be
case-sensitive only in the current buffer's local value. In this case the
buffer would be the @file{init.el} file. Since this would not be too
helpful and we want to have case-sensitive searches in all buffers, we
have to use "setq-default".

@item
This expression will enable the font-lock mode when you are using
texinfo mode:

@example
(add-hook 'texinfo-mode-hook 'turn-on-font-lock)
@end example

@noindent
@xref{Minor Modes}, for information on font-lock mode. 

@item 
Rebinds the key @kbd{C-x l} to run the function
@code{make-symbolic-link}:

@example
(global-set-key "\C-xl" 'make-symbolic-link)
@end example

@noindent
We use the single quote before "make-symbolic-link" because its a
function name. You can also use the following expression which does the
same thing:

@example
(define-key global-map "C-xl" 'make-symbolic-link)
@end example

@item
The following expression will bind @kbd{C-x l} to run the function
@code{make-symbolic-link} in C mode only:

@example
(define-key c-mode-map "C-xl" 'make-symbolic-link)
@end example

@noindent
Instead of binding @kbd{C-xl} to run @code{make-symbolic-link}, you can
bind the @key{F1} key to run this function:

@example
(define-key c-mode-map 'f1 'make-symbolic-link)
@end example

@noindent
Here, you have to use lower case for naming function keys like @key{F1}.

@item
You can bind the function @code{undo} i.e. @kbd{C-x u} to any key, for
example to @key{F2}:

@example
(global-set-key 'f2 'undo)
@end example

@item 
The following statement will display the current time in the modeline of
the buffer:

@vindex display-time
@cindex displaying time
@example
(display-time)
@end example

@item 
This displays the current line number on which the cursor is present in
the modeline:

@example
(setq line-number-mode t)
@end example

@item
If you don't want the text to be highlighted when you use commands for
marking regions so as to use the @dfn{kill} and @dfn{yank} commands
later, you can use the following expression in your @file{init.el} file:

@vindex zmacs-regions
@example
(setq zmacs-regions nil)
@end example

@noindent
Now if you use a command like @kbd{C-x C-p} (@code{mark-page}), the text
will not be highlighted.

@item 
To control the number of buffers listed when you select the @b{Buffers}
menu, you need to set the variable @code{buffers-menu-max-size} to
whatever value you wish. For example, if you want 20 buffers to be listed
when you select @b{Buffers} use:

@vindex buffers-menu-max-size
@example
(setq buffers-menu-max-size 20)
@end example

@item
If you want the window title area to display the full directory/name of
the current buffer's file, and not just the name, use:

@vindex frame-title-format
@example
(setq frame-title-format "%S: %f")
@end example

@item
To get rid of the menu, use :

@example
(set-menubar nil)
@end example

@item
If you want an extensive menu-bar use the following expression in your
@file{init.el} file.

@example
(load "big-menubar")
@end example

@noindent
If you want to write your own menus, you can look at some of the
examples in
@file{/usr/local/lib/xemacs/xemacs-packages/lisp/edit-utils/big-menubar.el} file.

@end itemize

   For more information on initializing your @file{init.el} file,
@xref{Init File,,,xemacs,XEmacs User's Manual}. You should also look at
@file{/usr/local/lib/xemacs-VERSION/etc/sample.init.el}, which is a sample
@file{init.el} file. It contains some of the commonly desired
customizations in Emacs.