onews.3

windows版本的emacs

is determined from the specified bounds before any copying takes place.

* New function `substitute-key-definition'.

This is a new way to replace one command with another command as the
binding of whatever keys may happen to refer to it.

(substitute-key-definition OLDDEF NEWDEF KEYMAP) looks through KEYMAP
for keys defined to run OLDDEF, and rebinds those keys to run NEWDEF
instead.

* New function `insert-char'.

Insert a specified character, a specified number of times.

* `mark-marker' changed.

When there is no mark, this now returns a marker that points
nowhere, rather than `nil'.

* `ding' accepts argument.

When given an argument, the function `ding' does not terminate
execution of a keyboard macro.  Normally, `ding' does terminate
all macros that are currently executing.

* New function `minibuffer-depth'.

This function returns the current depth in minibuffer activations.
The value is zero when the minibuffer is not in use.
Values greater than one are possible if the user has entered the
minibuffer recursively.

* New function `documentation-property'.

(documentation-property SYMBOL PROPNAME) is like (get SYMBOL PROPNAME),
except that if the property value is a number `documentation-property'
will take that number (or its absolute value) as a character position
in the DOC file and return the string found there.

(documentation-property VAR 'variable-documentation) is the proper
way for a Lisp program to get the documentation of variable VAR.

* New documentation-string expansion feature.

If a documentation string (for a variable or function) contains text
of the form `\<FOO>', it means that all command names specified in
`\[COMMAND]' construct from that point on should be turned into keys
using the value of the variable FOO as the local keymap.  Thus, for example,

  `\<emacs-lisp-mode-map>\[eval-defun] evaluates the defun containing point.'

will expand into

  "ESC C-x evaluates the defun containing point."

regardless of the current major mode, because ESC C-x is defined to
run `eval-defun' in the keymap `emacs-lisp-mode-map'.  The effect is
to show the key for `eval-defun' in Emacs Lisp mode regardless of the
current major mode.

The `\<...>' construct applies to all `\[...]' constructs that follow it,
up to the end of the documentation string or the next `\<...>'.

Without `\<...>', the keys for commands specified in `\[...]' are found
in the current buffer's local map.

The current global keymap is always searched second, whether `\<...>'
has been used or not.

* Multiple hooks allowed in certain contexts.

The old hook variables `find-file-hook', `find-file-not-found-hook' and
`write-file-hook' have been replaced.

The replacements are `find-file-hooks', `find-file-not-found-hooks'
and `write-file-hooks'.  Each holds a list of functions to be called;
by default, `nil', for no functions.  The functions are called in
order of appearance in the list.

In the case of `find-file-hooks', all the functions are executed.

In the case of `find-file-not-found-hooks', if any of the functions
returns non-`nil', the rest of the functions are not called.

In the case of `write-file-hooks', if any of the functions returns
non-`nil', the rest of the functions are not called, and the file is
considered to have been written already; so actual writing in the
usual way is not done.  If `write-file-hooks' is local to a buffer,
it is set to its global value if `set-visited-file-name' is called
(and thus by C-x C-w as well).

`find-file-not-found-hooks' and `write-file-hooks' can be used
together to implement editing of files that are not stored as Unix
files: stored in archives, or inside version control systems, or on
other machines running other operating systems and accessible via ftp.

* New hooks for suspending Emacs.

Suspending Emacs runs the hook `suspend-hook' before suspending
and the hook `suspend-resume-hook' if the suspended Emacs is resumed.
Running a hook is done by applying the variable's value to no arguments
if the variable has a non-`nil' value.  If `suspend-hook' returns
non-`nil', then suspending is inhibited and so is running the
`suspend-resume-hook'.  The non-`nil' value means that the `suspend-hook'
has done whatever suspending is required.

* Disabling commands can print a special message.

A command is disabled by giving it a non-`nil' `disabled' property.
Now, if this property is a string, it is included in the message
printed when the user tries to run the command.

* Emacs can open TCP connections.

The function `open-network-stream' opens a TCP connection to
a specified host and service.  Its value is a Lisp object that represents
the connection.  The object is a kind of "subprocess", and I/O are
done like I/O to subprocesses.

* Display-related changes.

** New mode-line control features.

The display of the mode line used to be controlled by a format-string
that was the value of the variable `mode-line-format'.

This variable still exists, but it now allows more general values,
not just strings.  Lists, cons cells and symbols are also meaningful.

The mode line contents are created by outputting various mode elements
one after the other.  Here are the kinds of objects that can be
used as mode elements, and what they do in the display:

  string        the contents of the string are output to the mode line,
		and %-constructs are replaced by other text.

  t or nil	ignored; no output results.

  symbol	the symbol's value is used.  If the value is a string,
		the string is output verbatim to the mode line
		(so %-constructs are not interpreted).  Otherwise,
		the symbol's value is processed as a mode element.

  list (whose first element is a string or list or cons cell)
		the elements of the list are treated as as mode elements,
		so that the output they generate is concatenated,

  list (whose car is a symbol)
		if the symbol's value is non-nil, the second element of the
		list is treated as a mode element.  Otherwise, the third
		element (if any) of the list is treated as a mode element.

  cons (whose car is a positive integer)
		the cdr of the cons is used as a mode element, but
		the text it produces is padded, if necessary, to have
		at least the width specified by the integer.

  cons (whose car is a negative integer)
		the cdr of the cons is used as a mode element, but
		the text it produces is truncated, if necessary, to have
		at most the width specified by the integer.

There is always one mode element to start with, that being the value of
`mode-line-format', but if this value is a list then it leads to several
more mode elements, which can lead to more, and so on.

There is one new %-construct for mode elements that are strings:
`%n' displays ` Narrow' for a buffer that is narrowed.

The default value of `mode-line-format' refers to several other variables.
These variables are `mode-name', `mode-line-buffer-identification',
`mode-line-process', `mode-line-modified', `global-mode-string' and
`minor-mode-alist'.  The first four are local in every buffer in which they
are changed from the default.

mode-name	Name of buffer's major mode.  Local in every buffer.

mode-line-buffer-identification
		Normally the list ("Emacs: %17b"), it is responsible
		for displaying text to indicate what buffer is being shown
		and what kind of editing it is doing.  `Emacs' means
		that a file of characters is being edited.  Major modes
		such as Info and Dired which edit or view other kinds
		of data often change this value.  This variables becomes
		local to the current buffer if it is setq'd.

mode-line-process
		Normally nil, this variable is responsible for displaying
		information about the process running in the current buffer.
		M-x shell-mode and M-x compile alter this variable.

mode-line-modified
		This variable is responsible for displaying the indication
		of whether the current buffer is modified or read-only.
		By default its value is `("--%*%*-")'.

minor-mode-alist
		This variable is responsible for displaying text for those
		minor modes that are currently enabled.  Its value
		is a list of elements of the form (VARIABLE STRING),
		where STRING is to be displayed if VARIABLE's value
		(in the buffer whose mode line is being displayed)
		is non-nil.  This variable is not made local to particular
		buffers, but loading some libraries may add elements to it.

global-mode-string
		This variable is used to display the time, if you ask
		for that.

The idea of these variables is to eliminate the need for major modes
to alter mode-line-format itself.

** `window-point' valid for selected window.

The value returned by `window-point' used to be incorrect when its
argument was the selected window.  Now the value is correct.

** Window configurations may be saved as Lisp objects.

The function `current-window-configuration' returns a special type of
Lisp object that represents the current layout of windows: the
sizes and positions of windows, which buffers appear in them, and
which parts of the buffers appear on the screen.

The function `set-window-configuration' takes one argument, which must
be a window configuration object, and restores that configuration.

** New hook `temp-output-buffer-show-hook'.

This hook allows you to control how help buffers are displayed.
Whenever `with-output-to-temp-buffer' has executed its body and wants
to display the temp buffer, if this variable is bound and non-`nil'
then its value is called with one argument, the temp buffer.
The hook function is solely responsible for displaying the buffer.
The standard manner of display--making the buffer appear in a window--is
used only if there is no hook function.

** New function `minibuffer-window'.

This function returns the window used (sometimes) for displaying
the minibuffer.  It can be used even when the minibuffer is not active.

** New feature to `next-window'.

If the optional second argument is neither `nil' nor `t', the minibuffer
window is omitted from consideration even when active; if the starting
window was the last non-minibuffer window, the value will be the first
non-minibuffer window.

** New variable `minibuffer-scroll-window'.

When this variable is non-`nil', the command `scroll-other-window'
uses it as the window to be scrolled.  Displays of completion-lists
set this variable to the window containing the display.

** New argument to `sit-for'.

A non-nil second argument to `sit-for' means do not redisplay;
just wait for the specified time or until input is available.

** Deleted function `set-minor-mode'; minor modes must be changed.

The function `set-minor-mode' has been eliminated.  The display
of minor mode names in the mode line is now controlled by the
variable `minor-mode-alist'.  To specify display of a new minor
mode, it is sufficient to add an element to this list.  Once that
is done, you can turn the mode on and off just by setting a variable,
and the display will show its status automatically.

** New variable `cursor-in-echo-area'.

If this variable is non-nil, the screen cursor appears on the
last line of the screen, at the end of the text displayed there.

Binding this variable to t is useful at times when reading single
characters of input with `read-char'.

** New per-buffer variable `selective-display-ellipses'.

If this variable is non-nil, an ellipsis (`...') appears on the screen
at the end of each text line that is followed by invisible text.

If this variable is nil, no ellipses appear.  Then there is no sign
on the screen that invisible text is present.

Text is made invisible under the control of the variable
`selective-display'; this is how Outline mode and C-x $ work.

** New variable `no-redraw-on-reenter'.

If you set this variable non-nil, Emacs will not clear the screen when
you resume it after suspending it.  This is for the sake of terminals
with multiple screens of memory, where the termcap entry has been set
up to switch between screens when Emacs is suspended and resumed.

** New argument to `set-screen-height' or `set-screen-width'.

These functions now take an optional second argument which says
what significance the newly specified height or width has.

If the argument is nil, or absent, it means that Emacs should
believe that the terminal height or width really is as just specified.

If the argument is t, it means Emacs should not believe that the
terminal really is this high or wide, but it should use the
specific height or width as the number of lines or columns to display.
Thus, you could display only 24 lines on a screen known to have 48 lines.

What practical difference is there between using only 24 lines for display
and really believing that the terminal has 24 lines?

1. The ``real'' height of the terminal says what the terminal command
to move the cursor to the last line will do.

2. The ``real'' height of the terminal determines how much padding is
needed.

* File-related changes.

** New parameter `backup-by-copying-when-mismatch'.