@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000
@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/text
@item help-echo
@kindex help-echo @r{(text property)}
+@anchor{Text help-echo}
If text has a string as its @code{help-echo} property, then when you
move the mouse onto that text, Emacs displays that string in the echo
-area, or in the tooltip window. This feature is used in the mode line.
-It is available starting in Emacs 21.
+area, or in the tooltip window.
+
+If the value of the @code{help-echo property} is a function, that
+function is called with three arguments, @var{window}, @var{object} and
+@var{position} and should return a help string or nil for
+none. The first argument, @var{window} is the window in which
+the help was found. The second, @var{object}, is the buffer, overlay or
+string which had the @code{help-echo} property. The @var{position}
+argument is as follows:
+
+@itemize @bullet{}
+@item
+If @var{object} is a buffer, @var{pos} is the position in the buffer
+where the @code{help-echo} text property was found.
+@item
+If @var{object} is an overlay, that overlay has a @code{help-echo}
+property, and @var{pos} is the position in the overlay's buffer under
+the mouse.
+@item
+If @var{object} is a string (an overlay string or a string displayed
+with the @code{display} property) @var{pos} is the position in that
+string under the mouse.
+@end itemize
+
+If the value of the @code{help-echo} property is neither a function nor
+a string, it is evaluated to obtain a help string.
+
+Variable @code{show-help-function} (@pxref{Help display}) provides a
+hook to alter the way help text is displayed.
+
+This feature is used in the mode line and for other active text. It is
+available starting in Emacs 21.
@item local-map
@cindex keymap of character
@code{let}.
@end defvar
+@defvar show-help-function
+@tindex show-help-function
+@anchor{Help display}
+If this variable is non-@code{nil} it specifies a function called to
+display help strings. These may be @code{help-echo} properties or menu
+(@pxref{Simple Menu Items}, @pxref{Extended Menu Items}) or tool bar
+(@pxref{Tool Bar}) help strings. The specified function is called with
+one argument, the help string to display. Tooltip mode
+(@pxref{(emacs)Tooltips}) provides an example.
+@end defvar
+
@node Format Properties
@subsection Formatted Text Properties
made within the @code{combine-after-change-calls} body.
@strong{Warning:} You must not alter the values of
-@code{after-change-functions} and @code{after-change-function} within
+@code{after-change-functions} within
the body of a @code{combine-after-change-calls} form.
@strong{Note:} If the changes you combine occur in widely scattered
functions.
@end defmac
-@defvar before-change-function
-This obsolete variable holds one function to call before any buffer
-modification (or @code{nil} for no function). It is called just like
-the functions in @code{before-change-functions}.
-@end defvar
-
-@defvar after-change-function
-This obsolete variable holds one function to call after any buffer modification
-(or @code{nil} for no function). It is called just like the functions in
-@code{after-change-functions}.
-@end defvar
-
-The four variables above are temporarily bound to @code{nil} during the
+The two variables above are temporarily bound to @code{nil} during the
time that any of these functions is running. This means that if one of
these functions changes the buffer, that change won't run these
functions. If you do want a hook function to make changes that run