+ A @dfn{fontset} is a list of fonts, each assigned to a range of
+character codes. An individual font cannot display the whole range of
+characters that Emacs supports, but a fontset can. Fontsets have names,
+just as fonts do, and you can use a fontset name in place of a font name
+when you specify the ``font'' for a frame or a face. Here is
+information about defining a fontset under Lisp program control.
+
+@defun create-fontset-from-fontset-spec fontset-spec &optional style-variant-p noerror
+This function defines a new fontset according to the specification
+string @var{fontset-spec}. The string should have this format:
+
+@smallexample
+@var{fontpattern}, @r{[}@var{charsetname}:@var{fontname}@r{]@dots{}}
+@end smallexample
+
+@noindent
+Whitespace characters before and after the commas are ignored.
+
+The first part of the string, @var{fontpattern}, should have the form of
+a standard X font name, except that the last two fields should be
+@samp{fontset-@var{alias}}.
+
+The new fontset has two names, one long and one short. The long name is
+@var{fontpattern} in its entirety. The short name is
+@samp{fontset-@var{alias}}. You can refer to the fontset by either
+name. If a fontset with the same name already exists, an error is
+signaled, unless @var{noerror} is non-@code{nil}, in which case this
+function does nothing.
+
+If optional argument @var{style-variant-p} is non-@code{nil}, that says
+to create bold, italic and bold-italic variants of the fontset as well.
+These variant fontsets do not have a short name, only a long one, which
+is made by altering @var{fontpattern} to indicate the bold or italic
+status.
+
+The specification string also says which fonts to use in the fontset.
+See below for the details.
+@end defun
+
+ The construct @samp{@var{charset}:@var{font}} specifies which font to
+use (in this fontset) for one particular character set. Here,
+@var{charset} is the name of a character set, and @var{font} is the font
+to use for that character set. You can use this construct any number of
+times in the specification string.
+
+ For the remaining character sets, those that you don't specify
+explicitly, Emacs chooses a font based on @var{fontpattern}: it replaces
+@samp{fontset-@var{alias}} with a value that names one character set.
+For the @acronym{ASCII} character set, @samp{fontset-@var{alias}} is replaced
+with @samp{ISO8859-1}.
+
+ In addition, when several consecutive fields are wildcards, Emacs
+collapses them into a single wildcard. This is to prevent use of
+auto-scaled fonts. Fonts made by scaling larger fonts are not usable
+for editing, and scaling a smaller font is not useful because it is
+better to use the smaller font in its own size, which Emacs does.
+
+ Thus if @var{fontpattern} is this,
+
+@example
+-*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24
+@end example
+
+@noindent
+the font specification for @acronym{ASCII} characters would be this:
+
+@example
+-*-fixed-medium-r-normal-*-24-*-ISO8859-1
+@end example
+
+@noindent
+and the font specification for Chinese GB2312 characters would be this:
+
+@example
+-*-fixed-medium-r-normal-*-24-*-gb2312*-*
+@end example
+
+ You may not have any Chinese font matching the above font
+specification. Most X distributions include only Chinese fonts that
+have @samp{song ti} or @samp{fangsong ti} in the @var{family} field. In
+such a case, @samp{Fontset-@var{n}} can be specified as below:
+
+@smallexample
+Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\
+ chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-*
+@end smallexample
+
+@noindent
+Then, the font specifications for all but Chinese GB2312 characters have
+@samp{fixed} in the @var{family} field, and the font specification for
+Chinese GB2312 characters has a wild card @samp{*} in the @var{family}
+field.
+
+@defun set-fontset-font name character fontname &optional frame
+This function modifies the existing fontset @var{name} to
+use the font name @var{fontname} for the character @var{character}.
+
+If @var{name} is @code{nil}, this function modifies the default
+fontset, whose short name is @samp{fontset-default}.
+
+@var{character} may be a cons; @code{(@var{from} . @var{to})}, where
+@var{from} and @var{to} are non-generic characters. In that case, use
+@var{fontname} for all characters in the range @var{from} and @var{to}
+(inclusive).
+
+@var{character} may be a charset. In that case, use
+@var{fontname} for all character in the charsets.
+
+@var{fontname} may be a cons; @code{(@var{family} . @var{registry})},
+where @var{family} is a family name of a font (possibly including a
+foundry name at the head), @var{registry} is a registry name of a font
+(possibly including an encoding name at the tail).
+
+For instance, this changes the default fontset to use a font of which
+registry name is @samp{JISX0208.1983} for all characters belonging to
+the charset @code{japanese-jisx0208}.
+
+@example
+(set-fontset-font nil 'japanese-jisx0208 '(nil . "JISX0208.1983"))
+@end example
+
+@end defun
+
+@defun char-displayable-p char
+This function returns @code{t} if Emacs ought to be able to display
+@var{char}. More precisely, if the selected frame's fontset has a
+font to display the character set that @var{char} belongs to.
+
+Fontsets can specify a font on a per-character basis; when the fontset
+does that, this function's value may not be accurate.
+@end defun
+
+@node Fringes
+@section Fringes
+@cindex Fringes
+
+ The @dfn{fringes} of a window are thin vertical strips down the
+sides that are used for displaying bitmaps that indicate truncation,
+continuation, horizontal scrolling, and the overlay arrow.
+
+@menu
+* Fringe Size/Pos:: Specifying where to put the window fringes.
+* Fringe Bitmaps:: Displaying bitmaps in the window fringes.
+* Customizing Bitmaps:: Specifying your own bitmaps to use in the fringes.
+* Overlay Arrow:: Display of an arrow to indicate position.
+@end menu
+
+@node Fringe Size/Pos
+@subsection Fringe Size and Position
+
+ Here's how to control the position and width of the window fringes.
+
+@defvar fringes-outside-margins
+If the value is non-@code{nil}, the frames appear outside the display
+margins. The fringes normally appear between the display margins and
+the window text. It works to set @code{fringes-outside-margins}
+buffer-locally. @xref{Display Margins}.
+@end defvar
+
+@defvar left-fringe-width
+This variable, if non-@code{nil}, specifies the width of the left
+fringe in pixels.
+@end defvar
+
+@defvar right-fringe-width
+This variable, if non-@code{nil}, specifies the width of the right
+fringe in pixels.
+@end defvar
+
+ The values of these variables take effect when you display the
+buffer in a window. If you change them while the buffer is visible,
+you can call @code{set-window-buffer} to display it once again in the
+same window, to make the changes take effect.
+
+@defun set-window-fringes window left &optional right outside-margins
+This function sets the fringe widths of window @var{window}.
+If @var{window} is @code{nil}, the selected window is used.
+
+The argument @var{left} specifies the width in pixels of the left
+fringe, and likewise @var{right} for the right fringe. A value of
+@code{nil} for either one stands for the default width. If
+@var{outside-margins} is non-@code{nil}, that specifies that fringes
+should appear outside of the display margins.
+@end defun
+
+@defun window-fringes &optional window
+This function returns information about the fringes of a window
+@var{window}. If @var{window} is omitted or @code{nil}, the selected
+window is used. The value has the form @code{(@var{left-width}
+@var{right-width} @var{outside-margins})}.
+@end defun
+
+@defvar overflow-newline-into-fringe
+If this is non-@code{nil}, lines exactly as wide as the window (not
+counting the final newline character) are not continued. Instead,
+when point is at the end of the line, the cursor appears in the right
+fringe.
+@end defvar
+
+@node Fringe Bitmaps
+@subsection Fringe Bitmaps
+@cindex fringe bitmaps
+@cindex bitmaps, fringe
+
+ The @dfn{fringe bitmaps} are tiny icons Emacs displays in the window
+fringe (on a graphic display) to indicate truncated or continued
+lines, buffer boundaries, overlay arrow, etc. The fringe bitmaps are
+shared by all frames and windows. You can redefine the built-in
+fringe bitmaps, and you can define new fringe bitmaps.
+
+ The way to display a bitmap in the left or right fringes for a given
+line in a window is by specifying the @code{display} property for one
+of the characters that appears in it. Use a display specification of
+the form @code{(left-fringe @var{bitmap} [@var{face}])} or
+@code{(right-fringe @var{bitmap} [@var{face}])} (@pxref{Display
+Property}). Here, @var{bitmap} is a symbol identifying the bitmap you
+want, and @var{face} (which is optional) is the name of the face whose
+colors should be used for displaying the bitmap, instead of the
+default @code{fringe} face. @var{face} is automatically merged with
+the @code{fringe} face, so normally @var{face} need only specify the
+foreground color for the bitmap.
+
+ These are the symbols identify the standard fringe bitmaps.
+Evaluate @code{(require 'fringe)} to define them. Fringe bitmap
+symbols have their own name space.
+
+@table @asis
+@item Truncation and continuation line bitmaps:
+@code{left-truncation}, @code{right-truncation},
+@code{continued-line}, @code{continuation-line}.
+
+@item Buffer indication bitmaps:
+@code{up-arrow}, @code{down-arrow},
+@code{top-left-angle}, @code{top-right-angle},
+@code{bottom-left-angle}, @code{bottom-right-angle},
+@code{left-bracket}, @code{right-bracket}.
+
+@item Empty line indication bitmap:
+@code{empty-line}.
+
+@item Overlay arrow bitmap:
+@code{overlay-arrow}.
+
+@item Bitmaps for displaying the cursor in right fringe:
+@code{filled-box-cursor}, @code{hollow-box-cursor}, @code{hollow-square},
+@code{bar-cursor}, @code{hbar-cursor}.
+@end table
+
+@defun fringe-bitmaps-at-pos &optional pos window
+This function returns the fringe bitmaps of the display line
+containing position @var{pos} in window @var{window}. The return
+value has the form @code{(@var{left} @var{right} @var{ov})}, where @var{left}
+is the symbol for the fringe bitmap in the left fringe (or @code{nil}
+if no bitmap), @var{right} is similar for the right fringe, and @var{ov}
+is non-@code{nil} if there is an overlay arrow in the left fringe.
+
+The value is @code{nil} if @var{pos} is not visible in @var{window}.
+If @var{window} is @code{nil}, that stands for the selected window.
+If @var{pos} is @code{nil}, that stands for the value of point in
+@var{window}.
+@end defun
+
+@node Customizing Bitmaps
+@subsection Customizing Fringe Bitmaps
+
+@defun define-fringe-bitmap bitmap bits &optional height width align
+This function defines the symbol @var{bitmap} as a new fringe bitmap,
+or replaces an existing bitmap with that name.
+
+The argument @var{bits} specifies the image to use. It should be
+either a string or a vector of integers, where each element (an
+integer) corresponds to one row of the bitmap. Each bit of an integer
+corresponds to one pixel of the bitmap, where the low bit corresponds
+to the rightmost pixel of the bitmap.
+
+The height is normally the length of @var{bits}. However, you
+can specify a different height with non-@code{nil} @var{height}. The width
+is normally 8, but you can specify a different width with non-@code{nil}
+@var{width}. The width must be an integer between 1 and 16.
+
+The argument @var{align} specifies the positioning of the bitmap
+relative to the range of rows where it is used; the default is to
+center the bitmap. The allowed values are @code{top}, @code{center},
+or @code{bottom}.
+
+The @var{align} argument may also be a list @code{(@var{align}
+@var{periodic})} where @var{align} is interpreted as described above.
+If @var{periodic} is non-@code{nil}, it specifies that the rows in
+@code{bits} should be repeated enough times to reach the specified
+height.
+
+The return value on success is an integer identifying the new bitmap.
+You should save that integer in a variable so it can be used to select
+this bitmap.
+
+This function signals an error if there are no more free bitmap slots.
+@end defun
+
+@defun destroy-fringe-bitmap bitmap
+This function destroy the fringe bitmap identified by @var{bitmap}.
+If @var{bitmap} identifies a standard fringe bitmap, it actually
+restores the standard definition of that bitmap, instead of
+eliminating it entirely.
+@end defun
+
+@defun set-fringe-bitmap-face bitmap &optional face
+This sets the face for the fringe bitmap @var{bitmap} to @var{face}.
+If @var{face} is @code{nil}, it selects the @code{fringe} face. The
+bitmap's face controls the color to draw it in.
+
+@var{face} is merged with the @code{fringe} face, so normally
+@var{face} should specify only the foreground color.
+@end defun
+
+@node Overlay Arrow
+@subsection The Overlay Arrow
+@cindex overlay arrow
+
+ The @dfn{overlay arrow} is useful for directing the user's attention
+to a particular line in a buffer. For example, in the modes used for
+interface to debuggers, the overlay arrow indicates the line of code
+about to be executed. This feature has nothing to do with
+@dfn{overlays} (@pxref{Overlays}).
+
+@defvar overlay-arrow-string
+This variable holds the string to display to call attention to a
+particular line, or @code{nil} if the arrow feature is not in use.
+On a graphical display the contents of the string are ignored; instead a
+glyph is displayed in the fringe area to the left of the display area.
+@end defvar
+
+@defvar overlay-arrow-position
+This variable holds a marker that indicates where to display the overlay
+arrow. It should point at the beginning of a line. On a non-graphical
+display the arrow text
+appears at the beginning of that line, overlaying any text that would
+otherwise appear. Since the arrow is usually short, and the line
+usually begins with indentation, normally nothing significant is
+overwritten.
+
+The overlay string is displayed only in the buffer that this marker
+points into. Thus, only one buffer can have an overlay arrow at any
+given time.
+@c !!! overlay-arrow-position: but the overlay string may remain in the display
+@c of some other buffer until an update is required. This should be fixed
+@c now. Is it?
+@end defvar
+
+ You can do a similar job by creating an overlay with a
+@code{before-string} property. @xref{Overlay Properties}.
+
+ You can define multiple overlay arrows via the variable
+@code{overlay-arrow-variable-list}.