@c This is part of the Emacs manual.
@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Frames, International, Windows, Top
@chapter Frames and X Windows
@cindex frames

  When using the X Window System, you can create multiple windows at the
X level in a single Emacs session.  Each X window that belongs to Emacs
displays a @dfn{frame} which can contain one or several Emacs windows.
A frame initially contains a single general-purpose Emacs window which
you can subdivide vertically or horizontally into smaller windows.  A
frame normally contains its own echo area and minibuffer, but you can
make frames that don't have these---they use the echo area and
minibuffer of another frame.

  Editing you do in one frame also affects the other frames.  For
instance, if you put text in the kill ring in one frame, you can yank it
in another frame.  If you exit Emacs through @kbd{C-x C-c} in one frame,
it terminates all the frames.  To delete just one frame, use @kbd{C-x 5
0}.

  To avoid confusion, we reserve the word ``window'' for the
subdivisions that Emacs implements, and never use it to refer to a
frame.

  Emacs compiled for MS-DOS emulates some aspects of the window system
so that you can use many of the features described in this chapter.
@xref{MS-DOS Input}, for more information.

@menu
* Mouse Commands::      Moving, cutting, and pasting, with the mouse.
* Secondary Selection:: Cutting without altering point and mark.
* Mouse References::    Using the mouse to select an item from a list.
* Menu Mouse Clicks::   Mouse clicks that bring up menus.
* Mode Line Mouse::     Mouse clicks on the mode line.
* Creating Frames::     Creating additional Emacs frames with various contents.
* Multiple Displays::   How one Emacs job can talk to several displays.
* Special Buffer Frames::  You can make certain buffers have their own frames.
* Frame Parameters::    Changing the colors and other modes of frames.
* Scroll Bars::	        How to enable and disable scroll bars; how to use them.
* Menu Bars::	        Enabling and disabling the menu bar.
* Faces::	        How to change the display style using faces.
* Font Lock::           Minor mode for syntactic highlighting using faces.
* Support Modes::       Font Lock support modes make Font Lock faster.
* Misc X::	        Iconifying and deleting frames.	Region highlighting.
* Non-Window Terminals::  Multiple frames on terminals that show only one.
@end menu

@node Mouse Commands
@section Mouse Commands for Editing
@cindex mouse buttons (what they do)

  The mouse commands for selecting and copying a region are mostly
compatible with the @code{xterm} program.  You can use the same mouse
commands for copying between Emacs and other X client programs.

@kindex DELETE
  If you select a region with any of these mouse commands, and then
immediately afterward type the @key{DELETE} function key, it deletes the
region that you selected.  The @key{BACKSPACE} function key and the
ASCII character @key{DEL} do not do this; if you type any other key
in between the mouse command and @key{DELETE}, it does not do this.

@findex mouse-set-region
@findex mouse-set-point
@findex mouse-yank-at-click
@findex mouse-save-then-click
@kindex Mouse-1
@kindex Mouse-2
@kindex Mouse-3
@table @kbd
@item Mouse-1
Move point to where you click (@code{mouse-set-point}).
This is normally the left button.

@item Drag-Mouse-1
Set the region to the text you select by dragging, and copy it to the
kill ring (@code{mouse-set-region}).  You can specify both ends of the
region with this single command.

@vindex mouse-scroll-min-lines
If you move the mouse off the top or bottom of the window while
dragging, the window scrolls at a steady rate until you move the mouse
back into the window.  This way, you can select regions that don't fit
entirely on the screen.  The number of lines scrolled per step depends
on how far away from the window edge the mouse has gone; the variable
@code{mouse-scroll-min-lines} specifies a minimum step size.

@item Mouse-2
Yank the last killed text, where you click (@code{mouse-yank-at-click}).
This is normally the middle button.

@item Mouse-3
This command, @code{mouse-save-then-kill}, has several functions
depending on where you click and the status of the region.

The most basic case is when you click @kbd{Mouse-1} in one place and
then @kbd{Mouse-3} in another.  This selects the text between those two
positions as the region.  It also copies the new region to the kill
ring, so that you can copy it to someplace else.

If you click @kbd{Mouse-1}, scroll with the scroll bar, and then click
@kbd{Mouse-3}, it remembers where point was before scrolling (where you
put it with @kbd{Mouse-1}), and uses that position as the other end of
the region.  This is so that you can select a region that doesn't fit
entirely on the screen.

More generally, if you do not have a highlighted region, @kbd{Mouse-3}
selects the text between point and the click position as the region.  It
does this by setting the mark where point was, and moving point to where
you click.

If you have a highlighted region, or if the region was set just before
by dragging button 1, @kbd{Mouse-3} adjusts the nearer end of the region
by moving it to where you click.  The adjusted region's text also
replaces the old region's text in the kill ring.

If you originally specified the region using a double or triple
@kbd{Mouse-1}, so that the region is defined to consist of entire words
or lines, then adjusting the region with @kbd{Mouse-3} also proceeds by
entire words or lines.

If you use @kbd{Mouse-3} a second time consecutively, at the same place,
that kills the region already selected.

@item Double-Mouse-1
This key sets the region around the word which you click on.  If you
click on a character with ``symbol'' syntax (such as underscore, in C
mode), it sets the region around the symbol surrounding that character.

If you click on a character with open-parenthesis or close-parenthesis
syntax, it sets the region around the parenthetical grouping (sexp)
which that character starts or ends.  If you click on a character with
string-delimiter syntax (such as a singlequote or doublequote in C), it
sets the region around the string constant (using heuristics to figure
out whether that character is the beginning or the end of it).

@item Double-Drag-Mouse-1
This key selects a region made up of the words you drag across.

@item Triple-Mouse-1
This key sets the region around the line you click on.

@item Triple-Drag-Mouse-1
This key selects a region made up of the lines you drag across.
@end table

  The simplest way to kill text with the mouse is to press @kbd{Mouse-1}
at one end, then press @kbd{Mouse-3} twice at the other end.
@xref{Killing}.  To copy the text into the kill ring without deleting it
from the buffer, press @kbd{Mouse-3} just once---or just drag across the
text with @kbd{Mouse-1}.  Then you can copy it elsewhere by yanking it.

@vindex mouse-yank-at-point
  To yank the killed or copied text somewhere else, move the mouse there
and press @kbd{Mouse-2}.  @xref{Yanking}.  However, if
@code{mouse-yank-at-point} is non-@code{nil}, @kbd{Mouse-2} yanks at
point.  Then it does not matter precisely where you click; all that
matters is which window you click on.  The default value is @code{nil}.
This variable also affects yanking the secondary selection.

@cindex cutting and X
@cindex pasting and X
@cindex X cutting and pasting
  To copy text to another X window, kill it or save it in the kill ring.
Under X, this also sets the @dfn{primary selection}.  Then use the
``paste'' or ``yank'' command of the program operating the other window
to insert the text from the selection.

  To copy text from another X window, use the ``cut'' or ``copy'' command
of the program operating the other window, to select the text you want.
Then yank it in Emacs with @kbd{C-y} or @kbd{Mouse-2}.

  These cutting and pasting commands also work on MS-Windows.

@cindex primary selection
@cindex cut buffer
@cindex selection, primary
@vindex x-cut-buffer-max
  When Emacs puts text into the kill ring, or rotates text to the front
of the kill ring, it sets the @dfn{primary selection} in the X server.
This is how other X clients can access the text.  Emacs also stores the
text in the cut buffer, but only if the text is short enough
(@code{x-cut-buffer-max} specifies the maximum number of characters);
putting long strings in the cut buffer can be slow.

  The commands to yank the first entry in the kill ring actually check
first for a primary selection in another program; after that, they check
for text in the cut buffer.  If neither of those sources provides text
to yank, the kill ring contents are used.

@node Secondary Selection
@section Secondary Selection
@cindex secondary selection

  The @dfn{secondary selection} is another way of selecting text using
X.  It does not use point or the mark, so you can use it to kill text
without setting point or the mark.

@table @kbd
@findex mouse-set-secondary
@kindex M-Drag-Mouse-1
@item M-Drag-Mouse-1
Set the secondary selection, with one end at the place where you press
down the button, and the other end at the place where you release it
(@code{mouse-set-secondary}).  The highlighting appears and changes as
you drag.

If you move the mouse off the top or bottom of the window while
dragging, the window scrolls at a steady rate until you move the mouse
back into the window.  This way, you can mark regions that don't fit
entirely on the screen.

@findex mouse-start-secondary
@kindex M-Mouse-1
@item M-Mouse-1
Set one endpoint for the @dfn{secondary selection}
(@code{mouse-start-secondary}).

@findex mouse-secondary-save-then-kill
@kindex M-Mouse-3
@item M-Mouse-3
Make a secondary selection, using the place specified with @kbd{M-Mouse-1}
as the other end (@code{mouse-secondary-save-then-kill}).  A second click
at the same place kills the secondary selection just made.

@findex mouse-yank-secondary
@kindex M-Mouse-2
@item M-Mouse-2
Insert the secondary selection where you click
(@code{mouse-yank-secondary}).  This places point at the end of the
yanked text.
@end table

Double or triple clicking of @kbd{M-Mouse-1} operates on words and
lines, much like @kbd{Mouse-1}.

If @code{mouse-yank-at-point} is non-@code{nil}, @kbd{M-Mouse-2}
yanks at point.  Then it does not matter precisely where you click; all
that matters is which window you click on.  @xref{Mouse Commands}.

@node Mouse References
@section Following References with the Mouse
@kindex Mouse-2 @r{(selection)}

  Some Emacs buffers display lists of various sorts.  These include
lists of files, of buffers, of possible completions, of matches for
a pattern, and so on.

  Since yanking text into these buffers is not very useful, most of them
define @kbd{Mouse-2} specially, as a command to use or view the item you
click on.

  For example, if you click @kbd{Mouse-2} on a file name in a Dired
buffer, you visit that file.  If you click @kbd{Mouse-2} on an error
message in the @samp{*Compilation*} buffer, you go to the source code
for that error message.  If you click @kbd{Mouse-2} on a completion in
the @samp{*Completions*} buffer, you choose that completion.

  You can usually tell when @kbd{Mouse-2} has this special sort of
meaning because the sensitive text highlights when you move the mouse
over it.

@node Menu Mouse Clicks
@section Mouse Clicks for Menus

  Mouse clicks modified with the @key{CTRL} and @key{SHIFT} keys
bring up menus.

@kindex C-Mouse-3
@table @kbd
@item C-Mouse-1
This menu is for selecting a buffer.

@item C-Mouse-2
This menu is for specifying faces and other text properties
for editing formatted text.  @xref{Formatted Text}.

@item C-Mouse-3
This menu is mode-specific.  For most modes, this menu has the same
items as all the mode-specific menu-bar menus put together.  Some modes
may specify a different menu for this button.@footnote{Some systems use
@kbd{Mouse-3} for a mode-specific menu.  We took a survey of users, and
found they preferred to keep @kbd{Mouse-3} for selecting and killing
regions.  Hence the decision to use @kbd{C-Mouse-3} for this menu.}

@item S-mouse-1
This menu is for specifying the frame's principal font.
@end table

@node Mode Line Mouse
@section Mode Line Mouse Commands

  You can use mouse clicks on window mode lines to select and manipulate
windows.

@table @kbd
@item Mouse-1
@kbd{Mouse-1} on a mode line selects the window above.  By dragging
@kbd{Mouse-1} on the mode line, you can move it, thus changing the
height of the windows above and below.

@item Mouse-2
@kbd{Mouse-2} on a mode line expands that window to fill its frame.

@item Mouse-3
@kbd{Mouse-3} on a mode line deletes the window above.

@item C-Mouse-2
@kbd{C-Mouse-2} on a mode line splits the window above
horizontally, above the place in the mode line where you click.
@end table

  @kbd{C-Mouse-2} on a scroll bar splits the corresponding window
vertically.  @xref{Split Window}.

@node Creating Frames
@section Creating Frames
@cindex creating frames

@kindex C-x 5
  The prefix key @kbd{C-x 5} is analogous to @kbd{C-x 4}, with parallel
subcommands.  The difference is that @kbd{C-x 5} commands create a new
frame rather than just a new window in the selected frame  (@xref{Pop
Up Window}).  If an existing visible or iconified frame already displays
the requested material, these commands use the existing frame, after
raising or deiconifying as necessary. 

  The various @kbd{C-x 5} commands differ in how they find or create the
buffer to select:

@table @kbd
@item C-x 5 2
@kindex C-x 5 2
@findex make-frame
Create a new frame (@code{make-frame}).
@item C-x 5 b @var{bufname} @key{RET}
Select buffer @var{bufname} in another window.  This runs
@code{switch-to-buffer-other-frame}.
@item C-x 5 f @var{filename} @key{RET}
Visit file @var{filename} and select its buffer in another frame.  This
runs @code{find-file-other-frame}.  @xref{Visiting}.
@item C-x 5 d @var{directory} @key{RET}
Select a Dired buffer for directory @var{directory} in another frame.
This runs @code{dired-other-frame}.  @xref{Dired}.
@item C-x 5 m
Start composing a mail message in another frame.  This runs
@code{mail-other-frame}.  It is the other-frame variant of @kbd{C-x m}.
@xref{Sending Mail}.
@item C-x 5 .
Find a tag in the current tag table in another frame.  This runs
@code{find-tag-other-frame}, the multiple-frame variant of @kbd{M-.}.
@xref{Tags}.
@item C-x 5 r @var{filename} @key{RET}
@kindex C-x 5 r
@findex find-file-read-only-other-frame
Visit file @var{filename} read-only, and select its buffer in another
frame.  This runs @code{find-file-read-only-other-frame}.
@xref{Visiting}.
@end table

@cindex default-frame-alist
@cindex initial-frame-alist
  You can control the appearance of new frames you create by setting the
frame parameters in @code{default-frame-alist}.  You can use the
variable @code{initial-frame-alist} to specify parameters that affect
only the initial frame.  @xref{Initial Parameters,,, elisp, The Emacs
Lisp Reference Manual}, for more information.

@node Multiple Displays
@section Multiple Displays
@cindex multiple displays

  A single Emacs can talk to more than one X Windows display.
Initially, Emacs uses just one display---the one specified with the
@code{DISPLAY} environment variable or with the @samp{--display} option
(@pxref{Initial Options}).  To connect to another display, use the
command @code{make-frame-on-display}:

@findex make-frame-on-display
@table @kbd
@item M-x make-frame-on-display @key{RET} @var{display} @key{RET}
Create a new frame on display @var{display}.
@end table

  A single X server can handle more than one screen.  When you open
frames on two screens belonging to one server, Emacs knows they share a
single keyboard, and it treats all the commands arriving from these
screens as a single stream of input.

  When you open frames on different X servers, Emacs makes a separate
input stream for each server.  This way, two users can type
simultaneously on the two displays, and Emacs will not garble their
input.  Each server also has its own selected frame.  The commands you
enter with a particular X server apply to that server's selected frame.

  Despite these features, people using the same Emacs job from different
displays can still interfere with each other if they are not careful.
For example, if any one types @kbd{C-x C-c}, that exits the Emacs job
for all of them!

@node Special Buffer Frames
@section Special Buffer Frames

@vindex special-display-buffer-names
  You can make certain chosen buffers, for which Emacs normally creates
a second window when you have just one window, appear in special frames
of their own.  To do this, set the variable
@code{special-display-buffer-names} to a list of buffer names; any
buffer whose name is in that list automatically gets a special frame,
when an Emacs command wants to display it ``in another window.''

  For example, if you set the variable this way,

@example
(setq special-display-buffer-names
      '("*Completions*" "*grep*" "*tex-shell*"))
@end example

@noindent
then completion lists, @code{grep} output and the @TeX{} mode shell
buffer get individual frames of their own.  These frames, and the
windows in them, are never automatically split or reused for any other
buffers.  They continue to show the buffers they were created for,
unless you alter them by hand.  Killing the special buffer deletes its
frame automatically.

@vindex special-display-regexps
  More generally, you can set @code{special-display-regexps} to a list
of regular expressions; then a buffer gets its own frame if its name
matches any of those regular expressions.  (Once again, this applies only
to buffers that normally get displayed for you in a separate window.)

@vindex special-display-frame-alist
  The variable @code{special-display-frame-alist} specifies the frame
parameters for these frames.  It has a default value, so you don't need
to set it.

  For those who know Lisp, an element of
@code{special-display-buffer-names} or @code{special-display-regexps}
can also be a list.  Then the first element is the buffer name or
regular expression; the rest of the list specifies how to create the
frame.  It can be an association list specifying frame parameter values;
these values take precedence over parameter values specified in
@code{special-display-frame-alist}.  Alternatively, it can have this
form:

@example
(@var{function} @var{args}...)
@end example

@noindent
where @var{function} is a symbol.  Then the frame is constructed by
calling @var{function}; its first argument is the buffer, and its
remaining arguments are @var{args}.

   An analogous feature lets you specify buffers which should be
displayed in the selected window.  @xref{Force Same Window}.  The
same-window feature takes precedence over the special-frame feature;
therefore, if you add a buffer name to
@code{special-display-buffer-names} and it has no effect, check to see
whether that feature is also in use for the same buffer name.

@node Frame Parameters
@section Setting Frame Parameters
@cindex colors
@cindex Auto-Raise mode
@cindex Auto-Lower mode

  This section describes commands for altering the display style and
window management behavior of the selected frame.

@findex set-foreground-color
@findex set-background-color
@findex set-cursor-color
@findex set-mouse-color
@findex set-border-color
@findex auto-raise-mode
@findex auto-lower-mode
@table @kbd
@item M-x set-foreground-color @key{RET} @var{color} @key{RET}
Specify color @var{color} for the foreground of the selected frame.

@item M-x set-background-color @key{RET} @var{color} @key{RET}
Specify color @var{color} for the background of the selected frame.
This changes the foreground color of the @code{modeline} face also, so
that it remains in inverse video compared with the default.

@item M-x set-cursor-color @key{RET} @var{color} @key{RET}
Specify color @var{color} for the cursor of the selected frame.

@item M-x set-mouse-color @key{RET} @var{color} @key{RET}
Specify color @var{color} for the mouse cursor when it is over the
selected frame.

@item M-x set-border-color @key{RET} @var{color} @key{RET}
Specify color @var{color} for the border of the selected frame.

@item M-x list-colors-display
Display the defined color names and show what the colors look like.
This command is somewhat slow.

@item M-x auto-raise-mode
Toggle whether or not the selected frame should auto-raise.  Auto-raise
means that every time you move the mouse onto the frame, it raises the
frame.

Note that this auto-raise feature is implemented by Emacs itself.  Some
window managers also implement auto-raise.  If you enable auto-raise for
Emacs frames in your X window manager, it should work, but it is beyond
Emacs's control and therefore @code{auto-raise-mode} has no effect on
it.

@item M-x auto-lower-mode
Toggle whether or not the selected frame should auto-lower.
Auto-lower means that every time you move the mouse off the frame,
the frame moves to the bottom of the stack of X windows.

The command @code{auto-lower-mode} has no effect on auto-lower
implemented by the X window manager.  To control that, you must use
the appropriate window manager features.

@findex set-frame-font
@item M-x set-frame-font @key{RET} @var{font} @key{RET}
Specify font @var{font} as the principal font for the selected frame.
The principal font is used for all text displayed in the frame, except
when a face specifies a different font to use.  @xref{Font X}, for ways
to list the available fonts on your system.

@kindex S-Mouse-1
You can also set a frame's principal font through a pop-up menu.
Press @kbd{S-Mouse-1} to activate this menu.
@end table

  In Emacs versions that use an X toolkit, the color-setting and
font-setting functions don't affect menus and the menu bar, since they
are displayed by their own widget classes.  To change the appearance of
the menus and menu bar, you must use X resources (@pxref{Resources X}).
@xref{Colors X}, regarding colors.  @xref{Font X}, regarding choice of
font.

  For information on frame parameters and customization, see @ref{Frame
Parameters,,, elisp, The Emacs Lisp Reference Manual}.

@node Scroll Bars
@section Scroll Bars
@cindex Scroll Bar mode
@cindex mode, Scroll Bar

  When using X, Emacs normally makes a @dfn{scroll bar} at the left of
each Emacs window.  The scroll bar runs the height of the window, and
shows a moving rectangular inner box which represents the portion of the
buffer currently displayed.  The entire height of the scroll bar
represents the entire length of the buffer.

  You can use @kbd{Mouse-2} (normally, the middle button) in the scroll
bar to move or drag the inner box up and down.  If you move it to the
top of the scroll bar, you see the top of the buffer.  If you move it to
the bottom of the scroll bar, you see the bottom of the buffer.

  The left and right buttons in the scroll bar scroll by controlled
increments.  @kbd{Mouse-1} (normally, the left button) moves the line at
the level where you click up to the top of the window.  @kbd{Mouse-3}
(normally, the right button) moves the line at the top of the window
down to the level where you click.  By clicking repeatedly in the same
place, you can scroll by the same distance over and over.

  Aside from scrolling, you can also click @kbd{C-Mouse-2} in the scroll
bar to split a window vertically.  The split occurs on the line where
you click.

@findex scroll-bar-mode
  You can enable or disable Scroll Bar mode with the command @kbd{M-x
scroll-bar-mode}.  With no argument, it toggles the use of scroll bars.
With an argument, it turns use of scroll bars on if and only if the
argument is positive.  This command applies to all frames, including
frames yet to be created.  You can use the X resource
@samp{verticalScrollBars} to control the initial setting of Scroll Bar
mode.  @xref{Resources X}.

@findex toggle-scroll-bar
  To enable or disable scroll bars for just the selected frame, use the
@kbd{M-x toggle-scroll-bar} command.

@node Menu Bars
@section Menu Bars
@cindex Menu Bar mode
@cindex mode, Menu Bar

  You can turn display of menu bars on or off with @kbd{M-x
menu-bar-mode}.  With no argument, this command toggles Menu Bar mode, a
minor mode.  With an argument, the command turns Menu Bar mode on if the
argument is positive, off if the argument is not positive.  You can use
the X resource @samp{menuBarLines} to control the initial setting of
Menu Bar mode.  @xref{Resources X}.  Expert users often turn off the
menu bar, especially on text-only terminals, where this makes one
additional line available for text.

  @xref{Menu Bar} for information on how to invoke commands with the
menu bar.

@node Faces
@section Using Multiple Typefaces
@cindex faces

  When using Emacs with X, you can set up multiple styles of displaying
characters.  The aspects of style that you can control are the type
font, the foreground color, the background color, and whether to
underline.  Emacs on MS-DOS supports faces partially by letting you
control the foreground and background colors of each face
(@pxref{MS-DOS}).

  The way you control display style is by defining named @dfn{faces}.
Each face can specify a type font, a foreground color, a background
color, and an underline flag; but it does not have to specify all of
them.

  The style of display used for a given character in the text is
determined by combining several faces.  Any aspect of the display style
that isn't specified by overlays or text properties comes from the frame
itself.

  Enriched mode, the mode for editing formatted text, includes several
commands and menus for specifying faces.  @xref{Format Faces}, for how
to specify the font for text in the buffer.  @xref{Format Colors}, for
how to specify the foreground and background color.

  To alter the appearance of a face, use the customization buffer.
@xref{Face Customization}.  You can also use X resources to specify
attributes of particular faces (@pxref{Resources X}).

@findex list-faces-display
  To see what faces are currently defined, and what they look like, type
@kbd{M-x list-faces-display}.  It's possible for a given face to look
different in different frames; this command shows the appearance in the
frame in which you type it.  Here's a list of the standardly defined
faces:

@table @code
@item default
This face is used for ordinary text that doesn't specify any other face.
@item modeline
This face is used for mode lines.  By default, it's set up as the
inverse of the default face.  @xref{Display Vars}.
@item highlight
This face is used for highlighting portions of text, in various modes.
@item region
This face is used for displaying a selected region (when Transient Mark
mode is enabled---see below).
@item secondary-selection
This face is used for displaying a secondary selection (@pxref{Secondary
Selection}).
@item bold
This face uses a bold variant of the default font, if it has one.
@item italic
This face uses an italic variant of the default font, if it has one.
@item bold-italic
This face uses a bold italic variant of the default font, if it has one.
@item underline
This face underlines text.
@end table

@cindex @code{region} face
  When Transient Mark mode is enabled, the text of the region is
highlighted when the mark is active.  This uses the face named
@code{region}; you can control the style of highlighting by changing the
style of this face (@pxref{Face Customization}).  @xref{Transient Mark},
for more information about Transient Mark mode and activation and
deactivation of the mark.

  One easy way to use faces is to turn on Font Lock mode.  This minor
mode, which is always local to a particular buffer, arranges to
choose faces according to the syntax of the text you are editing.  It
can recognize comments and strings in most languages; in several
languages, it can also recognize and properly highlight various other
important constructs.  @xref{Font Lock}, for more information about
Font Lock mode and syntactic highlighting.

  You can print out the buffer with the highlighting that appears
on your screen using the command @code{ps-print-buffer-with-faces}.
@xref{Postscript}.

@node Font Lock
@section Font Lock mode
@cindex Font Lock mode
@cindex mode. Font Lock

  Font Lock mode is a minor mode, always local to a particular
buffer, which highlights (or ``fontifies'') using various faces
according to the syntax of the text you are editing.  It can
recognize comments and strings in most languages; in several
languages, it can also recognize and properly highlight various other
important constructs---for example, names of functions being defined
or reserved keywords.

@findex font-lock-mode
@findex turn-on-font-lock
  The command @kbd{M-x font-lock-mode} turns Font Lock mode on or off
according to the argument, and toggles the mode when it has no argument.
The function @code{turn-on-font-lock} unconditionally enables Font Lock
mode.  This is useful in mode-hook functions.  For example, to enable
Font Lock mode whenever you edit a C file, you can do this:

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

@findex global-font-lock-mode
  To turn on Font Lock mode automatically in all modes which support it,
use the function @code{global-font-lock-mode}, like this:

@example
(global-font-lock-mode t)
@end example

@kindex M-g M-g
@findex font-lock-fontify-block
  In Font Lock mode, when you edit the text, the highlighting updates
automatically in the line that you changed.  Most changes don't affect
the highlighting of subsequent lines, but occasionally they do.  To
rehighlight a range of lines, use the command @kbd{M-g M-g}
(@code{font-lock-fontify-block}).

@vindex font-lock-mark-block-function
  In certain major modes, @kbd{M-g M-g} refontifies the entire current
function.  (The variable @code{font-lock-mark-block-function} controls
how to find the current function.)  In other major modes, @kbd{M-g M-g}
refontifies 16 lines above and below point.

  With a prefix argument @var{n}, @kbd{M-g M-g} refontifies @var{n}
lines above and below point, regardless of the mode.

  To get the full benefit of Font Lock mode, you need to choose a
default font which has bold, italic, and bold-italic variants; or else
you need to have a color or gray-scale screen.

@vindex font-lock-maximum-decoration
  The variable @code{font-lock-maximum-decoration} specifies the
preferred level of fontification, for modes that provide multiple
levels.  Level 1 is the least amount of fontification; some modes
support levels as high as 3.  The normal default is ``as high as
possible.''  You can specify an integer, which applies to all modes, or
you can specify different numbers for particular major modes; for
example, to use level 1 for C/C++ modes, and the default level
otherwise, use this:

@example
(setq font-lock-maximum-decoration
      '((c-mode . 1) (c++-mode . 1)))
@end example

@vindex font-lock-maximum-size
  Fontification can be too slow for large buffers, so you can suppress
it.  The variable @code{font-lock-maximum-size} specifies a buffer size,
beyond which buffer fontification is suppressed.

@c @w is used below to prevent a bad page-break.
@vindex font-lock-beginning-of-syntax-function
  Comment and string fontification (or ``syntactic'' fontification)
relies on analysis of the syntactic structure of the buffer text.  For
the purposes of speed, some modes including C mode and Lisp mode rely on
a special convention: an open-parenthesis in the leftmost column always
defines the @w{beginning} of a defun, and is thus always outside any string
or comment.  (@xref{Defuns}.)  If you don't follow this convention,
then Font Lock mode can misfontify the text after an open-parenthesis in
the leftmost column that is inside a string or comment.

  The variable @code{font-lock-beginning-of-syntax-function} (always
buffer-local) specifies how Font Lock mode can find a position
guaranteed to be outside any comment or string.  In modes which use the
leftmost column parenthesis convention, the default value of the variable
is @code{beginning-of-defun}---that tells Font Lock mode to use the
convention.  If you set this variable to @code{nil}, Font Lock no longer
relies on the convention.  This avoids incorrect results, but the price
is that, in some cases, fontification for a changed text must rescan
buffer text from the beginning of the buffer.

@findex font-lock-add-keywords
  Font Lock highlighting patterns already exist for many modes, but you
may want to fontify additional patterns.  You can use the function
@code{font-lock-add-keywords}, to add your own highlighting patterns for
a particular mode.  For example, to highlight @samp{FIXME:} words in C
comments, use this:

@example
(font-lock-add-keywords
 'c-mode
 '(("\\<\\(FIXME\\):" 1 font-lock-warning-face t)))
@end example

@node Support Modes
@section Font Lock Support Modes

  Font Lock support modes make Font Lock mode faster for large buffers.
There are two support modes: Fast Lock mode and Lazy Lock mode.  They
use two different methods of speeding up Font Lock mode.

@menu
* Fast Lock Mode::      Saving font information in files.
* Lazy Lock Mode::      Fontifying only text that is actually displayed.
* Fast or Lazy::        Which support mode is best for you?
@end menu

@node Fast Lock Mode
@subsection Fast Lock Mode

@cindex Fast Lock mode
@cindex mode, Fast Lock
  To make Font Lock mode faster for buffers visiting large files, you
can use Fast Lock mode.  Fast Lock mode saves the font information for
each file in a separate cache file; each time you visit the file, it
rereads the font information from the cache file instead of refontifying
the text from scratch.

@findex fast-lock-mode
  The command @kbd{M-x fast-lock-mode} turns Fast Lock mode on or off,
according to the argument (with no argument, it toggles).  You can also
arrange to enable Fast Lock mode whenever you use Font Lock mode, like
this:

@example
(setq font-lock-support-mode 'fast-lock-mode)
@end example

@vindex fast-lock-minimum-size
  It is not worth writing a cache file for small buffers.  Therefore,
the variable @code{fast-lock-minimum-size} specifies a minimum file size
for caching font information.

@vindex fast-lock-cache-directories
  The variable @code{fast-lock-cache-directories} specifies where to put
the cache files.  Its value is a list of directories to try; @code{"."}
means the same directory as the file being edited.  The default value is
@w{@code{("." "~/.emacs-flc")}}, which means to use the same directory if
possible, and otherwise the directory @file{~/.emacs-flc}.

@vindex fast-lock-save-others
  The variable @code{fast-lock-save-others} specifies whether Fast Lock
mode should save cache files for files that you do not own.  A
non-@code{nil} value means yes (and that is the default).

@node Lazy Lock Mode
@subsection Lazy Lock Mode
@cindex Lazy Lock mode
@cindex mode, Lazy Lock

  To make Font Lock mode faster for large buffers, you can use Lazy Lock
mode to reduce the amount of text that is fontified.  In Lazy Lock mode,
buffer fontification is demand-driven; it happens to portions of the
buffer that are about to be displayed.  And fontification of your
changes is deferred; it happens only when Emacs has been idle for a
certain short period of time.

@findex lazy-lock-mode
  The command @kbd{M-x lazy-lock-mode} turns Lazy Lock mode on or off,
according to the argument (with no argument, it toggles).  You can also
arrange to enable Lazy Lock mode whenever you use Font Lock mode, like
this:

@example
(setq font-lock-support-mode 'lazy-lock-mode)
@end example

@vindex lazy-lock-minimum-size
  It is not worth avoiding buffer fontification for small buffers.
Therefore, the variable @code{lazy-lock-minimum-size} specifies a
minimum buffer size for demand-driven buffer fontification.  Buffers
smaller than that are fontified all at once, as in plain Font Lock mode.

@vindex lazy-lock-defer-time
  When you alter the buffer, Lazy Lock mode defers fontification of the
text you changed.  The variable @code{lazy-lock-defer-time} specifies
how many seconds Emacs must be idle before it starts fontifying your
changes.  If the value is 0, then changes are fontified immediately, as
in plain Font Lock mode.

@vindex lazy-lock-defer-on-scrolling
  Lazy Lock mode normally fontifies newly visible portions of the buffer
before they are first displayed.  However, if the value of
@code{lazy-lock-defer-on-scrolling} is non-@code{nil}, newly visible
text is fontified only when Emacs is idle for
@code{lazy-lock-defer-time} seconds.

@vindex lazy-lock-defer-contextually
  In some modes, including C mode and Emacs Lisp mode, changes in one
line's contents can alter the context for subsequent lines, and thus
change how they ought to be fontified.  Ordinarily, you must type
@kbd{M-g M-g} to refontify the subsequent lines.  However, if you set
the variable @code{lazy-lock-defer-contextually} to non-@code{nil}, Lay
Lock mode does this automatically, after @code{lazy-lock-defer-time}
seconds.

@cindex stealth fontification
  When Emacs is idle for a long time, Lazy Lock fontifies additional
portions of the buffer, not yet displayed, in case you will display them
later.  This is called @dfn{stealth fontification}.

@vindex lazy-lock-stealth-time
@vindex lazy-lock-stealth-lines
@vindex lazy-lock-stealth-verbose
  The variable @code{lazy-lock-stealth-time} specifies how many seconds
Emacs has to be idle before stealth fontification starts.  A value of
@code{nil} means no stealth fontification.  The variables
@code{lazy-lock-stealth-lines} and @code{lazy-lock-stealth-verbose}
specify the granularity and verbosity of stealth fontification.

@node Fast or Lazy
@subsection Fast Lock or Lazy Lock?

  Here is a simple guide to help you choose one of the Font Lock support
modes.

@itemize @bullet
@item
Fast Lock mode intervenes only during file visiting and buffer
killing (and related events); therefore buffer editing and window
scrolling are no faster or slower than in plain Font Lock mode.

@item
Fast Lock mode is slower at reading a cache file than Lazy Lock
mode is at fontifying a window; therefore Fast Lock mode is slower at
visiting a file than Lazy Lock mode.

@item
Lazy Lock mode intervenes during window scrolling to fontify text that
scrolls onto the screen; therefore, scrolling is slower than in plain
Font Lock mode.

@item
Lazy Lock mode doesn't fontify during buffer editing (it defers
fontification of changes); therefore, editing is faster than in plain
Font Lock mode.

@item
Fast Lock mode can be fooled by a file that is kept under version
control software; therefore buffer fontification may occur even when
a cache file exists for the file.

@item
Fast Lock mode only works with a buffer visiting a file; Lazy Lock
mode works with any buffer.

@item
Fast Lock mode generates cache files; Lazy Lock mode does not.
@end itemize

@vindex font-lock-support-mode
  The variable @code{font-lock-support-mode} specifies which of these
support modes to use; for example, to specify that Fast Lock mode is
used for C/C++ modes, and Lazy Lock mode otherwise, set the variable
like this:

@example
(setq font-lock-support-mode
      '((c-mode . fast-lock-mode) (c++-mode . fast-lock-mode)
        (t . lazy-lock-mode)))
@end example

@node Misc X
@section Miscellaneous X Window Features

  The following commands let you create, delete and operate on frames:

@table @kbd
@item C-z
@kindex C-z @r{(X windows)}
@findex iconify-or-deiconify-frame
Iconify the selected Emacs frame (@code{iconify-or-deiconify-frame}).
The normal meaning of @kbd{C-z}, to suspend Emacs, is not useful under a
window system, so it has a different binding in that case.

If you type this command on an Emacs frame's icon, it deiconifies the frame.

@item C-x 5 0
@kindex C-x 5 0
@findex delete-frame
Delete the selected frame (@code{delete-frame}).  This is not allowed if
there is only one frame.

@item C-x 5 o
@kindex C-x 5 o
@findex other-frame
Select another frame, raise it, and warp the mouse to it so that it
stays selected.  If you repeat this command, it cycles through all the
frames on your terminal.
@end table

@node Non-Window Terminals
@section Non-Window Terminals
@cindex non-window terminals
@cindex single-frame terminals

  If your terminal does not have a window system that Emacs supports,
then it can display only one Emacs frame at a time.  However, you can
still create multiple Emacs frames, and switch between them.  Switching
frames on these terminals is much like switching between different
window configurations.

  Use @kbd{C-x 5 2} to create a new frame and switch to it; use @kbd{C-x
5 o} to cycle through the existing frames; use @kbd{C-x 5 0} to delete
the current frame.

  Each frame has a number to distinguish it.  If your terminal can
display only one frame at a time, the selected frame's number @var{n}
appears near the beginning of the mode line, in the form
@samp{F@var{n}}.

