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@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
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@c Copyright (C) 1990-1995, 1998-1999, 2001-2011
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@c   Free Software Foundation, Inc.
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@c See the file elisp.texi for copying conditions.
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@setfilename ../../info/frames
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@node Frames, Positions, Windows, Top
@chapter Frames
@cindex frame

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  A @dfn{frame} is a screen object that contains one or more Emacs
windows (@pxref{Windows}).  It is the kind of object called a
``window'' in the terminology of graphical environments; but we can't
call it a ``window'' here, because Emacs uses that word in a different
way.  In Emacs Lisp, a @dfn{frame object} is a Lisp object that
represents a frame on the screen.  @xref{Frame Type}.
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  A frame initially contains a single main window and/or a minibuffer
window; you can subdivide the main window vertically or horizontally
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into smaller windows.  @xref{Splitting Windows}.
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@cindex terminal
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  A @dfn{terminal} is a display device capable of displaying one or
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more Emacs frames.  In Emacs Lisp, a @dfn{terminal object} is a Lisp
object that represents a terminal.  @xref{Terminal Type}.
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@cindex terminal frame
@cindex window frame
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  There are two classes of terminals: text-only terminals and
graphical terminals.  Text-only terminals are non-graphics-capable
display devices, including ``terminal emulators'' such as xterm.  On
text-only terminals, each frame occupies the entire terminal screen;
although you can create additional frames and switch between them,
only one frame can be shown at any given time.  We refer to frames on
text-only terminals as @dfn{terminal frames}.  Graphical terminals, on
the other hand, are graphics-capable windowing systems, such as the X
Window System.  On a graphical terminal, Emacs can display multiple
frames simultaneously.  We refer to such frames as @dfn{window
frames}.

  On GNU and Unix systems, you can create additional frames on any
available terminal, within a single Emacs session, regardless of
whether Emacs was started on a text-only or graphical terminal.  Emacs
can display on both graphical and text-only terminals simultaneously.
This comes in handy, for instance, when you connect to the same
session from several remote locations.  @xref{Multiple Terminals}.
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@defun framep object
This predicate returns a non-@code{nil} value if @var{object} is a
frame, and @code{nil} otherwise.  For a frame, the value indicates which
kind of display the frame uses:

@table @code
@item x
The frame is displayed in an X window.
@item t
A terminal frame on a character display.
@item w32
The frame is displayed on MS-Windows 9X/NT.
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@item ns
The frame is displayed on a GNUstep or Macintosh Cocoa display.
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@item pc
The frame is displayed on an MS-DOS terminal.
@end table
@end defun

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@defun frame-terminal &optional frame
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This function returns the terminal object that displays @var{frame}.
If @var{frame} is @code{nil} or unspecified, it defaults to the
selected frame.
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@end defun

@defun terminal-live-p object
This predicate returns a non-@code{nil} value if @var{object} is a
terminal that is alive (i.e.@: was not deleted), and @code{nil}
otherwise.  For live terminals, the return value indicates what kind
of frames are displayed on that terminal; the list of possible values
is the same as for @code{framep} above.
@end defun

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@menu
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* Creating Frames::             Creating additional frames.
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* Multiple Terminals::          Displaying on several different devices.
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* Frame Parameters::            Controlling frame size, position, font, etc.
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* Terminal Parameters::         Parameters common for all frames on terminal.
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* Frame Titles::                Automatic updating of frame titles.
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* Deleting Frames::             Frames last until explicitly deleted.
* Finding All Frames::          How to examine all existing frames.
* Minibuffers and Frames::      How a frame finds the minibuffer to use.
* Input Focus::                 Specifying the selected frame.
* Visibility of Frames::        Frames may be visible or invisible, or icons.
* Raising and Lowering::        Raising a frame makes it hide other windows;
                                  lowering it makes the others hide it.
* Frame Configurations::        Saving the state of all frames.
* Mouse Tracking::              Getting events that say when the mouse moves.
* Mouse Position::              Asking where the mouse is, or moving it.
* Pop-Up Menus::                Displaying a menu for the user to select from.
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* Dialog Boxes::                Displaying a box to ask yes or no.
* Pointer Shape::               Specifying the shape of the mouse pointer.
* Window System Selections::    Transferring text to and from other X clients.
* Drag and Drop::               Internals of Drag-and-Drop implementation.
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* Color Names::                 Getting the definitions of color names.
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* Text Terminal Colors::        Defining colors for text-only terminals.
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* Resources::                   Getting resource values from the server.
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* Display Feature Testing::     Determining the features of a terminal.
@end menu

@node Creating Frames
@section Creating Frames

To create a new frame, call the function @code{make-frame}.

@defun make-frame &optional alist
This function creates and returns a new frame, displaying the current
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buffer.

The @var{alist} argument is an alist that specifies frame parameters
for the new frame.  @xref{Frame Parameters}.  If you specify the
@code{terminal} parameter in @var{alist}, the new frame is created on
that terminal.  Otherwise, if you specify the @code{window-system}
frame parameter in @var{alist}, that determines whether the frame
should be displayed on a text-only or graphical terminal.
@xref{Window Systems}.  If neither is specified, the new frame is
created in the same terminal as the selected frame.

Any parameters not mentioned in @var{alist} default to the values in
the alist @code{default-frame-alist} (@pxref{Initial Parameters});
parameters not specified there default from the X resources or its
equivalent on your operating system (@pxref{X Resources,, X Resources,
emacs, The GNU Emacs Manual}).  After the frame is created, Emacs
applies any parameters listed in @code{frame-inherited-parameters}
(see below) and not present in the argument, taking the values from
the frame that was selected when @code{make-frame} was called.
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This function itself does not make the new frame the selected frame.
@xref{Input Focus}.  The previously selected frame remains selected.
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On graphical terminals, however, the windowing system may select the
new frame for its own reasons.
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@end defun

@defvar before-make-frame-hook
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A normal hook run by @code{make-frame} before it creates the frame.
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@end defvar

@defvar after-make-frame-functions
An abnormal hook run by @code{make-frame} after it creates the frame.
Each function in @code{after-make-frame-functions} receives one argument, the
frame just created.
@end defvar

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@defvar frame-inherited-parameters
This variable specifies the list of frame parameters that a newly
created frame inherits from the currently selected frame.  For each
parameter (a symbol) that is an element in the list and is not present
in the argument to @code{make-frame}, the function sets the value of
that parameter in the created frame to its value in the selected
frame.
@end defvar

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@node Multiple Terminals
@section Multiple Terminals
@cindex multiple terminals
@cindex multi-tty
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@cindex multiple X displays
@cindex displays, multiple

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  Emacs represents each terminal, whether graphical or text-only, as a
@dfn{terminal object} data type (@pxref{Terminal Type}).  On GNU and
Unix systems, Emacs can use multiple terminals simultaneously in each
session.  On other systems, it can only use a single terminal.  Each
terminal object has the following attributes:

@itemize @bullet
@item
The name of the device used by the terminal (e.g., @samp{:0.0} or
@file{/dev/tty}).

@item
The terminal and keyboard coding systems used on the terminal.
@xref{Terminal I/O Encoding}.
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@item
The kind of display associated with the terminal.  This is the symbol
returned by the function @code{terminal-live-p} (i.e., @code{x},
@code{t}, @code{w32}, @code{ns}, or @code{pc}).  @xref{Frames}.
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@item
A list of terminal parameters.  @xref{Terminal Parameters}.
@end itemize

  There is no primitive for creating terminal objects.  Emacs creates
them as needed, such as when you call @code{make-frame-on-display}
(which is described below).

@defun terminal-name &optional terminal
This function returns the file name of the device used by
@var{terminal}.  If @var{terminal} is omitted or @code{nil}, it
defaults to the selected frame's terminal.  @var{terminal} can also be
a frame, meaning that frame's terminal.
@end defun

@defun terminal-list
This function returns a list of all terminal objects currently in use.
@end defun

@defun get-device-terminal device
This function returns a terminal whose device name is given by
@var{device}.  If @var{device} is a string, it can be either the file
name of a terminal device, or the name of an X display of the form
@samp{@var{host}:@var{server}.@var{screen}}.  If @var{device} is a
frame, this function returns that frame's terminal; @code{nil} means
the selected frame.  Finally, if @var{device} is a terminal object
that represents a live terminal, that terminal is returned.  The
function signals an error if its argument is none of the above.
@end defun

@defun delete-terminal &optional terminal force
This function deletes all frames on @var{terminal} and frees the
resources used by it.  It runs the abnormal hook
@code{delete-terminal-functions}, passing @var{terminal} as the
argument to each function.

If @var{terminal} is omitted or @code{nil}, it defaults to the
selected frame's terminal.  @var{terminal} can also be a frame,
meaning that frame's terminal.

Normally, this function signals an error if you attempt to delete the
sole active terminal, but if @var{force} is non-@code{nil}, you are
allowed to do so.  Emacs automatically calls this function when the
last frame on a terminal is deleted (@pxref{Deleting Frames}).
@end defun

@defvar delete-terminal-functions
An abnormal hook run by @code{delete-terminal}.  Each function
receives one argument, the @var{terminal} argument passed to
@code{delete-terminal}.  Due to technical details, the functions may
be called either just before the terminal is deleted, or just
afterwards.
@end defvar

@cindex terminal-local variables
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  A few Lisp variables are @dfn{terminal-local}; that is, they have a
separate binding for each terminal.  The binding in effect at any time
is the one for the terminal that the currently selected frame belongs
to.  These variables include @code{default-minibuffer-frame},
@code{defining-kbd-macro}, @code{last-kbd-macro}, and
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@code{system-key-alist}.  They are always terminal-local, and can
never be buffer-local (@pxref{Buffer-Local Variables}).

  On GNU and Unix systems, each X display is a separate graphical
terminal.  When Emacs is started from within the X window system, it
uses the X display chosen with the @code{DISPLAY} environment
variable, or with the @samp{--display} option.  @xref{Initial
Options,,, emacs, The GNU Emacs Manual}.  Emacs can connect to other X
displays via the command @code{make-frame-on-display}.  Each X display
has its own selected frame and its own minibuffer windows; however,
only one of those frames is ``@emph{the} selected frame'' at any given
moment (@pxref{Input Focus}).  Emacs can even connect to other
text-only terminals, by interacting with the @command{emacsclient}
program.  @xref{Emacs Server,,, emacs, The GNU Emacs Manual}.

  A single X server can handle more than one display.  Each X display
has a three-part name, @samp{@var{host}:@var{server}.@var{screen}}.
The first two parts, @var{host} and @var{server}, identify the X
server; the third part, @var{screen}, identifies a screen number on
that X server.  When you use two or more screens belonging to one
server, Emacs knows by the similarity in their names that they share a
single keyboard.

  On some ``multi-monitor'' setups, a single X display outputs to more
than one monitor.  Currently, there is no way for Emacs to distinguish
between the different physical monitors.
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@deffn Command make-frame-on-display display &optional parameters
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This function creates and returns a new frame on @var{display}, taking
the other frame parameters from the alist @var{parameters}.
@var{display} should be the name of an X display (a string).

Before creating the frame, this function ensures that Emacs is ``set
up'' to display graphics.  For instance, if Emacs has not processed X
resources (e.g., if it was started on a text-only terminal), it does
so at this time.  In all other respects, this function behaves like
@code{make-frame} (@pxref{Creating Frames}).
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@end deffn

@defun x-display-list
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This function returns a list that indicates which X displays Emacs has
a connection to.  The elements of the list are strings, and each one
is a display name.
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@end defun

@defun x-open-connection display &optional xrm-string must-succeed
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This function opens a connection to the X display @var{display},
without creating a frame on that display.  Normally, Emacs Lisp
programs need not call this function, as @code{make-frame-on-display}
calls it automatically.  The only reason for calling it is to check
whether communication can be established with a given X display.

The optional argument @var{xrm-string}, if not @code{nil}, is a string
of resource names and values, in the same format used in the
@file{.Xresources} file.  @xref{X Resources,, X Resources, emacs, The
GNU Emacs Manual}.  These values apply to all Emacs frames created on
this display, overriding the resource values recorded in the X server.
Here's an example of what this string might look like:
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@example
"*BorderWidth: 3\n*InternalBorder: 2\n"
@end example

If @var{must-succeed} is non-@code{nil}, failure to open the connection
terminates Emacs.  Otherwise, it is an ordinary Lisp error.
@end defun

@defun x-close-connection display
This function closes the connection to display @var{display}.  Before
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you can do this, you must first delete all the frames that were open
on that display (@pxref{Deleting Frames}).
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@end defun

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@node Frame Parameters
@section Frame Parameters
@cindex frame parameters

  A frame has many parameters that control its appearance and behavior.
Just what parameters a frame has depends on what display mechanism it
uses.

  Frame parameters exist mostly for the sake of window systems.  A
terminal frame has a few parameters, mostly for compatibility's sake;
only the @code{height}, @code{width}, @code{name}, @code{title},
@code{menu-bar-lines}, @code{buffer-list} and @code{buffer-predicate}
parameters do something special.  If the terminal supports colors, the
parameters @code{foreground-color}, @code{background-color},
@code{background-mode} and @code{display-type} are also meaningful.
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If the terminal supports frame transparency, the parameter
@code{alpha} is also meaningful.
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@menu
* Parameter Access::       How to change a frame's parameters.
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* Initial Parameters::     Specifying frame parameters when you make a frame.
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* Window Frame Parameters:: List of frame parameters for window systems.
* Size and Position::      Changing the size and position of a frame.
* Geometry::               Parsing geometry specifications.
@end menu

@node Parameter Access
@subsection Access to Frame Parameters

These functions let you read and change the parameter values of a
frame.

@defun frame-parameter frame parameter
This function returns the value of the parameter @var{parameter} (a
symbol) of @var{frame}.  If @var{frame} is @code{nil}, it returns the
selected frame's parameter.  If @var{frame} has no setting for
@var{parameter}, this function returns @code{nil}.
@end defun

@defun frame-parameters &optional frame
The function @code{frame-parameters} returns an alist listing all the
parameters of @var{frame} and their values.  If @var{frame} is
@code{nil} or omitted, this returns the selected frame's parameters
@end defun

@defun modify-frame-parameters frame alist
This function alters the parameters of frame @var{frame} based on the
elements of @var{alist}.  Each element of @var{alist} has the form
@code{(@var{parm} . @var{value})}, where @var{parm} is a symbol naming a
parameter.  If you don't mention a parameter in @var{alist}, its value
doesn't change.  If @var{frame} is @code{nil}, it defaults to the selected
frame.
@end defun

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@defun set-frame-parameter frame parm value
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This function sets the frame parameter @var{parm} to the specified
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@var{value}.  If @var{frame} is @code{nil}, it defaults to the
selected frame.
@end defun

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@defun modify-all-frames-parameters alist
This function alters the frame parameters of all existing frames
according to @var{alist}, then modifies @code{default-frame-alist}
(and, if necessary, @code{initial-frame-alist}) to apply the same
parameter values to frames that will be created henceforth.
@end defun

@node Initial Parameters
@subsection Initial Frame Parameters

You can specify the parameters for the initial startup frame
by setting @code{initial-frame-alist} in your init file (@pxref{Init File}).

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@defopt initial-frame-alist
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This variable's value is an alist of parameter values used when creating
the initial window frame.  You can set this variable to specify the
appearance of the initial frame without altering subsequent frames.
Each element has the form:

@example
(@var{parameter} . @var{value})
@end example

Emacs creates the initial frame before it reads your init
file.  After reading that file, Emacs checks @code{initial-frame-alist},
and applies the parameter settings in the altered value to the already
created initial frame.

If these settings affect the frame geometry and appearance, you'll see
the frame appear with the wrong ones and then change to the specified
ones.  If that bothers you, you can specify the same geometry and
appearance with X resources; those do take effect before the frame is
created.  @xref{X Resources,, X Resources, emacs, The GNU Emacs Manual}.

X resource settings typically apply to all frames.  If you want to
specify some X resources solely for the sake of the initial frame, and
you don't want them to apply to subsequent frames, here's how to achieve
this.  Specify parameters in @code{default-frame-alist} to override the
X resources for subsequent frames; then, to prevent these from affecting
the initial frame, specify the same parameters in
@code{initial-frame-alist} with values that match the X resources.
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@end defopt
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If these parameters specify a separate minibuffer-only frame with
@code{(minibuffer . nil)}, and you have not created one, Emacs creates
one for you.

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@defopt minibuffer-frame-alist
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This variable's value is an alist of parameter values used when
creating an initial minibuffer-only frame.  This is the
minibuffer-only frame that Emacs creates if @code{initial-frame-alist}
specifies a frame with no minibuffer.
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@end defopt
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@defopt default-frame-alist
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This is an alist specifying default values of frame parameters for all
Emacs frames---the first frame, and subsequent frames.  When using the X
Window System, you can get the same results by means of X resources
in many cases.

Setting this variable does not affect existing frames.
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@end defopt
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Functions that display a buffer in a separate frame can override the
default parameters by supplying their own parameters.  @xref{Definition
of special-display-frame-alist}.
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If you use options that specify window appearance when you invoke Emacs,
they take effect by adding elements to @code{default-frame-alist}.  One
exception is @samp{-geometry}, which adds the specified position to
@code{initial-frame-alist} instead.  @xref{Emacs Invocation,, Command
Line Arguments for Emacs Invocation, emacs, The GNU Emacs Manual}.

@node Window Frame Parameters
@subsection Window Frame Parameters
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@cindex frame parameters for windowed displays
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  Just what parameters a frame has depends on what display mechanism
it uses.  This section describes the parameters that have special
meanings on some or all kinds of terminals.  Of these, @code{name},
@code{title}, @code{height}, @code{width}, @code{buffer-list} and
@code{buffer-predicate} provide meaningful information in terminal
frames, and @code{tty-color-mode} is meaningful @emph{only} in
terminal frames.

@menu
* Basic Parameters::            Parameters that are fundamental.
* Position Parameters::         The position of the frame on the screen.
* Size Parameters::             Frame's size.
* Layout Parameters::           Size of parts of the frame, and
                                  enabling or disabling some parts.
* Buffer Parameters::           Which buffers have been or should be shown.
* Management Parameters::       Communicating with the window manager.
* Cursor Parameters::           Controlling the cursor appearance.
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* Font and Color Parameters::   Fonts and colors for the frame text.
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@end menu

@node Basic Parameters
@subsubsection Basic Parameters

  These frame parameters give the most basic information about the
frame.  @code{title} and @code{name} are meaningful on all terminals.

@table @code
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@vindex display, a frame parameter
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@item display
The display on which to open this frame.  It should be a string of the
form @code{"@var{host}:@var{dpy}.@var{screen}"}, just like the
@code{DISPLAY} environment variable.

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@vindex display-type, a frame parameter
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@item display-type
This parameter describes the range of possible colors that can be used
in this frame.  Its value is @code{color}, @code{grayscale} or
@code{mono}.

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@vindex title, a frame parameter
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@item title
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If a frame has a non-@code{nil} title, it appears in the window
system's title bar at the top of the frame, and also in the mode line
of windows in that frame if @code{mode-line-frame-identification} uses
@samp{%F} (@pxref{%-Constructs}).  This is normally the case when
Emacs is not using a window system, and can only display one frame at
a time.  @xref{Frame Titles}.
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@vindex name, a frame parameter
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@item name
The name of the frame.  The frame name serves as a default for the frame
title, if the @code{title} parameter is unspecified or @code{nil}.  If
you don't specify a name, Emacs sets the frame name automatically
(@pxref{Frame Titles}).

If you specify the frame name explicitly when you create the frame, the
name is also used (instead of the name of the Emacs executable) when
looking up X resources for the frame.
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@item explicit-name
If the frame name was specified explicitly when the frame was created,
this parameter will be that name.  If the frame wasn't explicitly
named, this parameter will be @code{nil}.
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@end table

@node Position Parameters
@subsubsection Position Parameters
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@cindex window position on display
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  Position parameters' values are normally measured in pixels, but on
text-only terminals they count characters or lines instead.

@table @code
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@vindex left, a frame parameter
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@item left
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The position, in pixels, of the left (or right) edge of the frame with
respect to the left (or right) edge of the screen.  The value may be:
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@table @asis
@item an integer
A positive integer relates the left edge of the frame to the left edge
of the screen.  A negative integer relates the right frame edge to the
right screen edge.

@item @code{(+ @var{pos})}
This specifies the position of the left frame edge relative to the left
screen edge.  The integer @var{pos} may be positive or negative; a
negative value specifies a position outside the screen.

@item @code{(- @var{pos})}
This specifies the position of the right frame edge relative to the right
screen edge.  The integer @var{pos} may be positive or negative; a
negative value specifies a position outside the screen.
@end table
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Some window managers ignore program-specified positions.  If you want to
be sure the position you specify is not ignored, specify a
non-@code{nil} value for the @code{user-position} parameter as well.

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@vindex top, a frame parameter
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@item top
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The screen position of the top (or bottom) edge, in pixels, with respect
to the top (or bottom) edge of the screen.  It works just like
@code{left}, except vertically instead of horizontally.
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@vindex icon-left, a frame parameter
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@item icon-left
The screen position of the left edge @emph{of the frame's icon}, in
pixels, counting from the left edge of the screen.  This takes effect if
and when the frame is iconified.

If you specify a value for this parameter, then you must also specify
a value for @code{icon-top} and vice versa.  The window manager may
ignore these two parameters.

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@vindex icon-top, a frame parameter
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@item icon-top
The screen position of the top edge @emph{of the frame's icon}, in
pixels, counting from the top edge of the screen.  This takes effect if
and when the frame is iconified.

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@vindex user-position, a frame parameter
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@item user-position
When you create a frame and specify its screen position with the
@code{left} and @code{top} parameters, use this parameter to say whether
the specified position was user-specified (explicitly requested in some
way by a human user) or merely program-specified (chosen by a program).
A non-@code{nil} value says the position was user-specified.

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@cindex window positions and window managers
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Window managers generally heed user-specified positions, and some heed
program-specified positions too.  But many ignore program-specified
positions, placing the window in a default fashion or letting the user
place it with the mouse.  Some window managers, including @code{twm},
let the user specify whether to obey program-specified positions or
ignore them.

When you call @code{make-frame}, you should specify a non-@code{nil}
value for this parameter if the values of the @code{left} and @code{top}
parameters represent the user's stated preference; otherwise, use
@code{nil}.
@end table

@node Size Parameters
@subsubsection Size Parameters
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@cindex window size on display
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  Size parameters' values are normally measured in pixels, but on
text-only terminals they count characters or lines instead.

@table @code
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@vindex height, a frame parameter
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@item height
The height of the frame contents, in characters.  (To get the height in
pixels, call @code{frame-pixel-height}; see @ref{Size and Position}.)

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@vindex width, a frame parameter
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@item width
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The width of the frame contents, in characters.  (To get the width in
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pixels, call @code{frame-pixel-width}; see @ref{Size and Position}.)

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@vindex user-size, a frame parameter
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@item user-size
This does for the size parameters @code{height} and @code{width} what
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the @code{user-position} parameter (@pxref{Position Parameters,
user-position}) does for the position parameters @code{top} and
@code{left}.
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@cindex full-screen frames
@vindex fullscreen, a frame parameter
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@item fullscreen
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Specify that width, height or both shall be maximized.  The value
@code{fullwidth} specifies that width shall be as wide as possible.
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The value @code{fullheight} specifies that height shall be as tall as
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possible.  The value @code{fullboth} specifies that both the width and
the height shall be set to the size of the screen.  The value
@code{maximized} specifies that the frame shall be maximized.  The
difference between @code{maximized} and @code{fullboth} is that the
former still has window manager decorations while the latter really
covers the whole screen.
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@end table

@node Layout Parameters
@subsubsection Layout Parameters
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@cindex layout parameters of frames
@cindex frame layout parameters
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  These frame parameters enable or disable various parts of the
frame, or control their sizes.

@table @code
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@vindex border-width, a frame parameter
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@item border-width
The width in pixels of the frame's border.

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@vindex internal-border-width, a frame parameter
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@item internal-border-width
The distance in pixels between text (or fringe) and the frame's border.

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@vindex vertical-scroll-bars, a frame parameter
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@item vertical-scroll-bars
Whether the frame has scroll bars for vertical scrolling, and which side
of the frame they should be on.  The possible values are @code{left},
@code{right}, and @code{nil} for no scroll bars.

@ignore
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@vindex horizontal-scroll-bars, a frame parameter
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@item horizontal-scroll-bars
Whether the frame has scroll bars for horizontal scrolling
(non-@code{nil} means yes).  Horizontal scroll bars are not currently
implemented.
@end ignore

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@vindex scroll-bar-width, a frame parameter
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@item scroll-bar-width
The width of vertical scroll bars, in pixels, or @code{nil} meaning to
use the default width.

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@vindex left-fringe, a frame parameter
@vindex right-fringe, a frame parameter
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@item left-fringe
@itemx right-fringe
The default width of the left and right fringes of windows in this
frame (@pxref{Fringes}).  If either of these is zero, that effectively
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removes the corresponding fringe.

When you use @code{frame-parameter} to query the value of either of
these two frame parameters, the return value is always an integer.
When using @code{set-frame-parameter}, passing a @code{nil} value
imposes an actual default value of 8 pixels.
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The combined fringe widths must add up to an integral number of
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columns, so the actual default fringe widths for the frame, as
reported by @code{frame-parameter}, may be larger than what you
specify.  Any extra width is distributed evenly between the left and
right fringe.  However, you can force one fringe or the other to a
precise width by specifying that width as a negative integer.  If both
widths are negative, only the left fringe gets the specified width.
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@vindex menu-bar-lines frame parameter
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@item menu-bar-lines
The number of lines to allocate at the top of the frame for a menu
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bar.  The default is 1 if Menu Bar mode is enabled, and 0 otherwise.
@xref{Menu Bars,,,emacs, The GNU Emacs Manual}.
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@vindex tool-bar-lines frame parameter
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@item tool-bar-lines
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The number of lines to use for the tool bar.  The default is 1 if Tool
Bar mode is enabled, and 0 otherwise.  @xref{Tool Bars,,,emacs, The
GNU Emacs Manual}.
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@vindex tool-bar-position frame parameter
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@item tool-bar-position
The position of the tool bar.  Currently only for the GTK tool bar.
Value can be one of @code{top}, @code{bottom} @code{left}, @code{right}.
The default is  @code{top}.

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@vindex line-spacing, a frame parameter
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@item line-spacing
Additional space to leave below each text line, in pixels (a positive
integer).  @xref{Line Height}, for more information.
@end table

@node Buffer Parameters
@subsubsection Buffer Parameters

  These frame parameters, meaningful on all kinds of terminals, deal
with which buffers have been, or should, be displayed in the frame.

@table @code
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@vindex minibuffer, a frame parameter
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@item minibuffer
Whether this frame has its own minibuffer.  The value @code{t} means
yes, @code{nil} means no, @code{only} means this frame is just a
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minibuffer.  If the value is a minibuffer window (in some other
frame), the frame uses that minibuffer.

This frame parameter takes effect when the frame is created, and can
not be changed afterwards.
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@vindex buffer-predicate, a frame parameter
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@item buffer-predicate
The buffer-predicate function for this frame.  The function
@code{other-buffer} uses this predicate (from the selected frame) to
decide which buffers it should consider, if the predicate is not
@code{nil}.  It calls the predicate with one argument, a buffer, once for
each buffer; if the predicate returns a non-@code{nil} value, it
considers that buffer.

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@vindex buffer-list, a frame parameter
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@item buffer-list
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A list of buffers that have been selected in this frame, ordered
most-recently-selected first.
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@vindex unsplittable, a frame parameter
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@item unsplittable
If non-@code{nil}, this frame's window is never split automatically.
@end table

@node Management Parameters
@subsubsection Window Management Parameters
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@cindex window manager interaction, and frame parameters
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  These frame parameters, meaningful only on window system displays,
interact with the window manager.

@table @code
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@vindex visibility, a frame parameter
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@item visibility
The state of visibility of the frame.  There are three possibilities:
@code{nil} for invisible, @code{t} for visible, and @code{icon} for
iconified.  @xref{Visibility of Frames}.

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@vindex auto-raise, a frame parameter
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@item auto-raise
Whether selecting the frame raises it (non-@code{nil} means yes).

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@vindex auto-lower, a frame parameter
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@item auto-lower
Whether deselecting the frame lowers it (non-@code{nil} means yes).

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@vindex icon-type, a frame parameter
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@item icon-type
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The type of icon to use for this frame.  If the value is a string,
that specifies a file containing a bitmap to use; @code{nil} specifies
no icon (in which case the window manager decides what to show); any
other non-@code{nil} value specifies the default Emacs icon.
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@vindex icon-name, a frame parameter
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@item icon-name
The name to use in the icon for this frame, when and if the icon
appears.  If this is @code{nil}, the frame's title is used.

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@vindex window-id, a frame parameter
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@item window-id
The number of the window-system window used by the frame
to contain the actual Emacs windows.

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@vindex outer-window-id, a frame parameter
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@item outer-window-id
The number of the outermost window-system window used for the whole frame.

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@vindex wait-for-wm, a frame parameter
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@item wait-for-wm
If non-@code{nil}, tell Xt to wait for the window manager to confirm
geometry changes.  Some window managers, including versions of Fvwm2
and KDE, fail to confirm, so Xt hangs.  Set this to @code{nil} to
prevent hanging with those window managers.

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@vindex sticky, a frame parameter
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@item sticky
If non-@code{nil}, the frame is visible on all virtual desktops on systems
with virtual desktops.

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@ignore
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@vindex parent-id, a frame parameter
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@item parent-id
@c ??? Not yet working.
The X window number of the window that should be the parent of this one.
Specifying this lets you create an Emacs window inside some other
application's window.  (It is not certain this will be implemented; try
it and see if it works.)
@end ignore
@end table

@node Cursor Parameters
@subsubsection Cursor Parameters
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@cindex cursor, and frame parameters
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  This frame parameter controls the way the cursor looks.

@table @code
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@vindex cursor-type, a frame parameter
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@item cursor-type
How to display the cursor.  Legitimate values are:

@table @code
@item box
Display a filled box.  (This is the default.)
@item hollow
Display a hollow box.
@item nil
Don't display a cursor.
@item bar
Display a vertical bar between characters.
@item (bar . @var{width})
Display a vertical bar @var{width} pixels wide between characters.
@item hbar
Display a horizontal bar.
@item (hbar . @var{height})
Display a horizontal bar @var{height} pixels high.
@end table
@end table

@vindex cursor-type
The buffer-local variable @code{cursor-type} overrides the value of
the @code{cursor-type} frame parameter, but if it is @code{t}, that
means to use the cursor specified for the frame.

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@defopt blink-cursor-alist
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This variable specifies how to blink the cursor.  Each element has the
form @code{(@var{on-state} . @var{off-state})}.  Whenever the cursor
type equals @var{on-state} (comparing using @code{equal}), the
corresponding @var{off-state} specifies what the cursor looks like
when it blinks ``off.''  Both @var{on-state} and @var{off-state}
should be suitable values for the @code{cursor-type} frame parameter.

There are various defaults for how to blink each type of cursor, if
the type is not mentioned as an @var{on-state} here.  Changes in this
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variable do not take effect immediately, only when you specify the
@code{cursor-type} frame parameter.
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@end defopt
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@defopt cursor-in-non-selected-windows
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This variable controls how the cursor looks in a window that is not
selected.  It supports the same values as the @code{cursor-type} frame
parameter; also, @code{nil} means don't display a cursor in
nonselected windows, and @code{t} (the default) means use a standard
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modification of the usual cursor type (solid box becomes hollow box,
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and bar becomes a narrower bar).
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@end defopt
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@node Font and Color Parameters
@subsubsection Font and Color Parameters
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@cindex font and color, frame parameters
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  These frame parameters control the use of fonts and colors.
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@table @code
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@vindex font-backend, a frame parameter
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@item font-backend
A list of symbols, specifying the @dfn{font backends} to use for
drawing fonts in the frame, in order of priority.  On X, there are
currently two available font backends: @code{x} (the X core font
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driver) and @code{xft} (the Xft font driver).  On Windows, there
are currently two available font backends: @code{gdi} and
@code{uniscribe}.  On other systems, there is only one available
font backend, so it does not make sense to modify this frame
parameter.
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@vindex background-mode, a frame parameter
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@item background-mode
This parameter is either @code{dark} or @code{light}, according
to whether the background color is a light one or a dark one.

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@vindex tty-color-mode, a frame parameter
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@item tty-color-mode
@cindex standard colors for character terminals
This parameter overrides the terminal's color support as given by the
system's terminal capabilities database in that this parameter's value
specifies the color mode to use in terminal frames.  The value can be
either a symbol or a number.  A number specifies the number of colors
to use (and, indirectly, what commands to issue to produce each
color).  For example, @code{(tty-color-mode . 8)} specifies use of the
ANSI escape sequences for 8 standard text colors.  A value of -1 turns
off color support.

If the parameter's value is a symbol, it specifies a number through
the value of @code{tty-color-mode-alist}, and the associated number is
used instead.

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@vindex screen-gamma, a frame parameter
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@item screen-gamma
@cindex gamma correction
If this is a number, Emacs performs ``gamma correction'' which adjusts
the brightness of all colors.  The value should be the screen gamma of
your display, a floating point number.

Usual PC monitors have a screen gamma of 2.2, so color values in
Emacs, and in X windows generally, are calibrated to display properly
on a monitor with that gamma value.  If you specify 2.2 for
@code{screen-gamma}, that means no correction is needed.  Other values
request correction, designed to make the corrected colors appear on
your screen the way they would have appeared without correction on an
ordinary monitor with a gamma value of 2.2.

If your monitor displays colors too light, you should specify a
@code{screen-gamma} value smaller than 2.2.  This requests correction
that makes colors darker.  A screen gamma value of 1.5 may give good
results for LCD color displays.
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@vindex alpha, a frame parameter
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@item alpha
@cindex opacity, frame
@cindex transparency, frame
@vindex frame-alpha-lower-limit
This parameter specifies the opacity of the frame, on graphical
displays that support variable opacity.  It should be an integer
between 0 and 100, where 0 means completely transparent and 100 means
completely opaque.  It can also have a @code{nil} value, which tells
Emacs not to set the frame opacity (leaving it to the window manager).

To prevent the frame from disappearing completely from view, the
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variable @code{frame-alpha-lower-limit} defines a lower opacity limit.
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If the value of the frame parameter is less than the value of this
variable, Emacs uses the latter.  By default,
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@code{frame-alpha-lower-limit} is 20.
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The @code{alpha} frame parameter can also be a cons cell
@code{(@samp{active} . @samp{inactive})}, where @samp{active} is the
opacity of the frame when it is selected, and @samp{inactive} is the
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opacity when it is not selected.
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@end table

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The following frame parameters are semi-obsolete in that they are
automatically equivalent to particular face attributes of particular
faces (@pxref{Standard Faces,,, emacs, The Emacs Manual}):
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@table @code
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@vindex font, a frame parameter
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@item font
The name of the font for displaying text in the frame.  This is a
string, either a valid font name for your system or the name of an Emacs
fontset (@pxref{Fontsets}).  It is equivalent to the @code{font}
attribute of the @code{default} face.

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@vindex foreground-color, a frame parameter
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@item foreground-color
The color to use for the image of a character.  It is equivalent to
the @code{:foreground} attribute of the @code{default} face.

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@vindex background-color, a frame parameter
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@item background-color
The color to use for the background of characters.  It is equivalent to
the @code{:background} attribute of the @code{default} face.

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@vindex mouse-color, a frame parameter
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@item mouse-color
The color for the mouse pointer.  It is equivalent to the @code{:background}
attribute of the @code{mouse} face.

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@vindex cursor-color, a frame parameter
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@item cursor-color
The color for the cursor that shows point.  It is equivalent to the
@code{:background} attribute of the @code{cursor} face.

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@vindex border-color, a frame parameter
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@item border-color
The color for the border of the frame.  It is equivalent to the
@code{:background} attribute of the @code{border} face.

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@vindex scroll-bar-foreground, a frame parameter
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@item scroll-bar-foreground
If non-@code{nil}, the color for the foreground of scroll bars.  It is
equivalent to the @code{:foreground} attribute of the
@code{scroll-bar} face.

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@vindex scroll-bar-background, a frame parameter
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@item scroll-bar-background
If non-@code{nil}, the color for the background of scroll bars.  It is
equivalent to the @code{:background} attribute of the
@code{scroll-bar} face.
@end table

@node Size and Position
@subsection Frame Size And Position
@cindex size of frame
@cindex screen size
@cindex frame size
@cindex resize frame

  You can read or change the size and position of a frame using the
frame parameters @code{left}, @code{top}, @code{height}, and
@code{width}.  Whatever geometry parameters you don't specify are chosen
by the window manager in its usual fashion.

  Here are some special features for working with sizes and positions.
(For the precise meaning of ``selected frame'' used by these functions,
see @ref{Input Focus}.)

@defun set-frame-position frame left top
This function sets the position of the top left corner of @var{frame} to
@var{left} and @var{top}.  These arguments are measured in pixels, and
normally count from the top left corner of the screen.

Negative parameter values position the bottom edge of the window up from
the bottom edge of the screen, or the right window edge to the left of
the right edge of the screen.  It would probably be better if the values
were always counted from the left and top, so that negative arguments
would position the frame partly off the top or left edge of the screen,
but it seems inadvisable to change that now.
@end defun

@defun frame-height &optional frame
@defunx frame-width &optional frame
These functions return the height and width of @var{frame}, measured in
lines and columns.  If you don't supply @var{frame}, they use the
selected frame.
@end defun

@defun frame-pixel-height &optional frame
@defunx frame-pixel-width &optional frame
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These functions return the height and width of the main display area
of @var{frame}, measured in pixels.  If you don't supply @var{frame},
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they use the selected frame.  For a text-only terminal, the results are
in characters rather than pixels.

These values include the internal borders, and windows' scroll bars and
fringes (which belong to individual windows, not to the frame itself).
The exact value of the heights depends on the window-system and toolkit
in use.  With Gtk+, the height does not include any tool bar or menu
bar.  With the Motif or Lucid toolkits, it includes the tool bar but
not the menu bar.  In a graphical version with no toolkit, it includes
both the tool bar and menu bar.  For a text-only terminal, the result
includes the menu bar.
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@end defun

@defun frame-char-height &optional frame
@defunx frame-char-width &optional frame
These functions return the height and width of a character in
@var{frame}, measured in pixels.  The values depend on the choice of
font.  If you don't supply @var{frame}, these functions use the selected
frame.
@end defun

@defun set-frame-size frame cols rows
This function sets the size of @var{frame}, measured in characters;
@var{cols} and @var{rows} specify the new width and height.

To set the size based on values measured in pixels, use
@code{frame-char-height} and @code{frame-char-width} to convert
them to units of characters.
@end defun

@defun set-frame-height frame lines &optional pretend
This function resizes @var{frame} to a height of @var{lines} lines.  The
sizes of existing windows in @var{frame} are altered proportionally to
fit.

If @var{pretend} is non-@code{nil}, then Emacs displays @var{lines}
lines of output in @var{frame}, but does not change its value for the
actual height of the frame.  This is only useful for a terminal frame.
Using a smaller height than the terminal actually implements may be
useful to reproduce behavior observed on a smaller screen, or if the
terminal malfunctions when using its whole screen.  Setting the frame
height ``for real'' does not always work, because knowing the correct
actual size may be necessary for correct cursor positioning on a
terminal frame.
@end defun

@defun set-frame-width frame width &optional pretend
This function sets the width of @var{frame}, measured in characters.
The argument @var{pretend} has the same meaning as in
@code{set-frame-height}.
@end defun

@findex set-screen-height
@findex set-screen-width
  The older functions @code{set-screen-height} and
@code{set-screen-width} were used to specify the height and width of the
screen, in Emacs versions that did not support multiple frames.  They
are semi-obsolete, but still work; they apply to the selected frame.

@node Geometry
@subsection Geometry

  Here's how to examine the data in an X-style window geometry
specification:

@defun x-parse-geometry geom
@cindex geometry specification
The function @code{x-parse-geometry} converts a standard X window
geometry string to an alist that you can use as part of the argument to
@code{make-frame}.

The alist describes which parameters were specified in @var{geom}, and
gives the values specified for them.  Each element looks like
@code{(@var{parameter} . @var{value})}.  The possible @var{parameter}
values are @code{left}, @code{top}, @code{width}, and @code{height}.

For the size parameters, the value must be an integer.  The position
parameter names @code{left} and @code{top} are not totally accurate,
because some values indicate the position of the right or bottom edges
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instead.  The @var{value} possibilities for the position parameters are:
an integer, a list @code{(+ @var{pos})}, or a list @code{(- @var{pos})};
as previously described (@pxref{Position Parameters}).
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Here is an example:

@example
(x-parse-geometry "35x70+0-0")
     @result{} ((height . 70) (width . 35)
         (top - 0) (left . 0))
@end example
@end defun

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@node Terminal Parameters
@section Terminal Parameters
@cindex terminal parameters

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  Each terminal has a list of associated parameters.  These
@dfn{terminal parameters} are mostly a convenient way of storage for
terminal-local variables, but some terminal parameters have a special
meaning.

  This section describes functions to read and change the parameter values
of a terminal.  They all accept as their argument either a terminal or
a frame; the latter means use that frame's terminal.  An argument of
@code{nil} means the selected frame's terminal.
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@defun terminal-parameters &optional terminal
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This function returns an alist listing all the parameters of
@var{terminal} and their values.
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@end defun

@defun terminal-parameter terminal parameter
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This function returns the value of the parameter @var{parameter} (a
symbol) of @var{terminal}.  If @var{terminal} has no setting for
@var{parameter}, this function returns @code{nil}.
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@end defun

@defun set-terminal-parameter terminal parameter value
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This function sets the parameter @var{parm} of @var{terminal} to the
specified @var{value}, and returns the previous value of that
parameter.
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@end defun

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Here's a list of a few terminal parameters that have a special
meaning:

@table @code
@item background-mode
The classification of the terminal's background color, either
@code{light} or @code{dark}.
@item normal-erase-is-backspace
Value is either 1 or 0, depending on whether
@code{normal-erase-is-backspace-mode} is turned on or off on this
terminal.  @xref{DEL Does Not Delete,,, emacs, The Emacs Manual}.
@item terminal-initted
After the terminal is initialized, this is set to the
terminal-specific initialization function.
@end table

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@node Frame Titles
@section Frame Titles
@cindex frame title

  Every frame has a @code{name} parameter; this serves as the default
for the frame title which window systems typically display at the top of
the frame.  You can specify a name explicitly by setting the @code{name}
frame property.

  Normally you don't specify the name explicitly, and Emacs computes the
frame name automatically based on a template stored in the variable
@code{frame-title-format}.  Emacs recomputes the name each time the
frame is redisplayed.

@defvar frame-title-format
This variable specifies how to compute a name for a frame when you have
not explicitly specified one.  The variable's value is actually a mode
line construct, just like @code{mode-line-format}, except that the
@samp{%c} and @samp{%l} constructs are ignored.  @xref{Mode Line
Data}.
@end defvar

@defvar icon-title-format
This variable specifies how to compute the name for an iconified frame,
when you have not explicitly specified the frame title.  This title
appears in the icon itself.
@end defvar

@defvar multiple-frames
This variable is set automatically by Emacs.  Its value is @code{t} when
there are two or more frames (not counting minibuffer-only frames or
invisible frames).  The default value of @code{frame-title-format} uses
@code{multiple-frames} so as to put the buffer name in the frame title
only when there is more than one frame.

The value of this variable is not guaranteed to be accurate except
while processing @code{frame-title-format} or
@code{icon-title-format}.
@end defvar

@node Deleting Frames
@section Deleting Frames
@cindex deleting frames

Frames remain potentially visible until you explicitly @dfn{delete}
them.  A deleted frame cannot appear on the screen, but continues to
exist as a Lisp object until there are no references to it.

@deffn Command delete-frame &optional frame force
@vindex delete-frame-functions
This function deletes the frame @var{frame}.  Unless @var{frame} is a
tooltip, it first runs the hook @code{delete-frame-functions} (each
function gets one argument, @var{frame}).  By default, @var{frame} is
the selected frame.

A frame cannot be deleted if its minibuffer is used by other frames.
Normally, you cannot delete a frame if all other frames are invisible,
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but if @var{force} is non-@code{nil}, then you are allowed to do so.
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@end deffn

@defun frame-live-p frame
The function @code{frame-live-p} returns non-@code{nil} if the frame
@var{frame} has not been deleted.  The possible non-@code{nil} return
values are like those of @code{framep}.  @xref{Frames}.
@end defun

  Some window managers provide a command to delete a window.  These work
by sending a special message to the program that operates the window.
When Emacs gets one of these commands, it generates a
@code{delete-frame} event, whose normal definition is a command that
calls the function @code{delete-frame}.  @xref{Misc Events}.

@node Finding All Frames
@section Finding All Frames
@cindex frames, scanning all

@defun frame-list
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The function @code{frame-list} returns a list of all the live frames,
i.e.@: those that have not been deleted.  It is analogous to
@code{buffer-list} for buffers, and includes frames on all terminals.
The list that you get is newly created, so modifying the list doesn't
have any effect on the internals of Emacs.
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@end defun

@defun visible-frame-list
This function returns a list of just the currently visible frames.
@xref{Visibility of Frames}.  (Terminal frames always count as
``visible,'' even though only the selected one is actually displayed.)
@end defun

@defun next-frame &optional frame minibuf
The function @code{next-frame} lets you cycle conveniently through all
the frames on the current display from an arbitrary starting point.  It
returns the ``next'' frame after @var{frame} in the cycle.  If
@var{frame} is omitted or @code{nil}, it defaults to the selected frame
(@pxref{Input Focus}).

The second argument, @var{minibuf}, says which frames to consider:

@table @asis
@item @code{nil}
Exclude minibuffer-only frames.
@item @code{visible}
Consider all visible frames.
@item 0
Consider all visible or iconified frames.
@item a window
Consider only the frames using that particular window as their
minibuffer.
@item anything else
Consider all frames.
@end table
@end defun

@defun previous-frame &optional frame minibuf
Like @code{next-frame}, but cycles through all frames in the opposite
direction.
@end defun

  See also @code{next-window} and @code{previous-window}, in @ref{Cyclic
Window Ordering}.

@node Minibuffers and Frames
@section Minibuffers and Frames

Normally, each frame has its own minibuffer window at the bottom, which
is used whenever that frame is selected.  If the frame has a minibuffer,
you can get it with @code{minibuffer-window} (@pxref{Definition of
minibuffer-window}).

However, you can also create a frame with no minibuffer.  Such a frame
must use the minibuffer window of some other frame.  When you create the
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frame, you can explicitly specify the minibuffer window to use (in some
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other frame).  If you don't, then the minibuffer is found in the frame
which is the value of the variable @code{default-minibuffer-frame}.  Its
value should be a frame that does have a minibuffer.

If you use a minibuffer-only frame, you might want that frame to raise
when you enter the minibuffer.  If so, set the variable
@code{minibuffer-auto-raise} to @code{t}.  @xref{Raising and Lowering}.

@defvar default-minibuffer-frame
This variable specifies the frame to use for the minibuffer window, by
default.  It does not affect existing frames.  It is always local to
the current terminal and cannot be buffer-local.  @xref{Multiple
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Terminals}.
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@end defvar

@node Input Focus
@section Input Focus
@cindex input focus
@c @cindex selected frame    Duplicates selected-frame

At any time, one frame in Emacs is the @dfn{selected frame}.  The selected
window always resides on the selected frame.

When Emacs displays its frames on several terminals (@pxref{Multiple
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Terminals}), each terminal has its own selected frame.  But only one
of these is ``@emph{the} selected frame'': it's the frame that belongs
to the terminal from which the most recent input came.  That is, when
Emacs runs a command that came from a certain terminal, the selected
frame is the one of that terminal.  Since Emacs runs only a single
command at any given time, it needs to consider only one selected
frame at a time; this frame is what we call @dfn{the selected frame}
in this manual.  The display on which the selected frame is shown is
the @dfn{selected frame's display}.
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@defun selected-frame
This function returns the selected frame.
@end defun

Some window systems and window managers direct keyboard input to the
window object that the mouse is in; others require explicit clicks or
commands to @dfn{shift the focus} to various window objects.  Either
way, Emacs automatically keeps track of which frame has the focus.  To
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explicitly switch to a different frame from a Lisp function, call
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@code{select-frame-set-input-focus}.

Lisp programs can also switch frames ``temporarily'' by calling the
function @code{select-frame}.  This does not alter the window system's
concept of focus; rather, it escapes from the window manager's control
until that control is somehow reasserted.

When using a text-only terminal, only one frame can be displayed at a
time on the terminal, so after a call to @code{select-frame}, the next
redisplay actually displays the newly selected frame.  This frame
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remains selected until a subsequent call to @code{select-frame}.  Each
terminal frame has a number which appears in the mode line before the
buffer name (@pxref{Mode Line Variables}).
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@defun select-frame-set-input-focus frame
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This function selects @var{frame}, raises it (should it happen to be
obscured by other frames) and tries to give it the X server's focus.  On
a text-only terminal, the next redisplay displays the new frame on the
entire terminal screen.  The return value of this function is not
significant.
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@end defun

@c ??? This is not yet implemented properly.
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@defun select-frame frame &optional norecord
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This function selects frame @var{frame}, temporarily disregarding the
focus of the X server if any.  The selection of @var{frame} lasts until
the next time the user does something to select a different frame, or
until the next time this function is called.  (If you are using a
window system, the previously selected frame may be restored as the
selected frame after return to the command loop, because it still may
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have the window system's input focus.)

The specified @var{frame} becomes the selected frame, as explained
above, and the terminal that @var{frame} is on becomes the selected
terminal.  The window selected within @var{frame} becomes the selected
window.  This function returns @var{frame}, or @code{nil} if @var{frame}
has been deleted.

Optional argument @var{norecord} non-@code{nil} means to neither change
the order of recently selected windows nor the buffer list.  @xref{The
Buffer List}.
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