Frames
******

A frame is a rectangle on the screen that contains one or more Emacs windows.  A frame initially contains a single main window (plus perhaps a minibuffer window), which you can subdivide vertically or horizontally into smaller windows.

When Emacs runs on a text-only terminal, it starts with one terminal frame.  If you create additional ones, Emacs displays one and only one at any given time---on the terminal screen, of course.

When Emacs communicates directly with a supported window system, such as X, it does not have a terminal frame; instead, it starts with a single window frame, but you can create more, and Emacs can display several such frames at once as is usual for window systems.

 -- Function: framep object
     This predicate returns a non-nil value if OBJECT is a frame, and nil otherwise.  For a frame, the value indicates which kind of display the frame uses:

     x
          The frame is displayed in an X window.

     t
          A terminal frame on a character display.

     mac
          The frame is displayed on a Macintosh.

     w32
          The frame is displayed on MS-Windows 9X/NT.

     pc
          The frame is displayed on an MS-DOS terminal.

See Display, for information about the related topic of controlling Emacs redisplay.

Creating Frames
===============

To create a new frame, call the function make-frame.

 -- Function: make-frame &optional alist
     This function creates a new frame.  If you are using a supported window system, it makes a window frame; otherwise, it makes a terminal frame.

     The argument is an alist specifying frame parameters.  Any parameters not mentioned in ALIST default according to the value of the variable default-frame-alist; parameters not specified even there default from the standard X resources or whatever is used instead on your system.

     The set of possible parameters depends in principle on what kind of window system Emacs uses to display its frames.  See Window Frame Parameters, for documentation of individual parameters you can specify.

 -- Variable: before-make-frame-hook
     A normal hook run by make-frame before it actually creates the frame.

 -- Variable: after-make-frame-functions
     An abnormal hook run by make-frame after it creates the frame. Each function in after-make-frame-functions receives one argument, the frame just created.

Multiple Displays
=================

A single Emacs can talk to more than one X display. Initially, Emacs uses just one display---the one chosen with the DISPLAY environment variable or with the --display option (see Initial Options (The GNU Emacs Manual)).  To connect to another display, use the command make-frame-on-display or specify the display frame parameter when you create the frame.

Emacs treats each X server as a separate terminal, giving each one its own selected frame and its own minibuffer windows.  However, only one of those frames is ``the selected frame'' at any given moment, see Input Focus.

A few Lisp variables are 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 default-minibuffer-frame, defining-kbd-macro, last-kbd-macro, and system-key-alist.  They are always terminal-local, and can never be buffer-local (see Buffer-Local Variables) or frame-local.

A single X server can handle more than one screen.  A display name HOST:SERVER.SCREEN has three parts; the last part specifies the screen number for a given server.  When you use two screens belonging to one server, Emacs knows by the similarity in their names that they share a single keyboard, and it treats them as a single terminal.

 -- Command: make-frame-on-display display &optional parameters
     This creates a new frame on display DISPLAY, taking the other frame parameters from PARAMETERS.  Aside from the DISPLAY argument, it is like make-frame (see Creating Frames).

 -- Function: x-display-list
     This 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.

 -- Function: x-open-connection display &optional xrm-string must-succeed
     This function opens a connection to the X display DISPLAY.  It does not create a frame on that display, but it permits you to check that communication can be established with that display.

     The optional argument XRM-STRING, if not nil, is a string of resource names and values, in the same format used in the .Xresources file.  The values you specify override the resource values recorded in the X server itself; they apply to all Emacs frames created on this display.  Here's an example of what this string might look like:

          "*BorderWidth: 3\n*InternalBorder: 2\n"

     See Resources.

     If MUST-SUCCEED is non-nil, failure to open the connection terminates Emacs.  Otherwise, it is an ordinary Lisp error.

 -- Function: x-close-connection display
     This function closes the connection to display DISPLAY.  Before you can do this, you must first delete all the frames that were open on that display (see Deleting Frames).

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 height, width, name, title, menu-bar-lines, buffer-list and buffer-predicate parameters do something special.  If the terminal supports colors, the parameters foreground-color, background-color, background-mode and display-type are also meaningful.

Access to Frame Parameters
--------------------------

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

 -- Function: frame-parameter frame parameter
     This function returns the value of the parameter named PARAMETER of FRAME.  If FRAME is nil, it returns the selected  frame's parameter.

 -- Function: frame-parameters frame
     The function frame-parameters returns an alist listing all the parameters of FRAME and their values.

 -- Function: modify-frame-parameters frame alist
     This function alters the parameters of frame FRAME based on the elements of ALIST.  Each element of ALIST has the form (PARM . VALUE), where PARM is a symbol naming a parameter.  If you don't mention a parameter in ALIST, its value doesn't change.

Initial Frame Parameters
------------------------

You can specify the parameters for the initial startup frame by setting initial-frame-alist in your init file (see Init File).

 -- Variable: initial-frame-alist
     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:

          (PARAMETER . VALUE)

     Emacs creates the initial frame before it reads your init file.  After reading that file, Emacs checks 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.  See X Resources (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 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 initial-frame-alist with values that match the X resources.

If these parameters specify a separate minibuffer-only frame with (minibuffer . nil), and you have not created one, Emacs creates one for you.

 -- Variable: minibuffer-frame-alist
     This variable's value is an alist of parameter values used when creating an initial minibuffer-only frame---if such a frame is needed, according to the parameters for the main initial frame.

 -- Variable: default-frame-alist
     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.

See also special-display-frame-alist, in Choosing Window.

If you use options that specify window appearance when you invoke Emacs, they take effect by adding elements to default-frame-alist.  One exception is -geometry, which adds the specified position to initial-frame-alist instead.  See Command Arguments (The GNU Emacs Manual).

Window Frame Parameters
-----------------------

Just what parameters a frame has depends on what display mechanism it uses.  Here is a table of the parameters that have special meanings in a window frame; of these, name, title, height, width, buffer-list and buffer-predicate provide meaningful information in terminal frames.

display
     The display on which to open this frame.  It should be a string of the form "HOST:DPY.SCREEN", just like the DISPLAY environment variable.

title
     If a frame has a non-nil title, it appears in the window system's border for the frame, and also in the mode line of windows in that frame if mode-line-frame-identification uses %F (see %-Constructs).  This is normally the case when Emacs is not using a window system, and can only display one frame at a time. See Frame Titles.

name
     The name of the frame.  The frame name serves as a default for the frame title, if the title parameter is unspecified or nil.  If you don't specify a name, Emacs sets the frame name automatically (see 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.

left
     The screen position of the left edge, in pixels, with respect to the left edge of the screen.  The value may be a positive number POS, or a list of the form (+ POS) which permits specifying a negative POS value.

     A negative number -POS, or a list of the form (- POS), actually specifies the position of the right edge of the window with respect to the right edge of the screen.  A positive value of POS counts toward the left.  Reminder: if the parameter is a negative integer -POS, then POS is positive.

     Some window managers ignore program-specified positions.  If you want to be sure the position you specify is not ignored, specify a non-nil value for the user-position parameter as well.

top
     The screen position of the top edge, in pixels, with respect to the top edge of the screen.  The value may be a positive number POS, or a list of the form (+ POS) which permits specifying a negative POS value.

     A negative number -POS, or a list of the form (- POS), actually specifies the position of the bottom edge of the window with respect to the bottom edge of the screen.  A positive value of POS counts toward the top.  Reminder: if the parameter is a negative integer -POS, then POS is positive.

     Some window managers ignore program-specified positions.  If you want to be sure the position you specify is not ignored, specify a non-nil value for the user-position parameter as well.

icon-left
     The screen position of the left edge 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.

icon-top
     The screen position of the top edge 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.

user-position
     When you create a frame and specify its screen position with the left and 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-nil value says the position was user-specified.

     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 twm, let the user specify whether to obey program-specified positions or ignore them.

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

height
     The height of the frame contents, in characters.  (To get the height in pixels, call frame-pixel-height; see Size and Position.)

width
     The width of the frame contents, in characters.  (To get the height in pixels, call frame-pixel-width; see Size and Position.)

window-id
     The number of the window-system window used by the frame to contain the actual Emacs windows.

outer-window-id
     The number of the outermost window-system window used for the whole frame.

minibuffer
     Whether this frame has its own minibuffer.  The value t means yes, nil means no, only means this frame is just a minibuffer.  If the value is a minibuffer window (in some other frame), the new frame uses that minibuffer.

buffer-predicate
     The buffer-predicate function for this frame.  The function other-buffer uses this predicate (from the selected frame) to decide which buffers it should consider, if the predicate is not nil.  It calls the predicate with one argument, a buffer, once for each buffer; if the predicate returns a non-nil value, it considers that buffer.

buffer-list
     A list of buffers that have been selected in this frame, ordered most-recently-selected first.

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 (see Fontsets).  Changing this frame parameter on a frame also changes the font-related attributes of the default face on that frame.

auto-raise
     Whether selecting the frame raises it (non-nil means yes).

auto-lower
     Whether deselecting the frame lowers it (non-nil means yes).

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 left, right, and nil for no scroll bars.

horizontal-scroll-bars
     Whether the frame has scroll bars for horizontal scrolling (non-nil means yes).  (Horizontal scroll bars are not currently implemented.)

scroll-bar-width
     The width of the vertical scroll bar, in pixels.

icon-type
     The type of icon to use for this frame when it is iconified.  If the value is a string, that specifies a file containing a bitmap to use. Any other non-nil value specifies the default bitmap icon (a picture of a gnu); nil specifies a text icon.

icon-name
     The name to use in the icon for this frame, when and if the icon appears.  If this is nil, the frame's title is used.

foreground-color
     The color to use for the image of a character.  This is a string; the window system defines the meaningful color names.  Changing this parameter is equivalent to changing the foreground color of the face default on the frame in question.

background-color
     The color to use for the background of characters.  Changing this parameter is equivalent to changing the foreground color of the face default on the frame in question.

background-mode
     This parameter is either dark or light, according to whether the background color is a light one or a dark one.

mouse-color
     The color for the mouse pointer.  Changing this parameter is equivalent to changing the background color of face mouse.

cursor-color
     The color for the cursor that shows point. Changing this parameter is equivalent to changing the background color of face cursor.

border-color
     The color for the border of the frame. Changing this parameter is equivalent to changing the background color of face border.

scroll-bar-foreground
     If non-nil, the color for the foreground of scroll bars. Changing this parameter is equivalent to setting the foreground color of face scroll-bar.

scroll-bar-background
     If non-nil, the color for the background of scroll bars. Changing this parameter is equivalent to setting the foreground color of face scroll-bar.

display-type
     This parameter describes the range of possible colors that can be used in this frame.  Its value is color, grayscale or mono.

cursor-type
     The way to display the cursor.  The legitimate values are bar, box, and (bar . WIDTH).  The symbol box specifies an ordinary black box overlaying the character after point; that is the default.  The symbol bar specifies a vertical bar between characters as the cursor.  (bar . WIDTH) specifies a bar WIDTH pixels wide.

     The buffer-local variable cursor-type overrides the value of the cursor-type frame parameter, and can in addition have values t (use the cursor specified for the frame) and nil (don't display a cursor).

border-width
     The width in pixels of the window border.

internal-border-width
     The distance in pixels between text and border.

unsplittable
     If non-nil, this frame's window is never split automatically.

visibility
     The state of visibility of the frame.  There are three possibilities: nil for invisible, t for visible, and icon for iconified.  See Visibility of Frames.

menu-bar-lines
     The number of lines to allocate at the top of the frame for a menu bar. The default is 1.  See Menu Bar.  (In Emacs versions that use the X toolkit, there is only one menu bar line; all that matters about the number you specify is whether it is greater than zero.)

screen-gamma
     If this is a number, Emacs performs ``gamma correction'' on 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 the default is to display for that gamma value.  Specifying a smaller value results in darker colors, which is desirable for a monitor that tends to display colors too light.  A screen gamma value of 1.5 may give good results for LCD color displays.

tool-bar-lines
     The number of lines to use for the toolbar.  A value of nil means don't display a tool bar.

line-spacing
     Additional space put below text lines in pixels (a positive integer).

Frame Size And Position
-----------------------

You can read or change the size and position of a frame using the frame parameters left, top, height, and 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 Input Focus.)

 -- Function: set-frame-position frame left top
     This function sets the position of the top left corner of FRAME to LEFT and 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.

 -- Function: frame-height &optional frame
 -- Function: frame-width &optional frame
     These functions return the height and width of FRAME, measured in lines and columns.  If you don't supply FRAME, they use the selected frame.

 -- Function: screen-height
 -- Function: screen-width
     These functions are old aliases for frame-height and frame-width.  When you are using a non-window terminal, the size of the frame is normally the same as the size of the terminal screen.

 -- Function: frame-pixel-height &optional frame
 -- Function: frame-pixel-width &optional frame
     These functions return the height and width of FRAME, measured in pixels.  If you don't supply FRAME, they use the selected frame.

 -- Function: frame-char-height &optional frame
 -- Function: frame-char-width &optional frame
     These functions return the height and width of a character in FRAME, measured in pixels.  The values depend on the choice of font.  If you don't supply FRAME, these functions use the selected frame.

 -- Function: set-frame-size frame cols rows
     This function sets the size of FRAME, measured in characters; COLS and ROWS specify the new width and height.

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

 -- Function: set-frame-height frame lines &optional pretend
     This function resizes FRAME to a height of LINES lines.  The sizes of existing windows in FRAME are altered proportionally to fit.

     If PRETEND is non-nil, then Emacs displays LINES lines of output in 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.

 -- Function: set-frame-width frame width &optional pretend
     This function sets the width of FRAME, measured in characters. The argument PRETEND has the same meaning as in set-frame-height.

The older functions set-screen-height and 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.

 -- Function: x-parse-geometry geom
     The function x-parse-geometry converts a standard X window geometry string to an alist that you can use as part of the argument to make-frame.

     The alist describes which parameters were specified in GEOM, and gives the values specified for them.  Each element looks like (PARAMETER . VALUE).  The possible PARAMETER values are left, top, width, and height.

     For the size parameters, the value must be an integer.  The position parameter names left and top are not totally accurate, because some values indicate the position of the right or bottom edges instead.  These are the VALUE possibilities for the position parameters:

     an integer
          A positive integer relates the left edge or top edge of the window to the left or top edge of the screen.  A negative integer relates the right or bottom edge of the window to the right or bottom edge of the screen.

     (+ POSITION)
          This specifies the position of the left or top edge of the window relative to the left or top edge of the screen.  The integer POSITION may be positive or negative; a negative value specifies a position outside the screen.

     (- POSITION)
          This specifies the position of the right or bottom edge of the window relative to the right or bottom edge of the screen.  The integer POSITION may be positive or negative; a negative value specifies a position outside the screen.

     Here is an example:

          (x-parse-geometry "35x70+0-0")
               => ((height . 70) (width . 35)
                   (top - 0) (left . 0))

Frame Titles
============

Every frame has a 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 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 frame-title-format.  Emacs recomputes the name each time the frame is redisplayed.

 -- Variable: 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 mode-line-format.  See Mode Line Data.

 -- Variable: 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.

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

Deleting Frames
===============

Frames remain potentially visible until you explicitly 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.  There is no way to cancel the deletion of a frame aside from restoring a saved frame configuration (see Frame Configurations); this is similar to the way windows behave.

 -- Command: delete-frame &optional frame force
     This function deletes the frame FRAME after running the hook delete-frame-hook.  By default, 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, but if the FORCE is non-nil, then you are allowed to do so.

 -- Function: frame-live-p frame
     The function frame-live-p returns non-nil if the frame FRAME has not been deleted.

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 delete-frame event, whose normal definition is a command that calls the function delete-frame.  See Misc Events.

Finding All Frames
==================

 -- Function: frame-list
     The function frame-list returns a list of all the frames that have not been deleted.  It is analogous to buffer-list for buffers.  The list that you get is newly created, so modifying the list doesn't have any effect on the internals of Emacs.

 -- Function: visible-frame-list
     This function returns a list of just the currently visible frames. See Visibility of Frames.  (Terminal frames always count as ``visible'', even though only the selected one is actually displayed.)

 -- Function: next-frame &optional frame minibuf
     The function next-frame lets you cycle conveniently through all the frames from an arbitrary starting point.  It returns the ``next'' frame after FRAME in the cycle.  If FRAME is omitted or nil, it defaults to the selected frame (see Input Focus).

     The second argument, MINIBUF, says which frames to consider:

     nil
          Exclude minibuffer-only frames.

     visible
          Consider all visible frames.

     0
          Consider all visible or iconified frames.

     a window
          Consider only the frames using that particular window as their minibuffer.

     anything else
          Consider all frames.

 -- Function: previous-frame &optional frame minibuf
     Like next-frame, but cycles through all frames in the opposite direction.

See also next-window and previous-window, in Cyclic Window Ordering.

Frames and Windows
==================

Each window is part of one and only one frame; you can get the frame with window-frame.

 -- Function: window-frame window
     This function returns the frame that WINDOW is on.

All the non-minibuffer windows in a frame are arranged in a cyclic order.  The order runs from the frame's top window, which is at the upper left corner, down and to the right, until it reaches the window at the lower right corner (always the minibuffer window, if the frame has one), and then it moves back to the top.  See Cyclic Window Ordering.

 -- Function: frame-first-window frame
     This returns the topmost, leftmost window of frame FRAME.

At any time, exactly one window on any frame is selected within the frame.  The significance of this designation is that selecting the frame also selects this window.  You can get the frame's current selected window with frame-selected-window.

 -- Function: frame-selected-window frame
     This function returns the window on FRAME that is selected within FRAME.

Conversely, selecting a window for Emacs with select-window also makes that window selected within its frame.  See Selecting Windows.

Another function that (usually) returns one of the windows in a given frame is minibuffer-window.  See Minibuffer Misc.

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 minibuffer-window (see Minibuffer Misc).

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 frame, you can specify explicitly the minibuffer window to use (in some other frame).  If you don't, then the minibuffer is found in the frame which is the value of the variable 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 minibuffer-auto-raise to t.  See Raising and Lowering.

 -- Variable: default-minibuffer-frame
     This variable specifies the frame to use for the minibuffer window, by default.  It is always local to the current terminal and cannot be buffer-local.  See Multiple Displays.

Input Focus
===========

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

When Emacs displays its frames on several terminals (see Multiple Displays), each terminal has its own selected frame.  But only one of these is ``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 the selected frame in this manual.  The display on which the selected frame is displayed is the selected frame's display.

 -- Function: selected-frame
     This function returns the selected frame.

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 shift the focus to various window objects.  Either way, Emacs automatically keeps track of which frame has the focus.

Lisp programs can also switch frames ``temporarily'' by calling the function 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 the selected terminal frame is actually displayed on the terminal.  switch-frame is the only way to switch frames, and the change lasts until overridden by a subsequent call to switch-frame.  Each terminal screen except for the initial one has a number, and the number of the selected frame appears in the mode line before the buffer name (see Mode Line Variables).

 -- Function: select-frame frame
     This function selects frame FRAME, temporarily disregarding the focus of the X server if any.  The selection of FRAME lasts until the next time the user does something to select a different frame, or until the next time this function is called.  The specified FRAME becomes the selected frame, as explained above, and the terminal that FRAME is on becomes the selected terminal.

     In general, you should never use select-frame in a way that could switch to a different terminal without switching back when you're done.

Emacs cooperates with the window system by arranging to select frames as the server and window manager request.  It does so by generating a special kind of input event, called a focus event, when appropriate.  The command loop handles a focus event by calling handle-switch-frame.  See Focus Events.

 -- Command: handle-switch-frame frame
     This function handles a focus event by selecting frame FRAME.

     Focus events normally do their job by invoking this command. Don't call it for any other reason.

 -- Function: redirect-frame-focus frame focus-frame
     This function redirects focus from FRAME to FOCUS-FRAME. This means that FOCUS-FRAME will receive subsequent keystrokes and events intended for FRAME.  After such an event, the value of last-event-frame will be FOCUS-FRAME.  Also, switch-frame events specifying FRAME will instead select FOCUS-FRAME.

     If FOCUS-FRAME is nil, that cancels any existing redirection for FRAME, which therefore once again receives its own events.

     One use of focus redirection is for frames that don't have minibuffers. These frames use minibuffers on other frames.  Activating a minibuffer on another frame redirects focus to that frame.  This puts the focus on the minibuffer's frame, where it belongs, even though the mouse remains in the frame that activated the minibuffer.

     Selecting a frame can also change focus redirections.  Selecting frame bar, when foo had been selected, changes any redirections pointing to foo so that they point to bar instead.  This allows focus redirection to work properly when the user switches from one frame to another using select-window.

     This means that a frame whose focus is redirected to itself is treated differently from a frame whose focus is not redirected. select-frame affects the former but not the latter.

     The redirection lasts until redirect-frame-focus is called to change it.

 -- User Option: focus-follows-mouse
     This option is how you inform Emacs whether the window manager transfers focus when the user moves the mouse.  Non-nil says that it does. When this is so, the command other-frame moves the mouse to a position consistent with the new selected frame.

Visibility of Frames
====================

A window frame may be visible, invisible, or iconified.  If it is visible, you can see its contents.  If it is iconified, the frame's contents do not appear on the screen, but an icon does.  If the frame is invisible, it doesn't show on the screen, not even as an icon.

Visibility is meaningless for terminal frames, since only the selected one is actually displayed in any case.

 -- Command: make-frame-visible &optional frame
     This function makes frame FRAME visible.  If you omit FRAME, it makes the selected frame visible.

 -- Command: make-frame-invisible &optional frame
     This function makes frame FRAME invisible.  If you omit FRAME, it makes the selected frame invisible.

 -- Command: iconify-frame &optional frame
     This function iconifies frame FRAME.  If you omit FRAME, it iconifies the selected frame.

 -- Function: frame-visible-p frame
     This returns the visibility status of frame FRAME.  The value is t if FRAME is visible, nil if it is invisible, and icon if it is iconified.

The visibility status of a frame is also available as a frame parameter.  You can read or change it as such.  See Window Frame Parameters.

The user can iconify and deiconify frames with the window manager. This happens below the level at which Emacs can exert any control, but Emacs does provide events that you can use to keep track of such changes.  See Misc Events.

Raising and Lowering Frames
===========================

Most window systems use a desktop metaphor.  Part of this metaphor is the idea that windows are stacked in a notional third dimension perpendicular to the screen surface, and thus ordered from ``highest'' to ``lowest''.  Where two windows overlap, the one higher up covers the one underneath.  Even a window at the bottom of the stack can be seen if no other window overlaps it.

A window's place in this ordering is not fixed; in fact, users tend to change the order frequently.  Raising a window means moving it ``up'', to the top of the stack.  Lowering a window means moving it to the bottom of the stack.  This motion is in the notional third dimension only, and does not change the position of the window on the screen.

You can raise and lower Emacs frame Windows with these functions:

 -- Command: raise-frame &optional frame
     This function raises frame FRAME (default, the selected frame).

 -- Command: lower-frame &optional frame
     This function lowers frame FRAME (default, the selected frame).

 -- User Option: minibuffer-auto-raise
     If this is non-nil, activation of the minibuffer raises the frame that the minibuffer window is in.

You can also enable auto-raise (raising automatically when a frame is selected) or auto-lower (lowering automatically when it is deselected) for any frame using frame parameters.  See Window Frame Parameters.

Frame Configurations
====================

A frame configuration records the current arrangement of frames, all their properties, and the window configuration of each one. (see Window Configurations.)

 -- Function: current-frame-configuration
     This function returns a frame configuration list that describes the current arrangement of frames and their contents.

 -- Function: set-frame-configuration configuration &optional nodelete
     This function restores the state of frames described in CONFIGURATION.

     Ordinarily, this function deletes all existing frames not listed in CONFIGURATION.  But if NODELETE is non-nil, the unwanted frames are iconified instead.

Mouse Tracking
==============

Sometimes it is useful to track the mouse, which means to display something to indicate where the mouse is and move the indicator as the mouse moves.  For efficient mouse tracking, you need a way to wait until the mouse actually moves.

The convenient way to track the mouse is to ask for events to represent mouse motion.  Then you can wait for motion by waiting for an event.  In addition, you can easily handle any other sorts of events that may occur.  That is useful, because normally you don't want to track the mouse forever---only until some other event, such as the release of a button.

 -- Special Form: track-mouse body...
     This special form executes BODY, with generation of mouse motion events enabled.  Typically BODY would use read-event to read the motion events and modify the display accordingly.  See Motion Events, for the format of mouse motion events.

     The value of track-mouse is that of the last form in BODY. You should design BODY to return when it sees the up-event that indicates the release of the button, or whatever kind of event means it is time to stop tracking.

The usual purpose of tracking mouse motion is to indicate on the screen the consequences of pushing or releasing a button at the current position.

In many cases, you can avoid the need to track the mouse by using the mouse-face text property (see Special Properties). That works at a much lower level and runs more smoothly than Lisp-level mouse tracking.

Mouse Position
==============

The functions mouse-position and set-mouse-position give access to the current position of the mouse.

 -- Function: mouse-position
     This function returns a description of the position of the mouse.  The value looks like (FRAME X . Y), where X and Y are integers giving the position in characters relative to the top left corner of the inside of FRAME.

 -- Variable: mouse-position-function
     If non-nil, the value of this variable is a function for mouse-position to call.  mouse-position calls this function just before returning, with its normal return value as the sole argument, and it returns whatever this function returns to it.

     This abnormal hook exists for the benefit of packages like xt-mouse.el that need to do mouse handling at the Lisp level.

 -- Function: set-mouse-position frame x y
     This function warps the mouse to position X, Y in frame FRAME.  The arguments X and Y are integers, giving the position in characters relative to the top left corner of the inside of FRAME.  If FRAME is not visible, this function does nothing.  The return value is not significant.

 -- Function: mouse-pixel-position
     This function is like mouse-position except that it returns coordinates in units of pixels rather than units of characters.

 -- Function: set-mouse-pixel-position frame x y
     This function warps the mouse like set-mouse-position except that X and Y are in units of pixels rather than units of characters.  These coordinates are not required to be within the frame.

     If FRAME is not visible, this function does nothing.  The return value is not significant.

Pop-Up Menus
============

When using a window system, a Lisp program can pop up a menu so that the user can choose an alternative with the mouse.

 -- Function: x-popup-menu position menu
     This function displays a pop-up menu and returns an indication of what selection the user makes.

     The argument POSITION specifies where on the screen to put the menu.  It can be either a mouse button event (which says to put the menu where the user actuated the button) or a list of this form:

          ((XOFFSET YOFFSET) WINDOW)

     where XOFFSET and YOFFSET are coordinates, measured in pixels, counting from the top left corner of WINDOW's frame.

     If POSITION is t, it means to use the current mouse position.  If POSITION is nil, it means to precompute the key binding equivalents for the keymaps specified in MENU, without actually displaying or popping up the menu.

     The argument MENU says what to display in the menu.  It can be a keymap or a list of keymaps (see Menu Keymaps).  Alternatively, it can have the following form:

          (TITLE PANE1 PANE2...)

     where each pane is a list of form

          (TITLE (LINE . ITEM)...)

     Each LINE should be a string, and each ITEM should be the value to return if that LINE is chosen.

Usage note: Don't use x-popup-menu to display a menu if you could do the job with a prefix key defined with a menu keymap. If you use a menu keymap to implement a menu, C-h c and C-h a can see the individual items in that menu and provide help for them. If instead you implement the menu by defining a command that calls x-popup-menu, the help facilities cannot know what happens inside that command, so they cannot give any help for the menu's items.

The menu bar mechanism, which lets you switch between submenus by moving the mouse, cannot look within the definition of a command to see that it calls x-popup-menu.  Therefore, if you try to implement a submenu using x-popup-menu, it cannot work with the menu bar in an integrated fashion.  This is why all menu bar submenus are implemented with menu keymaps within the parent menu, and never with x-popup-menu.  See Menu Bar,

If you want a menu bar submenu to have contents that vary, you should still use a menu keymap to implement it.  To make the contents vary, add a hook function to menu-bar-update-hook to update the contents of the menu keymap as necessary.

Dialog Boxes
============

A dialog box is a variant of a pop-up menu---it looks a little different, it always appears in the center of a frame, and it has just one level and one pane.  The main use of dialog boxes is for asking questions that the user can answer with ``yes'', ``no'', and a few other alternatives.  The functions y-or-n-p and yes-or-no-p use dialog boxes instead of the keyboard, when called from commands invoked by mouse clicks.

 -- Function: x-popup-dialog position contents
     This function displays a pop-up dialog box and returns an indication of what selection the user makes.  The argument CONTENTS specifies the alternatives to offer; it has this format:

          (TITLE (STRING . VALUE)...)

     which looks like the list that specifies a single pane for x-popup-menu.

     The return value is VALUE from the chosen alternative.

     An element of the list may be just a string instead of a cons cell (STRING . VALUE).  That makes a box that cannot be selected.

     If nil appears in the list, it separates the left-hand items from the right-hand items; items that precede the nil appear on the left, and items that follow the nil appear on the right.  If you don't include a nil in the list, then approximately half the items appear on each side.

     Dialog boxes always appear in the center of a frame; the argument POSITION specifies which frame.  The possible values are as in x-popup-menu, but the precise coordinates don't matter; only the frame matters.

     In some configurations, Emacs cannot display a real dialog box; so instead it displays the same items in a pop-up menu in the center of the frame.

Pointer Shapes
==============

These variables specify which shape to use for the mouse pointer in various situations, when using the X Window System:

x-pointer-shape
     This variable specifies the pointer shape to use ordinarily in the Emacs frame.

x-sensitive-text-pointer-shape
     This variable specifies the pointer shape to use when the mouse is over mouse-sensitive text.

These variables affect newly created frames.  They do not normally affect existing frames; however, if you set the mouse color of a frame, that also updates its pointer shapes based on the current values of these variables.  See Window Frame Parameters.

The values you can use, to specify either of these pointer shapes, are defined in the file lisp/term/x-win.el.  Use M-x apropos RET x-pointer RET to see a list of them.

Window System Selections
========================

The X server records a set of selections which permit transfer of data between application programs.  The various selections are distinguished by selection types, represented in Emacs by symbols.  X clients including Emacs can read or set the selection for any given type.

 -- Function: x-set-selection type data
     This function sets a ``selection'' in the X server.  It takes two arguments: a selection type TYPE, and the value to assign to it, DATA.  If DATA is nil, it means to clear out the selection.  Otherwise, DATA may be a string, a symbol, an integer (or a cons of two integers or list of two integers), an overlay, or a cons of two markers pointing to the same buffer.  An overlay or a pair of markers stands for text in the overlay or between the markers.

     The argument DATA may also be a vector of valid non-vector selection values.

     Each possible TYPE has its own selection value, which changes independently.  The usual values of TYPE are PRIMARY and SECONDARY; these are symbols with upper-case names, in accord with X Window System conventions.  The default is PRIMARY.

 -- Function: x-get-selection &optional type data-type
     This function accesses selections set up by Emacs or by other X clients.  It takes two optional arguments, TYPE and DATA-TYPE.  The default for TYPE, the selection type, is PRIMARY.

     The DATA-TYPE argument specifies the form of data conversion to use, to convert the raw data obtained from another X client into Lisp data.  Meaningful values include TEXT, STRING, TARGETS, LENGTH, DELETE, FILE_NAME, CHARACTER_POSITION, LINE_NUMBER, COLUMN_NUMBER, OWNER_OS, HOST_NAME, USER, CLASS, NAME, ATOM, and INTEGER.  (These are symbols with upper-case names in accord with X conventions.)  The default for DATA-TYPE is STRING.

The X server also has a set of numbered cut buffers which can store text or other data being moved between applications.  Cut buffers are considered obsolete, but Emacs supports them for the sake of X clients that still use them.

 -- Function: x-get-cut-buffer n
     This function returns the contents of cut buffer number N.

 -- Function: x-set-cut-buffer string &optional push
     This function stores STRING into the first cut buffer (cut buffer 0).  If PUSH is nil, only the first cut buffer is changed. If PUSH is non-nil, that says to move the values down through the series of cut buffers, much like the way successive kills in Emacs move down the kill ring.  In other words, the previous value of the first cut buffer moves into the second cut buffer, and the second to the third, and so on through all eight cut buffers.

 -- Variable: selection-coding-system
     This variable specifies the coding system to use when reading and writing selections, the clipboard, or a cut buffer.  See Coding Systems.  The default is compound-text, which converts to the text representation that X11 normally uses.

When Emacs runs on MS-Windows, it does not implement X selections in general, but it does support the clipboard.  x-get-selection and x-set-selection on MS-Windows support the text data type only; if the clipboard holds other types of data, Emacs treats the clipboard as empty.

 -- User Option: x-select-enable-clipboard
     If this is non-nil, the Emacs yank functions consult the clipboard before the primary selection, and the kill functions store in the clipboard as well as the primary selection.  Otherwise they do not access the clipboard at all.  The default is nil on most systems, but t on MS-Windows.

Color Names
===========

These functions provide a way to determine which color names are valid, and what they look like.  In some cases, the value depends on the selected frame, as described below; see Input Focus, for the meaning of the term ``selected frame''.

 -- Function: color-defined-p color &optional frame
     This function reports whether a color name is meaningful.  It returns t if so; otherwise, nil.  The argument FRAME says which frame's display to ask about; if FRAME is omitted or nil, the selected frame is used.

     Note that this does not tell you whether the display you are using really supports that color.  When using X, you can ask for any defined color on any kind of display, and you will get some result---typically, the closest it can do.  To determine whether a frame can really display a certain color, use color-supported-p (see below).

     This function used to be called x-color-defined-p, and that name is still supported as an alias.

 -- Function: defined-colors &optional frame
     This function returns a list of the color names that are defined and supported on frame FRAME (default, the selected frame).

     This function used to be called x-defined-colors, and that name is still supported as an alias.

 -- Function: color-supported-p color &optional frame background-p
     This returns t if FRAME can really display the color COLOR (or at least something close to it).  If FRAME is omitted or nil, the question applies to the selected frame.

     Some terminals support a different set of colors for foreground and background.  If BACKGROUND-P is non-nil, that means you are asking whether COLOR can be used as a background; otherwise you are asking whether it can be used as a foreground.

     The argument COLOR must be a valid color name.

 -- Function: color-gray-p color &optional frame
     This returns t if COLOR is a shade of gray, as defined on FRAME's display.  If FRAME is omitted or nil, the question applies to the selected frame.  The argument COLOR must be a valid color name.

 -- Function: color-values color &optional frame
     This function returns a value that describes what COLOR should ideally look like.  If COLOR is defined, the value is a list of three integers, which give the amount of red, the amount of green, and the amount of blue.  Each integer ranges in principle from 0 to 65535, but in practice no value seems to be above 65280.  This kind of three-element list is called an rgb value.

     If COLOR is not defined, the value is nil.

          (color-values "black")
               => (0 0 0)
          (color-values "white")
               => (65280 65280 65280)
          (color-values "red")
               => (65280 0 0)
          (color-values "pink")
               => (65280 49152 51968)
          (color-values "hungry")
               => nil

     The color values are returned for FRAME's display.  If FRAME is omitted or nil, the information is returned for the selected frame's display.

     This function used to be called x-color-values, and that name is still supported as an alias.

Text Terminal Colors
====================

Emacs can display color on text-only terminals, starting with version 21.  These terminals support only a small number of colors, and the computer uses small integers to select colors on the terminal.  This means that the computer cannot reliably tell what the selected color looks like; instead, you have to inform your application which small integers correspond to which colors.  However, Emacs does know the standard set of colors and will try to use them automatically.

Several of these functions use or return rgb values.  An rgb value is a list of three integers, which give the amount of red, the amount of green, and the amount of blue.  Each integer ranges in principle from 0 to 65535, but in practice the largest value used is 65280.

These functions accept a display (either a frame or the name of a terminal) as an optional argument.  We hope in the future to make Emacs support more than one text-only terminal at one time; then this argument will specify which terminal to operate on (the default being the selected frame's terminal; see Input Focus).  At present, though, the DISPLAY argument has no effect.

 -- Function: tty-color-define name number &optional rgb display
     This function associates the color name NAME with color number NUMBER on the terminal.

     The optional argument RGB, if specified, is an rgb value; it says what the color actually looks like.  If you do not specify RGB, then this color cannot be used by tty-color-approximate to approximate other colors, because Emacs does not know what it looks like.

 -- Function: tty-color-clear &optional display
     This function clears the table of defined colors for a text-only terminal.

 -- Function: tty-color-alist &optional display
     This function returns an alist recording the known colors supported by a text-only terminal.

     Each element has the form (NAME NUMBER . RGB) or (NAME NUMBER).  Here, NAME is the color name, NUMBER is the number used to specify it to the terminal. If present, RGB is an rgb value that says what the color actually looks like.

 -- Function: tty-color-approximate rgb &optional display
     This function finds the closest color, among the known colors supported for DISPLAY, to that described by the rgb value RGB.

 -- Function: tty-color-translate color &optional display
     This function finds the closest color to COLOR among the known colors supported for DISPLAY.  If the name COLOR is not defined, the value is nil.

     COLOR can be an X-style "#XXXYYYZZZ" specification instead of an actual name.  The format "RGB:XX/YY/ZZ" is also supported.

X Resources
===========

 -- Function: x-get-resource attribute class &optional component subclass
     The function x-get-resource retrieves a resource value from the X Windows defaults database.

     Resources are indexed by a combination of a key and a class. This function searches using a key of the form INSTANCE.ATTRIBUTE (where INSTANCE is the name under which Emacs was invoked), and using Emacs.CLASS as the class.

     The optional arguments COMPONENT and SUBCLASS add to the key and the class, respectively.  You must specify both of them or neither. If you specify them, the key is INSTANCE.COMPONENT.ATTRIBUTE, and the class is Emacs.CLASS.SUBCLASS.

 -- Variable: x-resource-class
     This variable specifies the application name that x-get-resource should look up.  The default value is "Emacs".  You can examine X resources for application names other than ``Emacs'' by binding this variable to some other string, around a call to x-get-resource.

See X Resources (The GNU Emacs Manual).

Display Feature Testing
=======================

The functions in this section describe the basic capabilities of a particular display.  Lisp programs can use them to adapt their behavior to what the display can do.  For example, a program that ordinarly uses a popup menu could use the minibuffer if popup menus are not supported.

The optional argument DISPLAY in these functions specifies which display to ask the question about.  It can be a display name, a frame (which designates the display that frame is on), or nil (which refers to the selected frame's display, see Input Focus).

See Color Names, Text Terminal Colors, for other functions to obtain information about displays.

 -- Function: display-popup-menus-p &optional display
     This function returns t if popup menus are supported on DISPLAY, nil if not.  Support for popup menus requires that the mouse be available, since the user cannot choose menu items without a mouse.

 -- Function: display-graphic-p &optional display
     This function returns t if DISPLAY is a graphic display capable of displaying several frames and several different fonts at once.  This is true for displays that use a window system such as X, and false for text-only terminals.

 -- Function: display-mouse-p &optional display
     This function returns t if DISPLAY has a mouse available, nil if not.

 -- Function: display-color-p &optional display
     This function returns t if the screen is a color screen. It used to be called x-display-color-p, and that name is still supported as an alias.

 -- Function: display-grayscale-p &optional display
     This function returns t if the screen can display shades of gray. (All color displays can do this.)

 -- Function: display-selections-p &optional display
     This function returns t if DISPLAY supports selections. Windowed displays normally support selections, but they may also be supported in some other cases.

 -- Function: display-images-p &optional display
     This function returns t if DISPLAY can display images. Windowed displays ought in principle to handle images, but some systems lack the support for that.  On a display that does not support images, Emacs cannot display a tool bar.

 -- Function: display-screens &optional display
     This function returns the number of screens associated with the display.

 -- Function: display-pixel-height &optional display
     This function returns the height of the screen in pixels.

 -- Function: display-mm-height &optional display
     This function returns the height of the screen in millimeters, or nil if Emacs cannot get that information.

 -- Function: display-pixel-width &optional display
     This function returns the width of the screen in pixels.

 -- Function: display-mm-width &optional display
     This function returns the width of the screen in millimeters, or nil if Emacs cannot get that information.

 -- Function: display-backing-store &optional display
     This function returns the backing store capability of the display. Backing store means recording the pixels of windows (and parts of windows) that are not exposed, so that when exposed they can be displayed very quickly.

     Values can be the symbols always, when-mapped, or not-useful.  The function can also return nil when the question is inapplicable to a certain kind of display.

 -- Function: display-save-under &optional display
     This function returns non-nil if the display supports the SaveUnder feature.  That feature is used by pop-up windows to save the pixels they obscure, so that they can pop down quickly.

 -- Function: display-planes &optional display
     This function returns the number of planes the display supports. This is typically the number of bits per pixel. For a tty display, it is log to base two of the number of colours supported.

 -- Function: display-visual-class &optional display
     This function returns the visual class for the screen.  The value is one of the symbols static-gray, gray-scale, static-color, pseudo-color, true-color, and direct-color.

 -- Function: display-color-cells &optional display
     This function returns the number of color cells the screen supports.

These functions obtain additional information specifically about X displays.

 -- Function: x-server-version &optional display
     This function returns the list of version numbers of the X server running the display.

 -- Function: x-server-vendor &optional display
     This function returns the vendor that provided the X server software.