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 has just one frame, a terminal frame.  There is no way to create another terminal frame after startup.  If Emacs has an X display, it does not make a terminal frame; instead, it initially creates a single X window frame.  You can create more; see Creating Frames.

 -- Function: framep object
     This predicate returns t if OBJECT is a frame, and nil otherwise.

See Emacs Display, for related information.

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

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

 -- Function: make-frame alist
     This function creates a new frame, if the display mechanism permits creation of frames.  (An X server does; an ordinary terminal does not.)

     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 there either default from the standard X defaults file and X resources.

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

 -- Variable: default-frame-alist
     An alist specifying default values of frame parameters. Each element has the form:

          (PARAMETER . VALUE)

     If you use options that specify window appearance when you invoke Emacs, they take effect by adding elements to default-frame-alist.

Frame Parameters
================

A frame has many parameters that control how it displays.

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

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

 -- Function: frame-parameters frame
     The function frame-parameters returns an alist of all the parameters of FRAME.

 -- 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 .emacs file.

 -- Variable: initial-frame-alist
     This variable's value is an alist of parameter values to when creating the initial X window frame.

If these parameters specify a separate minibuffer-only frame, 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 to when creating an initial minibuffer-only frame---if such a frame is needed, according to the parameters for the main initial frame.

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

Just what parameters a frame has depends on what display mechanism it uses.  Here is a table of the parameters of an X window frame:

name
     The name of the frame.

left
     The screen position of the left edge, in pixels.

top
     The screen position of the top edge, in pixels.

height
     The height of the frame contents, in pixels.

width
     The width of the frame contents, in pixels.

window-id
     The number of the X window for the 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, a minibuffer window (in some other frame) means the new frame uses that minibuffer.

font
     The name of the font for text in the frame.  This is a string.

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 a scroll bar for vertical scrolling (non-nil means yes).

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

icon-type
     The type of icon to use for this frame when it is iconified. Non-nil specifies a bitmap icon, nil a text icon.

foreground-color
     The color to use for the inside of a character.  We use strings to designate colors; the X server defines the meaningful color names.

background-color
     The color to use for the background of text.

mouse-color
     The color for the mouse cursor.

cursor-color
     The color for the cursor that shows point.

border-color
     The color for the border of the frame.

cursor-type
     The way to display the cursor.  There are two legitimate values: bar and box.  The value bar specifies a vertical bar between characters as the cursor.  The value box specifies an ordinary black box overlaying the character after point; that is the default.

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 zero.  See Menu Bar.

parent-id
     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.)

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.  When you create a frame, you must specify either both size parameters or neither.  Likewise, you must specify either both position parameters or neither.  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:

 -- 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, counting from the top left corner of the screen.

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

 -- 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, respectively, 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 with values measured in pixels, use modify-frame-parameters to set the width and height parameters.  See X Frame Parameters.

The old-fashioned functions set-screen-height and set-screen-width, which were used to specify the height and width of the screen in Emacs versions that did not support multiple frames, are still usable.  They apply to the selected frame.  See Screen Size.

 -- Function: x-parse-geometry geom
     The function x-parse-geometry converts a standard X windows geometry string to an alist which you can use as part of the argument to x-create-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.

          (x-geometry "35x70+0-0")
               => ((width . 35) (height . 70) (left . 0) (top . -1))

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
     This function deletes the frame FRAME.  By default, FRAME is the selected frame.

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

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.

 -- 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.

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

     nil
          Exclude minibuffer-only frames.

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

     anything else
          Consider all frames.

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

All the non-minibuffer windows in a frame are arranged in a tree of subdivisions; the root of this tree is available via the function frame-root-window.  Each window is part of one and only one frame; you can get the frame with window-frame.

 -- Function: frame-root-window frame
     This returns the root window of frame FRAME.

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

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 which is selected within FRAME.

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

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 frame on which to find the minibuffer to use.  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 which does have a minibuffer.

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

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

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

The X server normally directs keyboard input to the X window that the mouse is in.  Some window managers use mouse clicks or keyboard events to shift the focus to various X windows, overriding the normal behavior of the server.

Lisp programs can switch frames ``temporarily'' by calling the function select-frame.  This does not override the window manager; rather, it escapes from the window manager's control until that control is somehow reasserted.

 -- Function: select-frame frame
     This function selects frame FRAME, temporarily disregarding the X Windows focus.  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.

Emacs cooperates with the X server and the window managers by arranging to select frames according to what the server and window manager ask for.  It does so by generating a special kind of input event, called a focus event.  The command loop handles a focus event by calling internal-select-frame.  See Focus Events.

 -- Function: internal-select-frame frame
     This function selects frame FRAME, assuming that the X server focus already points to FRAME.

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

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

A 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 in the screen, not even as an icon.

 -- 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 X Frame Parameters.

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

The X window system uses 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's X windows with these functions:

 -- Function: raise-frame frame
     This function raises frame FRAME.

 -- Function: lower-frame frame
     This function lowers frame FRAME.

You can also specify 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 X Frame Parameters.

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

 -- Function: current-frame-configuration
     This function returns a frame configuration list which describes the current arrangement of frames, all their properties, and the window configuration of each one.

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

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...
     Execute BODY, meanwhile generating input events for mouse motion. The code in BODY can read these events with read-event or read-key-sequence.  See Motion Events, for the format of mouse motion events.

     The value of track-mouse is that of the last form in BODY.

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.

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

The new 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 pixels relative to the top left corner of the inside of FRAME.

 -- Function: set-mouse-position frame x y
     Thus function warps the mouse to position X, Y in frame FRAME.  The arguments X and Y are integers, giving the position in pixels relative to the top left corner of the inside of FRAME.

     Warping the mouse means changing the screen position of the mouse as if the user had moved the physical mouse---thus simulating the effect of actual mouse motion.

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

 -- 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 positions measured in characters, counting from the top left corner of WINDOW's frame.

     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.

X 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), or a cons of two markers pointing to the same buffer.  In the last case, the selection is considered to be the text between the markers.  The 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 Windows conventions.  The default is PRIMARY.

 -- Function: x-get-selection 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
     This function stores STRING into the first cut buffer (cut buffer 0), moving the other values down through the series of cut buffers, kill-ring-style.

X Server
========

This section describes how to access and change the overall status of the X server Emacs is using.

X Connections
-------------

You can close the connection with the X server with the function x-close-current-connection, and open a new one with x-open-connection (perhaps with a different server and display).

 -- Function: x-close-current-connection
     This function closes the connection to the X server.  It deletes all frames, making Emacs effectively inaccessible to the user; therefore, a Lisp program that closes the connection should open another one.

 -- Function: x-open-connection display &optional resource-string
     This function opens a connection to an X server, for use of display DISPLAY.

     The optional argument RESOURCE-STRING 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.  Here's an example of what this string might look like:

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

 -- Function: x-color-display-p
     This returns t if the connected X display has color, and nil otherwise.

 -- Function: x-color-defined-p color
     This function reports whether a color name is meaningful and supported on the X display Emacs is using.  It returns t if the display supports that color; otherwise, nil.

     Black-and-white displays support just two colors, "black" or "white".  Color displays support many other colors.

 -- Function: x-synchronize flag
     The function x-synchronize enables or disables synchronous communication with the X server.  It enables synchronous communication if FLAG is non-nil, and disables it if FLAG is nil.

     In synchronous mode, Emacs waits for a response to each X protocol command before doing anything else.  This is useful for debugging Emacs, because protocol errors are reported right away, which helps you find the erroneous command.  Synchronous mode is not the default because it is much slower.

Resources
---------

 -- Function: x-get-resource attribute &optional name class
     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 uses Emacs 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.SUBCLASS.

Rebinding X Server Keys
-----------------------

The X server allows each client to specify what sequence of characters each keyboard key should generate, depending on the set of shift keys held down.  Emacs has functions to redefine these sequences in the X server.  Redefinitions via x-rebind-key apply only to Emacs. Other clients using the same X server are not affected.

 -- Function: x-rebind-key keysym modifiers newstring
     This function redefines a keyboard key in the X server.  KEYSYM is a string which conforms to the X keysym definitions found in X11/keysymdef.h, but without the prefix XK_. MODIFIERS is either nil, meaning no modifier keys, or a list of names of modifier keys, again using the names from X11/keysymdef.h but without the XK_ prefix.

     The third argument, NEWSTRING, is the new definition of the key. It is the sequence of characters that the key should produce as input.

     For example,

          (x-rebind-key "F1" nil "abc")

     causes the F1 function key to generate the string "abc".  Similarly,

          (x-rebind-key "BackSpace"
                        (list "Shift" "Control_L" "c-s-BackSpace")

     makes the BS key send the string "c-s-BackSpace" if either the shift key or the left-hand control key is held down.

 -- Function: x-rebind-keys keysym strings
     This function redefines the complete meaning of a single keyboard key, specifying the behavior for each of the 16 shift masks independently.

     The argument KEYSYM specifies the key to rebind, as in x-rebind-key.

     The argument STRINGS is a list of 16 elements, one for each possible shift mask value; the Nth element says how to redefine the key KEYCODE with shift mask value N.  If element N is a string, it is the new definition for shift mask N.  If element N is nil, the definition for shift mask N is unchanged.

Data about the X Server
-----------------------

This section describes functions and a variable that you can use to get information about the capabilities and origin of the X server that Emacs is displaying its frames on.

 -- Function: x-display-screens
     This function returns the number of screens associated with the current display.

 -- Function: x-server-version
     This function returns the list of version numbers of the X server in use.

 -- Function: x-server-vendor
     This function returns the vendor supporting the X server in use.

 -- Function: x-display-pixel-height
     This function returns the height of this X screen in pixels.

 -- Function: x-display-mm-height
     This function returns the height of this X screen in millimeters.

 -- Function: x-display-pixel-width
     This function returns the width of this X screen in pixels.

 -- Function: x-display-mm-width
     This function returns the width of this X screen in millimeters.

 -- Function: x-display-backing-store
     This function returns the backing store capability of this screen. Values can be the symbols always, when-mapped, or not-useful.

 -- Function: x-display-save-under
     This function returns non-nil if this X screen supports the SaveUnder feature.

 -- Function: x-display-planes
     This function returns the number of planes this display supports.

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

 -- Function: x-display-color-p
     This function returns t if the X screen in use is a color screen.

 -- Function: x-display-color-cells
     This function returns the number of color cells this X screen supports.

 -- Variable: x-no-window-manager
     This variable's value is is t if no X window manager is in use.