Emacs now supports multiple X windows via a new data type known as a frame.
A frame is a rectangle on the screen that contains one or more Emacs windows. Subdividing a frame works just like subdividing the screen in earlier versions of Emacs.
There are two kinds of frames: terminal frames and X window frames. Emacs creates one terminal frame when it starts up with no X display; it uses Termcap or Terminfo to display using characters. There is no way to create another terminal frame after startup. If Emacs has an X display, it does not make a terminal frame, and there is none.
When you are using X windows, Emacs starts out with a single X window
frame. You can create any number of X window frames using
make-frame.
Use the predicate framep to determine whether a given Lisp object
is a frame.
The function redraw-frame redisplays the entire contents of a
given frame.
Use make-frame to create a new frame. This is the only primitive
for creating frames. In principle it could work under any window system
which Emacs understands; the only one we support is X.
make-frame takes just one argument, which is an alist
specifying frame parameters. Any parameters not mentioned in the
argument alist default based on the value of default-frame-alist;
parameters not specified there default from the standard X defaults file
and X resources.
When you invoke Emacs, if you specify arguments for window appearance
and so forth, these go into default-frame-alist and that is how
they have their effect.
You can specify the parameters for the initial startup X window frame by
setting initial-frame-alist in your `.emacs' file. If these
parameters specify a separate minibuffer-only frame, and you have not
created one, Emacs creates one for you, using the parameter values
specified in minibuffer-frame-alist.
You can specify the size and position of a frame using the frame
parameters left, top, height and width. You
must specify either both size parameters or neither. You must specify
either both position parameters or neither. The geometry parameters
that you don't specify are chosen by the window manager in its usual
fashion.
The function x-parse-geometry converts a standard X-style
geometry string to an alist which you can use as part of the argument to
make-frame.
Use the function delete-frame to eliminate a frame. Frames are
like buffers where deletion is concerned; a frame actually continues to
exist as a Lisp object until it is deleted and there are no
references to it, but once it is deleted, it has no further effect on
the screen.
The function frame-live-p returns non-nil if the argument
(a frame) has not been deleted.
The function frame-list returns a list of all the frames that have
not been deleted. It is analogous to buffer-list. The list that
you get is newly created, so modifying the list doesn't have any effect
on the internals of Emacs. The function visible-frame-list returns
the list of just the frames that are visible.
next-frame lets you cycle conveniently through all the frames from an
arbitrary starting point. Its first argument is a frame. Its second
argument minibuf says what to do about minibuffers:
nil
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.
At any time, exactly one window on any frame is selected within the
frame. You can get the frame's current selected window with
frame-selected-window. The significance of this designation is
that selecting the frame selects for Emacs as a whole the window
currently selected within that frame.
Conversely, selecting a window for Emacs with select-window also
makes that window selected within its frame.
A frame may be visible, invisible, or iconified. If
it is invisible, it doesn't show in the screen, not even as an icon.
You can set the visibility status of a frame with
make-frame-visible, make-frame-invisible, and
iconify-frame. You can examine the visibility status with
frame-visible-p---it returns t for a visible frame,
nil for an invisible frame, and icon for an iconified
frame.
At any time, one frame in Emacs is the selected frame. The selected window always resides on 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. The function takes one argument, a frame, and
selects that frame. The selection 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.
The new functions frame-height and frame-width return the
height and width of a specified frame (or of the selected frame),
measured in characters.
The new functions frame-pixel-height and frame-pixel-width
return the height and width of a specified frame (or of the selected
frame), measured in pixels.
The new functions frame-char-height and frame-char-width
return the height and width of a character in a specified frame (or in
the selected frame), measured in pixels.
set-frame-size sets the size of a frame, measured in characters;
its arguments are frame, cols and rows. To set the
size with values measured in pixels, you can use
modify-frame-parameters.
The function set-frame-position sets the position of the top left
corner of a frame. Its arguments are frame, left and
top.
A frame has many parameters that affect how it displays. Use the
function frame-parameters to get an alist of all the parameters
of a given frame. To alter parameters, use
modify-frame-parameters, which takes two arguments: the frame to
modify, and an alist of parameters to change and their new values. Each
element of alist has the form (parm . value),
where parm is a symbol. Parameters that aren't meaningful are
ignored. If you don't mention a parameter in alist, its value
doesn't change.
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
left
top
height
width
window-id
minibuffer
t means yes, none 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
foreground-color
background-color
mouse-color
cursor-color
border-color
cursor-type
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.
icon-type
nil for a bitmap icon, nil for a text icon.
border-width
internal-border-width
auto-raise
nil means selecting the frame raises it.
auto-lower
nil means deselecting the frame lowers it.
vertical-scroll-bars
nil gives the frame a scroll bar
for vertical scrolling.
Normally, each frame has its own minibuffer window at the bottom, which is used whenever that frame is selected. However, you can also create frames with no minibuffers. These frames must use the minibuffer window of some other frame.
The variable default-minibuffer-frame specifies where to find a
minibuffer for frames created without minibuffers of their own. Its
value should be a frame which does have a minibuffer.
You can also specify a minibuffer window explicitly when you create a
frame; then default-minibuffer-frame is not used.