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### 27.4 Resizing Windows

This section describes functions for resizing a window without changing the size of its frame. Because live windows do not overlap, these functions are meaningful only on frames that contain two or more windows: resizing a window also changes the size of a neighboring window. If there is just one window on a frame, its size cannot be changed except by resizing the frame (see Size and Position).

Except where noted, these functions also accept internal windows as arguments. Resizing an internal window causes its child windows to be resized to fit the same space.

Function: window-resizable window delta &optional horizontal ignore pixelwise

  This function returns delta if the size of window can be changed vertically by delta lines. If the optional argument horizontal is non-`nil`, it instead returns delta if window can be resized horizontally by delta columns. It does not actually change the window size.

  If window is `nil`, it defaults to the selected window.

  A positive value of delta means to check whether the window can be enlarged by that number of lines or columns; a negative value of delta means to check whether the window can be shrunk by that many lines or columns. If delta is non-zero, a return value of 0 means that the window cannot be resized.

  Normally, the variables `window-min-height` and `window-min-width` specify the smallest allowable window size (see Window Sizes). However, if the optional argument ignore is non-`nil`, this function ignores `window-min-height` and `window-min-width`, as well as `window-size-fixed`. Instead, it considers the minimum-height window to be one consisting of a header and a mode line, a horizontal scrollbar and a bottom divider (if any), plus a text area one line tall; and a minimum-width window as one consisting of fringes, margins, a scroll bar and a right divider (if any), plus a text area two columns wide.

  If the optional argument pixelwise is non-`nil`, delta is interpreted as pixels.

Function: window-resize window delta &optional horizontal ignore pixelwise

  This function resizes window by delta increments. If horizontal is `nil`, it changes the height by delta lines; otherwise, it changes the width by delta columns. A positive delta means to enlarge the window, and a negative delta means to shrink it.

  If window is `nil`, it defaults to the selected window. If the window cannot be resized as demanded, an error is signaled.

  The optional argument ignore has the same meaning as for the function `window-resizable` above.

  If the optional argument pixelwise is non-`nil`, delta will be interpreted as pixels.

  The choice of which window edges this function alters depends on the values of the option `window-combination-resize` and the combination limits of the involved windows; in some cases, it may alter both edges. See Recombining Windows. To resize by moving only the bottom or right edge of a window, use the function `adjust-window-trailing-edge`.

Function: adjust-window-trailing-edge window delta &optional horizontal pixelwise

  This function moves window’s bottom edge by delta lines. If optional argument horizontal is non-`nil`, it instead moves the right edge by delta columns. If window is `nil`, it defaults to the selected window.

  If the optional argument pixelwise is non-`nil`, delta is interpreted as pixels.

  A positive delta moves the edge downwards or to the right; a negative delta moves it upwards or to the left. If the edge cannot be moved as far as specified by delta, this function moves it as far as possible but does not signal a error.

  This function tries to resize windows adjacent to the edge that is moved. If this is not possible for some reason (e.g., if that adjacent window is fixed-size), it may resize other windows.

User Option: window-resize-pixelwise

  If the value of this option is non-`nil`, Emacs resizes windows in units of pixels. This currently affects functions like `split-window` (see Splitting Windows), `maximize-window`, `minimize-window`, `fit-window-to-buffer`, `fit-frame-to-buffer` and `shrink-window-if-larger-than-buffer` (all listed below).

  Note that when a frame’s pixel size is not a multiple of its character size, at least one window may get resized pixelwise even if this option is `nil`. The default value is `nil`.

The following commands resize windows in more specific ways. When called interactively, they act on the selected window.

Command: fit-window-to-buffer &optional window max-height min-height max-width min-width preserve-size

  This command adjusts the height or width of window to fit the text in it. It returns non-`nil` if it was able to resize window, and `nil` otherwise. If window is omitted or `nil`, it defaults to the selected window. Otherwise, it should be a live window.

  If window is part of a vertical combination, this function adjusts window’s height. The new height is calculated from the actual height of the accessible portion of its buffer. The optional argument max-height, if non-`nil`, specifies the maximum total height that this function can give window. The optional argument min-height, if non-`nil`, specifies the minimum total height that it can give, which overrides the variable `window-min-height`. Both max-height and min-height are specified in lines and include mode and header line and a bottom divider, if any.

  If window is part of a horizontal combination and the value of the option `fit-window-to-buffer-horizontally` (see below) is non-`nil`, this function adjusts window’s height. The new width of window is calculated from the maximum length of its buffer’s lines that follow the current start position of window. The optional argument max-width specifies a maximum width and defaults to the width of window’s frame. The optional argument min-width specifies a minimum width and defaults to `window-min-width`. Both max-width and min-width are specified in columns and include fringes, margins and scrollbars, if any.

  The optional argument preserve-size, if non-`nil`, will install a parameter to preserve the size of window during future resize operations (see Preserving Window Sizes).

  If the option `fit-frame-to-buffer` (see below) is non-`nil`, this function will try to resize the frame of window to fit its contents by calling `fit-frame-to-buffer` (see below).

User Option: fit-window-to-buffer-horizontally

  If this is non-`nil`, `fit-window-to-buffer` can resize windows horizontally. If this is `nil` (the default) `fit-window-to-buffer` never resizes windows horizontally. If this is `only`, it can resize windows horizontally only. Any other value means `fit-window-to-buffer` can resize windows in both dimensions.

User Option: fit-frame-to-buffer

  If this option is non-`nil`, `fit-window-to-buffer` can fit a frame to its buffer. A frame is fit if and only if its root window is a live window and this option is non-`nil`. If this is `horizontally`, frames are fit horizontally only. If this is `vertically`, frames are fit vertically only. Any other non-`nil` value means frames can be resized in both dimensions.

If you have a frame that displays only one window, you can fit that frame to its buffer using the command `fit-frame-to-buffer`.

Command: fit-frame-to-buffer &optional frame max-height min-height max-width min-width only

  This command adjusts the size of frame to display the contents of its buffer exactly. frame can be any live frame and defaults to the selected one. Fitting is done only if frame’s root window is live. The arguments max-height, min-height, max-width and min-width specify bounds on the new total size of frame’s root window. min-height and min-width default to the values of `window-min-height` and `window-min-width` respectively.

  If the optional argument only is `vertically`, this function may resize the frame vertically only. If only is `horizontally`, it may resize the frame horizontally only.

The behavior of `fit-frame-to-buffer` can be controlled with the help of the two options listed next.

User Option: fit-frame-to-buffer-margins

  This option can be used to specify margins around frames to be fit by `fit-frame-to-buffer`. Such margins can be useful to avoid, for example, that such frames overlap the taskbar.

  It specifies the numbers of pixels to be left free on the left, above, the right, and below a frame that shall be fit. The default specifies `nil` for each which means to use no margins. The value specified here can be overridden for a specific frame by that frame’s `fit-frame-to-buffer-margins` parameter, if present.

User Option: fit-frame-to-buffer-sizes

  This option specifies size boundaries for `fit-frame-to-buffer`. It specifies the total maximum and minimum lines and maximum and minimum columns of the root window of any frame that shall be fit to its buffer. If any of these values is non-`nil`, it overrides the corresponding argument of `fit-frame-to-buffer`.

Command: shrink-window-if-larger-than-buffer &optional window

  This command attempts to reduce window’s height as much as possible while still showing its full buffer, but no less than `window-min-height` lines. The return value is non-`nil` if the window was resized, and `nil` otherwise. If window is omitted or `nil`, it defaults to the selected window. Otherwise, it should be a live window.

  This command does nothing if the window is already too short to display all of its buffer, or if any of the buffer is scrolled off-screen, or if the window is the only live window in its frame.

  This command calls `fit-window-to-buffer` (see above) to do its work.

Command: balance-windows &optional window-or-frame

  This function balances windows in a way that gives more space to full-width and/or full-height windows. If window-or-frame specifies a frame, it balances all windows on that frame. If window-or-frame specifies a window, it balances only that window and its siblings (see Windows and Frames).

Command: balance-windows-area

  This function attempts to give all windows on the selected frame approximately the same share of the screen area. Full-width or full-height windows are not given more space than other windows.

Command: maximize-window &optional window

  This function attempts to make window as large as possible, in both dimensions, without resizing its frame or deleting other windows. If window is omitted or `nil`, it defaults to the selected window.

Command: minimize-window &optional window

  This function attempts to make window as small as possible, in both dimensions, without deleting it or resizing its frame. If window is omitted or `nil`, it defaults to the selected window.

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