Purpose

Note: a full explanation can be found in the GitHub wiki.

Introduction

Purpose ("window-purpose" on MELPA) provides a new window management system for Emacs, which gives you a better control over where Emacs displays buffers.

With Purpose, each buffer has a configurable "purpose" and each window can interactively be dedicated to a certain "purpose". When you dedicate a window (C-c , d), Purpose makes sure that this window will be used only for buffers which have the same purpose as the buffer that is currently displayed in that window. The purpose of a buffer can be customized via the variables purpose-user-mode-purposes, purpose-user-name-purposes, purpose-user-regexp-purposes and purpose-use-default-configuration (see the wiki).

Supported Emacs Versions

Purpose is tested with Emacs versions 24.3, 24.4 and 24.5. Backward-compatibility for earlier versions might be added in the future - if you want such support, contact me.

Quickstart

Activate Purpose

Manually: M-x purpose-mode

In your init file:

(require 'window-purpose)
(purpose-mode)

Configure Purpose

Manually: M-x customize-group purpose. Look at:

• "Purpose User Mode Purposes": recognize purpose according to major mode
• "Purpose User Name Purposes": recognize purpose according to buffer name (for exact names)
• "Purpose User Regexp Purposes": recognize purpose according to buffer name (for name patterns)
• "Purpose Use Default Configuration": toggle default configuration on/off

In init file:

(add-to-list 'purpose-user-mode-purposes '(<major-mode> . <purpose>))
(add-to-list 'purpose-user-name-purposes '(<name> . <purpose>))
(add-to-list 'purpose-user-regexp-purposes '(<pattern> . <purpose>))
(setq purpose-use-default-configuration t) ; not really necessary, default is t
(purpose-compile-user-configuration) ; activates your changes

Useful Commands

Key	Command
C-c , b	purpose-switch-buffer-with-purpose: switch to a buffer with the same purpose as the current one
C-u C-x b	switch-buffer-without-purpose: switch to a buffer, but don't use Purpose for it. Handy for changing the current layout.
C-c , d	purpose-toggle-window-purpose-dedicated
C-c , D	purpose-toggle-window-buffer-dedicated
C-c , 1	purpose-delete-non-dedicated-windows
	purpose-save-window-layout: save current layout (by name)
	purpose-load-window-layout: load layout (by name)
	purpose-save-window-layout-file: save current layout directly to file
	purpose-load-window-layout-file: load layout directly from file
	purpose-reset-window-layout: reload previously loaded layout

Example: Simple Python Layout

How to get a simple and persistent layout for coding in Python that looks like this:

step 1: configuration

(add-to-list 'purpose-user-mode-purposes '(python-mode . py))
(add-to-list 'purpose-user-mode-purposes '(inferior-python-mode . py-repl))
(purpose-compile-user-configuration)

step 2: change window layout

If you have a previously saved layout, you can load it with purpose-load-window-layout and skip step 2 and step 3.

1. open a Python file
2. C-c , d (purpose-toggle-window-purpose-dedicated) so window is dedicated ("[py]" in the status bar will change to "[py!]")
3. C-x 1 (delete-other-windows)
4. C-x 2 (split-window-below)
5. C-c C-z (python-shell-switch-to-shell)
6. C-c , d so window is dedicated
7. C-x o (other-window) to select the python file's window
8. C-x ^ (enlarge-window) until you like the sizes of the windows

step 3: save window layout

M-x purpose-save-window-layout

Using Purpose

Dedicating windows

Dedicating a window limits which buffers will be displayed in it. There are two types of window dedication: buffer-dedication and purpose-dedication.

Use purpose-toggle-window-buffer-dedicated to dedicate a window to its buffer. This window will not display any other buffer while it is buffer-dedicated. A "#" in the mode-line next to the window's purpose indicates that the window is buffer-dedicated.

Use purpose-toggle-window-purpose-dedicated to dedicate a window to its purpose. This window will only display buffers with the same purpose. A "!" in the mode-line next to the window's purpose indicates that the window is purpose-dedicated.

You can delete all non-dedicated windows by using purpose-delete-non-dedicated-windows.

Switching buffers

When switching buffers, Purpose will display the new buffer in the correct window, according to the current configuration.

Use switch-to-buffer to switch to any buffer. The buffer will be displayed according to the current purpose-configuration.

Use purpose-switch-buffer-with-purpose to switch to another buffer with the same purpose as the current buffer.

Use purpose-switch-buffer-with-some-purpose to select a purpose and then switch to a buffer with that purpose.

Use switch-buffer-without-purpose to switch to any buffer. The buffer will be displayed using Emacs' original behavior. This is useful when you want to change the window layout.

Use purpose-set-window-purpose to switch the purpose of the current window. If there is a buffer with the chosen purpose, that buffer will be displayed in the current window. Otherwise, a dummy buffer will be created and used.

Changing layout

Purpose lets you save, load and reset the window layout.

Use purpose-save-window-layout to save the current window layout. The layout will be saved in a directory of your choice, in a file named <layout-name>.window-layout.

Use purpose-load-window-layout to load a window layout. The available layouts are located the directories specified in customizable variable purpose-layout-dirs.

Use purpose-save-window-layout-file to save the current window layout directly to a file of your choice.

Use purpose-load-window-layout-file to load a window layout directly from a file of your choice.

Use purpose-reset-window-layout to reset the window layout to the latest layout that you loaded.

In addition to window layouts, Purpose also lets save, load and reset the frame layout. A "frame layout" consists of the window layouts of multiple frames. All of the window layout commands have frame layout equivalents, e.g. purpose-load-frame-layout is equivalent to purpose-load-window-layout.

Customizing Purpose

Prompts

In the past, the variable purpose-preferred-prompt, allowed you to choose whether you want Purpose to use IDO or Helm when it needs information from the user. This variable has been removed. Instead, the prompt relies on the normal mechanism. For Helm prompts enable helm-mode, for Ivy mode enable ivy-mode, for IDO prompts enable ido-mode, etc. If using ido-mode, note that because how IDO works it doesn't cover all commands, and some commands won't have an IDO prompt. To work around that, please see the package ido-completion-read+ (formerly ido-ubiquitous).

Changing purpose configuration

Purpose lets you define your own purposes. You can do so by using the variables purpose-user-mode-purposes, purpose-user-name-purposes and purpose-user-regexp-purposes. You can also deactivate the default purpose configuration if it bothers you, by setting purpose-use-default-configuration to nil.

Changing display rules

If you want, you can the rules of how certain buffers are displayed. To do so, use the variable purpose-special-action-sequences. Let's explain this with an example. The following code makes all help buffers appear in a separate frame. This means you will get a "popup" frame for help buffers.

(setq pop-up-frames t) ; allows emacs to popup new frames
;; give help buffers the 'popup-frame purpose
(add-to-list 'purpose-user-mode-purposes
             '(help-mode . popup-frame))
(purpose-compile-user-configuration)
;; new rules for buffers with the 'popup-frame purpose
(add-to-list 'purpose-special-action-sequences
             '(popup-frame
               purpose-display-reuse-window-buffer
               purpose-display-reuse-window-purpose
               purpose-display-pop-up-frame))

Respect purposes when killing a buffer

When killing a visible buffer, Emacs has to decide which buffer to show instead. Enabling the purpose-x-kill extension will make Emacs consider the purpose of the window that needs to show a new buffer. If the window is purpose-dedicated, the killed buffer is replaced with another buffer with the same purpose. If there are no buffers with the same purpose as the killed buffer, the window is deleted. To enable the purpose-x-kill extension:

(require 'window-purpose-x)
(purpose-x-kill-setup)

Location of Layout Files

Window layout and frame layout files are stored in the directories specified by purpose-layout-dirs. By default, its value is ("~/.emacs.d/layouts/"). To store layouts in a different location, simply change the value of this variable.

Using Purpose with other packages

See Integration With Other Packages for information about how some packages relate to Purpose.