40. Folding Extensions for Outline-Mode

This file provides folding editor extensions for outline-mode and outline-minor-mode buffers. What’s a "folding editor"? Read on...

Imagine you’re in an outline-mode buffer and you’ve hidden all the text and subheadings under your level-1 headings. You now want to look at the stuff hidden under one of these headings. Normally you’d do C-c C-e (show-entry) to expose the body or C-c C-i to expose the child (level-2) headings.

With foldout, you do C-c C-z (foldout-zoom-subtree). This exposes the body and child subheadings and narrows the buffer so that only the level-1 heading, the body and the level-2 headings are visible. If you now want to look under one of the level-2 headings, position the cursor on it and do C-c C-z again. This exposes the level-2 body and its level-3 child subheadings and narrows the buffer again. You can keep on zooming in on successive subheadings as much as you like. A string in the modeline tells you how deep you’ve gone.

When zooming in on a heading you might only want to see the child subheadings. You do this by specifying a numeric argument: C-u C-c C-z. You can specify the number of levels of children too (c.f. show-children): e.g. M-2 C-c C-z exposes two levels of child subheadings. Alternatively, you might only be interested in the body. You do this by specifying a negative argument: M-- C-c C-z. You can also cause the whole subtree to be expanded, similar to C-c C-s (show-subtree), by specifying a zero argument: M-0 C-c C-z.

While you’re zoomed in you can still use outline-mode’s exposure and hiding functions. It won’t upset foldout at all. Also, since the buffer is narrowed, "global" editing actions will only affect the stuff under the zoomed-in heading. This is useful for restricting changes to a particular chapter or section of your document.

You unzoom (exit) a fold by doing C-c C-x (foldout-exit-fold). This hides all the text and subheadings under the top-level heading and returns you to the previous view of the buffer. Specifying a numeric argument exits that many folds. Specifying a zero argument exits *all* folds.

You might want to exit a fold *without* hiding the text and subheadings. You do this by specifying a negative argument. For example, M--2 C-c C-x exits two folds and leaves the text and subheadings exposed.

Foldout also provides mouse bindings for entering and exiting folds and for showing and hiding text. Hold down Meta and Control, then click a mouse button as follows:-

• mouse-1 (foldout-mouse-zoom) zooms in on the heading clicked on:
  • - single click – expose body
  • - double click – expose subheadings
  • - triple click – expose body and subheadings
  • - quad click – expose entire subtree
• mouse-2 (foldout-mouse-show) exposes text under the heading clicked on:
  • - single click – expose body
  • - double click – expose subheadings
  • - triple click – expose body and subheadings
  • - quad click – expose entire subtree
• mouse-3 (foldout-mouse-hide-or-exit) hides text under the heading clicked on or exits the fold:
  • - single click – hide subtree
  • - double click – exit fold and hide text
  • - triple click – exit fold without hiding text
  • - quad click – exit all folds and hide text

You can change the modifier keys used by setting foldout-mouse-modifiers.

To use foldout, put this in your initialization file:

  (require 'foldout)

If you don’t want it loaded until you need it, try this instead:

  (eval-after-load "outline" '(require 'foldout))

This document was generated by Aidan Kehoe on December 27, 2016 using texi2html 1.82.