Folding This is the one function whose name is confusing because many products use the term for what we called “collapsing” above. For this article, collapsing is the process of making whole headers and paragraphs invisible, tucking them up under a “parent.” Folding is a different kind of tucking under; it works on paragraphs and blocks to reduce them to a single line, hiding the rest. A simple case of folding might involve a long paragraph that is reduced to just the first line—plus some indication that it is folded; this shows that a paragraph is there and something about its content without showing the whole thing. Folding is most common in single-pane outline displays, and a common use is to fold everything so that every header and paragraph is reduced to a single line. This can show the overall structure of a huge document, including paragraph leaves in a single view. You can use folding and collapsing independently. At one time, folding was one of the basics of text editors, but it has faded somewhat. Now only about half of the full-featured editors employ folding. One of the most interesting of these is jEdit. It has a very strong implementation of folding, so strong in fact it subsumes outlining. Though intended as a full editor, it can easily be used as an outliner front end to TeX-based systems. jEdit is shown in the example screenshot in both modes. The view on the right shows an outline folded like MORE and NoteBook do it, where the folds correspond to the outline structure. But see on the left we have shifted to “explicit folding” mode where blocks are marked with triple brackets. Then these entire blocks can be folded independent of the outline. Alas, folding is one area where the Mac is weak, but NoteBook has an implementation that is handy. It is like MORE’s was, and is bound to the outline structure, meaning you can only fold headers, not arbitrary blocks. But it has a nice touch: just entering a folded header temporarily expands it.