Folding

Remarks#

Folding causes multiple lines of text to be collapsed and displayed as a single line. It is useful for hiding portions of a document considered unimportant for the current task. Folding is purely a visual change to the document: the folded lines are still present, unchanged.

A fold is persistent. Once created, a fold can be opened and closed without needing to re-create it. When closed, folds can be moved over or yanked and put as if they were a single line, even though the underlying operation will operate on all of the text underneath the fold

Configuring the Fold Method

:set foldmethod={method} sets the fold method for the current window. This determines how folds are manipulated within that window. Valid options for “method” are:

• manual (folds are manually created and destroyed by the user)
• indent (folds are created for lines of equal indentation)
• marker (substring markers are used to indicate the beginning and end of a fold)
• syntax (syntax highlighting items define folds)
• expr (a Vimscript expression is evaluated per line to define its fold level)
• diff (text change isn’t changed in a diff view is folded)

The default is manual.

Creating a Fold Manually

• zf{motion} creates a fold that covers the text that “motion” would cover.
• {count}zF creates a fold that covers “count” lines.
• {range}fo[ld] creates a fold for the lines in the provided range.

All three commands are valid only when foldmethod is set to manual or marker. In the case of the former fold method, the newly-created folds are closed immediately.

Opening, Closing and Toggling Folds

• zo opens a fold underneath the cursor.
• zO opens all folds underneath the cursor, recursively.
• zc closes a fold underneath the cursor.
• zC closes all folds underneath the cursor, recursively.
• za toggles a fold under the cursor (a closed fold is opened, an opened fold is closed).
• zM closes all folds in the buffer.
• zR opens all folds in the buffer.
• zm closes a level of fold in the buffer.
• zr opens a level of fold in the buffer.

Showing the Line Containing the Cursor

zv will ensure the line containing the cursor is not folded. The minimum number of folds required to expose the cursor line will be opened.

Folding C blocks

This is our buffer:

void write_buffer(size_t size, char ** buffer)
{
    char * buf = *buffer;
    size_t iter;
    for(iter = 0; iter < size; iter++)
    {
        putc(*(buf + iter));
    }
}

The cursor is at [1][1] ([line][col]). Move the cursor to the curl bracket of the for loop:
/for<Enter>j cursor is [6][2].

Now enter zf% (create folding, move to matching bracket). You have successfully create the first folding.

Now enter :2<Enter>_, the cursor is now at [2][1] and zf%: the complete function body is folded.

You are able to open all foldings you just created using zO and re-close them using zC.