*fold.txt*      For Vim version 6.0m.  Last change: 2000 Aug 21


		  VIM REFERENCE MANUAL    by Bram Moolenaar


Folding						*Folding* *folding*

First read the User manual on folding: |usr_28.txt|

1. Fold methods		|fold-methods|
2. Fold commands	|fold-commands|
3. Fold options		|fold-options|
4. Behavior of folds	|fold-behavior|

{Vi has no Folding}
{not available when compiled without the +folding feature}

==============================================================================
1. Fold methods					*fold-methods*

The folding method can be set with the 'foldmethod' option.

When setting 'foldmethod' to a value other than "manual", all folds are
deleted and new ones created.  Switching to the "manual" method doesn't remove
the existing folds.  This can be used to first define the folds automatically
and then change them manually.

There are five methods to select folds:

"manual":					*fold-manual*
Use commands to manually define the fold regions.  This can also be used by a
script that parses text to find folds.

The level of a fold is only defined by its nesting.  To increase the fold
level of a fold for a range of lines, define a fold inside it that has the
same lines.


"indent":					*fold-indent*
The folds are automatically defined by the indent of the lines.

The foldlevel is computed from the indent of the line, divided by the
'shiftwidth' (rounded down).  A sequence of lines with the same or higher fold
level form a fold, with the lines with a higher level forming a nested fold.

Some lines are ignored and get the fold level of the line above or below it,
whatever is the lowest.  These are empty or white lines and lines starting
with a character in 'foldignore'.  White space is skipped before checking for
characters in 'foldignore'.  For C use "#" to ignore preprocessor lines.

When you want to ignore lines in another way, use the 'expr' method.  The
|indent()| function can be used in 'foldexpr' to get the indent of a line.


"expr":						*fold-expr*
The folds are automatically defined by their foldlevel, like with the "indent"
method.  The value of the 'foldexpr' option is evaluated to get the foldlevel
of a line.  Examples:
This will create a fold for all consecutive lines that start with a Tab: >
	:set foldexpr=getline(v:lnum)[0]==\"\\t\"
This will call a function to compute the fold level: >
	:set foldexpr=MyFoldLevel(v:lnum)
This will make a fold out of paragraphs separated by blank lines: >
	:set foldexpr=getline(v:lnum)=~'^\\s*$'&&getline(v:lnum+1)=~'\\S'?'<1':1
this does the same: >
	:set foldexpr=getline(v:lnum-1)=~'^\\s*$'&&getline(v:lnum)=~'\\S'?'>1':1

Note that backslashes must be used to escape characters that ":set" handles
differently (space, backslash, double quote, etc., see |option-backslash|).
Alternatively, use ":set foldexpr@{expression}" |:set@|.

These are the conditions with which the expression is evaluated:
- The current buffer and window are set for the line.
- The variable "v:lnum" is set to the line number.
- The result is used for the fold level in this way:
  value			meaning ~
  0  			the line is not in a fold
  1, 2, ..		the line is in a fold with this level
  -1			the fold level is undefined, use the fold level of a
			line before or after this line, whichever is the
			lowest.
  "="			use fold level from previous line
  "a1", "a2", ..	add one, two, .. to the fold level
  "s1", "s2", ..	subtract one, two, .. from the fold level for the line
  "<1", "<2", ..	a fold with this level ends at this line
  ">1", ">2", ..	a fold with this level starts at this line

It is not required to mark the start (end) of a fold with ">1" ("<1"), a fold
will also start (end) when the fold level is higher (lower) than the fold
level of the previous line.

There must be no side effects from the expression.  The text in the buffer,
cursor position, the search patterns, options etc. must not be changed.

If there is some error in the expression, or the resulting value isn't
recognized, there is no error message and the fold level will be zero.

Note: Since the expression has to be evaluated for every line, this fold
method can be very slow!


"syntax":					*fold-syntax*
A fold is defined by syntax items that have the "fold" argument. |:syn-fold|

The fold level is defined by nesting folds.


"marker":					*fold-marker*
Markers in the text tell where folds start and end.  This allows you to
precisely specify the folds.  This will allow deleting and putting a fold,
without the risk of including the wrong lines.  The 'foldtext' option is
normally set such that the text before the marker shows up in the folded line.
This makes it possible to give a name to the fold.

Markers can have a level included, or can use matching pairs.  Including a
level is easier, you don't have to add end markers and avoid problems with
non-matching marker pairs.  Example: >
	/* global variables {{{1 */
	int varA, varB;

	/* functions {{{1 */
	/* funcA() {{{2 */
	void funcA() {}

	/* funcB() {{{2 */
	void funcB() {}

A fold starts at a "{{{" marker.  The following number specifies the fold
level.  What happens depends on the difference between the current fold level
and the level given by the marker:
1. If a marker with the same fold level is encountered, the previous fold
   ends and another fold with the same level starts.
2. If a marker with a higher fold level is found, a nested fold is started.
3. if a marker with a lower fold level is found, all folds up to and including
   this level end and a fold with the specified level starts.

The number indicates the fold level.  A zero cannot be used.
You can use "}}}" with a digit to indicate the level of the fold that
ends.  The fold level of the following line will be one less than the
indicated level.  Note that Vim doesn't look back to the level of the matching
marker (that would take too much time).  Example: >

	{{{1
	fold level here is 1
	{{{3
	fold level here is 3
	}}}3
	fold level here is 2

You can also use matching pairs of "{{{" and "}}}" markers to define folds.
Each "{{{" increases the fold level by one, each "}}}" decreases the fold
level by one.  Be careful to keep the markers matching!  Example: >

	{{{
	fold level here is 1
	{{{
	fold level here is 2
	}}}
	fold level here is 1

You can mix using markers with a number and without a number.  A useful way of
doing this is to use numbered markers for large folds, and unnumbered markers
locally in a function.  For example use level one folds for the sections of
your file like "structure definitions", "local variables" and "functions".
Use level 2 markers for each definition and function,  Use unnumbered markers
inside functions.  When you make changes in a function to split up folds, you
don't have to renumber the markers.

The markers can be set with the 'foldmarker' option.  It is recommended to
keep this at the default value of "{{{,}}}", so that files can be exchanged
between Vim users.  Only change it when it is required for the language of the
file.

==============================================================================
2. Fold commands				*fold-commands*

All folding commands start with "z".  Hint: the "z" looks like a folded piece
of paper, seen from the side.

							*zf*
zf{motion}  or
{Visual}zf	Operator to create a fold.
		This only works when 'foldmethod' is "manual".
		The new fold will be closed.
		'foldenable' will be set.

							*:fold* *:fo*
:{range}fo[ld]
		Create a fold for the lines in {range}.  Works like "zf".

							*zd*
zd		Delete a fold at the cursor, and all nested folds in it.
		When the cursor is on folded line, that fold is deleted.
		This only works when 'foldmethod' is "manual".

							*zD*
zD		Delete all folds in the window.
		This only works when 'foldmethod' is "manual".

							*zo*
zo		Open one fold under the cursor.
		'foldenable' will be set.

							*zO*
zO		Open all folds under the cursor recursively.
		'foldenable' will be set.

							*zc*
zc		Close one fold under the cursor.

							*zC*
zC		Close all folds under the cursor recursively.

							*za*
za		When on a closed fold: open it. When folds are nested, you
		might have to use "za" several times.
		When on an open fold: close it.  This will only close one
		level, since using "za" again will open the fold.

							*zA*
zA		When on a closed fold: open it recursively.
		When on an open fold: close it recursively.

							*zm*
zm		Fold more: Subtract one from 'foldlevel'.  If 'foldlevel' was
		already zero nothing happens.

							*zM*
zM		Close all folds: set 'foldlevel' to 0.

							*zr*
zr		Reduce folding: Add one to 'foldlevel'.
		'foldenable' will be set.

							*zR*
zR		Open all folds.  This sets 'foldlevel' to highest fold level.
		'foldenable' will be set.

							*:foldo* *:foldopen*
:{range}foldo[pen]
		Open all folds in {range}.  Useful to see all the text in
		{range}.

							*zn*
zn		Fold none: reset 'foldenable'.  All folds will be open.

							*zN*
zN		Fold normal: set 'foldenable'.  All folds will be as they
		were before.

							*zi*
zi		Invert 'foldenable'.

==============================================================================
3. Fold options					*fold-options*

						*fold-foldlevel*
'foldlevel' is a number option: The higher the more folded regions are open.
When 'foldlevel' is 0, all folds are closed.
When 'foldlevel' is positive, some folds closed.
When 'foldlevel' is very high, all folds are open.
'foldlevel' is applied when it it changed.  After that manually folds can be
opened and closed.
When increased, folds above the new level are opened.  No manually opened
folds will be closed.
When decreased, folds above the new level are closed.  No manually closed
folds will be opened.

						*fold-foldtext*
'foldtext' is a string option of the form: /{pattern}/{replacement}
It is used to set the text which is shown for a closed fold.

The first character is used as a separator between the {pattern} and the
{replacement}.  It can be any character, but it must not appear anywhere in
the {pattern} or {replacement}.

The {pattern} is matched on the first line of closed fold.  Items matched with
it can be used in the {replacement} to give information about what the fold
contains.  The {pattern} can contain a multi-line pattern, so that text from
further down in the fold can be shown.  But be careful not to include lines
from below the fold!

Two special items in the {replacement} are recognized:
\f  is replaced by the number of lines in the fold
\d  is replaced by a string of dashes.  The number of dashes is the level of
    the fold.

The resulting line is truncated to fit in the window, it never wraps.
When there is room after the text, it is filled with the character specified
by 'fillchars'.

Example: >
	:set foldtext=/\\(\\S.*\\)/+\\d\ \\f\ lines:\ \\1/
This will show a line like this:
	+- 5 lines: foobar
Note that backslashes need to be used for characters that the ":set" command
handles differently: Space, backslash and double-quote. |option-backslash|


Other options for folding:
'foldcolumn' 'fdc':	When set, show a small column on the left of the
			window to indicate folds.
'foldenable' 'fen':	Open all folds while set.
'foldexpr'   'fde':	Expression used for "expr" folding.
'foldignore' 'fdi':	Characters used for "indent" folding.
'foldmarker' 'fmr':	Defined markers used for "marker" folding.
'foldmethod' 'fdm':	Name of the current folding method.

==============================================================================
4. Behavior of folds					*fold-behavior*

When moving the cursor downwards, it will move to the first line of a sequence
of folded lines.  When the cursor is already on a folded line, it moves to the
next unfolded line.

When moving the cursor upwards, it will move to the last line of a sequence of
folded lines.  When the cursor is already on a folded line, it moves to the
previous unfolded line.

While the cursor is on a folded lines, the cursor is always displayed in the
first column.  The ruler does show the actual cursor position, but since the
line is folded, it cannot be displayed there.

Movement commands handle a sequence of folded lines like an empty line.  For
example, the "w" command stops once in the first column.

When in Insert mode, the cursor line is never folded.  That allows you to see
what you type!

==============================================================================
 vim:tw=78:
