Automatic folds (that is, folds generated by a fold method different from manual), bog down VIM considerably in insert mode and are often reevaluated prematurely (for example, when inserting an opening fold marker whose closing counterpart has yet to be added to complete the fold.)

See http://vim.wikia.com/wiki/Keep_folds_closed_while_inserting_text for a discussion.

With this plug-in, the folds in the currently edited buffer are updated by an automatic fold method only

• when saving the buffer, or
• when closing or opening folds, or
• when typing zuz in normal mode

and are kept as is otherwise (by keeping the fold method set to manual). Each of these triggers for updating folds can be disabled by adding

• let g:fastfold_savehook = 0, or
• let g:fastfold_togglehook = 0 (which is the default), or
• let g:fastfold_map = 0

to the .vimrc file.

For example, by adding

set foldmethod=syntax

let g:tex_fold_enabled=1
let g:vimsyn_folding='af'
let g:xml_syntax_folding = 1
let g:php_folding = 1
let g:perl_fold = 1

to the .vimrc file and installing this plug-in, the folds in a TeX, Vim, XML, PHP or Perl file are updated by the syntax fold method when saving the buffer or typing zuz in normal mode and are kept as is otherwise.

==

• If you prefer that folds are only updated manually but not when saving the buffer, then add let g:fastfold_savehook = 0 to your .vimrc.

• If you prefer that folds are updated whenever you close or open folds by a standard keystroke such as zx,zo or zc, then add let g:fastfold_togglehook = 1 to your .vimrc.

  The exact list of these standard keystrokes is zx,zX,za,zA,zo,zO,zc,zC,zr,zR,zm,zM,zi,zn,zN and it can be customized by changing the global variable g:fastfold_mapsuffixes (that defaults to let g:fastfold_mapsuffixes = ['x','X','a','A','o','O','c','C','r','R','m','M','i','n','N']).

  A suggested setting is to add

  let g:fastfold_togglehook = 1
  let g:fastfold_mapsuffixes = ['x','X']
  

  to your .vimrc file.

• If you prefer that this plug-in does not add a normal mode mapping that updates folds (that defaults to zuz), then add let g:fastfold_map = 0 to your .vimrc.

  You can remap zuz to your favorite keystroke, say <F5>, by adding nmap <F5> <Plug>(FastFoldUpdate) to your .Vimrc.

  There is also a command FastFoldUpdate that updates all folds and its variant FastFoldUpdate! that updates all folds and echos by which fold method the folds were updated.

==

Note that this plug-in will overwrite your manual folds when saving the currently edited buffer, unless you either

• explicitly tell this plug-in to refrain from it via g:fastfold_skipfiles, a list of regular expressions against which the current file name is matched, or
• when entering the buffer the local and global foldmethod were equal to manual and

• since then the local and global foldmethod have remained equal to manual, or
• since then the buffer has not been saved (if let g:fastfold_savehook = 1) and no fold has been toggled (if let g:fastfold_savehook = 1) and zuz (if let g:fastfold_map = 1) has not been typed in normal mode.

===

FastFold.vim integrates with version 1.2 and above of the restore_view.vim plug-in that stores and restores the last folds by the :mkview and :loadview if restore_view.vim is loaded AFTER FastFold.vim. (To ensure the correct autocmd execution order.)

A recent fork of it is available at

http://www.github.com/Konfekt/restore_view

==

A CustomFoldText() function that displays the percentage of the number of buffer lines that the folded text takes up and indents folds according to their nesting level is available at

http://www.github.com/Konfekt/FoldText