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diff --git a/runtime/doc/usr_28.txt b/runtime/doc/usr_28.txt new file mode 100644 index 0000000..9e18c5c --- /dev/null +++ b/runtime/doc/usr_28.txt @@ -0,0 +1,426 @@ +*usr_28.txt* For Vim version 8.1. Last change: 2008 Jun 14 + + VIM USER MANUAL - by Bram Moolenaar + + Folding + + +Structured text can be separated in sections. And sections in sub-sections. +Folding allows you to display a section as one line, providing an overview. +This chapter explains the different ways this can be done. + +|28.1| What is folding? +|28.2| Manual folding +|28.3| Working with folds +|28.4| Saving and restoring folds +|28.5| Folding by indent +|28.6| Folding with markers +|28.7| Folding by syntax +|28.8| Folding by expression +|28.9| Folding unchanged lines +|28.10| Which fold method to use? + + Next chapter: |usr_29.txt| Moving through programs + Previous chapter: |usr_27.txt| Search commands and patterns +Table of contents: |usr_toc.txt| + +============================================================================== +*28.1* What is folding? + +Folding is used to show a range of lines in the buffer as a single line on the +screen. Like a piece of paper which is folded to make it shorter: + + +------------------------+ + | line 1 | + | line 2 | + | line 3 | + |_______________________ | + \ \ + \________________________\ + / folded lines / + /________________________/ + | line 12 | + | line 13 | + | line 14 | + +------------------------+ + +The text is still in the buffer, unchanged. Only the way lines are displayed +is affected by folding. + +The advantage of folding is that you can get a better overview of the +structure of text, by folding lines of a section and replacing it with a line +that indicates that there is a section. + +============================================================================== +*28.2* Manual folding + +Try it out: Position the cursor in a paragraph and type: > + + zfap + +You will see that the paragraph is replaced by a highlighted line. You have +created a fold. |zf| is an operator and |ap| a text object selection. You +can use the |zf| operator with any movement command to create a fold for the +text that it moved over. |zf| also works in Visual mode. + +To view the text again, open the fold by typing: > + + zo + +And you can close the fold again with: > + + zc + +All the folding commands start with "z". With some fantasy, this looks like a +folded piece of paper, seen from the side. The letter after the "z" has a +mnemonic meaning to make it easier to remember the commands: + + zf F-old creation + zo O-pen a fold + zc C-lose a fold + +Folds can be nested: A region of text that contains folds can be folded +again. For example, you can fold each paragraph in this section, and then +fold all the sections in this chapter. Try it out. You will notice that +opening the fold for the whole chapter will restore the nested folds as they +were, some may be open and some may be closed. + +Suppose you have created several folds, and now want to view all the text. +You could go to each fold and type "zo". To do this faster, use this command: > + + zr + +This will R-educe the folding. The opposite is: > + + zm + +This folds M-ore. You can repeat "zr" and "zm" to open and close nested folds +of several levels. + +If you have nested several levels deep, you can open all of them with: > + + zR + +This R-educes folds until there are none left. And you can close all folds +with: > + + zM + +This folds M-ore and M-ore. + +You can quickly disable the folding with the |zn| command. Then |zN| brings +back the folding as it was. |zi| toggles between the two. This is a useful +way of working: +- create folds to get overview on your file +- move around to where you want to do your work +- do |zi| to look at the text and edit it +- do |zi| again to go back to moving around + +More about manual folding in the reference manual: |fold-manual| + +============================================================================== +*28.3* Working with folds + +When some folds are closed, movement commands like "j" and "k" move over a +fold like it was a single, empty line. This allows you to quickly move around +over folded text. + +You can yank, delete and put folds as if it was a single line. This is very +useful if you want to reorder functions in a program. First make sure that +each fold contains a whole function (or a bit less) by selecting the right +'foldmethod'. Then delete the function with "dd", move the cursor and put it +with "p". If some lines of the function are above or below the fold, you can +use Visual selection: +- put the cursor on the first line to be moved +- hit "V" to start Visual mode +- put the cursor on the last line to be moved +- hit "d" to delete the selected lines. +- move the cursor to the new position and "p"ut the lines there. + +It is sometimes difficult to see or remember where a fold is located, thus +where a |zo| command would actually work. To see the defined folds: > + + :set foldcolumn=4 + +This will show a small column on the left of the window to indicate folds. +A "+" is shown for a closed fold. A "-" is shown at the start of each open +fold and "|" at following lines of the fold. + +You can use the mouse to open a fold by clicking on the "+" in the foldcolumn. +Clicking on the "-" or a "|" below it will close an open fold. + +To open all folds at the cursor line use |zO|. +To close all folds at the cursor line use |zC|. +To delete a fold at the cursor line use |zd|. +To delete all folds at the cursor line use |zD|. + +When in Insert mode, the fold at the cursor line is never closed. That allows +you to see what you type! + +Folds are opened automatically when jumping around or moving the cursor left +or right. For example, the "0" command opens the fold under the cursor +(if 'foldopen' contains "hor", which is the default). The 'foldopen' option +can be changed to open folds for specific commands. If you want the line +under the cursor always to be open, do this: > + + :set foldopen=all + +Warning: You won't be able to move onto a closed fold then. You might want to +use this only temporarily and then set it back to the default: > + + :set foldopen& + +You can make folds close automatically when you move out of it: > + + :set foldclose=all + +This will re-apply 'foldlevel' to all folds that don't contain the cursor. +You have to try it out if you like how this feels. Use |zm| to fold more and +|zr| to fold less (reduce folds). + +The folding is local to the window. This allows you to open two windows on +the same buffer, one with folds and one without folds. Or one with all folds +closed and one with all folds open. + +============================================================================== +*28.4* Saving and restoring folds + +When you abandon a file (starting to edit another one), the state of the folds +is lost. If you come back to the same file later, all manually opened and +closed folds are back to their default. When folds have been created +manually, all folds are gone! To save the folds use the |:mkview| command: > + + :mkview + +This will store the settings and other things that influence the view on the +file. You can change what is stored with the 'viewoptions' option. +When you come back to the same file later, you can load the view again: > + + :loadview + +You can store up to ten views on one file. For example, to save the current +setup as the third view and load the second view: > + + :mkview 3 + :loadview 2 + +Note that when you insert or delete lines the views might become invalid. +Also check out the 'viewdir' option, which specifies where the views are +stored. You might want to delete old views now and then. + +============================================================================== +*28.5* Folding by indent + +Defining folds with |zf| is a lot of work. If your text is structured by +giving lower level items a larger indent, you can use the indent folding +method. This will create folds for every sequence of lines with the same +indent. Lines with a larger indent will become nested folds. This works well +with many programming languages. + +Try this by setting the 'foldmethod' option: > + + :set foldmethod=indent + +Then you can use the |zm| and |zr| commands to fold more and reduce folding. +It's easy to see on this example text: + +This line is not indented + This line is indented once + This line is indented twice + This line is indented twice + This line is indented once +This line is not indented + This line is indented once + This line is indented once + +Note that the relation between the amount of indent and the fold depth depends +on the 'shiftwidth' option. Each 'shiftwidth' worth of indent adds one to the +depth of the fold. This is called a fold level. + +When you use the |zr| and |zm| commands you actually increase or decrease the +'foldlevel' option. You could also set it directly: > + + :set foldlevel=3 + +This means that all folds with three times a 'shiftwidth' indent or more will +be closed. The lower the foldlevel, the more folds will be closed. When +'foldlevel' is zero, all folds are closed. |zM| does set 'foldlevel' to zero. +The opposite command |zR| sets 'foldlevel' to the deepest fold level that is +present in the file. + +Thus there are two ways to open and close the folds: +(A) By setting the fold level. + This gives a very quick way of "zooming out" to view the structure of the + text, move the cursor, and "zoom in" on the text again. + +(B) By using |zo| and |zc| commands to open or close specific folds. + This allows opening only those folds that you want to be open, while other + folds remain closed. + +This can be combined: You can first close most folds by using |zm| a few times +and then open a specific fold with |zo|. Or open all folds with |zR| and +then close specific folds with |zc|. + +But you cannot manually define folds when 'foldmethod' is "indent", as that +would conflict with the relation between the indent and the fold level. + +More about folding by indent in the reference manual: |fold-indent| + +============================================================================== +*28.6* Folding with markers + +Markers in the text are used to specify the start and end of a fold region. +This gives precise control over which lines are included in a fold. The +disadvantage is that the text needs to be modified. + +Try it: > + + :set foldmethod=marker + +Example text, as it could appear in a C program: + + /* foobar () {{{ */ + int foobar() + { + /* return a value {{{ */ + return 42; + /* }}} */ + } + /* }}} */ + +Notice that the folded line will display the text before the marker. This is +very useful to tell what the fold contains. + +It's quite annoying when the markers don't pair up correctly after moving some +lines around. This can be avoided by using numbered markers. Example: + + /* global variables {{{1 */ + int varA, varB; + + /* functions {{{1 */ + /* funcA() {{{2 */ + void funcA() {} + + /* funcB() {{{2 */ + void funcB() {} + /* }}}1 */ + +At every numbered marker a fold at the specified level begins. This will make +any fold at a higher level stop here. You can just use numbered start markers +to define all folds. Only when you want to explicitly stop a fold before +another starts you need to add an end marker. + +More about folding with markers in the reference manual: |fold-marker| + +============================================================================== +*28.7* Folding by syntax + +For each language Vim uses a different syntax file. This defines the colors +for various items in the file. If you are reading this in Vim, in a terminal +that supports colors, the colors you see are made with the "help" syntax file. + In the syntax files it is possible to add syntax items that have the "fold" +argument. These define a fold region. This requires writing a syntax file +and adding these items in it. That's not so easy to do. But once it's done, +all folding happens automatically. + Here we'll assume you are using an existing syntax file. Then there is +nothing more to explain. You can open and close folds as explained above. +The folds will be created and deleted automatically when you edit the file. + +More about folding by syntax in the reference manual: |fold-syntax| + +============================================================================== +*28.8* Folding by expression + +This is similar to folding by indent, but instead of using the indent of a +line a user function is called to compute the fold level of a line. You can +use this for text where something in the text indicates which lines belong +together. An example is an e-mail message where the quoted text is indicated +by a ">" before the line. To fold these quotes use this: > + + :set foldmethod=expr + :set foldexpr=strlen(substitute(substitute(getline(v:lnum),'\\s','',\"g\"),'[^>].*','','')) + +You can try it out on this text: + +> quoted text he wrote +> quoted text he wrote +> > double quoted text I wrote +> > double quoted text I wrote + +Explanation for the 'foldexpr' used in the example (inside out): + getline(v:lnum) gets the current line + substitute(...,'\\s','','g') removes all white space from the line + substitute(...,'[^>].*','','') removes everything after leading '>'s + strlen(...) counts the length of the string, which + is the number of '>'s found + +Note that a backslash must be inserted before every space, double quote and +backslash for the ":set" command. If this confuses you, do > + + :set foldexpr + +to check the actual resulting value. To correct a complicated expression, use +the command-line completion: > + + :set foldexpr=<Tab> + +Where <Tab> is a real Tab. Vim will fill in the previous value, which you can +then edit. + +When the expression gets more complicated you should put it in a function and +set 'foldexpr' to call that function. + +More about folding by expression in the reference manual: |fold-expr| + +============================================================================== +*28.9* Folding unchanged lines + +This is useful when you set the 'diff' option in the same window. The +|vimdiff| command does this for you. Example: > + + :setlocal diff foldmethod=diff scrollbind nowrap foldlevel=1 + +Do this in every window that shows a different version of the same file. You +will clearly see the differences between the files, while the text that didn't +change is folded. + +For more details see |fold-diff|. + +============================================================================== +*28.10* Which fold method to use? + +All these possibilities make you wonder which method you should choose. +Unfortunately, there is no golden rule. Here are some hints. + +If there is a syntax file with folding for the language you are editing, that +is probably the best choice. If there isn't one, you might try to write it. +This requires a good knowledge of search patterns. It's not easy, but when +it's working you will not have to define folds manually. + +Typing commands to manually fold regions can be used for unstructured text. +Then use the |:mkview| command to save and restore your folds. + +The marker method requires you to change the file. If you are sharing the +files with other people or you have to meet company standards, you might not +be allowed to add them. + The main advantage of markers is that you can put them exactly where you +want them. That avoids that a few lines are missed when you cut and paste +folds. And you can add a comment about what is contained in the fold. + +Folding by indent is something that works in many files, but not always very +well. Use it when you can't use one of the other methods. However, it is +very useful for outlining. Then you specifically use one 'shiftwidth' for +each nesting level. + +Folding with expressions can make folds in almost any structured text. It is +quite simple to specify, especially if the start and end of a fold can easily +be recognized. + If you use the "expr" method to define folds, but they are not exactly how +you want them, you could switch to the "manual" method. This will not remove +the defined folds. Then you can delete or add folds manually. + +============================================================================== + +Next chapter: |usr_29.txt| Moving through programs + +Copyright: see |manual-copyright| vim:tw=78:ts=8:noet:ft=help:norl: |