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1 *usr_28.txt* For Vim version 7.1. Last change: 2006 Apr 24
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3 VIM USER MANUAL - by Bram Moolenaar
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4
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5 Folding
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6
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7
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8 Structured text can be separated in sections. And sections in sub-sections.
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9 Folding allows you to display a section as one line, providing an overview.
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10 This chapter explains the different ways this can be done.
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11
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12 |28.1| What is folding?
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13 |28.2| Manual folding
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14 |28.3| Working with folds
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15 |28.4| Saving and restoring folds
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16 |28.5| Folding by indent
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17 |28.6| Folding with markers
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18 |28.7| Folding by syntax
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19 |28.8| Folding by expression
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20 |28.9| Folding unchanged lines
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21 |28.10| Which fold method to use?
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22
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23 Next chapter: |usr_29.txt| Moving through programs
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24 Previous chapter: |usr_27.txt| Search commands and patterns
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25 Table of contents: |usr_toc.txt|
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26
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27 ==============================================================================
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28 *28.1* What is folding?
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29
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30 Folding is used to show a range of lines in the buffer as a single line on the
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31 screen. Like a piece of paper which is folded to make it shorter:
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32
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33 +------------------------+
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34 | line 1 |
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35 | line 2 |
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36 | line 3 |
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37 |_______________________ |
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38 \ \
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39 \________________________\
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40 / folded lines /
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41 /________________________/
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42 | line 12 |
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43 | line 13 |
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44 | line 14 |
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45 +------------------------+
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46
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47 The text is still in the buffer, unchanged. Only the way lines are displayed
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48 is affected by folding.
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49
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50 The advantage of folding is that you can get a better overview of the
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51 structure of text, by folding lines of a section and replacing it with a line
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52 that indicates that there is a section.
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53
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54 ==============================================================================
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55 *28.2* Manual folding
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56
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57 Try it out: Position the cursor in a paragraph and type: >
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58
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59 zfap
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60
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61 You will see that the paragraph is replaced by a highlighted line. You have
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62 created a fold. |zf| is an operator and |ap| a text object selection. You
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63 can use the |zf| operator with any movement command to create a fold for the
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64 text that it moved over. |zf| also works in Visual mode.
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65
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66 To view the text again, open the fold by typing: >
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67
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68 zo
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69
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70 And you can close the fold again with: >
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71
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72 zc
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73
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74 All the folding commands start with "z". With some fantasy, this looks like a
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75 folded piece of paper, seen from the side. The letter after the "z" has a
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76 mnemonic meaning to make it easier to remember the commands:
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77
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78 zf F-old creation
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79 zo O-pen a fold
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80 zc C-lose a fold
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81
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82 Folds can be nested: A region of text that contains folds can be folded
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83 again. For example, you can fold each paragraph in this section, and then
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84 fold all the sections in this chapter. Try it out. You will notice that
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85 opening the fold for the whole chapter will restore the nested folds as they
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86 were, some may be open and some may be closed.
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87
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88 Suppose you have created several folds, and now want to view all the text.
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89 You could go to each fold and type "zo". To do this faster, use this command: >
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90
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91 zr
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92
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93 This will R-educe the folding. The opposite is: >
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94
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95 zm
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96
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97 This folds M-ore. You can repeat "zr" and "zm" to open and close nested folds
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98 of several levels.
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99
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100 If you have nested several levels deep, you can open all of them with: >
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101
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102 zR
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103
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104 This R-educes folds until there are none left. And you can close all folds
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105 with: >
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106
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107 zM
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108
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109 This folds M-ore and M-ore.
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110
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111 You can quickly disable the folding with the |zn| command. Then |zN| brings
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112 back the folding as it was. |zi| toggles between the two. This is a useful
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113 way of working:
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114 - create folds to get overview on your file
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115 - move around to where you want to do your work
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116 - do |zi| to look at the text and edit it
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117 - do |zi| again to go back to moving around
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118
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119 More about manual folding in the reference manual: |fold-manual|
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120
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121 ==============================================================================
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122 *28.3* Working with folds
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123
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124 When some folds are closed, movement commands like "j" and "k" move over a
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125 fold like it was a single, empty line. This allows you to quickly move around
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126 over folded text.
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127
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128 You can yank, delete and put folds as if it was a single line. This is very
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129 useful if you want to reorder functions in a program. First make sure that
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130 each fold contains a whole function (or a bit less) by selecting the right
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131 'foldmethod'. Then delete the function with "dd", move the cursor and put it
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132 with "p". If some lines of the function are above or below the fold, you can
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133 use Visual selection:
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134 - put the cursor on the first line to be moved
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135 - hit "V" to start Visual mode
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136 - put the cursor on the last line to be moved
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137 - hit "d" to delete the selected lines.
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138 - move the cursor to the new position and "p"ut the lines there.
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139
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140 It is sometimes difficult to see or remember where a fold is located, thus
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141 where a |zo| command would actually work. To see the defined folds: >
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142
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143 :set foldcolumn=4
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144
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145 This will show a small column on the left of the window to indicate folds.
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146 A "+" is shown for a closed fold. A "-" is shown at the start of each open
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147 fold and "|" at following lines of the fold.
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148
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149 You can use the mouse to open a fold by clicking on the "+" in the foldcolumn.
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150 Clicking on the "-" or a "|" below it will close an open fold.
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151
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152 To open all folds at the cursor line use |zO|.
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153 To close all folds at the cursor line use |zC|.
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154 To delete a fold at the cursor line use |zd|.
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155 To delete all folds at the cursor line use |zD|.
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156
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157 When in Insert mode, the fold at the cursor line is never closed. That allows
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158 you to see what you type!
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159
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160 Folds are opened automatically when jumping around or moving the cursor left
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161 or right. For example, the "0" command opens the fold under the cursor
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162 (if 'foldopen' contains "hor", which is the default). The 'foldopen' option
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163 can be changed to open folds for specific commands. If you want the line
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164 under the cursor always to be open, do this: >
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165
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166 :set foldopen=all
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167
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168 Warning: You won't be able to move onto a closed fold then. You might want to
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169 use this only temporarily and then set it back to the default: >
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170
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171 :set foldopen&
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172
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173 You can make folds close automatically when you move out of it: >
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174
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175 :set foldclose=all
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176
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177 This will re-apply 'foldlevel' to all folds that don't contain the cursor.
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178 You have to try it out if you like how this feels. Use |zm| to fold more and
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179 |zr| to fold less (reduce folds).
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180
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181 The folding is local to the window. This allows you to open two windows on
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182 the same buffer, one with folds and one without folds. Or one with all folds
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183 closed and one with all folds open.
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184
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185 ==============================================================================
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186 *28.4* Saving and restoring folds
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187
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188 When you abandon a file (starting to edit another one), the state of the folds
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189 is lost. If you come back to the same file later, all manually opened and
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190 closed folds are back to their default. When folds have been created
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191 manually, all folds are gone! To save the folds use the |:mkview| command: >
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192
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193 :mkview
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194
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195 This will store the settings and other things that influence the view on the
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196 file. You can change what is stored with the 'viewoptions' option.
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197 When you come back to the same file later, you can load the view again: >
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198
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199 :loadview
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200
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201 You can store up to ten views on one file. For example, to save the current
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202 setup as the third view and load the second view: >
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203
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204 :mkview 3
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205 :loadview 2
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206
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207 Note that when you insert or delete lines the views might become invalid.
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208 Also check out the 'viewdir' option, which specifies where the views are
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209 stored. You might want to delete old views now and then.
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210
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211 ==============================================================================
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212 *28.5* Folding by indent
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213
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214 Defining folds with |zf| is a lot of work. If your text is structured by
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215 giving lower level items a larger indent, you can use the indent folding
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216 method. This will create folds for every sequence of lines with the same
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217 indent. Lines with a larger indent will become nested folds. This works well
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218 with many programming languages.
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219
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220 Try this by setting the 'foldmethod' option: >
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221
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222 :set foldmethod=indent
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223
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224 Then you can use the |zm| and |zr| commands to fold more and reduce folding.
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225 It's easy to see on this example text:
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226
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227 This line is not indented
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228 This line is indented once
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229 This line is indented twice
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230 This line is indented twice
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231 This line is indented once
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232 This line is not indented
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233 This line is indented once
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234 This line is indented once
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235
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236 Note that the relation between the amount of indent and the fold depth depends
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237 on the 'shiftwidth' option. Each 'shiftwidth' worth of indent adds one to the
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238 depth of the fold. This is called a fold level.
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239
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240 When you use the |zr| and |zm| commands you actually increase or decrease the
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241 'foldlevel' option. You could also set it directly: >
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242
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243 :set foldlevel=3
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244
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245 This means that all folds with three times a 'shiftwidth' indent or more will
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246 be closed. The lower the foldlevel, the more folds will be closed. When
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247 'foldlevel' is zero, all folds are closed. |zM| does set 'foldlevel' to zero.
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248 The opposite command |zR| sets 'foldlevel' to the deepest fold level that is
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249 present in the file.
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250
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251 Thus there are two ways to open and close the folds:
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252 (A) By setting the fold level.
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253 This gives a very quick way of "zooming out" to view the structure of the
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254 text, move the cursor, and "zoom in" on the text again.
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255
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256 (B) By using |zo| and |zc| commands to open or close specific folds.
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257 This allows opening only those folds that you want to be open, while other
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258 folds remain closed.
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259
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260 This can be combined: You can first close most folds by using |zm| a few times
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261 and then open a specific fold with |zo|. Or open all folds with |zR| and
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262 then close specific folds with |zc|.
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263
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264 But you cannot manually define folds when 'foldmethod' is "indent", as that
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265 would conflict with the relation between the indent and the fold level.
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266
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267 More about folding by indent in the reference manual: |fold-indent|
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268
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269 ==============================================================================
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270 *28.6* Folding with markers
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271
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272 Markers in the text are used to specify the start and end of a fold region.
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273 This gives precise control over which lines are included in a fold. The
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274 disadvantage is that the text needs to be modified.
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275
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276 Try it: >
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277
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278 :set foldmethod=marker
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279
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280 Example text, as it could appear in a C program:
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281
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282 /* foobar () {{{ */
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283 int foobar()
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284 {
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285 /* return a value {{{ */
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286 return 42;
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287 /* }}} */
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288 }
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289 /* }}} */
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290
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291 Notice that the folded line will display the text before the marker. This is
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292 very useful to tell what the fold contains.
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293
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294 It's quite annoying when the markers don't pair up correctly after moving some
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295 lines around. This can be avoided by using numbered markers. Example:
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296
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297 /* global variables {{{1 */
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298 int varA, varB;
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299
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300 /* functions {{{1 */
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301 /* funcA() {{{2 */
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302 void funcA() {}
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303
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304 /* funcB() {{{2 */
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305 void funcB() {}
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306 /* }}}1 */
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307
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308 At every numbered marker a fold at the specified level begins. This will make
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309 any fold at a higher level stop here. You can just use numbered start markers
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310 to define all folds. Only when you want to explicitly stop a fold before
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311 another starts you need to add an end marker.
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312
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313 More about folding with markers in the reference manual: |fold-marker|
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314
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315 ==============================================================================
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316 *28.7* Folding by syntax
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317
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318 For each language Vim uses a different syntax file. This defines the colors
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319 for various items in the file. If you are reading this in Vim, in a terminal
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320 that supports colors, the colors you see are made with the "help" syntax file.
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321 In the syntax files it is possible to add syntax items that have the "fold"
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322 argument. These define a fold region. This requires writing a syntax file
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323 and adding these items in it. That's not so easy to do. But once it's done,
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324 all folding happens automatically.
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325 Here we'll assume you are using an existing syntax file. Then there is
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326 nothing more to explain. You can open and close folds as explained above.
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327 The folds will be created and deleted automatically when you edit the file.
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328
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329 More about folding by syntax in the reference manual: |fold-syntax|
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330
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331 ==============================================================================
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332 *28.8* Folding by expression
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333
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334 This is similar to folding by indent, but instead of using the indent of a
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335 line a user function is called to compute the fold level of a line. You can
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336 use this for text where something in the text indicates which lines belong
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337 together. An example is an e-mail message where the quoted text is indicated
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338 by a ">" before the line. To fold these quotes use this: >
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339
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340 :set foldmethod=expr
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341 :set foldexpr=strlen(substitute(substitute(getline(v:lnum),'\\s','',\"g\"),'[^>].*','',''))
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342
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343 You can try it out on this text:
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344
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345 > quoted text he wrote
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346 > quoted text he wrote
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347 > > double quoted text I wrote
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348 > > double quoted text I wrote
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349
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350 Explanation for the 'foldexpr' used in the example (inside out):
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351 getline(v:lnum) gets the current line
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352 substitute(...,'\\s','','g') removes all white space from the line
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237
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353 substitute(...,'[^>].*','','') removes everything after leading '>'s
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354 strlen(...) counts the length of the string, which
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355 is the number of '>'s found
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356
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357 Note that a backslash must be inserted before every space, double quote and
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358 backslash for the ":set" command. If this confuses you, do >
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359
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360 :set foldexpr
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361
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362 to check the actual resulting value. To correct a complicated expression, use
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363 the command-line completion: >
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364
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365 :set foldexpr=<Tab>
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366
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367 Where <Tab> is a real Tab. Vim will fill in the previous value, which you can
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368 then edit.
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369
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370 When the expression gets more complicated you should put it in a function and
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371 set 'foldexpr' to call that function.
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372
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373 More about folding by expression in the reference manual: |fold-expr|
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374
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375 ==============================================================================
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376 *28.9* Folding unchanged lines
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377
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378 This is useful when you set the 'diff' option in the same window. The
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379 |vimdiff| command does this for you. Example: >
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380
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381 setlocal diff foldmethod=diff scrollbind nowrap foldlevel=1
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382
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383 Do this in every window that shows a different version of the same file. You
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384 will clearly see the differences between the files, while the text that didn't
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385 change is folded.
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386
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387 For more details see |fold-diff|.
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388
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389 ==============================================================================
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390 *28.10* Which fold method to use?
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391
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392 All these possibilities makes you wonder which method you should chose.
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393 Unfortunately, there is no golden rule. Here are some hints.
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394
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395 If there is a syntax file with folding for the language you are editing, that
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396 is probably the best choice. If there isn't one, you might try to write it.
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397 This requires a good knowledge of search patterns. It's not easy, but when
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398 it's working you will not have to define folds manually.
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399
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400 Typing commands to manually fold regions can be used for unstructured text.
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401 Then use the |:mkview| command to save and restore your folds.
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402
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403 The marker method requires you to change the file. If you are sharing the
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404 files with other people or you have to meet company standards, you might not
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405 be allowed to add them.
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406 The main advantage of markers is that you can put them exactly where you
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407 want them. That avoids that a few lines are missed when you cut and paste
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408 folds. And you can add a comment about what is contained in the fold.
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409
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410 Folding by indent is something that works in many files, but not always very
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411 well. Use it when you can't use one of the other methods. However, it is
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412 very useful for outlining. Then you specifically use one 'shiftwidth' for
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413 each nesting level.
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414
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415 Folding with expressions can make folds in almost any structured text. It is
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416 quite simple to specify, especially if the start and end of a fold can easily
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417 be recognized.
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418 If you use the "expr" method to define folds, but they are not exactly how
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419 you want them, you could switch to the "manual" method. This will not remove
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420 the defined folds. Then you can delete or add folds manually.
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421
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422 ==============================================================================
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423
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424 Next chapter: |usr_29.txt| Moving through programs
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425
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426 Copyright: see |manual-copyright| vim:tw=78:ts=8:ft=help:norl:
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