man/indent.texi

   1 @c This is part of the Emacs manual.
   2 @c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc.
   3 @c See file emacs.texi for copying conditions.
   4 @node Indentation, Text, Major Modes, Top
   5 @chapter Indentation
   6 @cindex indentation
   7 @cindex columns (indentation)
   8
   9   This chapter describes the Emacs commands that add, remove, or
  10 adjust indentation.
  11
  12 @c WideCommands
  13 @table @kbd
  14 @item @key{TAB}
  15 Indent the current line ``appropriately'' in a mode-dependent fashion.
  16 @item @kbd{C-j}
  17 Perform @key{RET} followed by @key{TAB} (@code{newline-and-indent}).
  18 @item M-^
  19 Merge the previous and the current line (@code{delete-indentation}).
  20 This would cancel out the effect of @kbd{C-j}.
  21 @item C-M-o
  22 Split the current line at point; text on the line after point becomes a
  23 new line indented to the same column where point is located
  24 (@code{split-line}).
  25 @item M-m
  26 Move (forward or back) to the first nonblank character on the current
  27 line (@code{back-to-indentation}).
  28 @item C-M-\
  29 Indent several lines to the same column (@code{indent-region}).
  30 @item C-x @key{TAB}
  31 Shift a block of lines rigidly right or left (@code{indent-rigidly}).
  32 @item M-i
  33 Indent from point to the next prespecified tab stop column
  34 (@code{tab-to-tab-stop}).
  35 @item M-x indent-relative
  36 Indent from point to under an indentation point in the previous line.
  37 @end table
  38
  39   Most programming languages have some indentation convention.  For Lisp
  40 code, lines are indented according to their nesting in parentheses.  The
  41 same general idea is used for C code, though many details are different.
  42
  43 @kindex TAB
  44   Whatever the language, to indent a line, use the @key{TAB} command.  Each
  45 major mode defines this command to perform the sort of indentation
  46 appropriate for the particular language.  In Lisp mode, @key{TAB} aligns
  47 the line according to its depth in parentheses.  No matter where in the
  48 line you are when you type @key{TAB}, it aligns the line as a whole.  In C
  49 mode, @key{TAB} implements a subtle and sophisticated indentation style that
  50 knows about many aspects of C syntax.
  51
  52   In Text mode, @key{TAB} runs the command @code{tab-to-tab-stop}, which
  53 indents to the next tab stop column.  You can set the tab stops with
  54 @kbd{M-x edit-tab-stops}.
  55
  56   Normally, @key{TAB} inserts an optimal mix of tabs and spaces to
  57 indent lines.  @xref{Just Spaces}, for how to override that.
  58
  59 @menu
  60 * Indentation Commands::  Various commands and techniques for indentation.
  61 * Tab Stops::             You can set arbitrary "tab stops" and then
  62                             indent to the next tab stop when you want to.
  63 * Just Spaces::           You can request indentation using just spaces.
  64 @end menu
  65
  66 @node Indentation Commands, Tab Stops, Indentation, Indentation
  67 @section Indentation Commands and Techniques
  68
  69 @kindex M-m
  70 @findex back-to-indentation
  71   To move over the indentation on a line, do @kbd{M-m}
  72 (@code{back-to-indentation}).  This command, given anywhere on a line,
  73 positions point at the first nonblank character on the line.
  74
  75   To insert an indented line before the current line, do @kbd{C-a C-o
  76 @key{TAB}}.  To make an indented line after the current line, use
  77 @kbd{C-e C-j}.
  78
  79   If you just want to insert a tab character in the buffer, you can type
  80 @kbd{C-q @key{TAB}}.
  81
  82 @kindex C-M-o
  83 @findex split-line
  84   @kbd{C-M-o} (@code{split-line}) moves the text from point to the end of
  85 the line vertically down, so that the current line becomes two lines.
  86 @kbd{C-M-o} first moves point forward over any spaces and tabs.  Then it
  87 inserts after point a newline and enough indentation to reach the same
  88 column point is on.  Point remains before the inserted newline; in this
  89 regard, @kbd{C-M-o} resembles @kbd{C-o}.
  90
  91 @kindex M-^
  92 @findex delete-indentation
  93   To join two lines cleanly, use the @kbd{M-^}
  94 (@code{delete-indentation}) command.  It deletes the indentation at the
  95 front of the current line, and the line boundary as well, replacing them
  96 with a single space.  As a special case (useful for Lisp code) the
  97 single space is omitted if the characters to be joined are consecutive
  98 open parentheses or closing parentheses, or if the junction follows
  99 another newline.  To delete just the indentation of a line, go to the
 100 beginning of the line and use @kbd{M-\}
 101 (@code{delete-horizontal-space}), which deletes all spaces and tabs
 102 around the cursor.
 103
 104   If you have a fill prefix, @kbd{M-^} deletes the fill prefix if it
 105 appears after the newline that is deleted.  @xref{Fill Prefix}.
 106
 107 @kindex C-M-\
 108 @kindex C-x TAB
 109 @findex indent-region
 110 @findex indent-rigidly
 111   There are also commands for changing the indentation of several lines
 112 at once.  @kbd{C-M-\} (@code{indent-region}) applies to all the lines
 113 that begin in the region; it indents each line in the ``usual'' way, as
 114 if you had typed @key{TAB} at the beginning of the line.  A numeric
 115 argument specifies the column to indent to, and each line is shifted
 116 left or right so that its first nonblank character appears in that
 117 column.  @kbd{C-x @key{TAB}} (@code{indent-rigidly}) moves all of the
 118 lines in the region right by its argument (left, for negative
 119 arguments).  The whole group of lines moves rigidly sideways, which is
 120 how the command gets its name.@refill
 121
 122 @findex indent-relative
 123   @kbd{M-x indent-relative} indents at point based on the previous line
 124 (actually, the last nonempty line).  It inserts whitespace at point, moving
 125 point, until it is underneath an indentation point in the previous line.
 126 An indentation point is the end of a sequence of whitespace or the end of
 127 the line.  If point is farther right than any indentation point in the
 128 previous line, the whitespace before point is deleted and the first
 129 indentation point then applicable is used.  If no indentation point is
 130 applicable even then, @code{indent-relative} runs @code{tab-to-tab-stop}
 131 @ifinfo
 132 (@pxref{Tab Stops}),
 133 @end ifinfo
 134 @iftex
 135 (see next section),
 136 @end iftex
 137 unless it is called with a numeric argument, in which case it does
 138 nothing.
 139
 140   @code{indent-relative} is the definition of @key{TAB} in Indented Text
 141 mode.  @xref{Text}.
 142
 143   @xref{Format Indentation}, for another way of specifying the
 144 indentation for part of your text.
 145
 146 @node Tab Stops, Just Spaces, Indentation Commands, Indentation
 147 @section Tab Stops
 148
 149 @cindex tab stops
 150 @cindex using tab stops in making tables
 151 @cindex tables, indentation for
 152 @kindex M-i
 153 @findex tab-to-tab-stop
 154   For typing in tables, you can use Text mode's definition of @key{TAB},
 155 @code{tab-to-tab-stop}.  This command inserts indentation before point,
 156 enough to reach the next tab stop column.  If you are not in Text mode,
 157 this command can be found on the key @kbd{M-i}.
 158
 159 @findex edit-tab-stops
 160 @findex edit-tab-stops-note-changes
 161 @kindex C-c C-c @r{(Edit Tab Stops)}
 162 @vindex tab-stop-list
 163   You can specify the tab stops used by @kbd{M-i}.  They are stored in a
 164 variable called @code{tab-stop-list}, as a list of column-numbers in
 165 increasing order.
 166
 167   The convenient way to set the tab stops is with @kbd{M-x
 168 edit-tab-stops}, which creates and selects a buffer containing a
 169 description of the tab stop settings.  You can edit this buffer to
 170 specify different tab stops, and then type @kbd{C-c C-c} to make those
 171 new tab stops take effect.  @code{edit-tab-stops} records which buffer
 172 was current when you invoked it, and stores the tab stops back in that
 173 buffer; normally all buffers share the same tab stops and changing them
 174 in one buffer affects all, but if you happen to make
 175 @code{tab-stop-list} local in one buffer then @code{edit-tab-stops} in
 176 that buffer will edit the local settings.
 177
 178   Here is what the text representing the tab stops looks like for ordinary
 179 tab stops every eight columns.
 180
 181 @example
 182         :       :       :       :       :       :
 183 0         1         2         3         4
 184 0123456789012345678901234567890123456789012345678
 185 To install changes, type C-c C-c
 186 @end example
 187
 188   The first line contains a colon at each tab stop.  The remaining lines
 189 are present just to help you see where the colons are and know what to do.
 190
 191   Note that the tab stops that control @code{tab-to-tab-stop} have nothing
 192 to do with displaying tab characters in the buffer.  @xref{Display Custom},
 193 for more information on that.
 194
 195 @node Just Spaces,, Tab Stops, Indentation
 196 @section Tabs vs. Spaces
 197
 198 @vindex indent-tabs-mode
 199   Emacs normally uses both tabs and spaces to indent lines.  If you
 200 prefer, all indentation can be made from spaces only.  To request
 201 this, set @code{indent-tabs-mode} to @code{nil}.  This is a per-buffer
 202 variable, so altering the variable affects only the current buffer,
 203 but there is a default value which you can change as well.
 204 @xref{Locals}.
 205
 206 @findex tabify
 207 @findex untabify
 208   There are also commands to convert tabs to spaces or vice versa, always
 209 preserving the columns of all nonblank text.  @kbd{M-x tabify} scans the
 210 region for sequences of spaces, and converts sequences of at least three
 211 spaces to tabs if that can be done without changing indentation.  @kbd{M-x
 212 untabify} changes all tabs in the region to appropriate numbers of spaces.