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