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