@c This is part of the Emacs manual.
-@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc.
+@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997, 2004 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Indentation, Text, Major Modes, Top
@chapter Indentation
This chapter describes the Emacs commands that add, remove, or
adjust indentation.
-@c WideCommands
@table @kbd
@item @key{TAB}
Indent the current line ``appropriately'' in a mode-dependent fashion.
Perform @key{RET} followed by @key{TAB} (@code{newline-and-indent}).
@item M-^
Merge the previous and the current line (@code{delete-indentation}).
-This would cancel out the effect of @kbd{C-j}.
+This would cancel the effect of a preceding @kbd{C-j}.
@item C-M-o
-Split the line at point; text on the line after point becomes a new line
-indented to the same column where point is located (@code{split-line}).
+Split the current line at point; text on the line after point becomes a
+new line indented to the same column where point is located
+(@code{split-line}).
@item M-m
Move (forward or back) to the first nonblank character on the current
line (@code{back-to-indentation}).
@item C-M-\
-Indent several lines to the same column (@code{indent-region}).
+Indent lines in the region to the same column (@code{indent-region}).
@item C-x @key{TAB}
-Shift a block of lines rigidly right or left (@code{indent-rigidly}).
+Shift lines in the region rigidly right or left (@code{indent-rigidly}).
@item M-i
Indent from point to the next prespecified tab stop column
(@code{tab-to-tab-stop}).
Indent from point to under an indentation point in the previous line.
@end table
- Most programming languages have some indentation convention. For Lisp
-code, lines are indented according to their nesting in parentheses. The
-same general idea is used for C code, though many details are different.
+ Emacs supports four general categories of operations that could all
+be called `indentation':
-@kindex TAB
- Whatever the language, to indent a line, use the @key{TAB} command. Each
-major mode defines this command to perform the sort of indentation
-appropriate for the particular language. In Lisp mode, @key{TAB} aligns
-the line according to its depth in parentheses. No matter where in the
-line you are when you type @key{TAB}, it aligns the line as a whole. In C
-mode, @key{TAB} implements a subtle and sophisticated indentation style that
-knows about many aspects of C syntax.
+@enumerate
+@item
+Insert a tab character. You can type @kbd{C-q @key{TAB}} to do this.
+
+A tab character is displayed as a stretch of whitespace which extends
+to the next display tab stop position, and the default width of a tab
+stop is eight. @xref{Display Custom}, for more details.
+
+@item
+Insert whitespace up to the next tab stop. You can set tab stops at
+your choice of column positions, then type @kbd{M-i} to advance to the
+next tab stop. The default tab stop settings have a tab stop every
+eight columns, which means by default @kbd{M-i} inserts a tab
+character. To set the tab stops, use @kbd{M-x edit-tab-stops}.
+
+@item
+Align a line with the previous line. More precisely, the command
+@kbd{M-x indent-relative} indents the current line under the beginning
+of some word in the previous line. In Fundamental mode and in Text
+mode, @key{TAB} runs the command @code{indent-relative}.
+
+@item
+The most sophisticated method is @dfn{syntax-driven indentation}.
+Most programming languages have an indentation convention. For Lisp
+code, lines are indented according to their nesting in parentheses. C
+code uses the same general idea, but many details are different.
- In Text mode, @key{TAB} runs the command @code{tab-to-tab-stop}, which
-indents to the next tab stop column. You can set the tab stops with
-@kbd{M-x edit-tab-stops}.
+@kindex TAB
+Type @key{TAB} to do syntax-driven indentation, in a mode that
+supports it. It realigns the current line according with the syntax
+of the preceding lines. No matter where in the line you are when you
+type @key{TAB}, it aligns the line as a whole.
+@end enumerate
- Normally, @key{TAB} inserts an optimal mix of tabs and spaces to
-indent lines. @xref{Just Spaces}, for how to override that.
+ Normally, most of the above methods insert an optimal mix of tabs and
+spaces to align to the desired column. @xref{Just Spaces}, for how to
+disable use of tabs. However, @kbd{C-q @key{TAB}} always inserts a
+tab, even when tabs are disabled for the indentation commands.
@menu
* Indentation Commands:: Various commands and techniques for indentation.
@findex back-to-indentation
To move over the indentation on a line, do @kbd{M-m}
(@code{back-to-indentation}). This command, given anywhere on a line,
-positions point at the first nonblank character on the line.
+positions point at the first nonblank character on the line, if any,
+or else at the end of the line.
To insert an indented line before the current line, do @kbd{C-a C-o
@key{TAB}}. To make an indented line after the current line, use
@findex indent-region
@findex indent-rigidly
There are also commands for changing the indentation of several lines
-at once. @kbd{C-M-\} (@code{indent-region}) applies to all the lines
-that begin in the region; it indents each line in the ``usual'' way, as
-if you had typed @key{TAB} at the beginning of the line. A numeric
-argument specifies the column to indent to, and each line is shifted
-left or right so that its first nonblank character appears in that
-column. @kbd{C-x @key{TAB}} (@code{indent-rigidly}) moves all of the
-lines in the region right by its argument (left, for negative
+at once. They apply to all the lines that begin in the region.
+@kbd{C-M-\} (@code{indent-region}) indents each line in the ``usual''
+way, as if you had typed @key{TAB} at the beginning of the line. A
+numeric argument specifies the column to indent to, and each line is
+shifted left or right so that its first nonblank character appears in
+that column. @kbd{C-x @key{TAB}} (@code{indent-rigidly}) moves all of
+the lines in the region right by its argument (left, for negative
arguments). The whole group of lines moves rigidly sideways, which is
how the command gets its name.@refill
+@cindex remove indentation
+ If you want to remove all indentation from all of the line in the
+region, invoke @kbd{C-x @key{TAB}} with a large negative argument,
+such as -1000.
+
@findex indent-relative
@kbd{M-x indent-relative} indents at point based on the previous line
(actually, the last nonempty line). It inserts whitespace at point, moving
-point, until it is underneath an indentation point in the previous line.
+point, until it is underneath the next indentation point in the previous line.
An indentation point is the end of a sequence of whitespace or the end of
the line. If point is farther right than any indentation point in the
-previous line, the whitespace before point is deleted and the first
-indentation point then applicable is used. If no indentation point is
-applicable even then, @code{indent-relative} runs @code{tab-to-tab-stop}
+previous line, @code{indent-relative} runs @code{tab-to-tab-stop}
@ifinfo
(@pxref{Tab Stops}),
@end ifinfo
unless it is called with a numeric argument, in which case it does
nothing.
- @code{indent-relative} is the definition of @key{TAB} in Indented Text
-mode. @xref{Text}.
-
@xref{Format Indentation}, for another way of specifying the
indentation for part of your text.
@node Tab Stops, Just Spaces, Indentation Commands, Indentation
@section Tab Stops
-@cindex tab stops
+@cindex tab stops
@cindex using tab stops in making tables
@cindex tables, indentation for
@kindex M-i
@findex tab-to-tab-stop
- For typing in tables, you can use Text mode's definition of @key{TAB},
-@code{tab-to-tab-stop}. This command inserts indentation before point,
-enough to reach the next tab stop column. If you are not in Text mode,
-this command can be found on the key @kbd{M-i}.
+ For typing in tables, you can use @kbd{M-i} (@code{tab-to-tab-stop}).
+This command inserts indentation before point, enough to reach the
+next tab stop column.
@findex edit-tab-stops
@findex edit-tab-stops-note-changes
edit-tab-stops}, which creates and selects a buffer containing a
description of the tab stop settings. You can edit this buffer to
specify different tab stops, and then type @kbd{C-c C-c} to make those
-new tab stops take effect. @code{edit-tab-stops} records which buffer
-was current when you invoked it, and stores the tab stops back in that
-buffer; normally all buffers share the same tab stops and changing them
-in one buffer affects all, but if you happen to make
+new tab stops take effect. The buffer uses Overwrite mode
+(@pxref{Minor Modes}). @code{edit-tab-stops} records which buffer was
+current when you invoked it, and stores the tab stops back in that
+buffer; normally all buffers share the same tab stops and changing
+them in one buffer affects all, but if you happen to make
@code{tab-stop-list} local in one buffer then @code{edit-tab-stops} in
that buffer will edit the local settings.
but there is a default value which you can change as well.
@xref{Locals}.
+ A tab is not always displayed in the same way. By default, tabs are
+eight columns wide, but some people like to customize their tools to
+use a different tab width. So by using spaces only, you can make sure
+that your file looks the same regardless of the tab width setting.
+
@findex tabify
@findex untabify
There are also commands to convert tabs to spaces or vice versa, always
preserving the columns of all nonblank text. @kbd{M-x tabify} scans the
-region for sequences of spaces, and converts sequences of at least three
+region for sequences of spaces, and converts sequences of at least two
spaces to tabs if that can be done without changing indentation. @kbd{M-x
untabify} changes all tabs in the region to appropriate numbers of spaces.
+
+@ignore
+ arch-tag: acc07de7-ae11-4ee8-a159-cb59c473f0fb
+@end ignore