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(Indentation): Explain the concepts.

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(Just Spaces): Explain why preventing tabs for indentation might
be useful.
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Kai Großjohann 2003-05-22 14:53:58 +00:00
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@ -1,3 +1,9 @@
2003-05-22 Kai Gro,A_(Bjohann <kai.grossjohann@gmx.net>
* indent.texi (Indentation): Explain the concepts.
(Just Spaces): Explain why preventing tabs for indentation might
be useful.
2003-05-03 Glenn Morris <gmorris@ast.cam.ac.uk>
* faq.texi: Improve previous changes.

70
man/indent.texi
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@ -35,10 +35,56 @@ Indent from point to the next prespecified tab stop column
Indent from point to under an indentation point in the previous line.
@end table
Emacs supports four general categories of operations that could all
be called `indentation':
@enumerate
@item
The most simple operation is to just insert a tab character. This
operation does not have a convenient key binding, because it is
subsumed by the more general operation described next. But you can use
@kbd{C-q @key{TAB}} to insert a literal tab character.
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
Emacs also supports tab stops. You can set them at arbitrary
positions, and then use @kbd{M-i} to advance to the next tab stop. The
default tab stop list contains positions (columns) that are a multiple
of eight, and so the effect of @kbd{M-i} is the same as that of
@kbd{C-q @key{TAB}} in the default case.
You can set the tab stops with @kbd{M-x edit-tab-stops}.
@item
You can align successive lines with each other. This is called
@dfn{relative indentation} in Emacs and is performed by the command
@kbd{M-x indent-relative}. The effect is best shown by an example:
@example
This shows the effect of relative indentation.
^ ^ ^ ^ ^ ^ ^
@end example
The positions for the @code{^} characters on the second line were
obtained using @kbd{M-x indent-relative}.
In Fundamental mode and in Text mode, @key{TAB} runs the command
@code{indent-relative}.
@item
The most sophisticated method is called @dfn{syntax-driven indentation}
and is the default behavior of the @key{TAB} key in Emacs.
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.
For some languages, different kinds of indentation styles are
commonly used. Emacs accomodates this by allowing users to customize
the indentation. For example, see @ref{Customizing Indentation,,,ccmode},
for a description of these facilities for the C language.
@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
@ -48,13 +94,20 @@ 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.
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}.
@end enumerate
Normally, @key{TAB} inserts an optimal mix of tabs and spaces for
the intended indentation. @xref{Just Spaces}, for how to prevent use
of tabs.
Normally, all of the above methods insert an optimal mix of tabs and
spaces for the needed indentation. @xref{Just Spaces}, for how to
prevent use of tabs. However, the first method (@kbd{C-q @key{TAB}})
always inserts a tab, even if you prevented their use.
@c In Text mode, @key{TAB} runs the command @code{tab-to-tab-stop}, which
@c indents to the next tab stop column. You can set the tab stops with
@c @kbd{M-x edit-tab-stops}.
@c Normally, @key{TAB} inserts an optimal mix of tabs and spaces for
@c the intended indentation. @xref{Just Spaces}, for how to prevent use
@c of tabs.
@menu
* Indentation Commands:: Various commands and techniques for indentation.
@ -208,6 +261,11 @@ variable, so altering the variable affects only the current buffer,
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