X-Git-Url: https://git.hcoop.net/bpt/emacs.git/blobdiff_plain/b14e3e21ec6702d27257a1400681fc36ee10282f..ba3189039adc8ec5eba5ed3e21d42019a4616b7c:/doc/emacs/indent.texi diff --git a/doc/emacs/indent.texi b/doc/emacs/indent.texi dissimilarity index 83% index c4ef4781aa..e0c269ad57 100644 --- a/doc/emacs/indent.texi +++ b/doc/emacs/indent.texi @@ -1,260 +1,254 @@ -@c This is part of the Emacs manual. -@c Copyright (C) 1985-1987, 1993-1995, 1997, 2001-2011 -@c Free Software Foundation, Inc. -@c See file emacs.texi for copying conditions. -@node Indentation, Text, Major Modes, Top -@chapter Indentation -@cindex indentation -@cindex tabs -@cindex columns (indentation) - - This chapter describes the Emacs commands that add, remove, or -adjust indentation. - -@table @kbd -@item @key{TAB} -Indent the current line appropriately, in a mode-dependent fashion. -@item @kbd{C-j} -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 the effect of a preceding @kbd{C-j}. -@item C-M-o -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 lines in the region to the same column (@code{indent-region}). -@item C-x @key{TAB} -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}). -@item M-x indent-relative -Indent from point to under an indentation point in the previous line. -@end table - -@noindent -The @key{TAB} key runs @code{indent-for-tab-command} in most major -modes (in C and related modes, @key{TAB} runs a separate command, -@code{c-indent-line-or-region}, which behaves similarly). The major -mode determines just what this entails. - - In text modes, @key{TAB} inserts some combination of space and tab -characters to advance point to the next tab stop (@pxref{Tab Stops}). -If the region is active and spans multiple lines, it advances the -first character of each of those lines to the next tab stop -(@pxref{Using Region}). For the purposes of this command, the -position of the first non-whitespace character on the preceding line -is treated as an additional tab stop. Thus, you can use @key{TAB} to -``align'' point with the preceding line. - - In programming modes, @key{TAB} adds or removes some combination of -space and tab characters at the start of the line, in a way that makes -sense given the text in the preceding lines. If the region is active -and spans multiple lines, all those lines are indented this way. If -point was initially within the current line's indentation, it is -positioned after that indentation; otherwise, it remains at same point -in the newly-indented text. @xref{Program Indent}. - -@vindex tab-width - Normally, indentation commands insert (or remove) an optimal mix of -@dfn{tab characters} and spaces to align to the desired column. Tab -characters (@acronym{ASCII} code 9) are displayed as a stretch of -empty space extending to the next @dfn{display tab stop}. By default, -there is one display tab stop every eight columns; the number of -columns is determined by the variable @code{tab-width}. You can -insert a single tab character by typing @kbd{C-q @key{TAB}}. -@xref{Text Display}. - -@findex edit-tab-stops -@findex tab-to-tab-stop -@kindex M-i - The command @kbd{M-i} (@code{tab-to-tab-stop}) adjusts the -whitespace characters around point, inserting just enough whitespace -to advance point up to the next tab stop. By default, this involves -deleting the existing whitespace and inserting a single tab character. - - @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. - -@vindex tab-always-indent - The variable @code{tab-always-indent} tweaks the behavior of the -@key{TAB} (@code{indent-for-tab-command}) command. The default value, -@code{t}, gives the behavior described above. If you change the value -to the symbol @code{complete}, then @key{TAB} first tries to indent -the current line, and if the line was already indented, it tries to -complete the text at point (@pxref{Symbol Completion}). If the value -is @code{nil}, then @key{TAB} indents the current line only if point -is at the left margin or in the line's indentation; otherwise, it -inserts a real tab character. - -@menu -* Indentation Commands:: Various commands and techniques for indentation. -* Tab Stops:: You can set arbitrary "tab stops" and then - indent to the next tab stop when you want to. -* Just Spaces:: You can request indentation using just spaces. -@end menu - -@node Indentation Commands, Tab Stops, Indentation, Indentation -@section Indentation Commands and Techniques - -@kindex M-m -@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, 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 -@kbd{C-e C-j}. - - If you just want to insert a tab character in the buffer, type -@kbd{C-q @key{TAB}}. - -@kindex C-M-o -@findex split-line - @kbd{C-M-o} (@code{split-line}) moves the text from point to the end of -the line vertically down, so that the current line becomes two lines. -@kbd{C-M-o} first moves point forward over any spaces and tabs. Then it -inserts after point a newline and enough indentation to reach the same -column point is on. Point remains before the inserted newline; in this -regard, @kbd{C-M-o} resembles @kbd{C-o}. - -@kindex M-^ -@findex delete-indentation - To join two lines cleanly, use the @kbd{M-^} -(@code{delete-indentation}) command. It deletes the indentation at -the front of the current line, and the line boundary as well, -replacing them with a single space. As a special case (useful for -Lisp code) the single space is omitted if the characters to be joined -are consecutive open parentheses or closing parentheses, or if the -junction follows another newline. To delete just the indentation of a -line, go to the beginning of the line and use @kbd{M-\} -(@code{delete-horizontal-space}), which deletes all spaces and tabs -around the cursor. - - If you have a fill prefix, @kbd{M-^} deletes the fill prefix if it -appears after the newline that is deleted. @xref{Fill Prefix}. - -@kindex C-M-\ -@kindex C-x TAB -@findex indent-region -@findex indent-rigidly - There are also commands for changing the indentation of several lines -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. - -@cindex remove indentation - To remove all indentation from all of the lines 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 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, @code{indent-relative} runs @code{tab-to-tab-stop} -@ifnottex -(@pxref{Tab Stops}), -@end ifnottex -@iftex -(see next section), -@end iftex -unless it is called with a numeric argument, in which case it does -nothing. - - @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 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 @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 -@kindex C-c C-c @r{(Edit Tab Stops)} -@vindex tab-stop-list - You can change the tab stops used by @kbd{M-i} and other indentation -commands, so that they need not be spaced every eight characters, or -even regularly spaced. The tab stops are stored in the variable -@code{tab-stop-list}, as a list of column numbers in increasing order. - - A convenient way to set the tab stops is with @kbd{M-x -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. 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. - - Here is what the text representing the tab stops looks like for ordinary -tab stops every eight columns. - -@example - : : : : : : -0 1 2 3 4 -0123456789012345678901234567890123456789012345678 -To install changes, type C-c C-c -@end example - - The first line contains a colon at each tab stop. The remaining lines -are present just to help you see where the colons are and know what to do. - - Note that the tab stops that control @code{tab-to-tab-stop} have -nothing to do with how tab characters are displayed in the buffer. -Tab characters are always displayed as empty spaces extending to the -next display tab stop, which occurs every @code{tab-width} columns -regardless of the contents of @code{tab-stop-list}. @xref{Text -Display}. - -@node Just Spaces,, Tab Stops, Indentation -@section Tabs vs. Spaces - -@vindex indent-tabs-mode - Emacs normally uses both tabs and spaces to indent lines. If you -prefer, all indentation can be made from spaces only. To request -this, set @code{indent-tabs-mode} to @code{nil}. This is a per-buffer -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 editors to -use a different tab width (e.g., by changing the variable -@code{tab-width} in Emacs). 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 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. +@c This is part of the Emacs manual. +@c Copyright (C) 1985-1987, 1993-1995, 1997, 2001-2014 Free Software +@c Foundation, Inc. +@c See file emacs.texi for copying conditions. +@node Indentation +@chapter Indentation +@cindex indentation +@cindex tabs +@cindex columns (indentation) + +@cindex whitespace character + @dfn{Indentation} refers to inserting or adjusting @dfn{whitespace +characters} (space and/or tab characters) at the beginning of a line +of text. This chapter documents indentation commands and options +which are common to Text mode and related modes, as well as +programming language modes. @xref{Program Indent}, for additional +documentation about indenting in programming modes. + +@findex indent-for-tab-command +@kindex TAB @r{(indentation)} + The simplest way to perform indentation is the @key{TAB} key. In +most major modes, this runs the command @code{indent-for-tab-command}. +(In C and related modes, @key{TAB} runs the command +@code{c-indent-line-or-region}, which behaves similarly). + +@table @key +@item TAB +Insert whitespace, or indent the current line, in a mode-appropriate +way (@code{indent-for-tab-command}). If the region is active, indent +all the lines within it. +@end table + + The exact behavior of @key{TAB} depends on the major mode. In Text +mode and related major modes, @key{TAB} normally inserts some +combination of space and tab characters to advance point to the next +tab stop (@pxref{Tab Stops}). For this purpose, the position of the +first non-whitespace character on the preceding line is treated as an +additional tab stop, so you can use @key{TAB} to ``align'' point with +the preceding line. If the region is active (@pxref{Using Region}), +@key{TAB} acts specially: it indents each line in the region so that +its first non-whitespace character is aligned with the preceding line. + + In programming modes, @key{TAB} indents the current line of code in +a way that makes sense given the code in the preceding lines. If the +region is active, all the lines in the region are indented this way. +If point was initially within the current line's indentation, it is +repositioned to the first non-whitespace character on the line. + + If you just want to insert a tab character in the buffer, type +@kbd{C-q @key{TAB}} (@pxref{Inserting Text}). + +@menu +* Indentation Commands:: More commands for performing indentation. +* Tab Stops:: Stop points for indentation in Text modes. +* Just Spaces:: Using only space characters for indentation. +* Indent Convenience:: Optional indentation features. +@end menu + +@node Indentation Commands +@section Indentation Commands + +Apart from the @key{TAB} (@code{indent-for-tab-command}) command, +Emacs provides a variety of commands to perform indentation in other +ways. + +@table @kbd +@item C-j +@kindex C-j +@findex newline-and-indent +Perform @key{RET} followed by @key{TAB} (@code{newline-and-indent}). + +@item C-M-o +@kindex C-M-o +@findex split-line +Split the current line at point (@code{split-line}). The text on the +line after point becomes a new line, indented to the same column where +point is located. This command first moves point forward over any +spaces and tabs. Afterward, point is positioned before the inserted +newline. + +@kindex M-m +@findex back-to-indentation +@item M-m +Move (forward or back) to the first non-whitespace character on the +current line (@code{back-to-indentation}). If there are no +non-whitespace characters on the line, move to the end of the line. + +@item M-i +@kindex M-i +@findex tab-to-tab-stop +Indent whitespace at point, up to the next tab stop +(@code{tab-to-tab-stop}). @xref{Tab Stops}. + +@findex indent-relative +@item M-x indent-relative +Insert whitespace at point, until point is aligned with the first +non-whitespace character on the previous line (actually, the last +non-blank line). If point is already farther right than that, run +@code{tab-to-tab-stop} instead---unless called with a numeric +argument, in which case do nothing. + +@item M-^ +@kindex M-^ +@findex delete-indentation +Merge the previous and the current line (@code{delete-indentation}). +This ``joins'' the two lines cleanly, by replacing any indentation at +the front of the current line, together with the line boundary, with a +single space. + +As a special case (useful for Lisp code), the single space is omitted +if the characters to be joined are consecutive opening and closing +parentheses, or if the junction follows another newline. + +If there is a fill prefix, @kbd{M-^} deletes the fill prefix if it +appears after the newline that is deleted. @xref{Fill Prefix}. + +@item C-M-\ +@kindex C-M-\ +@findex indent-region +Indent all the lines in the region, as though you had typed @key{TAB} +at the beginning of each line (@code{indent-region}). + +If a numeric argument is supplied, indent every line in the region to +that column number. + +@item C-x @key{TAB} +@kindex C-x TAB +@findex indent-rigidly +@cindex remove indentation +This command is used to change the indentation of all lines that begin +in the region, moving the affected lines as a ``rigid'' unit. + +If called with no argument, the command activates a transient mode for +adjusting the indentation of the affected lines interactively. While +this transient mode is active, typing @key{LEFT} or @key{RIGHT} +indents leftward and rightward, respectively, by one space. You can +also type @kbd{S-@key{LEFT}} or @kbd{S-@key{RIGHT}} to indent leftward +or rightward to the next tab stop (@pxref{Tab Stops}). Typing any +other key disables the transient mode, and resumes normal editing. + +If called with a prefix argument @var{n}, this command indents the +lines forward by @var{n} spaces (without enabling the transient mode). +Negative values of @var{n} indent backward, so you can remove all +indentation from the lines in the region using a large negative +argument, like this: + +@smallexample +C-u -999 C-x @key{TAB} +@end smallexample +@end table + +@node Tab Stops +@section Tab Stops +@cindex tab stops + +@vindex tab-stop-list + Emacs defines certain column numbers to be @dfn{tab stops}. These +are used as stopping points by @key{TAB} when inserting whitespace in +Text mode and related modes (@pxref{Indentation}), and by commands +like @kbd{M-i} (@pxref{Indentation Commands}). By default, tab stops +are located every 8 columns. These positions are stored in the +variable @code{tab-stop-list}, whose value is a list of column numbers +in increasing order. + +@findex edit-tab-stops +@kindex C-c C-c @r{(Edit Tab Stops)} + Instead of customizing the variable @code{tab-stop-list} directly, a +convenient way to view and set tab stops is via the command @kbd{M-x +edit-tab-stops}. This switches to a buffer containing a description +of the tab stop settings, which looks like this: + +@example + : : : : : : +0 1 2 3 4 +0123456789012345678901234567890123456789012345678 +To install changes, type C-c C-c +@end example + +@noindent +The first line contains a colon at each tab stop. The numbers on the +next two lines are present just to indicate where the colons are. It +is implicitly extended to infinity by repeating the last step. + + You can edit this buffer to specify different tab stops by placing +colons on the desired columns. The buffer uses Overwrite mode +(@pxref{Minor Modes}). When you are done, type @kbd{C-c C-c} to make +the new tab stops take effect. Normally, the new tab stop settings +apply to all buffers. However, if you have made the +@code{tab-stop-list} variable local to the buffer where you called +@kbd{M-x edit-tab-stops} (@pxref{Locals}), then the new tab stop +settings apply only to that buffer. To save the tab stop settings for +future Emacs sessions, use the Customize interface to save the value +of @code{tab-stop-list} (@pxref{Easy Customization}). + + Note that the tab stops discussed in this section have nothing to do +with how tab characters are displayed in the buffer. Tab characters +are always displayed as empty spaces extending to the next +@dfn{display tab stop}. @xref{Text Display}. + +@node Just Spaces +@section Tabs vs. Spaces + +@vindex tab-width + Normally, indentation commands insert (or remove) an optimal mix of +space characters and tab characters to align to the desired column. +Tab characters are displayed as a stretch of empty space extending to +the next @dfn{display tab stop}. By default, there is one display tab +stop every @code{tab-width} columns (the default is 8). @xref{Text +Display}. + +@vindex indent-tabs-mode + If you prefer, all indentation can be made from spaces only. To +request this, set the buffer-local variable @code{indent-tabs-mode} to +@code{nil}. @xref{Locals}, for information about setting buffer-local +variables. Note, however, that @kbd{C-q @key{TAB}} always inserts a +tab character, regardless of the value of @code{indent-tabs-mode}. + + One reason to set @code{indent-tabs-mode} to @code{nil} is that not +all editors display tab characters in the same way. Emacs users, too, +may have different customized values of @code{tab-width}. By using +spaces only, you can make sure that your file always looks the same. +If you only care about how it looks within Emacs, another way to +tackle this problem is to set the @code{tab-width} variable in a +file-local variable (@pxref{File Variables}). + +@findex tabify +@findex untabify + There are also commands to convert tabs to spaces or vice versa, always +preserving the columns of all non-whitespace text. @kbd{M-x tabify} scans the +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. + +@node Indent Convenience +@section Convenience Features for Indentation + +@vindex tab-always-indent + The variable @code{tab-always-indent} tweaks the behavior of the +@key{TAB} (@code{indent-for-tab-command}) command. The default value, +@code{t}, gives the behavior described in @ref{Indentation}. If you +change the value to the symbol @code{complete}, then @key{TAB} first +tries to indent the current line, and if the line was already +indented, it tries to complete the text at point (@pxref{Symbol +Completion}). If the value is @code{nil}, then @key{TAB} indents the +current line only if point is at the left margin or in the line's +indentation; otherwise, it inserts a tab character. + +@cindex Electric Indent mode +@cindex mode, Electric Indent +@findex electric-indent-mode + Electric Indent mode is a global minor mode that automatically +indents the line after every @key{RET} you type. This mode is enabled +by default. To toggle this minor mode, type @kbd{M-x +electric-indent-mode}.