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(Completion Styles): New node.

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Chong Yidong 2009-03-18 04:01:05 +00:00
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doc/lispref/minibuf.texi
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@ -634,6 +634,7 @@ for reading certain kinds of names with completion.
(reading buffer name, file name, etc.)
* Reading File Names:: Using completion to read file names and
shell commands.
* Completion Styles:: Specifying rules for performing completion.
* Programmed Completion:: Writing your own completion-function.
@end menu
@ -1532,6 +1533,58 @@ This keymap is used by @code{read-shell-command} for completing
command and file names that are part of a shell command.
@end defvar
@node Completion Styles
@subsection Completion Styles
@cindex completion styles
A @dfn{completion style} is a set of rules for generating
completions. The user option @code{completion-styles} stores a list
of completion styles, which are represented by symbols.
@defopt completion-styles
This is a list of completion style symbols to use for performing
completion. Each completion style in this list must be defined in
@code{completion-styles-alist}.
@end defopt
@defvar completion-styles-alist
This variable stores a list of available completion styles. Each
element in the list must have the form @samp{(@var{name}
@var{try-completion} @var{all-completions})}. Here, @var{name} is the
name of the completion style (a symbol), which may be used in
@code{completion-styles-alist} to refer to this style.
@var{try-completion} is the function that does the completion, and
@var{all-completions} is the function that lists the completions.
These functions should accept four arguments: @var{string},
@var{collection}, @var{predicate}, and @var{point}. The @var{string},
@var{collection}, and @var{predicate} arguments have the same meanings
as in @code{try-completion} (@pxref{Basic Completion}), and the
@var{point} argument is the position of point within @var{string}.
Each function should return a non-@code{nil} value if it performed its
job, and @code{nil} if it did not (e.g., if there is no way to
complete @var{string} according to the completion style).
When the user calls a completion command, such as
@code{minibuffer-complete} (@pxref{Completion Commands}), Emacs looks
for the first style listed in @code{completion-styles} and calls its
@var{try-completion} function. If this function returns @code{nil},
Emacs moves to the next completion style listed in
@code{completion-styles} and calls its @var{try-completion} function,
and so on until one of the @var{try-completion} functions successfully
performs completion and returns a non-@code{nil} value. A similar
procedure is used for listing completions, via the
@var{all-completions} functions.
@end defvar
By default, @code{completion-styles-alist} contains four pre-defined
completion styles: @code{basic}, a basic completion style;
@code{partial-completion}, which does partial completion (completing
each word in the input separately); @code{emacs22}, which performs
completion according to the rules used in Emacs 22; and
@code{emacs21}, which performs completion according to the rules used
in Emacs 21.
@node Programmed Completion
@subsection Programmed Completion
@cindex programmed completion