@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1998, 1999 Free Software Foundation, Inc.
+@c Copyright (C) 1998, 1999 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/characters
@node Non-ASCII Characters, Searching and Matching, Text, Top
* Translation of Characters:: Translation tables are used for conversion.
* Coding Systems:: Coding systems are conversions for saving files.
* Input Methods:: Input methods allow users to enter various
- non-ASCII characters without speciak keyboards.
+ non-ASCII characters without special keyboards.
* Locales:: Interacting with the POSIX locale.
@end menu
@defun string-make-unibyte string
This function converts the text of @var{string} to unibyte
representation, if it isn't already, and returns the result. If
-@var{string} is a unibyte string, it is returned unchanged.
-Multibyte character codes are converted to unibyte
-by using just the low 8 bits.
+@var{string} is a unibyte string, it is returned unchanged. Multibyte
+character codes are converted to unibyte according to
+@code{nonascii-translation-table} or, if that is @code{nil}, using
+@code{nonascii-insert-offset}. If the lookup in the translation table
+fails, this function takes just the low 8 bits of each character.
@end defun
@defun string-make-multibyte string
If @var{string} is already a unibyte string, then the value is
@var{string} itself. Otherwise it is a newly created string, with no
text properties. If @var{string} is multibyte, any characters it
-contains of charset @var{eight-bit-control} or @var{eight-bit-graphic}
+contains of charset @code{eight-bit-control} or @code{eight-bit-graphic}
are converted to the corresponding single byte.
@end defun
@var{string} itself. Otherwise it is a newly created string, with no
text properties. If @var{string} is unibyte and contains any individual
8-bit bytes (i.e.@: not part of a multibyte form), they are converted to
-the corresponding multibyte character of charset @var{eight-bit-control}
-or @var{eight-bit-graphic}.
+the corresponding multibyte character of charset @code{eight-bit-control}
+or @code{eight-bit-graphic}.
@end defun
@node Character Codes
@defun make-translation-table &rest translations
This function returns a translation table based on the argument
-@var{translations}. Each element of
-@var{translations} should be a list of the form @code{(@var{from}
-. @var{to})}; this says to translate the character @var{from} into
-@var{to}.
+@var{translations}. Each element of @var{translations} should be a
+list of elements of the form @code{(@var{from} . @var{to})}; this says
+to translate the character @var{from} into @var{to}.
+
+The arguments and the forms in each argument are processed in order,
+and if a previous form already translates @var{to} to some other
+character, say @var{to-alt}, @var{from} is also translated to
+@var{to-alt}.
You can also map one whole character set into another character set with
the same dimension. To do this, you specify a generic character (which
@defvar buffer-file-coding-system
This variable records the coding system that was used for visiting the
current buffer. It is used for saving the buffer, and for writing part
-of the buffer with @code{write-region}. When those operations ask the
-user to specify a different coding system,
-@code{buffer-file-coding-system} is updated to the coding system
-specified.
-
-However, @code{buffer-file-coding-system} does not affect sending text
+of the buffer with @code{write-region}. If the text to be written
+cannot be safely encoded using the coding system specified by this
+variable, these operations select an alternative encoding by calling
+the function @code{select-safe-coding-system} (@pxref{User-Chosen
+Coding Systems}). If selecting a different encoding requires to ask
+the user to specify a coding system, @code{buffer-file-coding-system}
+is updated to the newly selected coding system.
+
+@code{buffer-file-coding-system} does @emph{not} affect sending text
to a subprocess.
@end defvar
@code{buffer-file-coding-system} (or @code{save-buffer-coding-system}),
and that coding system cannot handle
the actual text in the buffer, the command asks the user to choose
-another coding system. After that happens, the command also updates
-@code{buffer-file-coding-system} to represent the coding system that the
-user specified.
+another coding system (by calling @code{select-safe-coding-system}).
+After that happens, the command also updates
+@code{buffer-file-coding-system} to represent the coding system that
+the user specified.
@end defvar
@defvar last-coding-system-used
@node User-Chosen Coding Systems
@subsection User-Chosen Coding Systems
-@defun select-safe-coding-system from to &optional preferred-coding-system
-This function selects a coding system for encoding the text between
-@var{from} and @var{to}, asking the user to choose if necessary.
-
-The optional argument @var{preferred-coding-system} specifies a coding
-system to try first. If that one can handle the text in the specified
-region, then it is used. If this argument is omitted, the current
-buffer's value of @code{buffer-file-coding-system} is tried first.
-
-If the region contains some multibyte characters that the preferred
-coding system cannot encode, this function asks the user to choose from
-a list of coding systems which can encode the text, and returns the
-user's choice.
-
-One other kludgy feature: if @var{from} is a string, the string is the
-target text, and @var{to} is ignored.
+@cindex select safe coding system
+@defun select-safe-coding-system from to &optional default-coding-system accept-default-p
+This function selects a coding system for encoding specified text,
+asking the user to choose if necessary. Normally the specified text
+is the text in the current buffer between @var{from} and @var{to},
+defaulting to the whole buffer if they are @code{nil}. If @var{from}
+is a string, the string specifies the text to encode, and @var{to} is
+ignored.
+
+If @var{default-coding-system} is non-@code{nil}, that is the first
+coding system to try; if that can handle the text,
+@code{select-safe-coding-system} returns that coding system. It can
+also be a list of coding systems; then the function tries each of them
+one by one. After trying all of them, it next tries the user's most
+preferred coding system (@pxref{Recognize Coding,
+prefer-coding-system, the description of @code{prefer-coding-system},
+emacs, GNU Emacs Manual}), and after that the current buffer's value
+of @code{buffer-file-coding-system} (if it is not @code{undecided}).
+
+If one of those coding systems can safely encode all the specified
+text, @code{select-safe-coding-system} chooses it and returns it.
+Otherwise, it asks the user to choose from a list of coding systems
+which can encode all the text, and returns the user's choice.
+
+The optional argument @var{accept-default-p}, if non-@code{nil},
+should be a function to determine whether the coding system selected
+without user interaction is acceptable. If this function returns
+@code{nil}, the silently selected coding system is rejected, and the
+user is asked to select a coding system from a list of possible
+candidates.
+
+@vindex select-safe-coding-system-accept-default-p
+If the variable @code{select-safe-coding-system-accept-default-p} is
+non-@code{nil}, its value overrides the value of
+@var{accept-default-p}.
@end defun
Here are two functions you can use to let the user specify a coding
@code{coding-system-for-read} and @code{coding-system-for-write}
(@pxref{Specifying Coding Systems}).
+@defvar auto-coding-regexp-alist
+This variable is an alist of text patterns and corresponding coding
+systems. Each element has the form @code{(@var{regexp}
+. @var{coding-system})}; a file whose first few kilobytes match
+@var{regexp} is decoded with @var{coding-system} when its contents are
+read into a buffer. The settings in this alist take priority over
+@code{coding:} tags in the files and the contents of
+@code{file-coding-system-alist} (see below). The default value is set
+so that Emacs automatically recognizes mail files in Babyl format and
+reads them with no code conversions.
+@end defvar
+
@defvar file-coding-system-alist
This variable is an alist that specifies the coding systems to use for
reading and writing particular files. Each element has the form
@defvar locale-coding-system
@tindex locale-coding-system
+@cindex keyboard input decoding on X
This variable specifies the coding system to use for decoding system
-error messages, for encoding the format argument to
-@code{format-time-string}, and for decoding the return value of
-@code{format-time-string}.
+error messages and---on X Window system only---keyboard input, for
+encoding the format argument to @code{format-time-string}, and for
+decoding the return value of @code{format-time-string}.
@end defvar
@defvar system-messages-locale