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(emacs)Input Methods

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Input Methods
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   An "input method" is a kind of character conversion designed
specifically for interactive input.  In Emacs, typically each language
has its own input method; sometimes several languages which use the same
characters can share one input method.  A few languages support several
input methods.

   The simplest kind of input method works by mapping ASCII letters
into another alphabet; this allows you to use one other alphabet
instead of ASCII.  The Greek and Russian input methods work this way.

   A more powerful technique is composition: converting sequences of
characters into one letter.  Many European input methods use composition
to produce a single non-ASCII letter from a sequence that consists of a
letter followed by accent characters (or vice versa).  For example, some
methods convert the sequence `a'' into a single accented letter.  These
input methods have no special commands of their own; all they do is
compose sequences of printing characters.

   The input methods for syllabic scripts typically use mapping followed
by composition.  The input methods for Thai and Korean work this way.
First, letters are mapped into symbols for particular sounds or tone
marks; then, sequences of these which make up a whole syllable are
mapped into one syllable sign.

   Chinese and Japanese require more complex methods.  In Chinese input
methods, first you enter the phonetic spelling of a Chinese word (in
input method `chinese-py', among others), or a sequence of portions of
the character (input methods `chinese-4corner' and `chinese-sw', and
others).  One input sequence typically corresponds to many possible
Chinese characters.  You select the one you mean using keys such as
`C-f', `C-b', `C-n', `C-p', and digits, which have special meanings in
this situation.

   The possible characters are conceptually arranged in several rows,
with each row holding up to 10 alternatives.  Normally, Emacs displays
just one row at a time, in the echo area; `(I/J)' appears at the
beginning, to indicate that this is the Ith row out of a total of J
rows.  Type `C-n' or `C-p' to display the next row or the previous row.

   Type `C-f' and `C-b' to move forward and backward among the
alternatives in the current row.  As you do this, Emacs highlights the
current alternative with a special color; type `C-<SPC>' to select the
current alternative and use it as input.  The alternatives in the row
are also numbered; the number appears before the alternative.  Typing a
digit N selects the Nth alternative of the current row and uses it as
input.

   <TAB> in these Chinese input methods displays a buffer showing all
the possible characters at once; then clicking `Mouse-2' on one of them
selects that alternative.  The keys `C-f', `C-b', `C-n', `C-p', and
digits continue to work as usual, but they do the highlighting in the
buffer showing the possible characters, rather than in the echo area.

   In Japanese input methods, first you input a whole word using
phonetic spelling; then, after the word is in the buffer, Emacs
converts it into one or more characters using a large dictionary.  One
phonetic spelling corresponds to a number of different Japanese words;
to select one of them, use `C-n' and `C-p' to cycle through the
alternatives.

   Sometimes it is useful to cut off input method processing so that the
characters you have just entered will not combine with subsequent
characters.  For example, in input method `latin-1-postfix', the
sequence `e '' combines to form an `e' with an accent.  What if you
want to enter them as separate characters?

   One way is to type the accent twice; this is a special feature for
entering the separate letter and accent.  For example, `e ' '' gives
you the two characters `e''.  Another way is to type another letter
after the `e'--something that won't combine with that--and immediately
delete it.  For example, you could type `e e <DEL> '' to get separate
`e' and `''.

   Another method, more general but not quite as easy to type, is to use
`C-\ C-\' between two characters to stop them from combining.  This is
the command `C-\' (`toggle-input-method') used twice.  Note: Select
Input Method.

   `C-\ C-\' is especially useful inside an incremental search, because
it stops waiting for more characters to combine, and starts searching
for what you have already entered.

   The variables `input-method-highlight-flag' and
`input-method-verbose-flag' control how input methods explain what is
happening.  If `input-method-highlight-flag' is non-`nil', the partial
sequence is highlighted in the buffer (for most input methods--some
disable this feature).  If `input-method-verbose-flag' is non-`nil',
the list of possible characters to type next is displayed in the echo
area (but not when you are in the minibuffer).

   Input methods are implemented in the separate Leim package: they are
available only if the system administrator used Leim when building
Emacs.  If Emacs was built without Leim, you will find that no input
methods are defined.