[PATCH] better isearch support for complex input methods

[Karl Fogel]

This patch adds a new binding to isearch mode, C-o, which grabs one
letter at a time from the buffer and adds it to the search string.

Here's why this is useful:

Until recently, there was no point having a special keybinding for
this in isearch mode, because it would almost always have been just as
easy to type the letter itself, as to type a special binding to grab
the letter.

However, with modern input methods (such as `chinese-tonepy'), typing
a letter can be an involved process.  In fact, in Chinese language
environments, what Emacs thinks of as a single letter is often
conceptually a whole word, i.e., one ideograph.  It's very useful to
be able to grab one ideograph at a time from the buffer and add it to
the search string.

Currently, if one uses C-w in isearch in Chinese text, it grabs to the
next punctuation mark or end of line.  This is usually not what the
user wanted -- it's much more likely that they want to grab one
Chinese character at a time.

This patch binds C-o to a new function `isearch-yank-letter'.  C-o
seemed like a key unlikely to be often used for exiting isearch.
There may be a better binding I haven't thought of, though.

-Karl

2001-04-02  Karl Fogel  <address@hidden>

        * isearch.el (isearch-mode-map): Bind C-o in isearch to yank the
        next letter from the buffer into the search string.
        (isearch-yank-internal): New helper function, contains common
        internals of next three.
        (isearch-yank-letter): New function.
        (isearch-yank-word): Implement using isearch-yank-internal.
        (isearch-yank-line): Implement using isearch-yank-internal.

Index: isearch.el
===================================================================
RCS file: /cvs/emacs/lisp/isearch.el,v
retrieving revision 1.188
diff -u -r1.188 isearch.el
--- isearch.el  2001/02/05 17:13:28     1.188
+++ isearch.el  2001/04/03 00:20:57
@@ -286,6 +286,7 @@
     (define-key map " " 'isearch-whitespace-chars)
     (define-key map [?\S-\ ] 'isearch-whitespace-chars)
     
+    (define-key map "\C-o" 'isearch-yank-letter)
     (define-key map "\C-w" 'isearch-yank-word)
     (define-key map "\C-y" 'isearch-yank-line)
 
@@ -1057,24 +1058,32 @@
        (isearch-yank-x-selection)
       (mouse-yank-at-click click arg))))
 
-(defun isearch-yank-word ()
-  "Pull next word from buffer into search string."
-  (interactive)
+(defun isearch-yank-internal (jumpform)
+  "Pull the text from point to the point reached by JUMPFORM.
+JUMPFORM is a lambda expression that takes no arguments and returns a
+buffer position, possibly having moved point to that position.  For
+example, it might move point forward by a word and return point, or it
+might return the position of the end of the line."
   (isearch-yank-string
    (save-excursion
      (and (not isearch-forward) isearch-other-end
          (goto-char isearch-other-end))
-     (buffer-substring-no-properties
-      (point) (progn (forward-word 1) (point))))))
+     (buffer-substring-no-properties (point) (funcall jumpform)))))
 
+(defun isearch-yank-letter ()
+  "Pull next letter from buffer into search string."
+  (interactive)
+  (isearch-yank-internal (lambda () (forward-char 1) (point))))
+
+(defun isearch-yank-word ()
+  "Pull next word from buffer into search string."
+  (interactive)
+  (isearch-yank-internal (lambda () (forward-word 1) (point))))
+
 (defun isearch-yank-line ()
   "Pull rest of line from buffer into search string."
   (interactive)
-  (isearch-yank-string
-   (save-excursion
-     (and (not isearch-forward) isearch-other-end
-         (goto-char isearch-other-end))
-     (buffer-substring-no-properties (point) (line-end-position)))))
+  (isearch-yank-internal (lambda () (line-end-position))))
 
 
 (defun isearch-search-and-update ()