bug#10368: 24.0.92; wrong char-width by display table

[Kenichi Handa]

I received the bug report about char-width used with display
table as this.

(progn
  (setq buffer-display-table (make-display-table))
  (aset buffer-display-table ?a [?エ ?イ])
  (char-width ?a))
=> 2

The attached is a patch to fix it.  As this bug exists in
Emacs 23.3 (so it is not a regression), I have not yet
installed it to the trunk.  What should I do?
  (1) commit it to emacs-23 branch now
  (2) commit it to trunk now
  (3) after the release of 24, commit it to trunk

---
Kenichi Handa
handa@m17n.org

=== modified file 'src/ChangeLog'
--- src/ChangeLog       2011-12-25 09:06:42 +0000
+++ src/ChangeLog       2011-12-26 04:57:25 +0000
@@ -1,3 +1,8 @@
+2011-12-26  Kenichi Handa  <handa@m17n.org>
+
+       * character.c (char_width): New function.
+       (Fchar_width, c_string_width, lisp_string_width): Use char_width.
+
 2011-12-24  Andreas Schwab  <schwab@linux-m68k.org>
 
        * callint.c (Fcall_interactively): Don't truncate prompt string.

=== modified file 'src/character.c'
--- src/character.c     2011-11-20 02:29:42 +0000
+++ src/character.c     2011-12-26 04:55:24 +0000
@@ -308,6 +308,31 @@
     }
 }
 
+
+/* Return width (columns) of C considering the buffer display table DP. */
+
+static int
+char_width (int c, struct Lisp_Char_Table *dp)
+{
+  int width = CHAR_WIDTH (c);
+
+  if (dp)
+    {
+      Lisp_Object disp = DISP_CHAR_VECTOR (dp, c), ch;
+      int i;
+
+      if (VECTORP (disp))
+       for (i = 0, width = 0; i < ASIZE (disp); i++)
+         {
+           ch = AREF (disp, i);
+           if (CHARACTERP (ch))
+             width += CHAR_WIDTH (XFASTINT (ch));
+         }
+    }
+  return width;
+}
+
+
 DEFUN ("char-width", Fchar_width, Schar_width, 1, 1, 0,
        doc: /* Return width of CHAR when displayed in the current buffer.
 The width is measured by how many columns it occupies on the screen.
@@ -315,21 +340,11 @@
 usage: (char-width CHAR)  */)
   (Lisp_Object ch)
 {
-  Lisp_Object disp;
   int c, width;
-  struct Lisp_Char_Table *dp = buffer_display_table ();
 
   CHECK_CHARACTER (ch);
   c = XINT (ch);
-
-  /* Get the way the display table would display it.  */
-  disp = dp ? DISP_CHAR_VECTOR (dp, c) : Qnil;
-
-  if (VECTORP (disp))
-    width = sanitize_char_width (ASIZE (disp));
-  else
-    width = CHAR_WIDTH (c);
-
+  width = char_width (c, buffer_display_table ());
   return make_number (width);
 }
 
@@ -350,22 +365,9 @@
 
   while (i_byte < len)
     {
-      int bytes, thiswidth;
-      Lisp_Object val;
+      int bytes;
       int c = STRING_CHAR_AND_LENGTH (str + i_byte, bytes);
-
-      if (dp)
-       {
-         val = DISP_CHAR_VECTOR (dp, c);
-         if (VECTORP (val))
-           thiswidth = sanitize_char_width (ASIZE (val));
-         else
-           thiswidth = CHAR_WIDTH (c);
-       }
-      else
-       {
-         thiswidth = CHAR_WIDTH (c);
-       }
+      int thiswidth = char_width (c, dp);
 
       if (precision > 0
          && (width + thiswidth > precision))
@@ -447,18 +449,7 @@
          else
            c = str[i_byte], bytes = 1;
          chars = 1;
-         if (dp)
-           {
-             val = DISP_CHAR_VECTOR (dp, c);
-             if (VECTORP (val))
-               thiswidth = sanitize_char_width (ASIZE (val));
-             else
-               thiswidth = CHAR_WIDTH (c);
-           }
-         else
-           {
-             thiswidth = CHAR_WIDTH (c);
-           }
+         thiswidth = char_width (c, dp);
        }
 
       if (precision <= 0)