[rfa] fix readline utf-8 display bug

[Michael Elizabeth Chastain <mec@shout.net>]

This is a patch from Chet Ramey, the maintainer of readline, to fix
the problem with perverse screen refresh with UTF-8.  This will fix
the problem with the test suite failing to run in UTF-8 environments
(the test suite patterns gets confuse by the bad perverse screen refresh).

I tested this in a standalone readline test program and in my gdb
testbed.  It works for me with LANG=en_US.UTF-8 (my normal language).
I tested with and without the "LC_ALL=C" kludge currently in lib/gdb.exp.

If this patch goes in, then I can submit to patch to revert the
assignment to LC_ALL in lib/gdb.exp, and we'll be back to testing
in the user's specified locale.

Okay to apply?

Michael C

===

2003-01-09  Michael Chastain  <mec@shout.net>

	From Chet Ramey, <chet@po.cwru.edu>, the readline maintainer:
	* display.c: Fix perverse screen refresh with UTF-8.

Index: display.c
===================================================================
RCS file: /cvs/src/src/readline/display.c,v
retrieving revision 1.6
diff -u -r1.6 display.c
--- display.c	8 Dec 2002 22:31:37 -0000	1.6
+++ display.c	9 Jan 2003 21:17:22 -0000
@@ -74,7 +74,7 @@
 static void cr PARAMS((void));
 
 #if defined (HANDLE_MULTIBYTE)
-static int _rl_col_width PARAMS((char *, int, int));
+static int _rl_col_width PARAMS((const char *, int, int));
 static int *_rl_wrapped_line;
 #else
 #  define _rl_col_width(l, s, e)	(((e) <= (s)) ? 0 : (e) - (s))
@@ -1352,9 +1352,9 @@
 	    {
 	      _rl_output_some_chars (nfd + lendiff, temp - lendiff);
 #if 0
-	      _rl_last_c_pos += _rl_col_width (nfd+lendiff, 0, temp-lendiff) - col_lendiff;
-#else
 	      _rl_last_c_pos += _rl_col_width (nfd+lendiff, 0, temp-col_lendiff);
+#else
+	      _rl_last_c_pos += _rl_col_width (nfd+lendiff, 0, temp-lendiff);
 #endif
 	    }
 	}
@@ -1514,8 +1514,15 @@
 #if defined (HANDLE_MULTIBYTE)
   /* If we have multibyte characters, NEW is indexed by the buffer point in
      a multibyte string, but _rl_last_c_pos is the display position.  In
-     this case, NEW's display position is not obvious. */
-  if ((MB_CUR_MAX == 1 || rl_byte_oriented ) && _rl_last_c_pos == new) return;
+     this case, NEW's display position is not obvious and must be
+     calculated. */
+  if (MB_CUR_MAX == 1 || rl_byte_oriented)
+    {
+      if (_rl_last_c_pos == new)
+	return;
+    }
+  else if (_rl_last_c_pos == _rl_col_width (data, 0, new))
+    return;
 #else
   if (_rl_last_c_pos == new) return;
 #endif
@@ -1598,11 +1605,7 @@
 #endif
     {
       if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
-	{
-	  tputs (_rl_term_cr, 1, _rl_output_character_function);
-	  for (i = 0; i < new; i++)
-	    putc (data[i], rl_outstream);
-	}
+	_rl_backspace (_rl_last_c_pos - _rl_col_width (data, 0, new));
       else
 	_rl_backspace (_rl_last_c_pos - new);
     }
@@ -2144,7 +2147,7 @@
    scan from the beginning of the string to take the state into account. */
 static int
 _rl_col_width (str, start, end)
-     char *str;
+     const char *str;
      int start, end;
 {
   wchar_t wc;
@@ -2220,4 +2223,3 @@
   return width;
 }
 #endif /* HANDLE_MULTIBYTE */
-