===================================================================
RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/less/line.c,v
retrieving revision 1.22
retrieving revision 1.23
diff -c -r1.22 -r1.23
*** src/usr.bin/less/line.c	2017/04/02 23:02:06	1.22
--- src/usr.bin/less/line.c	2019/02/24 04:54:36	1.23
***************
*** 15,20 ****
--- 15,22 ----
   * in preparation for output to the screen.
   */
  
+ #include <wchar.h>
+ 
  #include "charset.h"
  #include "less.h"
  
***************
*** 373,422 ****
   * attribute sequence to be inserted, so this must be taken into account.
   */
  static int
! pwidth(LWCHAR ch, int a, LWCHAR prev_ch)
  {
  	int w;
  
! 	if (ch == '\b')
! 		/*
! 		 * Backspace moves backwards one or two positions.
! 		 * XXX - Incorrect if several '\b' in a row.
! 		 */
! 		return ((utf_mode && is_wide_char(prev_ch)) ? -2 : -1);
! 
! 	if (!utf_mode || is_ascii_char(ch)) {
! 		if (control_char((char)ch)) {
! 			/*
! 			 * Control characters do unpredictable things,
! 			 * so we don't even try to guess; say it doesn't move.
! 			 * This can only happen if the -r flag is in effect.
! 			 */
! 			return (0);
! 		}
! 	} else {
! 		if (is_composing_char(ch) || is_combining_char(prev_ch, ch)) {
! 			/*
! 			 * Composing and combining chars take up no space.
! 			 *
! 			 * Some terminals, upon failure to compose a
! 			 * composing character with the character(s) that
! 			 * precede(s) it will actually take up one column
! 			 * for the composing character; there isn't much
! 			 * we could do short of testing the (complex)
! 			 * composition process ourselves and printing
! 			 * a binary representation when it fails.
! 			 */
! 			return (0);
! 		}
  	}
  
  	/*
  	 * Other characters take one or two columns,
  	 * plus the width of any attribute enter/exit sequence.
  	 */
- 	w = 1;
- 	if (is_wide_char(ch))
- 		w++;
  	if (curr > 0 && !is_at_equiv(attr[curr-1], a))
  		w += attr_ewidth(attr[curr-1]);
  	if ((apply_at_specials(a) != AT_NORMAL) &&
--- 375,427 ----
   * attribute sequence to be inserted, so this must be taken into account.
   */
  static int
! pwidth(wchar_t ch, int a, wchar_t prev_ch)
  {
  	int w;
  
! 	/*
! 	 * In case of a backspace, back up by the width of the previous
! 	 * character.  If that is non-printable (for example another
! 	 * backspace) or zero width (for example a combining accent),
! 	 * the terminal may actually back up to a character even further
! 	 * back, but we no longer know how wide that may have been.
! 	 * The best guess possible at this point is that it was
! 	 * hopefully width one.
! 	 */
! 	if (ch == L'\b') {
! 		w = wcwidth(prev_ch);
! 		if (w <= 0)
! 			w = 1;
! 		return (-w);
  	}
  
+ 	w = wcwidth(ch);
+ 
  	/*
+ 	 * Non-printable characters can get here if the -r flag is in
+ 	 * effect, and possibly in some other situations (XXX check that!).
+ 	 * Treat them as zero width.
+ 	 * That may not always match their actual behaviour,
+ 	 * but there is no reasonable way to be more exact.
+ 	 */
+ 	if (w == -1)
+ 		w = 0;
+ 
+ 	/*
+ 	 * Combining accents take up no space.
+ 	 * Some terminals, upon failure to compose them with the
+ 	 * characters that precede them, will actually take up one column
+ 	 * for the combining accent; there isn't much we could do short
+ 	 * of testing the (complex) composition process ourselves and
+ 	 * printing a binary representation when it fails.
+ 	 */
+ 	if (w == 0)
+ 		return (0);
+ 
+ 	/*
  	 * Other characters take one or two columns,
  	 * plus the width of any attribute enter/exit sequence.
  	 */
  	if (curr > 0 && !is_at_equiv(attr[curr-1], a))
  		w += attr_ewidth(attr[curr-1]);
  	if ((apply_at_specials(a) != AT_NORMAL) &&