Re: address@hidden: Cursor placement with mouse in long lines with wrapped tab]

[Chong Yidong]

> When I try to set the cursor via mouse-1 on a long line that wraps in a tab
> character, the placement is off by a few characters depending on the number 
> of columns of the emacs frame.

I think this is a bug in move_it_to.  When a line ends in a tab, some
of the glyphs associated with the tab are displayed on the current
line, and some may be displayed on the next.  In move_it_to, we call
move_it_in_display_line_to to move to an x position, check if the
y-position has been reached, and go to the next line if it hasn't.
For continued lines ending in a tab, at the end of
move_it_in_display_line_to the value of it->current_x is the x-value
of the beginning of the final tab, and does not include those tab
glyphs displayed on this line.  This causes the algorithm to get
confused.

I propose the following patch.  I think it shouldn't cause any harm in
other situations, but could someone please review it?

*** emacs/src/xdisp.c.~1.1130.~ 2006-11-26 16:47:55.000000000 -0500
--- emacs/src/xdisp.c   2006-11-30 13:27:12.000000000 -0500
***************
*** 6828,6834 ****
          break;
  
        case MOVE_LINE_CONTINUED:
!         it->continuation_lines_width += it->current_x;
          break;
  
        default:
--- 6828,6834 ----
          break;
  
        case MOVE_LINE_CONTINUED:
!         it->continuation_lines_width += it->last_visible_x;
          break;
  
        default: