Re: Bug in incremental undrawing of mouseover highlighting

[Chong Yidong <cyd@stupidchicken.com>]

Bob Rogers <rogers-emacs@rgrjr.dyndns.org> writes:

>    It seems that mouseover background highlighting is not undrawn if
> replaced by the same unhighlighted text.  This happens in the CVS
> version as of late on 11-Nov.

The problem occurs because note_mouse_highlight checks only the window
and glyph positions to see if it needs to maintain the mouse
highlight.  The relevant code is in xdisp.c:22819:

      same_region = (EQ (window, dpyinfo->mouse_face_window)
		     && vpos >= dpyinfo->mouse_face_beg_row
		     && vpos <= dpyinfo->mouse_face_end_row
		     && (vpos > dpyinfo->mouse_face_beg_row
			 || hpos >= dpyinfo->mouse_face_beg_col)
		     && (vpos < dpyinfo->mouse_face_end_row
			 || hpos < dpyinfo->mouse_face_end_col
			 || dpyinfo->mouse_face_past_end));

As far as I can tell, the simplest fix is to tell set_window_buffer to
reset the mouse face if the mouse face used to be associated with that
window.  The patch below implements this.

*** emacs/src/window.c.~1.564.~	2006-10-30 09:06:42.000000000 -0500
--- emacs/src/window.c	2006-11-20 14:13:08.000000000 -0500
***************
*** 3265,3270 ****
--- 3265,3275 ----
    struct window *w = XWINDOW (window);
    struct buffer *b = XBUFFER (buffer);
    int count = SPECPDL_INDEX ();
+ #ifdef HAVE_WINDOW_SYSTEM
+   struct frame *f = XFRAME (w->frame);
+   Display_Info *dpyinfo = (f && FRAME_X_OUTPUT (f)) ?
+     FRAME_X_DISPLAY_INFO (f) : NULL;
+ #endif
  
    w->buffer = buffer;
  
***************
*** 3345,3350 ****
--- 3350,3360 ----
  	call1 (Vrun_hooks, Qwindow_configuration_change_hook);
      }
  
+ #ifdef HAVE_WINDOW_SYSTEM
+   if (dpyinfo && EQ (window, dpyinfo->mouse_face_window))
+     clear_mouse_face (dpyinfo);
+ #endif
+ 
    unbind_to (count, Qnil);
  }