bug#50256: thing-at-mouse

[martin rudalics <rudalics@gmx.at>]

 > If we want to support the current documentation to the letter, the
 > only way of doing that I know of is to force WINDOW to display the
 > current buffer, at least internally, i.e. to switch to the WINDOW's
 > buffer for the duration of pos-visible-in-window-p.  If that leaves
 > everyone happy, it could be done relatively easily, but then I wonder
 > why does the code in question with-current-buffer, and what would
 > break when pos-visible-in-window-p internally switches back to the
 > buffer shown in WINDOW?

pos_visible_p already does

   if (XBUFFER (w->contents) != current_buffer)
     {
       old_buffer = current_buffer;
       set_buffer_internal_1 (XBUFFER (w->contents));
     }

martin