Re: long standing dnd bug fixes

[Owen Taylor <otaylor redhat com>]

Tim Janik <timj gtk org> writes:

> as far as the allocation is concerned, it is just size constrained,
> the required pointer offset is kept in x/y_offset.
> 
>           GtkDragFindData new_data = *data;
> 
>           new_data.x -= x_offset;
>           new_data.y -= y_offset;
> 
>                 gtk_drag_find_widget (tmp_list->data, &new_data);
> 
> this portion offsets the pointer relative to child->parent->window and
> then recurses to child, while:
> 
>           data->found = data->callback (widget,
>                                         data->context,
>                                         data->x - new_allocation.x,
>                                         data->y - new_allocation.y,
>                                         data->time);
> 
> only offsets the old pointer (still relative to widget->parent->window)
> with respect to the constrained allocation. it however fails to offset
> the pointer relative to widget->window via x/y_offset.

Ah, <sigh>, I _knew_ I was going to regret leaving merging up some of
the 1.2.9/1.2.10 fixes for "later".

Tue Feb 27 04:14:21 2001  Owen Taylor  <otaylor redhat com>

	* gtk/gtkdnd.c (gtk_drag_find_widget): Don't use
	new_allocation.x/new_allocation.y for coordinate,
	translation since they are clipped, use the 
	x_offset/y_offset variables we keep for the purpose instead.

> the apropriate fix is then:
> 
> diff -u -p -u -r1.77 gtkdnd.c
> --- gtkdnd.c    2002/01/04 18:28:18     1.77
> +++ gtkdnd.c    2002/01/07 07:47:12
> @@ -1342,8 +1342,8 @@ gtk_drag_find_widget (GtkWidget       *w
>         {
>           data->found = data->callback (widget,
>                                         data->context,
> -                                       data->x - new_allocation.x,
> -                                       data->y - new_allocation.y,
> +                                       data->x - new_allocation.x - x_offset,
> +                                       data->y - new_allocation.y - y_offset,
>                                         data->time);
>           /* If so, send a "drag_leave" to the last widget */
>           if (data->found)
> 
> it fixes beast, doesn't break testdnd, should be reasonably explained
> above and i had other changes pending in the same tree, so it's already
> committed.

This isn't right; new_allocation.x is completel meaningless here, and it
just happens to work in your case since you have new_allocation.x,y == 0.
The GTK+-1.2 fix was:

	  data->found = data->callback (widget,
					data->context,
					data->x - x_offset,
					data->y - y_offset,
					data->time);

Which unfortunately isn't right either [:-(, it must have broken some working
programs] since the coordinates passed to data->callback are supposed to be 
allocation relative, not widget->window relative.

The right fix is along the lines of:
  
  if (GTK_NO_WINDOW (widget))
   {
      gdk_window_get_position (window, &tx, &ty);

      window_allocation_offset_x = tx - widget->allocation.x;
      window_allocation_offset_y = ty - widget->allocation.y;
   } 
  else
   {
      window_allocation_offset_x = 0;
      window_allocation_offset_y = 0;
   }

[ This can be used in place of the existing condition at the top ]
    
	  data->found = data->callback (widget,
					data->context,
					data->x - x_offset + window_allocation_offset_x,
					data->y - y_offset + window_allocation_offset_y,
					data->time);

Regards,
                                                 Owen