Re: long standing dnd bug fixes

[Tim Janik <timj gtk org>]

On 4 Jan 2002, Owen Taylor wrote:

> Tim Janik <timj gtk org> writes:

> > 2) wrong drop position calculations within scrolled windows that have
> >    non-0 scroll offsets (and probably other cases where parent->window !=
> >    gtk_widget_get_parent_window (child)).

>  - A simple test case (sticking testdnd in a scrolled window)
>    works fine with the old code.

the setup i use in beast is actually a VBox in a scrolled window (i.e.
NO_WINDOW) which is drag destination.
after a couple of hours poking, i believe the issue going on is:

          gdk_window_get_position (window, &tx, &ty);
          new_allocation.x += tx;
          x_offset += tx;

          if (new_allocation.x < 0)
            {
              new_allocation.width += new_allocation.x;
              new_allocation.x = 0;
            }

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.

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.

> 
> Regards,
>                                         Owen

---
ciaoTJ