*
* B) grab the lower, drag 1 down, region (and mouse) are in dropzone, The End.
* upper region is only down one track and cannot be moved into the zone.
+ *
+ * Proposed solution:
+ * keep track of how many regions are in the DZ (private var),
+ * also count from how many tracks the dragged-regions come from (first move)
+ *
+ * if not all regions are in the DZ, keep going.
+ *
+ * Using 'default height' H for all dropzone regions will make things
+ * a lot simpler: (number_of_DZ_entries * H + Pointer_YPOS - DZ_YPOS) / H.
+ * (because at this point in time PlaylistDropzoneMap is not yet populated)
*/
delta_time_axis_view = _time_axis_views.size () - _last_pointer_time_axis_view;
#ifdef DEBUG_DROPZONEDRAG