Problem emitting singal with object-pointer as argument

[Shawn]

This is my first thought,
note: MyView* w; Element* pE;

item is clicked ---> emit MyRectItem::a_signal ---> MyRectItem::a_slot ---> call w->showTree(pE)

then I wander this one may be better,
item is clicked ---> emit MyRectItem::b_signal(pE) ---> MyView::shot: showTree(pE)

Actually which one is better ?
How should I design my code ?