On 2013-06-13 11:18, Dmitriy Igrishin wrote:
>
> Who owns the contents? WStackedWidget, or WMenuItem, or?
>
> WMenuItem.
>
> Who owns the menu items? WMenu, or?
>
> WMenu.
>
> Why doesn't WMenu have a setContentsStack?
>
> Why doesn't WMenuItem have a setContents?
>
> I believe because it does not worth it.
> Can you please explain why do we need these stuff?
> What real example usage?
>
>
Thanks for the reply. I'm creating classes the larger part of the widget
tree as values, to minimize allocations. I'm assuming the ownership /
memory model of Wt is the same as that of Qt.
E.g., if you write
WWidget parent_;
WWidget child_( &parent );
everything will be ok, because destruction and deregistration is done in
reversed order.
With WMenuItem and friends, stuff becomes a bit more confusing, because
you need to pass its child widget, and, more importantly, its child
widget needs to be heap allocated.
E.g., if you write
WStackedWidget stack_;
WMenu menu_( &stack_, &some_parent );
SomeContent contents_;
WMenuItem some_item_( "my label", &contents_ );
you will be in trouble, because contents_ will be deleted twice. If we
were able to write
WStackedWidget stack_;
WMenu menu_( &stack_, &some_parent );
WMenuItem some_item_( "my label" );
SomeContent contents_;
some_item_.setContents( contents_ );
and assuming the same ownership model is in place, this wouldn't fail.
Having said all this, I still don't understand the condition of the
destruction in WMenuItem. Why doesn't this read
~WMenuItem() {
if ( contents_ ) {
delete contents_;
}
}
Thanks,
Rutger
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