Adding the same component instance multiple times should throw

[Marc Englund]

Adding the same component instance to the same application multiple times (so that the same component instance exists in the application component hierarchy multiple times) should trow:

layoutA.addComponent(component);
layoutB.addComponent(component); // should throw

Currently it's very easy to make add the same component twice, which will not fail, but cause strange things to happen.

Something like:

AbstractComponentContainer.addComponent(Component c) {
   ComponentContainer parent = c.getParent();
   if (parent!=null&&parent.contains(c)) {
      // NOTE ComponentContainer does not have a contains() -method
      throw new SomeSuitableException("The component is already added to...");
   }
   c.setParent(this);
   fireComponentAttachEvent(c);
}

[Marc Englund]

Should fix #71 as well.

[Marc Englund]

Fixed in [3698].

AbstractComponent?.setParent(parent) cannot be called if component already has parent, unless the new parent is null (unsetting parent).

AbstractComponentContainer?.addComponent(component) removes the component from it's previous ComponentContainer? if needed (moves component), or throws if the component can't be removed.

All components that contain other components should implement ComponentContainer? for this to be perfect (e.g CustomComponent?, Table)"