class INodeHandler
{
    public:
       // Draws given Node
      	virtual void Draw(Node) = 0;

       // Returns size of describing rectangle. This function used by layouts to determine
       // nodes positions without intersections.
      	virtual idvc::dsize GetSize(Node)= 0;

       // Sets zoom factor which will be used for all subsequent Draw calls. This function
       // is used by control core part in zooming implementation.
	virtual void SetZoomFactor(double f) {};

       // Processes mouse click event
       virtual ChangesType HandleClick(Node n, double inX, double inY,
                                     int kstate, idvc::MouseButton Button);

	// Processes tooltip event
       virtual ChangesType HandleOnTooltip(Node n, CGraphTooltipEvent* pEvent);

}; // end INodeHandler

            

class ILayout
{
    public:

        /// This function should make new layout for all nodes inside
        /// given node and calculate it size. Positions for nodes inside
        /// must be defined regarding upper left corner of given node,
        /// assuming it has coordinates (0,0).
        virtual void Make( Node ) = 0;

        /// The same as Make, but it should use information from
        /// previous layouts and try keep mutual positions of already
        /// placed nodes.
        virtual void Update( Node ) = 0;

        /// This function recalculates coordinates of nodes and edges
        /// when changed sizes of owned nodes or skip parameters of 
  	 /// ILayout.
        /// It assumed that Make or Update was called before and sizes 
        /// of all owned nodes is known. Unlike Make and Update, it 
  	 /// is not recursive.
        virtual void Resize( Node ) = 0;
};
            

void CContent::DrawContent(idvc::IPainter* p)
{
    // determine invalid rectangles which should be repainted
    idvcfrw::CInvalidRegion InvalidRegions(draw_rect, valid_rect);

    for(int i = 0; i < InvalidRegions.size(); ++i)
    {   
	 // get rectangle corresponding to next invalid region
        idvc::drect rect = InvalidRegions[i];

        // find and repaint nodes which intersect with invalid rectangle
        NodeSet nodes = graph->HitNodeTest(rect.left, rect.top, rect.right, rect.bottom);
        for_each(nodes.begin(), nodes.end(), DrawNode(p,scale));

	 // find and repaint edges which intersect with invalid rectangle
        EdgeSet es = graph->HitEdgeTest(rect.left, rect.top, rect.right, rect.bottom);
        for_each(es->Begin(), es->End(), DrawEdge(p,scale));
    };
};
            

ChangesType PortNodeHandler::HandleClick(Node n, double inX, double inY, 
                                         int kstate, idvc::MouseButton Button)
{
    ChangesType processed = ctNone;
    idvc::dpoint pos = n->GetPosition();
    idvc::dsize size = n->GetSize();

    // if node doesn’t have nested nodes and was clicked by left mouse button
    if ( (n->GetOwned()->GetCount() == 0) && (Button == idvc::mbLeft) )
    {
        if (node_drawer.IsLeftPortClicked(n, inX, inY))
	 {
	     bool hide = ( CountAllParents(n) == CountVisibleParents(n) );
 	     // if all parents visible
	     if( hide )   Fold(n, fdParents);
	     else       Unfold(n, fdParents);
	 }
        else if (node_drawer.IsRightPortClicked(n, inX, inY))
	 {
	     bool hide = ( CountAllChildren(n) == CountVisibleChildren(n) );
	     // if all children visible
	     if( hide ) Fold(n, fdChildren);
	     else     Unfold(n, fdChildren);
	 }
        else
        {
            // if user clicks on node itself mark it as selected
            SetFlag(n, Node::fSelected, !IsFlagSet(n, Node::fSelected));
        };
        processed = ctAll;
    };
    OnClick.fire(n, inX, inY, kstate, Button);
    return processed;
};