Code for OnLButtonUp Message Map.


// nnodes: total number of nodes added to the graph
// nodeCount: current node selection state for adding edges (either 0 or 1)
// FindNode: If the user clicks on an existing node, FindNode returns the
             index of that node.  If user does not click on an existing node,
             FindNode returns -1.

void CDykstraView::OnLButtonUp(UINT nFlags, CPoint point)
{
   ~~ declare local variables.
   switch(state)
   {
      case: ADDNODES
          nodes[nnodes++] = new Node(point);
          break;
      case: ADDEDGES
          // If first node not selected yet
          if (nodeCount == 0)
          {
              fromNode = FindNode(point);
              if (fromNode != -1)
                  nodeCount++;
          }
          else
    	  {
              toNode = FindNode(point);
              if (toNode != -1)
              {
	          ~~ Show modal dialog to get cost.
	          ~~ Add two directed edges to CEdge array.
    	      }	
              ~~ Update node array.
              ~~ reset nodeCount back to 0
           }
           break;
        case: SETSTART
            index = FindNode(point);
            if (index != -1)
                startnode = index;
            break;
        case: SETDEST
            ~ Look at case SETSTART.       
            break;
    }     
    Invalidate();
}