Prevent the display of negative portions of x and y axes

I have a NodeTemplate that has the following form:

         var recttemplate =  GO(go.Node, "Horizontal", 
                                                    GO(go.Shape, "Rectangle", 
                                                        new go.Binding("fill", "fill"),
                                                        new go.Binding("width", "width"),
                                                        new go.Binding("height", "height")
                                                        ),
                                                      {
                                                            mouseEnter: function(e, node){
                                                                //alert("key on mouse Over is :" + node.data.key);
                                                                var nextRowObject = RowSeatRef_array[node.data.key];
                                                                var msg = "Row " + nextRowObject.RowNum + " in Section: " + nextRowObject.Section + " $" + nextRowObject.Price + " has " + nextRowObject.NumSeatsAvail + " available. Right-Click to select seats on this row.";
                                                                var xpos = node.location.x;
                                                                var ypos = node.location.y;
                                                                setMapInfoBoxOverlay(msg, xpos, ypos);
                                                            },
                                                            mouseLeave: function(e, node){
                                                                clearMapInfoBoxOverlay();
                                                            },
                                                            contextClick: function(e, node){
                                                                CurrentParentClickedOnRef =  RowSeatRef_array[node.data.key];
                                                                displayRowContextMenu();
                                                            }
                                                        },
                                                      new go.Binding("angle", "rotation"),
                                                        new go.Binding("location", "shapePosition")
                                                )

And I create nodes of the above category in my Diagram which is initialized with the following parameters:

       SeatingMapGraphicsRef    = GO(go.Diagram, 'seatingMapPanelGoJSDiagram',  {
      allowResize: true,
            allowZoom: false,
            allowHorizontalScroll: false,
            allowVerticalScroll: false,
            scrollMode: go.Diagram.InfiniteScroll,
            autoScrollRegion: new go.Margin(0, 0, 0, 0),
            initialContentAlignment: go.Spot.Center
            initialAutoScale:go.Diagram.Uniform
        });

I currently am having the following behavior. Currently, I can drag Nodes to say the upper left corner of my gojs Diagram. When I have an alert() message which tells me the node.location.x and node.location.y coordinates I start to get negative values for both the x and y coordinates, with my GraphObject being well within the boundaries of the diagram. THe only way that seems possible is if I had set up the diagram to somehow display the negative portions of the x and y axis , or if the visual part of the GraphObject somehow has a lot of invisible padding around which make invisible portions go off the grid. Is there anyway I can force all objects wihin the bounds of my Diagram to never have negative x and y location values? Thank you!
Ryan.

You’l want a Node.dragComputation that you can derive from: http://gojs.net/latest/samples/absolute.html. I assume you do not want to use Diagram.fixedBounds.

The main thing is to implement Diagram.positionComputation: http://gojs.net/latest/samples/scrollModes.html