fixed size of graphObject in gojs diagram

Question

I'm looking for a possibility to define graphObject fixed size, so that the scale will not affect it. (something like actualBounds- but not readOnly)

Answer 1

Perhaps you mean like the last example here: https://gojs.net/latest/intro/legends.html#StaticParts

It shows how to make a fixed title that is unaffected by scale. It does this by repositioning and re-scaling it every time the viewport changes via a "ViewportBoundsChanged" listener.

  diagram.add(
    $(go.Part,
      {
        layerName: "Grid",  // must be in a Layer that is Layer.isTemporary,
                            // to avoid being recorded by the UndoManager
        _viewPosition: new go.Point(0,0)  // some position in the viewport,
                                           // not in document coordinates
      },
      $(go.TextBlock, "A Title", { font: "bold 24pt sans-serif", stroke: "green" })));

  // Whenever the Diagram.position or Diagram.scale change,
  // update the position of all simple Parts that have a _viewPosition property.
  diagram.addDiagramListener("ViewportBoundsChanged", function(e) {
    e.diagram.commit(function(dia) {
      // only iterates through simple Parts in the diagram, not Nodes or Links
      dia.parts.each(function(part) {
        // and only on those that have the "_viewPosition" property set to a Point
        if (part._viewPosition) {
          part.position = dia.transformViewToDoc(part._viewPosition);
          part.scale = 1/dia.scale;
        }
      })
    }, "fix Parts");
  });