he canvas, we may have trouble, so just quit:
          if (!(can instanceof HTMLCanvasElement)) return;

          const bbox = can.getBoundingClientRect();
          let bbw = bbox.width;
          if (bbw === 0) bbw = 0.001;
          let bbh = bbox.height;
          if (bbh === 0) bbh = 0.001;
          const mx = event.clientX - bbox.left * (can.width / pixelratio / bbw);
          const my = event.clientY - bbox.top * (can.height / pixelratio / bbh);
          const point = myDiagram.transformViewToDo