sclass ImageSurface_PositionToolTip > ImageSurfaceMouseHandler {
  *(ImageSurface is) {
    if (containsInstance(is.tools, ImageSurface_PositionToolTip)) ret;
    register(is);
  }

  public void mouseMoved aka mouseDragged(MouseEvent e) {
    pcall {
      Pt p = getPt(e);
      S s = str(p);
      var img = is.getImage();
      if (img != null && p.x >= 0 && p.y >= 0
        && p.x < img.getWidth() && p.y < img.getHeight()) {
        IToolTipMaker toolTipMaker = lookupDynamicInterface_v2 IToolTipMaker(img);
        if (toolTipMaker != null)
          s = toolTipMaker.getToolTip(p);
        else
          s += " - " + intToHex_fullLength(img.getRGB(p.x, p.y));
      }
      setToolTip(is, s);
    }
  }
}

Began life as a copy of #1008773