code: @SuppressWarnings({"WeakerAccess", "unused"})
     public RectF  getDocumentViewBox()
     {
        if (this.rootElement == null)
           throw new IllegalArgumentException("SVG document is empty");
  
        if (this.rootElement.viewBox == null)
           return null;
  
        return this.rootElement.viewBox.toRectF();       
     }
docs: Returns the viewBox attribute of the current SVG document.
  
  @return the document's viewBox attribute as a {@code android.graphics.RectF} object, or null if not set.
  @throws IllegalArgumentException if there is no current SVG document loaded.