AddHiddenElements specifies if hidden elements are read.
The elements is hidden if in svg file its visibility attribute is set to "hidden" or display attribute is set to "none".
If visibility attribute is set to "hidden", than the element is hidden but it still occupies space (Visibility.Hidden).
If display attribute is set to "none", that the element is hidden and it does not occupy space (Visibility.Collapsed).
If AddHiddenElements is true (default) the hidden elements are read and their Visibility is set to Hidden or Collapsed value.
If AddHiddenElements is false the hidden elements are skipped.