Represents the "IX" entry of the appearance characteristics dictionary object.

It is an optional entry defined as part of the PDF 1.0 specification.

It contains a FormXObjectElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 189, page 410.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 192, page 497.

The down-state icon replaces I while the pointer button is held down. If absent the normal icon I is shown in the down state.