Represents the "R" entry of the appearance dictionary object.

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

This property may contain one of two different types:.

1) An Element.

2) A FormXObjectElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 168, page 389.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 170, page 472.

The rollover appearance is shown when the cursor is over the annotation, allowing interactive visual feedback without a mouse-button event.