ClearReadingHighlight metodas

Reading highlight rectangles are supplied in page coordinates and painted over the requested page. This is intended for the current paragraph, heading, table cell, or line being spoken

Clear the highlight when playback stops or when the application moves to another fragment. ReadingHighlightColor controls the overlay colour

• API names, type names, and PDF terms keep their original spelling so code search remains reliable
• Call the member only after the owning document or viewer is active unless the syntax describes an event or design-time property