Gets or sets the token that cancels a render of a page: its display-list build and its drawing.
public CancellationToken CancellationToken { get; set; }
Viewer capability 2 (issue #97). The build checks it as CancellationToken does (every 1,024 operators, every nested stream, and inside the decoding of content and images); the drawing before every operation of the display list. A cancelled render throws ; the bitmap keeps what was drawn, and nothing is left behind that changes a later render.