See Book Window.

Define extension points.

Below the book title bar is the book itself, where the book's selected page is presented.

The book can be resizible and has vertical and/or horizontal scroll bars when the book's page become bigger than the book window.

Dragging the edges or corners of a Sophie book window changes the window size. All edges and corners possess this behavior.

The X and Y fields in the bottom left corner show the value and can be manually changed.