Abstract: When viewing a document, a user may switch between detailed reading of the document, and glancing at the structure of the document, in a single smooth flow of actions. In one example, a document is shown with a navigation bar that has a thumb. Before the user clicks the thumb, the document is shown at its current position at a first zoom level. When the user clicks and holds the thumb, the current page of the document is shown at a second zoom level, which may be a full-page zoom level at which an entire page of the document fits in the viewing area. The user may drag the thumb, thereby changing the current page being shown at the second zoom level. When the use releases the thumb, the current page may be shown at the first zoom level.