Animations for scroll and zoom

Smooth animation effects during zooming are provided by retaining content displayed at a previous zoom level. If the zoom operation is a zoom out operation, new content is stretched to a current zoom level, aligned with the retained content, and placed underneath it. If the zoom operation is a zoom in operation, new content is scaled down to the current zoom level, aligned with the retained content, and displayed on top of the retained content. The new content is then zoomed with the retained content. The retained content is then deleted. When zooming out, the retained content fades out. When zooming in, the new content fades in. Smooth scrolling animation is also provided by pre-rendering a portion of content and teleporting to a final viewport position and thereby skipping over blank content.