This article describes the canvas portal framework that facilitates the development of alternative view-based space-management techniques on large displays. Implementations of the framework provide layout management, context switching, and space creation. The canvas portals are alternative views of display canvas areas where interacting with the portal's interior is equivalent to interacting with the depicted display area. To illustrate the generality of the canvas portals concept, we've instantiated a representative sample of existing large-display interaction techniques within the canvas portal design space, and developed several interaction techniques that address some of the challenges in new ways.