The reason that the Flash authoring tools work in a sane manner is because there is a single, consistent runtime that they target.<p>There is a vast graveyard of tools that tried to wrap html and javascript so you could make reasonable GUI authoring tools. To my knowledge they were all plagued by consistency and performance problems, or placed severe limits on what you could author.<p>This is less of a way forward than it is a pipe dream, no matter how promising Canvas looks.