Bug 10931

WebCore needs a separate AnimationCompositor class for animation calculations KSVG2 had a hackish animation model in which a single class (KSVGTimeScheduler) held all of the logic necessary for animation (in a single function with a large switch statement). A bette model for animation would involve at least: 1. a separate timer scheduling class 2. separate classes containing animation application logic for each of the basic animation elements 3. a animation compositor class, to orchestrate the application of animation This bug covers implementing #3, the compositor. The SMIL animation composition model (aka "AnimationSandwichModel") is pretty well spelled out in: http://www.w3.org/TR/2005/REC-SMIL2-20051213/animation.html#animationNS-AnimationSandwichModel 1. individual animation elements will need to know their priority (a monotonically increasing number based on parse order, or a override value manually specified on the element) 2. when the "applyAnimations()" method is called on the compositor, a specific target will be passed 3. animation elements targeting the passed element will be grabbed out of a hash and sorted into priority order. 4. the compositor will walk backwards through that priority list until either hitting the beginning or an animation with additive="replace". 5. the compositor can then walk forwards to generate the new value from the original baseValue or replaced value. This is a very rough sketch. This bug covers breaking the existing KSVGTimeScheduler composition logic out into its own class, and wiring things up enough to at least confirm that simple animations work.