Statefull animator library

All animators are updated during a static Animator.update(deltaMs) call that should be executed each frame.

Alternatively an animator can be created in detached mode, a detached animator has to be updated independently each frame.

During the update routine the current state's animation callback is executed. A single animator state lifecycle looks like this:

1. setup callback is called when a state is entered
2. animator is halted for delayBefore ms
3. for duration ms animation callback is called every update
4. animator is halted for delayAfter ms
5. if transition is a string stage is changed to given state and the cycle repeats, if its a function its called and the result is used as the next state

Few notes:

• all callbacks have two arguments, self pointing to the animator instance and params being simply a shortcut to self.parameters
• self.parameters can be used to store user data on the animation instance, it in not used internally
• default initial state is called initial. Animator can be started from a different initial state by passing the state name to the start method
• stop is a special state, transitioning to it will stop the animator
• animation callback is always called at least once, even if duration is 0
• progress of current state (based on duration) can be accessed as self.progress, the value is in the range from 0 to 1
• animation callback is always called with self.progress equal to 1 to ensure proper end states of animated objects
• returning false from transition callback prevents state transition. If state has loop set to true the state will reset (setup callback and delays will not executed). If loop is not set animator will retry calling transition next update.
• pause is a special state, transitioning to pause stops update calls until resume is called on the animator.
• interrupt callback, if set, is called after every animation callback. Returning false continues normal operation, returning a string executes a state transition. It can be used trigger a state transition mid duration.
• overflow controls precise timing. It is set by default. When set if a states duration is 20ms and update call happened and 25ms that 5s will be cut from next state's duration.
• duration / delays and other state parameters can be changed dynamically during runtime from callbacks. update callback is usually used for this. Current state configuration can be accessed via self.currentState, other states can be accessed via self.states.[state name]
• self.interpolate(from, to, func) call can be used to easily animate a value using a given easing function. self.progress will be used internally. Easing function can be selected from one of many presets (based on standard css easing functions) or be passed as a function.

full state configuration object below:

export interface State<P extends Record<string, any>, T extends string> {
    duration: number
    delayBefore: number
    delayAfter: number
    loop: boolean
    overflow: boolean
    transition: string | ((context: Animator<P, T>, params: P) => string | false)
    interrupt?: ((context: Animator<P, T>, params: P) => string | false)
    animation: (context: Animator<P, T>, params: P) => void
    setup?: (context: Animator<P, T>, params: P) => void
}