tween

type Engine struct {
	Duration   time.Duration  // The total duration of the tween.
	Framerate  int            // The number of tween data points per second (defaults to 60 fps - like the real gamers use).
	Transition TransitionFunc // Transition calculates the transition curve for the tween.
	Updater    Updater        // Updater updates the tween values for each frame.
	// contains filtered or unexported fields
}

type Frame struct {
	Completed    float64       // Completed is the percentage 0.0 - 1.0 of elapsed time.
	Transitioned float64       // Transitioned is the percentage 0.0 - 1.0 of transition between start and end values of the tween.
	Index        int           // Index is the current frame index
	Elapsed      time.Duration // Elapsed is the current elapsed time in the tween.
}

type TransitionFunc func(completed float64) float64

type Updater interface {
	// Start signals the beginning of a tween and is sent before the tweening
	// begins. Start may be used to setup or pre-calculate updates.
	//
	// framerate is the number of frames per second in the tween
	// frames is the total number of frames that be generated
	// frameTime is the duration for each frame
	// runningTime is the total duration for the entire tween
	Start(framerate, frames int, frameTime, runningTime time.Duration)
	// Update receives information about the current Tween Frame and should be
	// used to update output or state.
	Update(Frame Frame)
	// End signals the end of the tween and is called after all updates.
	// End may be used to clean up resources (e.g. update channels).
	End()
}