commonMain.io.nacular.doodle.animation.transition.FixedSpeedLinear.kt Maven / Gradle / Ivy

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A pure Kotlin, UI framework for the Web

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package io.nacular.doodle.animation.transition

import io.nacular.doodle.animation.Moment
import io.nacular.doodle.animation.Velocity
import io.nacular.measured.units.Measure
import io.nacular.measured.units.Time
import io.nacular.measured.units.Units
import io.nacular.measured.units.abs
import io.nacular.measured.units.div
import io.nacular.measured.units.times


/**
 * Created by Nicholas Eddy on 3/30/18.
 */

public class FixedSpeedLinear(private val speed: Measure>, private val endValue: Measure): Transition {

    override fun duration(initial: Moment): Measure = (endValue - initial.position) / speed

    override fun value(initial: Moment, timeOffset: Measure): Moment {
        val delta = endValue - initial.position
        val sign  = if (delta.amount < 0) -1 else 1

        return Moment(initial.position + minOf(abs(delta), abs(speed * timeOffset)) * sign, speed * sign)
    }

    override fun endState(initial: Moment): Moment = Moment(endValue, speed * if ((endValue - initial.position).amount < 0) -1 else 1)
}