PlayerAndroid/app/src/main/java/code/name/monkey/retromusic/transform/DepthTransformation.kt

/*
 * Copyright (c) 2019 Hemanth Savarala.
 *
 * Licensed under the GNU General Public License v3
 *
 * This is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by
 *  the Free Software Foundation either version 3 of the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 */

package code.name.monkey.retromusic.transform

import android.view.View
import androidx.viewpager.widget.ViewPager

class DepthTransformation : ViewPager.PageTransformer {
    override fun transformPage(page: View, position: Float) {
        if (position < -1) {    // [-Infinity,-1)
            // This page is way off-screen to the left.
            page.alpha = 0f
        } else if (position <= 0) {    // [-1,0]
            page.alpha = 1f
            page.translationX = 0f
            page.scaleX = 1f
            page.scaleY = 1f
        } else if (position <= 1) {    // (0,1]
            page.translationX = -position * page.width
            page.alpha = 1 - Math.abs(position)
            page.scaleX = 1 - Math.abs(position)
            page.scaleY = 1 - Math.abs(position)
        } else {    // (1,+Infinity]
            // This page is way off-screen to the right.
            page.alpha = 0f

        }
    }
}