1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
5 * except in compliance with the License. You may obtain a copy of the License at
6 *
7 *      http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the
10 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
11 * KIND, either express or implied. See the License for the specific language governing
12 * permissions and limitations under the License.
13 */
14
15package com.android.systemui.qs;
16
17import android.graphics.Path;
18import android.view.animation.BaseInterpolator;
19import android.view.animation.Interpolator;
20
21public class PathInterpolatorBuilder {
22
23    // This governs how accurate the approximation of the Path is.
24    private static final float PRECISION = 0.002f;
25
26    private float[] mX; // x coordinates in the line
27    private float[] mY; // y coordinates in the line
28    private float[] mDist; // Cumulative percentage length of the line
29
30    public PathInterpolatorBuilder(Path path) {
31        initPath(path);
32    }
33
34    public PathInterpolatorBuilder(float controlX, float controlY) {
35        initQuad(controlX, controlY);
36    }
37
38    public PathInterpolatorBuilder(float controlX1, float controlY1, float controlX2,
39            float controlY2) {
40        initCubic(controlX1, controlY1, controlX2, controlY2);
41    }
42
43    private void initQuad(float controlX, float controlY) {
44        Path path = new Path();
45        path.moveTo(0, 0);
46        path.quadTo(controlX, controlY, 1f, 1f);
47        initPath(path);
48    }
49
50    private void initCubic(float x1, float y1, float x2, float y2) {
51        Path path = new Path();
52        path.moveTo(0, 0);
53        path.cubicTo(x1, y1, x2, y2, 1f, 1f);
54        initPath(path);
55    }
56
57    private void initPath(Path path) {
58        float[] pointComponents = path.approximate(PRECISION);
59
60        int numPoints = pointComponents.length / 3;
61        if (pointComponents[1] != 0 || pointComponents[2] != 0
62                || pointComponents[pointComponents.length - 2] != 1
63                || pointComponents[pointComponents.length - 1] != 1) {
64            throw new IllegalArgumentException("The Path must start at (0,0) and end at (1,1)");
65        }
66
67        mX = new float[numPoints];
68        mY = new float[numPoints];
69        mDist = new float[numPoints];
70        float prevX = 0;
71        float prevFraction = 0;
72        int componentIndex = 0;
73        for (int i = 0; i < numPoints; i++) {
74            float fraction = pointComponents[componentIndex++];
75            float x = pointComponents[componentIndex++];
76            float y = pointComponents[componentIndex++];
77            if (fraction == prevFraction && x != prevX) {
78                throw new IllegalArgumentException(
79                        "The Path cannot have discontinuity in the X axis.");
80            }
81            if (x < prevX) {
82                throw new IllegalArgumentException("The Path cannot loop back on itself.");
83            }
84            mX[i] = x;
85            mY[i] = y;
86            if (i > 0) {
87                float dx = mX[i] - mX[i - 1];
88                float dy = mY[i] - mY[i - 1];
89                float dist = (float) Math.sqrt(dx * dx + dy * dy);
90                mDist[i] = mDist[i - 1] + dist;
91            }
92            prevX = x;
93            prevFraction = fraction;
94        }
95        // Scale down dist to 0-1.
96        float max = mDist[mDist.length - 1];
97        for (int i = 0; i < numPoints; i++) {
98            mDist[i] /= max;
99        }
100    }
101
102    public Interpolator getXInterpolator() {
103        return new PathInterpolator(mDist, mX);
104    }
105
106    public Interpolator getYInterpolator() {
107        return new PathInterpolator(mDist, mY);
108    }
109
110    private static class PathInterpolator extends BaseInterpolator {
111        private final float[] mX; // x coordinates in the line
112        private final float[] mY; // y coordinates in the line
113
114        private PathInterpolator(float[] xs, float[] ys) {
115            mX = xs;
116            mY = ys;
117        }
118
119        @Override
120        public float getInterpolation(float t) {
121            if (t <= 0) {
122                return 0;
123            } else if (t >= 1) {
124                return 1;
125            }
126            // Do a binary search for the correct x to interpolate between.
127            int startIndex = 0;
128            int endIndex = mX.length - 1;
129
130            while (endIndex - startIndex > 1) {
131                int midIndex = (startIndex + endIndex) / 2;
132                if (t < mX[midIndex]) {
133                    endIndex = midIndex;
134                } else {
135                    startIndex = midIndex;
136                }
137            }
138
139            float xRange = mX[endIndex] - mX[startIndex];
140            if (xRange == 0) {
141                return mY[startIndex];
142            }
143
144            float tInRange = t - mX[startIndex];
145            float fraction = tInRange / xRange;
146
147            float startY = mY[startIndex];
148            float endY = mY[endIndex];
149            return startY + (fraction * (endY - startY));
150        }
151    }
152
153}
154