1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16#ifndef MATHUTILS_H
17#define MATHUTILS_H
18
19#include <math.h>
20
21namespace android {
22namespace uirenderer {
23
24#define NON_ZERO_EPSILON (0.001f)
25#define ALPHA_EPSILON (0.001f)
26
27class MathUtils {
28public:
29    /**
30     * Check for floats that are close enough to zero.
31     */
32    inline static bool isZero(float value) {
33        return (value >= -NON_ZERO_EPSILON) && (value <= NON_ZERO_EPSILON);
34    }
35
36    inline static bool isPositive(float value) {
37        return value >= NON_ZERO_EPSILON;
38    }
39
40    /**
41     * Clamps alpha value, and snaps when very near 0 or 1
42     */
43    inline static float clampAlpha(float alpha) {
44        if (alpha <= ALPHA_EPSILON) {
45            return 0;
46        } else if (alpha >= (1 - ALPHA_EPSILON)) {
47            return 1;
48        } else {
49            return alpha;
50        }
51    }
52
53    /*
54     * Clamps positive tessellation scale values
55     */
56    inline static float clampTessellationScale(float scale) {
57        const float MIN_SCALE = 0.0001;
58        const float MAX_SCALE = 1e10;
59        if (scale < MIN_SCALE) {
60            return MIN_SCALE;
61        } else if (scale > MAX_SCALE) {
62            return MAX_SCALE;
63        }
64        return scale;
65    }
66
67    /**
68     * Returns the number of points (beyond two, the start and end) needed to form a polygonal
69     * approximation of an arc, with a given threshold value.
70     */
71    inline static int divisionsNeededToApproximateArc(float radius,
72            float angleInRads, float threshold) {
73        const float errConst = (-threshold / radius + 1);
74        const float targetCosVal = 2 * errConst * errConst - 1;
75
76        // needed divisions are rounded up from approximation
77        return (int)(ceilf(angleInRads / acos(targetCosVal)/2)) * 2;
78    }
79
80    inline static bool areEqual(float valueA, float valueB) {
81        return isZero(valueA - valueB);
82    }
83
84    template<typename T>
85    static inline T max(T a, T b) {
86        return a > b ? a : b;
87    }
88
89    template<typename T>
90    static inline T min(T a, T b) {
91        return a < b ? a : b;
92    }
93
94    template<typename T>
95    static inline T clamp(T a, T minValue, T maxValue) {
96        return min(max(a, minValue), maxValue);
97    }
98
99    inline static float lerp(float v1, float v2, float t) {
100        return v1 + ((v2 - v1) * t);
101    }
102}; // class MathUtils
103
104} /* namespace uirenderer */
105} /* namespace android */
106
107#endif /* MATHUTILS_H */
108