1/*
2 * Copyright (C) 2012 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
17#ifndef ANDROID_HWUI_PATH_TESSELLATOR_H
18#define ANDROID_HWUI_PATH_TESSELLATOR_H
19
20#include "Matrix.h"
21#include "Rect.h"
22#include "Vertex.h"
23#include "VertexBuffer.h"
24
25#include <algorithm>
26#include <vector>
27
28class SkPath;
29class SkPaint;
30
31namespace android {
32namespace uirenderer {
33
34/**
35 * Structure used for threshold values in outline path tessellation.
36 *
37 * TODO: PaintInfo should store one of this object, and initialized all values in constructor
38 * depending on its type (point, line or path).
39 */
40struct PathApproximationInfo {
41    PathApproximationInfo(float invScaleX, float invScaleY, float pixelThreshold)
42            : thresholdSquared(pixelThreshold * pixelThreshold)
43            , sqrInvScaleX(invScaleX * invScaleX)
44            , sqrInvScaleY(invScaleY * invScaleY)
45            , thresholdForConicQuads(pixelThreshold * std::min(invScaleX, invScaleY) / 2.0f){};
46
47    const float thresholdSquared;
48    const float sqrInvScaleX;
49    const float sqrInvScaleY;
50    const float thresholdForConicQuads;
51};
52
53class PathTessellator {
54public:
55    /**
56     * Populates scaleX and scaleY with the 'tessellation scale' of the transform - the effective X
57     * and Y scales that tessellation will take into account when generating the 1.0 pixel thick
58     * ramp.
59     *
60     * Two instances of the same shape (size, paint, etc.) will only generate the same vertices if
61     * their tessellation scales are equal.
62     */
63    static void extractTessellationScales(const Matrix4& transform, float* scaleX, float* scaleY);
64
65    /**
66     * Populates a VertexBuffer with a tessellated approximation of the input convex path, as a
67     * single
68     * triangle strip. Note: joins are not currently supported.
69     *
70     * @param path The path to be approximated
71     * @param paint The paint the path will be drawn with, indicating AA, painting style
72     *        (stroke vs fill), stroke width, stroke cap & join style, etc.
73     * @param transform The transform the path is to be drawn with, used to drive stretch-aware path
74     *        vertex approximation, and correct AA ramp offsetting.
75     * @param vertexBuffer The output buffer
76     */
77    static void tessellatePath(const SkPath& path, const SkPaint* paint, const mat4& transform,
78                               VertexBuffer& vertexBuffer);
79
80    /**
81     * Populates a VertexBuffer with a tessellated approximation of points as a single triangle
82     * strip (with degenerate tris separating), respecting the shape defined by the paint cap.
83     *
84     * @param points The center vertices of the points to be drawn
85     * @param count The number of floats making up the point vertices
86     * @param paint The paint the points will be drawn with indicating AA, stroke width & cap
87     * @param transform The transform the points will be drawn with, used to drive stretch-aware
88     * path
89     *        vertex approximation, and correct AA ramp offsetting
90     * @param vertexBuffer The output buffer
91     */
92    static void tessellatePoints(const float* points, int count, const SkPaint* paint,
93                                 const mat4& transform, VertexBuffer& vertexBuffer);
94
95    /**
96     * Populates a VertexBuffer with a tessellated approximation of lines as a single triangle
97     * strip (with degenerate tris separating).
98     *
99     * @param points Pairs of endpoints defining the lines to be drawn
100     * @param count The number of floats making up the line vertices
101     * @param paint The paint the lines will be drawn with indicating AA, stroke width & cap
102     * @param transform The transform the points will be drawn with, used to drive stretch-aware
103     * path
104     *        vertex approximation, and correct AA ramp offsetting
105     * @param vertexBuffer The output buffer
106     */
107    static void tessellateLines(const float* points, int count, const SkPaint* paint,
108                                const mat4& transform, VertexBuffer& vertexBuffer);
109
110    /**
111     * Approximates a convex outline into a clockwise Vector of 2d vertices.
112     *
113     * @param path The outline to be approximated
114     * @param threshold The threshold of acceptable error (in pixels) when approximating
115     * @param outputVertices An empty Vector which will be populated with the output
116     */
117    static bool approximatePathOutlineVertices(const SkPath& path, float threshold,
118                                               std::vector<Vertex>& outputVertices);
119
120private:
121    static bool approximatePathOutlineVertices(const SkPath& path, bool forceClose,
122                                               const PathApproximationInfo& approximationInfo,
123                                               std::vector<Vertex>& outputVertices);
124
125    /*
126      endpoints a & b,
127      control c
128     */
129    static void recursiveQuadraticBezierVertices(float ax, float ay, float bx, float by, float cx,
130                                                 float cy,
131                                                 const PathApproximationInfo& approximationInfo,
132                                                 std::vector<Vertex>& outputVertices,
133                                                 int depth = 0);
134
135    /*
136      endpoints p1, p2
137      control c1, c2
138     */
139    static void recursiveCubicBezierVertices(float p1x, float p1y, float c1x, float c1y, float p2x,
140                                             float p2y, float c2x, float c2y,
141                                             const PathApproximationInfo& approximationInfo,
142                                             std::vector<Vertex>& outputVertices, int depth = 0);
143};
144
145};  // namespace uirenderer
146};  // namespace android
147
148#endif  // ANDROID_HWUI_PATH_TESSELLATOR_H
149