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 28 class SkPath; 29 class SkPaint; 30 31 namespace android { 32 namespace 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 */ 40 struct 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 53 class PathTessellator { 54 public: 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); 119 120 private: 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
