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