1 2 /* 3 * Copyright 2011 Google Inc. 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 10 #ifndef GrPathUtils_DEFINED 11 #define GrPathUtils_DEFINED 12 13 #include "GrRect.h" 14 #include "SkPath.h" 15 #include "SkTArray.h" 16 17 class SkMatrix; 18 19 /** 20 * Utilities for evaluating paths. 21 */ 22 namespace GrPathUtils { 23 SkScalar scaleToleranceToSrc(SkScalar devTol, 24 const SkMatrix& viewM, 25 const GrRect& pathBounds); 26 27 /// Since we divide by tol if we're computing exact worst-case bounds, 28 /// very small tolerances will be increased to gMinCurveTol. 29 int worstCasePointCount(const SkPath&, 30 int* subpaths, 31 SkScalar tol); 32 33 /// Since we divide by tol if we're computing exact worst-case bounds, 34 /// very small tolerances will be increased to gMinCurveTol. 35 uint32_t quadraticPointCount(const GrPoint points[], SkScalar tol); 36 37 uint32_t generateQuadraticPoints(const GrPoint& p0, 38 const GrPoint& p1, 39 const GrPoint& p2, 40 SkScalar tolSqd, 41 GrPoint** points, 42 uint32_t pointsLeft); 43 44 /// Since we divide by tol if we're computing exact worst-case bounds, 45 /// very small tolerances will be increased to gMinCurveTol. 46 uint32_t cubicPointCount(const GrPoint points[], SkScalar tol); 47 48 uint32_t generateCubicPoints(const GrPoint& p0, 49 const GrPoint& p1, 50 const GrPoint& p2, 51 const GrPoint& p3, 52 SkScalar tolSqd, 53 GrPoint** points, 54 uint32_t pointsLeft); 55 56 // A 2x3 matrix that goes from the 2d space coordinates to UV space where 57 // u^2-v = 0 specifies the quad. The matrix is determined by the control 58 // points of the quadratic. 59 class QuadUVMatrix { 60 public: 61 QuadUVMatrix() {}; 62 // Initialize the matrix from the control pts 63 QuadUVMatrix(const GrPoint controlPts[3]) { this->set(controlPts); } 64 void set(const GrPoint controlPts[3]); 65 66 /** 67 * Applies the matrix to vertex positions to compute UV coords. This 68 * has been templated so that the compiler can easliy unroll the loop 69 * and reorder to avoid stalling for loads. The assumption is that a 70 * path renderer will have a small fixed number of vertices that it 71 * uploads for each quad. 72 * 73 * N is the number of vertices. 74 * STRIDE is the size of each vertex. 75 * UV_OFFSET is the offset of the UV values within each vertex. 76 * vertices is a pointer to the first vertex. 77 */ 78 template <int N, size_t STRIDE, size_t UV_OFFSET> 79 void apply(const void* vertices) { 80 intptr_t xyPtr = reinterpret_cast<intptr_t>(vertices); 81 intptr_t uvPtr = reinterpret_cast<intptr_t>(vertices) + UV_OFFSET; 82 float sx = fM[0]; 83 float kx = fM[1]; 84 float tx = fM[2]; 85 float ky = fM[3]; 86 float sy = fM[4]; 87 float ty = fM[5]; 88 for (int i = 0; i < N; ++i) { 89 const GrPoint* xy = reinterpret_cast<const GrPoint*>(xyPtr); 90 GrPoint* uv = reinterpret_cast<GrPoint*>(uvPtr); 91 uv->fX = sx * xy->fX + kx * xy->fY + tx; 92 uv->fY = ky * xy->fX + sy * xy->fY + ty; 93 xyPtr += STRIDE; 94 uvPtr += STRIDE; 95 } 96 } 97 private: 98 float fM[6]; 99 }; 100 101 102 // Converts a cubic into a sequence of quads. If working in device space 103 // use tolScale = 1, otherwise set based on stretchiness of the matrix. The 104 // result is sets of 3 points in quads (TODO: share endpoints in returned 105 // array) 106 // When we approximate a cubic {a,b,c,d} with a quadratic we may have to 107 // ensure that the new control point lies between the lines ab and cd. The 108 // convex path renderer requires this. It starts with a path where all the 109 // control points taken together form a convex polygon. It relies on this 110 // property and the quadratic approximation of cubics step cannot alter it. 111 // Setting constrainWithinTangents to true enforces this property. When this 112 // is true the cubic must be simple and dir must specify the orientation of 113 // the cubic. Otherwise, dir is ignored. 114 void convertCubicToQuads(const GrPoint p[4], 115 SkScalar tolScale, 116 bool constrainWithinTangents, 117 SkPath::Direction dir, 118 SkTArray<SkPoint, true>* quads); 119 }; 120 #endif 121