android / platform / frameworks / base / 5462b79d9fd787ab189bcd29b591ca72f900220f / . / libs / hwui / PathTessellator.h

/* | |

* Copyright (C) 2012 The Android Open Source Project | |

* | |

* Licensed under the Apache License, Version 2.0 (the "License"); | |

* you may not use this file except in compliance with the License. | |

* You may obtain a copy of the License at | |

* | |

* http://www.apache.org/licenses/LICENSE-2.0 | |

* | |

* Unless required by applicable law or agreed to in writing, software | |

* distributed under the License is distributed on an "AS IS" BASIS, | |

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |

* See the License for the specific language governing permissions and | |

* limitations under the License. | |

*/ | |

#ifndef ANDROID_HWUI_PATH_TESSELLATOR_H | |

#define ANDROID_HWUI_PATH_TESSELLATOR_H | |

#include "Matrix.h" | |

#include "Rect.h" | |

#include "Vertex.h" | |

#include "VertexBuffer.h" | |

#include <algorithm> | |

#include <vector> | |

class SkPath; | |

class SkPaint; | |

namespace android { | |

namespace uirenderer { | |

/** | |

* Structure used for threshold values in outline path tessellation. | |

* | |

* TODO: PaintInfo should store one of this object, and initialized all values in constructor | |

* depending on its type (point, line or path). | |

*/ | |

struct PathApproximationInfo { | |

PathApproximationInfo(float invScaleX, float invScaleY, float pixelThreshold) | |

: thresholdSquared(pixelThreshold * pixelThreshold) | |

, sqrInvScaleX(invScaleX * invScaleX) | |

, sqrInvScaleY(invScaleY * invScaleY) | |

, thresholdForConicQuads(pixelThreshold * std::min(invScaleX, invScaleY) / 2.0f) { | |

}; | |

const float thresholdSquared; | |

const float sqrInvScaleX; | |

const float sqrInvScaleY; | |

const float thresholdForConicQuads; | |

}; | |

class PathTessellator { | |

public: | |

/** | |

* Populates scaleX and scaleY with the 'tessellation scale' of the transform - the effective X | |

* and Y scales that tessellation will take into account when generating the 1.0 pixel thick | |

* ramp. | |

* | |

* Two instances of the same shape (size, paint, etc.) will only generate the same vertices if | |

* their tessellation scales are equal. | |

*/ | |

static void extractTessellationScales(const Matrix4& transform, float* scaleX, float* scaleY); | |

/** | |

* Populates a VertexBuffer with a tessellated approximation of the input convex path, as a single | |

* triangle strip. Note: joins are not currently supported. | |

* | |

* @param path The path to be approximated | |

* @param paint The paint the path will be drawn with, indicating AA, painting style | |

* (stroke vs fill), stroke width, stroke cap & join style, etc. | |

* @param transform The transform the path is to be drawn with, used to drive stretch-aware path | |

* vertex approximation, and correct AA ramp offsetting. | |

* @param vertexBuffer The output buffer | |

*/ | |

static void tessellatePath(const SkPath& path, const SkPaint* paint, | |

const mat4& transform, VertexBuffer& vertexBuffer); | |

/** | |

* Populates a VertexBuffer with a tessellated approximation of points as a single triangle | |

* strip (with degenerate tris separating), respecting the shape defined by the paint cap. | |

* | |

* @param points The center vertices of the points to be drawn | |

* @param count The number of floats making up the point vertices | |

* @param paint The paint the points will be drawn with indicating AA, stroke width & cap | |

* @param transform The transform the points will be drawn with, used to drive stretch-aware path | |

* vertex approximation, and correct AA ramp offsetting | |

* @param vertexBuffer The output buffer | |

*/ | |

static void tessellatePoints(const float* points, int count, const SkPaint* paint, | |

const mat4& transform, VertexBuffer& vertexBuffer); | |

/** | |

* Populates a VertexBuffer with a tessellated approximation of lines as a single triangle | |

* strip (with degenerate tris separating). | |

* | |

* @param points Pairs of endpoints defining the lines to be drawn | |

* @param count The number of floats making up the line vertices | |

* @param paint The paint the lines will be drawn with indicating AA, stroke width & cap | |

* @param transform The transform the points will be drawn with, used to drive stretch-aware path | |

* vertex approximation, and correct AA ramp offsetting | |

* @param vertexBuffer The output buffer | |

*/ | |

static void tessellateLines(const float* points, int count, const SkPaint* paint, | |

const mat4& transform, VertexBuffer& vertexBuffer); | |

/** | |

* Approximates a convex outline into a clockwise Vector of 2d vertices. | |

* | |

* @param path The outline to be approximated | |

* @param threshold The threshold of acceptable error (in pixels) when approximating | |

* @param outputVertices An empty Vector which will be populated with the output | |

*/ | |

static bool approximatePathOutlineVertices(const SkPath &path, float threshold, | |

std::vector<Vertex> &outputVertices); | |

private: | |

static bool approximatePathOutlineVertices(const SkPath &path, bool forceClose, | |

const PathApproximationInfo& approximationInfo, std::vector<Vertex> &outputVertices); | |

/* | |

endpoints a & b, | |

control c | |

*/ | |

static void recursiveQuadraticBezierVertices( | |

float ax, float ay, | |

float bx, float by, | |

float cx, float cy, | |

const PathApproximationInfo& approximationInfo, | |

std::vector<Vertex> &outputVertices, int depth = 0); | |

/* | |

endpoints p1, p2 | |

control c1, c2 | |

*/ | |

static void recursiveCubicBezierVertices( | |

float p1x, float p1y, | |

float c1x, float c1y, | |

float p2x, float p2y, | |

float c2x, float c2y, | |

const PathApproximationInfo& approximationInfo, | |

std::vector<Vertex> &outputVertices, int depth = 0); | |

}; | |

}; // namespace uirenderer | |

}; // namespace android | |

#endif // ANDROID_HWUI_PATH_TESSELLATOR_H |