text: /*
   * 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
  