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      1 /*
      2  * Copyright 2014 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef SkPatchUtils_DEFINED
      9 #define SkPatchUtils_DEFINED
     10 
     11 #include "SkColorPriv.h"
     12 #include "SkMatrix.h"
     13 
     14 class SK_API SkPatchUtils {
     15 
     16 public:
     17     /**
     18      * Structure that holds the vertex data related to the tessellation of a patch. It is passed
     19      * as a parameter to the function getVertexData which sets the points, colors and texture
     20      * coordinates of the vertices and the indices for them to be drawn as triangles.
     21      */
     22     struct VertexData {
     23         int fVertexCount, fIndexCount;
     24         SkPoint* fPoints;
     25         SkPoint* fTexCoords;
     26         uint32_t* fColors;
     27         uint16_t* fIndices;
     28 
     29         VertexData()
     30         : fVertexCount(0)
     31         , fIndexCount(0)
     32         , fPoints(nullptr)
     33         , fTexCoords(nullptr)
     34         , fColors(nullptr)
     35         , fIndices(nullptr) { }
     36 
     37         ~VertexData() {
     38             delete[] fPoints;
     39             delete[] fTexCoords;
     40             delete[] fColors;
     41             delete[] fIndices;
     42         }
     43     };
     44 
     45     // Enums for control points based on the order specified in the constructor (clockwise).
     46     enum CubicCtrlPts {
     47         kTopP0_CubicCtrlPts = 0,
     48         kTopP1_CubicCtrlPts = 1,
     49         kTopP2_CubicCtrlPts = 2,
     50         kTopP3_CubicCtrlPts = 3,
     51 
     52         kRightP0_CubicCtrlPts = 3,
     53         kRightP1_CubicCtrlPts = 4,
     54         kRightP2_CubicCtrlPts = 5,
     55         kRightP3_CubicCtrlPts = 6,
     56 
     57         kBottomP0_CubicCtrlPts = 9,
     58         kBottomP1_CubicCtrlPts = 8,
     59         kBottomP2_CubicCtrlPts = 7,
     60         kBottomP3_CubicCtrlPts = 6,
     61 
     62         kLeftP0_CubicCtrlPts = 0,
     63         kLeftP1_CubicCtrlPts = 11,
     64         kLeftP2_CubicCtrlPts = 10,
     65         kLeftP3_CubicCtrlPts = 9,
     66     };
     67 
     68     // Enum for corner also clockwise.
     69     enum Corner {
     70         kTopLeft_Corner = 0,
     71         kTopRight_Corner,
     72         kBottomRight_Corner,
     73         kBottomLeft_Corner
     74     };
     75 
     76     enum {
     77         kNumCtrlPts = 12,
     78         kNumCorners = 4,
     79         kNumPtsCubic = 4
     80     };
     81 
     82     /**
     83      * Method that calculates a level of detail (number of subdivisions) for a patch in both axis.
     84      */
     85     static SkISize GetLevelOfDetail(const SkPoint cubics[12], const SkMatrix* matrix);
     86 
     87     /**
     88      * Get the points corresponding to the top cubic of cubics.
     89      */
     90     static void getTopCubic(const SkPoint cubics[12], SkPoint points[4]);
     91 
     92     /**
     93      * Get the points corresponding to the bottom cubic of cubics.
     94      */
     95     static void getBottomCubic(const SkPoint cubics[12], SkPoint points[4]);
     96 
     97     /**
     98      * Get the points corresponding to the left cubic of cubics.
     99      */
    100     static void getLeftCubic(const SkPoint cubics[12], SkPoint points[4]);
    101 
    102     /**
    103      * Get the points corresponding to the right cubic of cubics.
    104      */
    105     static void getRightCubic(const SkPoint cubics[12], SkPoint points[4]);
    106 
    107     /**
    108      * Function that evaluates the coons patch interpolation.
    109      * data refers to the pointer of the PatchData struct in which the tessellation data is set.
    110      * cubics refers to the points of the cubics.
    111      * lod refers the level of detail for each axis.
    112      * colors refers to the corner colors that will be bilerp across the patch (optional parameter)
    113      * texCoords refers to the corner texture coordinates that will be bilerp across the patch
    114         (optional parameter)
    115      */
    116     static bool getVertexData(SkPatchUtils::VertexData* data, const SkPoint cubics[12],
    117                               const SkColor colors[4], const SkPoint texCoords[4],
    118                               int lodX, int lodY);
    119 };
    120 
    121 #endif
    122