SkCanvas::drawPatch param SkPoint[12]

src/utils/SkPatchUtils.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPatchUtils_DEFINED
 #define SkPatchUtils_DEFINED
 
-#include "SkPatch.h"
+#include "SkColorPriv.h"
 #include "SkMatrix.h"
 
 class SK_API SkPatchUtils {
-
+    
 public:
     /**
+     * Structure that holds the vertex data related to the tessellation of a patch. It is passed
+     * as a parameter to the function getVertexData which sets the points, colors and texture
+     * coordinates of the vertices and the indices for them to be drawn as triangles.
+     */
+    struct VertexData {
+        int fVertexCount, fIndexCount;
+        SkPoint* fPoints;
+        SkPoint* fTexCoords;
+        uint32_t* fColors;
+        uint16_t* fIndices;
+        
+        VertexData()
+        : fVertexCount(0)
+        , fIndexCount(0)
+        , fPoints(NULL)
+        , fTexCoords(NULL)
+        , fColors(NULL)
+        , fIndices(NULL) { }
+        
+        ~VertexData() {
+            SkDELETE_ARRAY(fPoints);
+            SkDELETE_ARRAY(fTexCoords);
+            SkDELETE_ARRAY(fColors);
+            SkDELETE_ARRAY(fIndices);
+        }
+    };
+    
+    // Enums for control points based on the order specified in the constructor (clockwise).
+    enum CubicCtrlPts {
+        kTopP0_CubicCtrlPts = 0,
+        kTopP1_CubicCtrlPts = 1,
+        kTopP2_CubicCtrlPts = 2,
+        kTopP3_CubicCtrlPts = 3,
+        
+        kRightP0_CubicCtrlPts = 3,
+        kRightP1_CubicCtrlPts = 4,
+        kRightP2_CubicCtrlPts = 5,
+        kRightP3_CubicCtrlPts = 6,
+        
+        kBottomP0_CubicCtrlPts = 9,
+        kBottomP1_CubicCtrlPts = 8,
+        kBottomP2_CubicCtrlPts = 7,
+        kBottomP3_CubicCtrlPts = 6,
+        
+        kLeftP0_CubicCtrlPts = 0,
+        kLeftP1_CubicCtrlPts = 11,
+        kLeftP2_CubicCtrlPts = 10,
+        kLeftP3_CubicCtrlPts = 9,
+    };
+    
+    // Enum for corner also clockwise.
+    enum Corner {
+        kTopLeft_Corner = 0,
+        kTopRight_Corner,
+        kBottomRight_Corner,
+        kBottomLeft_Corner
+    };
+    
+    enum {
+        kNumCtrlPts = 12,
+        kNumCorners = 4,
+        kNumPtsCubic = 4
+    };
+    
+    /**
      * Method that calculates a level of detail (number of subdivisions) for a patch in both axis. 
      */
-    static SkISize GetLevelOfDetail(const SkPatch& patch, const SkMatrix* matrix);
+    static SkISize GetLevelOfDetail(const SkPoint cubics[12], const SkMatrix* matrix);
+    
+    /**
+     * Get the points corresponding to the top cubic of cubics.
+     */
+    static void getTopCubic(const SkPoint cubics[12], SkPoint points[4]);
+    
+    /**
+     * Get the points corresponding to the bottom cubic of cubics.
+     */
+    static void getBottomCubic(const SkPoint cubics[12], SkPoint points[4]);
+    
+    /**
+     * Get the points corresponding to the left cubic of cubics.
+     */
+    static void getLeftCubic(const SkPoint cubics[12], SkPoint points[4]);
+    
+    /**
+     * Get the points corresponding to the right cubic of cubics.
+     */
+    static void getRightCubic(const SkPoint cubics[12], SkPoint points[4]);
+    
+    /**
+     * Function that evaluates the coons patch interpolation.
+     * data refers to the pointer of the PatchData struct in which the tessellation data is set.
+     * cubics refers to the points of the cubics.
+     * lod refers the level of detail for each axis.
+     * colors refers to the corner colors that will be bilerp across the patch (optional parameter)
+     * texCoords refers to the corner texture coordinates that will be bilerp across the patch 
+        (optional parameter)
+     */
+    static bool getVertexData(SkPatchUtils::VertexData* data, const SkPoint cubics[12],
+                              const SkColor colors[4], const SkPoint texCoords[4],
+                              int lodX, int lodY);
 };
 
 #endif