SkPatchGrid interface (after SkPatch/SkPicture rebase).

src/utils/SkPatchGrid.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 SkPatchGrid_DEFINED
+#define SkPatchGrid_DEFINED
+
+#include "SkCanvas.h"
+#include "SkPatchUtils.h"
+#include "SkXfermode.h"
+
+/**
+ * Class that represents a grid of patches. Adjacent patches share their corners and a color is 
+ * specified at each one of them. The colors are bilinearly interpolated across the patch.
+ *
+ * This implementation defines a bidimensional array of patches. There are 3 arrays to store the 
+ * control points of the patches to avoid storing repeated data since there are several points
+ * shared between adjacent patches. 
+ *
+ * The array fCornerPts stores the corner control points of the patches.
+ * The array fHrzPts holds the intermidiate control points of the top and bottom curves of a patch.
+ * The array fVrtPts holds the intermidiate control points of the left and right curves of a patch.
+ * The array fCornerColors holds the corner colors in the same format as fCornerPts.
+ * The array fTexCoords holds the texture coordinates in the same format as fCornerpts.
+ *
+ *               fCornerPts               fHrzPts                  fVrtPts
+ *             --------------       -------------------         --------------
+ *            | C0 | C1 | C2 |     | H0 | H1 | H2 | H3 |       | V0 | V1 | V2 |
+ *             --------------       ------------------         ---------------
+ *            | C3 | C4 | C5 |     | H4 | H5 | H6 | H7 |       | V4 | V5 | V6 |
+ *             --------------       -------------------         --------------
+ *            | C6 | C7 | C8 |     | H8 | H9 | H10| H11|       | V6 | V7 | V8 |
+ *             --------------       -------------------         --------------
+ *                                                             | V9 | V10| V11|
+ *                                                              --------------
+ *
+ * With the above configuration we would have a 2x2 grid of patches:
+ *               H0     H1 H2   H3
+ *              /        \/      \
+ *              C0-------C1-------C2
+ *             /|        |        |\
+ *           v0 |        v1       | v2
+ *           v3 |        V4       | v5
+ *             \|        |        |/
+ *              C3-H4-H5-C4-H6-H7-C5
+ *             /|        |        |\
+ *           v6 |        v7       | v8
+ *           v9 |        v10      | v11
+ *             \|        |        |/
+ *              C6-------C7-------C8
+ *               \      / \      /
+ *                H8   H9  H10  H11
+ *
+ * When trying to get a patch at a certain position it justs builds it with the corresponding 
+ * points.
+ * When adding a patch it tries to add the points at their corresponding position trying to comply
+ * with the adjacent points or overwriting them.
+ * 
+ * Based the idea on the SVG2 spec for mesh gradients in which a grid of patches is build as in the
+ * the following example:
+ * <meshGradient x="100" y="100">
+ *      <meshRow>
+ *          <meshPatch>
+ *              <stop .../>
+ *              Up to four stops in first patch. See details below.
+ *          </meshPatch>
+ *          <meshPatch>
+ *              Any number of meshPatches in row.
+ *          </meshPatch>
+ *      </meshRow>
+ *      <meshRow>
+ *          Any number of meshRows, each with the same number of meshPatches as in the first row.
+ *      </meshRow>
+ * </meshGradient>
+ */
+class SkPatchGrid {
+    
+public:
+    
+    enum VertexType {
+        kNone_VertexType = 0X00,
+        kColors_VertexType = 0x01,
+        kTexs_VertexType = 0x02,
+        kColorsAndTexs_VertexType = 0x03
+    };
+    
+    SkPatchGrid(int rows = 0, int cols = 0, VertexType flags = kNone_VertexType,
+                SkXfermode* xfer = NULL);
+    
+    ~SkPatchGrid();
+    
+    /**
+     * Add a patch at location (x,y) overwriting the previous patch and shared points so they 
+     * mantain C0 connectivity.
+     * The control points must be passed in a clockwise order starting at the top left corner.
+     * The colors and texCoords are the values at the corners of the patch which will be bilerp 
+     * across it, they must also be in counterclockwise order starting at the top left corner.
+     */
+    bool setPatch(int x, int y, const SkPoint cubics[12], const SkColor colors[4],
+                  const SkPoint texCoords[4]);
+    
+    /**
+     * Get patch at location (x,y). If cubics, colors or texCoords is not NULL it sets patch's
+     * array with its corresponding values.
+     * The function returns false if the cubics parameter is NULL or if the (x,y) coordinates are 
+     * not within the range of the grid.
+     */
+    bool getPatch(int x, int y, SkPoint cubics[12], SkColor colors[4], SkPoint texCoords[4]) const;
+    
+    /**
+     * Resets the grid of patches to contain rows and cols of patches.
+     */
+    void reset(int rows, int cols, VertexType flags, SkXfermode* xMode);
+    
+    /**
+     * Draws the grid of patches. The patches are drawn starting at patch (0,0) drawing columns, so 
+     * for a 2x2 grid the order would be (0,0)->(0,1)->(1,0)->(1,1). The order follows the order 
+     * of the parametric coordinates of the coons patch.
+     */
+    void draw(SkCanvas* canvas, SkPaint& paint);
+    
+    /**
+     * Get the dimensions of the grid of patches.
+     */
+    SkISize getDimensions() const {
+        return SkISize::Make(fCols, fRows);
+    }
+    
+private:
+    int fRows, fCols;
+    VertexType fModeFlags;
+    SkPoint* fCornerPts;
+    SkColor* fCornerColors;
+    SkPoint* fTexCoords;
+    SkPoint* fHrzCtrlPts;
+    SkPoint* fVrtCtrlPts;
+    SkXfermode* fXferMode;
+};
+
+
+#endif