SkPatchGrid interface (after SkPatch/SkPicture rebase).

include/core/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 SkMeshGradient_DEFINED
+#define SkMeshGradient_DEFINED
+
+#include "SkPatch.h"
+#include "SkCanvas.h"
+
+/**
+ * Class that represents a Mesh Gradient. A mesh gradient is an array of coons patches, adjacent 

[egdaniel, 2014/08/08 14:39:04]

no longer gradient, fix comment

[dandov, 2014/08/08 18:31:45]

Done.

+ * 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.
+ *
+ *               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: 
+ * <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:
+    SkPatchGrid(int rows, int cols);
+    
+    ~SkPatchGrid();
+    
+    /**
+     * Add a patch at location (x,y) overwriting the previous patch and shared points.
+     */
+    bool setPatch(int x, int y, const SkPatch& patch);
+    bool setPatch(int x, int y, const SkPoint ctrlPts[12], const SkColor colors[4]);
+    
+    /**
+     * Get patch at location (x,y). If the patch is not NULL it sets patch's
+     * control points and colors to the corresponding values.
+     */
+    void getPatch(int x, int y, SkPatch* patch) const;

[egdaniel, 2014/08/08 14:39:04]

maybe have this return a bool as well so it is known whether patch was set or
not

[dandov, 2014/08/08 18:31:45]

Done. returns false in case the coordinates x,y are out of bounds or if patch is
NULL. 

+    
+    /**
+     * Resets the mesh gradient to contain rows and cols of patches. The main difference between
+     * this and resize is that resize keeps the previous values of control points and colors and

[egdaniel, 2014/08/08 14:39:04]

no more resize so fix comment

[dandov, 2014/08/08 18:31:45]

Done.

+     * this doesn't.
+     */
+    void reset(int rows, int cols);
+    
+    /**
+     * Draws the mesh gradient.
+     */
+    void draw(SkCanvas* canvas, SkPaint& paint);

[egdaniel, 2014/08/08 14:39:04]

Since we are deciding the draw order of the patches in this version, add a
comment saying what that order is.

Future version maybe should allow the client to specify an order (no need to
implement this now)

[dandov, 2014/08/08 18:31:45]

Done.

+    
+    /**
+     * Get the dimensions of the grid of patches.
+     */
+    SkISize getDimensions() const {
+        return SkISize::Make(fCols, fRows);
+    }
+    
+private:
+    int fRows, fCols;
+    SkPoint* fCornerPts;
+    SkColor* fCornerColors;
+    SkPoint* fHrzCtrlPts;
+    SkPoint* fVrtCtrlPts;
+};
+
+
+#endif