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 SkPatchGrid_DEFINED
9 #define SkPatchGrid_DEFINED
10 
11 #include "SkCanvas.h"
12 #include "SkPatchUtils.h"
13 #include "SkXfermode.h"
14 
15 /**
16  * Class that represents a grid of patches. Adjacent patches share their corners and a color is
17  * specified at each one of them. The colors are bilinearly interpolated across the patch.
18  *
19  * This implementation defines a bidimensional array of patches. There are 3 arrays to store the
20  * control points of the patches to avoid storing repeated data since there are several points
21  * shared between adjacent patches.
22  *
23  * The array fCornerPts stores the corner control points of the patches.
24  * The array fHrzPts holds the intermidiate control points of the top and bottom curves of a patch.
25  * The array fVrtPts holds the intermidiate control points of the left and right curves of a patch.
26  * The array fCornerColors holds the corner colors in the same format as fCornerPts.
27  * The array fTexCoords holds the texture coordinates in the same format as fCornerpts.
28  *
29  *               fCornerPts               fHrzPts                  fVrtPts
30  *             --------------       -------------------         --------------
31  *            | C0 | C1 | C2 |     | H0 | H1 | H2 | H3 |       | V0 | V1 | V2 |
32  *             --------------       ------------------         ---------------
33  *            | C3 | C4 | C5 |     | H4 | H5 | H6 | H7 |       | V4 | V5 | V6 |
34  *             --------------       -------------------         --------------
35  *            | C6 | C7 | C8 |     | H8 | H9 | H10| H11|       | V6 | V7 | V8 |
36  *             --------------       -------------------         --------------
37  *                                                             | V9 | V10| V11|
38  *                                                              --------------
39  *
40  * With the above configuration we would have a 2x2 grid of patches:
41  *               H0     H1 H2   H3
42  *              /        \/      \
43  *              C0-------C1-------C2
44  *             /|        |        |\
45  *           v0 |        v1       | v2
46  *           v3 |        V4       | v5
47  *             \|        |        |/
48  *              C3-H4-H5-C4-H6-H7-C5
49  *             /|        |        |\
50  *           v6 |        v7       | v8
51  *           v9 |        v10      | v11
52  *             \|        |        |/
53  *              C6-------C7-------C8
54  *               \      / \      /
55  *                H8   H9  H10  H11
56  *
57  * When trying to get a patch at a certain position it justs builds it with the corresponding
58  * points.
59  * When adding a patch it tries to add the points at their corresponding position trying to comply
60  * with the adjacent points or overwriting them.
61  *
62  * Based the idea on the SVG2 spec for mesh gradients in which a grid of patches is build as in the
63  * the following example:
64  * <meshGradient x="100" y="100">
65  *      <meshRow>
66  *          <meshPatch>
67  *              <stop .../>
68  *              Up to four stops in first patch. See details below.
69  *          </meshPatch>
70  *          <meshPatch>
71  *              Any number of meshPatches in row.
72  *          </meshPatch>
73  *      </meshRow>
74  *      <meshRow>
75  *          Any number of meshRows, each with the same number of meshPatches as in the first row.
76  *      </meshRow>
77  * </meshGradient>
78  */
79 class SkPatchGrid {
80 
81 public:
82 
83     enum VertexType {
84         kNone_VertexType = 0X00,
85         kColors_VertexType = 0x01,
86         kTexs_VertexType = 0x02,
87         kColorsAndTexs_VertexType = 0x03
88     };
89 
90     SkPatchGrid(int rows = 0, int cols = 0, VertexType flags = kNone_VertexType,
91                 SkXfermode* xfer = NULL);
92 
93     ~SkPatchGrid();
94 
95     /**
96      * Add a patch at location (x,y) overwriting the previous patch and shared points so they
97      * mantain C0 connectivity.
98      * The control points must be passed in a clockwise order starting at the top left corner.
99      * The colors and texCoords are the values at the corners of the patch which will be bilerp
100      * across it, they must also be in counterclockwise order starting at the top left corner.
101      */
102     bool setPatch(int x, int y, const SkPoint cubics[12], const SkColor colors[4],
103                   const SkPoint texCoords[4]);
104 
105     /**
106      * Get patch at location (x,y). If cubics, colors or texCoords is not NULL it sets patch's
107      * array with its corresponding values.
108      * The function returns false if the cubics parameter is NULL or if the (x,y) coordinates are
109      * not within the range of the grid.
110      */
111     bool getPatch(int x, int y, SkPoint cubics[12], SkColor colors[4], SkPoint texCoords[4]) const;
112 
113     /**
114      * Resets the grid of patches to contain rows and cols of patches.
115      */
116     void reset(int rows, int cols, VertexType flags, SkXfermode* xMode);
117 
118     /**
119      * Draws the grid of patches. The patches are drawn starting at patch (0,0) drawing columns, so
120      * for a 2x2 grid the order would be (0,0)->(0,1)->(1,0)->(1,1). The order follows the order
121      * of the parametric coordinates of the coons patch.
122      */
123     void draw(SkCanvas* canvas, SkPaint& paint);
124 
125     /**
126      * Get the dimensions of the grid of patches.
127      */
getDimensions()128     SkISize getDimensions() const {
129         return SkISize::Make(fCols, fRows);
130     }
131 
132 private:
133     int fRows, fCols;
134     VertexType fModeFlags;
135     SkPoint* fCornerPts;
136     SkColor* fCornerColors;
137     SkPoint* fTexCoords;
138     SkPoint* fHrzCtrlPts;
139     SkPoint* fVrtCtrlPts;
140     SkXfermode* fXferMode;
141 };
142 
143 
144 #endif
145