1 
2 /*
3  * Copyright 2006 The Android Open Source Project
4  *
5  * Use of this source code is governed by a BSD-style license that can be
6  * found in the LICENSE file.
7  */
8 
9 
10 #ifndef SkComposeShader_DEFINED
11 #define SkComposeShader_DEFINED
12 
13 #include "SkShader.h"
14 
15 class SkXfermode;
16 
17 ///////////////////////////////////////////////////////////////////////////////////////////
18 
19 /** \class SkComposeShader
20     This subclass of shader returns the composition of two other shaders, combined by
21     a xfermode.
22 */
23 class SK_API SkComposeShader : public SkShader {
24 public:
25     /** Create a new compose shader, given shaders A, B, and a combining xfermode mode.
26         When the xfermode is called, it will be given the result from shader A as its
27         "dst", and the result from shader B as its "src".
28         mode->xfer32(sA_result, sB_result, ...)
29         @param shaderA  The colors from this shader are seen as the "dst" by the xfermode
30         @param shaderB  The colors from this shader are seen as the "src" by the xfermode
31         @param mode     The xfermode that combines the colors from the two shaders. If mode
32                         is null, then SRC_OVER is assumed.
33     */
34     SkComposeShader(SkShader* sA, SkShader* sB, SkXfermode* mode = NULL);
35     virtual ~SkComposeShader();
36 
37     size_t contextSize() const override;
38 
39     class ComposeShaderContext : public SkShader::Context {
40     public:
41         // When this object gets destroyed, it will call contextA and contextB's destructor
42         // but it will NOT free the memory.
43         ComposeShaderContext(const SkComposeShader&, const ContextRec&,
44                              SkShader::Context* contextA, SkShader::Context* contextB);
45 
getShaderContextA()46         SkShader::Context* getShaderContextA() const { return fShaderContextA; }
getShaderContextB()47         SkShader::Context* getShaderContextB() const { return fShaderContextB; }
48 
49         virtual ~ComposeShaderContext();
50 
51         void shadeSpan(int x, int y, SkPMColor[], int count) override;
52 
53     private:
54         SkShader::Context* fShaderContextA;
55         SkShader::Context* fShaderContextB;
56 
57         typedef SkShader::Context INHERITED;
58     };
59 
60 #ifdef SK_DEBUG
getShaderA()61     SkShader* getShaderA() { return fShaderA; }
getShaderB()62     SkShader* getShaderB() { return fShaderB; }
63 #endif
64 
65     bool asACompose(ComposeRec* rec) const override;
66 
67     SK_TO_STRING_OVERRIDE()
68     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkComposeShader)
69 
70 protected:
71     SkComposeShader(SkReadBuffer& );
72     void flatten(SkWriteBuffer&) const override;
73     Context* onCreateContext(const ContextRec&, void*) const override;
74 
75 private:
76     SkShader*   fShaderA;
77     SkShader*   fShaderB;
78     SkXfermode* fMode;
79 
80     typedef SkShader INHERITED;
81 };
82 
83 #endif
84