SkLayerDrawLooper.h revision 73cb15351f33459e0c861a96135c634dec77ef9d 
1/*
2 * Copyright 2011 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 SkLayerDrawLooper_DEFINED
9#define SkLayerDrawLooper_DEFINED
10
11#include "SkDrawLooper.h"
12#include "SkPaint.h"
13#include "SkPoint.h"
14#include "SkXfermode.h"
15
16class SK_API SkLayerDrawLooper : public SkDrawLooper {
17public:
18    SK_DECLARE_INST_COUNT(SkLayerDrawLooper)
19
20    virtual ~SkLayerDrawLooper();
21
22    /**
23     *  Bits specifies which aspects of the layer's paint should replace the
24     *  corresponding aspects on the draw's paint.
25     *  kEntirePaint_Bits means use the layer's paint completely.
26     *  0 means ignore the layer's paint... except for fColorMode, which is
27     *  always applied.
28     */
29    enum Bits {
30        kStyle_Bit      = 1 << 0,   //!< use this layer's Style/stroke settings
31        kTextSkewX_Bit  = 1 << 1,   //!< use this layer's textskewx
32        kPathEffect_Bit = 1 << 2,   //!< use this layer's patheffect
33        kMaskFilter_Bit = 1 << 3,   //!< use this layer's maskfilter
34        kShader_Bit     = 1 << 4,   //!< use this layer's shader
35        kColorFilter_Bit = 1 << 5,  //!< use this layer's colorfilter
36        kXfermode_Bit   = 1 << 6,   //!< use this layer's xfermode
37
38        /**
39         *  Use the layer's paint entirely, with these exceptions:
40         *  - We never override the draw's paint's text_encoding, since that is
41         *    used to interpret the text/len parameters in draw[Pos]Text.
42         *  - Color is always computed using the LayerInfo's fColorMode.
43         */
44        kEntirePaint_Bits = -1
45
46    };
47    typedef int32_t BitFlags;
48
49    /**
50     *  Info for how to apply the layer's paint and offset.
51     *
52     *  fColorMode controls how we compute the final color for the layer:
53     *      The layer's paint's color is treated as the SRC
54     *      The draw's paint's color is treated as the DST
55     *      final-color = Mode(layers-color, draws-color);
56     *  Any SkXfermode::Mode will work. Two common choices are:
57     *      kSrc_Mode: to use the layer's color, ignoring the draw's
58     *      kDst_Mode: to just keep the draw's color, ignoring the layer's
59     */
60    struct SK_API LayerInfo {
61        BitFlags            fPaintBits;
62        SkXfermode::Mode    fColorMode;
63        SkVector            fOffset;
64        bool                fPostTranslate; //!< applies to fOffset
65
66        /**
67         *  Initial the LayerInfo. Defaults to settings that will draw the
68         *  layer with no changes: e.g.
69         *      fPaintBits == 0
70         *      fColorMode == kDst_Mode
71         *      fOffset == (0, 0)
72         */
73        LayerInfo();
74    };
75
76    virtual SkDrawLooper::Context* createContext(SkCanvas*, void* storage) const SK_OVERRIDE;
77
78    virtual size_t contextSize() const SK_OVERRIDE { return sizeof(LayerDrawLooperContext); }
79
80    SK_TO_STRING_OVERRIDE()
81
82    /// Implements Flattenable.
83    virtual Factory getFactory() const SK_OVERRIDE { return CreateProc; }
84    static SkFlattenable* CreateProc(SkReadBuffer& buffer);
85
86protected:
87    SkLayerDrawLooper();
88
89    virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
90
91private:
92    struct Rec {
93        Rec*    fNext;
94        SkPaint fPaint;
95        LayerInfo fInfo;
96    };
97    Rec*    fRecs;
98    Rec*    fTopRec;
99    int     fCount;
100
101    // state-machine during the init/next cycle
102    class LayerDrawLooperContext : public SkDrawLooper::Context {
103    public:
104        explicit LayerDrawLooperContext(const SkLayerDrawLooper* looper);
105
106    protected:
107        virtual bool next(SkCanvas*, SkPaint* paint) SK_OVERRIDE;
108
109    private:
110        Rec* fCurrRec;
111
112        static void ApplyInfo(SkPaint* dst, const SkPaint& src, const LayerInfo&);
113    };
114
115    class MyRegistrar : public SkFlattenable::Registrar {
116    public:
117        MyRegistrar();
118    };
119
120    typedef SkDrawLooper INHERITED;
121
122public:
123    class SK_API Builder {
124    public:
125        Builder();
126        ~Builder();
127
128        /**
129         *  Call for each layer you want to add (from top to bottom).
130         *  This returns a paint you can modify, but that ptr is only valid until
131         *  the next call made to addLayer().
132         */
133        SkPaint* addLayer(const LayerInfo&);
134
135        /**
136         *  This layer will draw with the original paint, at the specified offset
137         */
138        void addLayer(SkScalar dx, SkScalar dy);
139
140        /**
141         *  This layer will with the original paint and no offset.
142         */
143        void addLayer() { this->addLayer(0, 0); }
144
145        /// Similar to addLayer, but adds a layer to the top.
146        SkPaint* addLayerOnTop(const LayerInfo&);
147
148        /**
149          * Pass list of layers on to newly built looper and return it. This will
150          * also reset the builder, so it can be used to build another looper.
151          */
152        SkLayerDrawLooper* detachLooper();
153
154    private:
155        Rec* fRecs;
156        Rec* fTopRec;
157        int  fCount;
158    };
159};
160
161#endif
162