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    virtual bool asABlurShadow(BlurShadowRec* rec) const SK_OVERRIDE;
81
82    SK_TO_STRING_OVERRIDE()
83
84    /// Implements Flattenable.
85    virtual Factory getFactory() const SK_OVERRIDE { return CreateProc; }
86    static SkFlattenable* CreateProc(SkReadBuffer& buffer);
87
88protected:
89    SkLayerDrawLooper();
90
91    virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
92
93private:
94    struct Rec {
95        Rec*    fNext;
96        SkPaint fPaint;
97        LayerInfo fInfo;
98    };
99    Rec*    fRecs;
100    Rec*    fTopRec;
101    int     fCount;
102
103    // state-machine during the init/next cycle
104    class LayerDrawLooperContext : public SkDrawLooper::Context {
105    public:
106        explicit LayerDrawLooperContext(const SkLayerDrawLooper* looper);
107
108    protected:
109        virtual bool next(SkCanvas*, SkPaint* paint) SK_OVERRIDE;
110
111    private:
112        Rec* fCurrRec;
113
114        static void ApplyInfo(SkPaint* dst, const SkPaint& src, const LayerInfo&);
115    };
116
117    class MyRegistrar : public SkFlattenable::Registrar {
118    public:
119        MyRegistrar();
120    };
121
122    typedef SkDrawLooper INHERITED;
123
124public:
125    class SK_API Builder {
126    public:
127        Builder();
128        ~Builder();
129
130        /**
131         *  Call for each layer you want to add (from top to bottom).
132         *  This returns a paint you can modify, but that ptr is only valid until
133         *  the next call made to addLayer().
134         */
135        SkPaint* addLayer(const LayerInfo&);
136
137        /**
138         *  This layer will draw with the original paint, at the specified offset
139         */
140        void addLayer(SkScalar dx, SkScalar dy);
141
142        /**
143         *  This layer will with the original paint and no offset.
144         */
145        void addLayer() { this->addLayer(0, 0); }
146
147        /// Similar to addLayer, but adds a layer to the top.
148        SkPaint* addLayerOnTop(const LayerInfo&);
149
150        /**
151          * Pass list of layers on to newly built looper and return it. This will
152          * also reset the builder, so it can be used to build another looper.
153          */
154        SkLayerDrawLooper* detachLooper();
155
156    private:
157        Rec* fRecs;
158        Rec* fTopRec;
159        int  fCount;
160    };
161};
162
163#endif
164