SkLayerDrawLooper.h revision 2880df2609eba09b555ca37be04b6ad89290c765 
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    virtual ~SkLayerDrawLooper();
19
20    /**
21     *  Bits specifies which aspects of the layer's paint should replace the
22     *  corresponding aspects on the draw's paint.
23     *  kEntirePaint_Bits means use the layer's paint completely.
24     *  0 means ignore the layer's paint... except for fColorMode, which is
25     *  always applied.
26     */
27    enum Bits {
28        kStyle_Bit      = 1 << 0,   //!< use this layer's Style/stroke settings
29        kTextSkewX_Bit  = 1 << 1,   //!< use this layer's textskewx
30        kPathEffect_Bit = 1 << 2,   //!< use this layer's patheffect
31        kMaskFilter_Bit = 1 << 3,   //!< use this layer's maskfilter
32        kShader_Bit     = 1 << 4,   //!< use this layer's shader
33        kColorFilter_Bit = 1 << 5,  //!< use this layer's colorfilter
34        kXfermode_Bit   = 1 << 6,   //!< use this layer's xfermode
35
36        /**
37         *  Use the layer's paint entirely, with these exceptions:
38         *  - We never override the draw's paint's text_encoding, since that is
39         *    used to interpret the text/len parameters in draw[Pos]Text.
40         *  - Color is always computed using the LayerInfo's fColorMode.
41         */
42        kEntirePaint_Bits = -1
43
44    };
45    typedef int32_t BitFlags;
46
47    /**
48     *  Info for how to apply the layer's paint and offset.
49     *
50     *  fColorMode controls how we compute the final color for the layer:
51     *      The layer's paint's color is treated as the SRC
52     *      The draw's paint's color is treated as the DST
53     *      final-color = Mode(layers-color, draws-color);
54     *  Any SkXfermode::Mode will work. Two common choices are:
55     *      kSrc_Mode: to use the layer's color, ignoring the draw's
56     *      kDst_Mode: to just keep the draw's color, ignoring the layer's
57     */
58    struct SK_API LayerInfo {
59        BitFlags            fPaintBits;
60        SkXfermode::Mode    fColorMode;
61        SkVector            fOffset;
62        bool                fPostTranslate; //!< applies to fOffset
63
64        /**
65         *  Initial the LayerInfo. Defaults to settings that will draw the
66         *  layer with no changes: e.g.
67         *      fPaintBits == 0
68         *      fColorMode == kDst_Mode
69         *      fOffset == (0, 0)
70         */
71        LayerInfo();
72    };
73
74    SkDrawLooper::Context* createContext(SkCanvas*, void* storage) const override;
75
76    size_t contextSize() const override { return sizeof(LayerDrawLooperContext); }
77
78    bool asABlurShadow(BlurShadowRec* rec) const override;
79
80    SK_TO_STRING_OVERRIDE()
81
82    Factory getFactory() const override { return CreateProc; }
83    static SkFlattenable* CreateProc(SkReadBuffer& buffer);
84
85protected:
86    SkLayerDrawLooper();
87
88    void flatten(SkWriteBuffer&) const override;
89
90private:
91    struct Rec {
92        Rec*    fNext;
93        SkPaint fPaint;
94        LayerInfo fInfo;
95    };
96    Rec*    fRecs;
97    int     fCount;
98
99    // state-machine during the init/next cycle
100    class LayerDrawLooperContext : public SkDrawLooper::Context {
101    public:
102        explicit LayerDrawLooperContext(const SkLayerDrawLooper* looper);
103
104    protected:
105        bool next(SkCanvas*, SkPaint* paint) override;
106
107    private:
108        Rec* fCurrRec;
109
110        static void ApplyInfo(SkPaint* dst, const SkPaint& src, const LayerInfo&);
111    };
112
113    typedef SkDrawLooper INHERITED;
114
115public:
116    class SK_API Builder {
117    public:
118        Builder();
119        ~Builder();
120
121        /**
122         *  Call for each layer you want to add (from top to bottom).
123         *  This returns a paint you can modify, but that ptr is only valid until
124         *  the next call made to addLayer().
125         */
126        SkPaint* addLayer(const LayerInfo&);
127
128        /**
129         *  This layer will draw with the original paint, at the specified offset
130         */
131        void addLayer(SkScalar dx, SkScalar dy);
132
133        /**
134         *  This layer will with the original paint and no offset.
135         */
136        void addLayer() { this->addLayer(0, 0); }
137
138        /// Similar to addLayer, but adds a layer to the top.
139        SkPaint* addLayerOnTop(const LayerInfo&);
140
141        /**
142          * Pass list of layers on to newly built looper and return it. This will
143          * also reset the builder, so it can be used to build another looper.
144          */
145        SkLayerDrawLooper* detachLooper();
146
147    private:
148        Rec* fRecs;
149        Rec* fTopRec;
150        int  fCount;
151    };
152};
153
154#endif
155