SkLayerDrawLooper.h revision 54924243c1b65b3ee6d8fa064b50a9b1bb2a19a5 
1
2/*
3 * Copyright 2011 Google Inc.
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#ifndef SkLayerDrawLooper_DEFINED
9#define SkLayerDrawLooper_DEFINED
10
11#include "SkDrawLooper.h"
12#include "SkXfermode.h"
13
14struct SkPoint;
15
16class SK_API SkLayerDrawLooper : public SkDrawLooper {
17public:
18            SkLayerDrawLooper();
19    virtual ~SkLayerDrawLooper();
20
21    /**
22     *  Bits specifies which aspects of the layer's paint should replace the
23     *  corresponding aspects on the draw's paint.
24     *  kEntirePaint_Bits means use the layer's paint completely.
25     *  0 means ignore the layer's paint... except that LayerInfo's fFlagsMask
26     *  and fColorMode are always applied.
27     */
28    enum Bits {
29        kStyle_Bit      = 1 << 0,   //!< use this layer's Style/stroke settings
30        kTextSkewX_Bit  = 1 << 1,   //!< use this layer's textskewx
31        kPathEffect_Bit = 1 << 2,   //!< use this layer's patheffect
32        kMaskFilter_Bit = 1 << 3,   //!< use this layer's maskfilter
33        kShader_Bit     = 1 << 4,   //!< use this layer's shader
34        kColorFilter_Bit = 1 << 5,  //!< use this layer's colorfilter
35        kXfermode_Bit   = 1 << 6,   //!< use this layer's xfermode
36
37        /**
38         *  Use the layer's paint entirely, with these exceptions:
39         *  - We never override the draw's paint's text_encoding, since that is
40         *    used to interpret the text/len parameters in draw[Pos]Text.
41         *  - Flags and Color are always computed using the LayerInfo's
42         *    fFlagsMask and 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     *  fFlagsMask selects which flags in the layer's paint should be applied.
53     *      result = (draw-flags & ~fFlagsMask) | (layer-flags & fFlagsMask)
54     *  In the extreme:
55     *      If fFlagsMask is 0, we ignore all of the layer's flags
56     *      If fFlagsMask is -1, we use all of the layer's flags
57     *
58     *  fColorMode controls how we compute the final color for the layer:
59     *      The layer's paint's color is treated as the SRC
60     *      The draw's paint's color is treated as the DST
61     *      final-color = Mode(layers-color, draws-color);
62     *  Any SkXfermode::Mode will work. Two common choices are:
63     *      kSrc_Mode: to use the layer's color, ignoring the draw's
64     *      kDst_Mode: to just keep the draw's color, ignoring the layer's
65     */
66    struct SK_API LayerInfo {
67        uint32_t            fFlagsMask; // SkPaint::Flags
68        BitFlags            fPaintBits;
69        SkXfermode::Mode    fColorMode;
70        SkVector            fOffset;
71        bool                fPostTranslate; //!< applies to fOffset
72
73        /**
74         *  Initial the LayerInfo. Defaults to settings that will draw the
75         *  layer with no changes: e.g.
76         *      fPaintBits == 0
77         *      fColorMode == kDst_Mode
78         *      fOffset == (0, 0)
79         */
80        LayerInfo();
81    };
82
83    /**
84     *  Call for each layer you want to add (from top to bottom).
85     *  This returns a paint you can modify, but that ptr is only valid until
86     *  the next call made to addLayer().
87     */
88    SkPaint* addLayer(const LayerInfo&);
89
90    /**
91     *  This layer will draw with the original paint, ad the specified offset
92     */
93    void addLayer(SkScalar dx, SkScalar dy);
94
95    /**
96     *  This layer will with the original paint and no offset.
97     */
98    void addLayer() { this->addLayer(0, 0); }
99
100    // overrides from SkDrawLooper
101    virtual void init(SkCanvas*);
102    virtual bool next(SkCanvas*, SkPaint* paint);
103
104    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLayerDrawLooper)
105
106protected:
107    SkLayerDrawLooper(SkFlattenableReadBuffer&);
108    virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
109
110private:
111    struct Rec {
112        Rec*    fNext;
113        SkPaint fPaint;
114        LayerInfo fInfo;
115
116        static Rec* Reverse(Rec*);
117    };
118    Rec*    fRecs;
119    int     fCount;
120
121    // state-machine during the init/next cycle
122    Rec* fCurrRec;
123
124    static void ApplyInfo(SkPaint* dst, const SkPaint& src, const LayerInfo&);
125
126    class MyRegistrar : public SkFlattenable::Registrar {
127    public:
128        MyRegistrar();
129    };
130
131    typedef SkDrawLooper INHERITED;
132};
133
134
135#endif
136