SkLayerDrawLooper.h revision 8b0e8ac5f582de80356019406e2975079bf0829d 
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            SkLayerDrawLooper();
21    virtual ~SkLayerDrawLooper();
22
23    /**
24     *  Bits specifies which aspects of the layer's paint should replace the
25     *  corresponding aspects on the draw's paint.
26     *  kEntirePaint_Bits means use the layer's paint completely.
27     *  0 means ignore the layer's paint... except that LayerInfo's fFlagsMask
28     *  and fColorMode are always applied.
29     */
30    enum Bits {
31        kStyle_Bit      = 1 << 0,   //!< use this layer's Style/stroke settings
32        kTextSkewX_Bit  = 1 << 1,   //!< use this layer's textskewx
33        kPathEffect_Bit = 1 << 2,   //!< use this layer's patheffect
34        kMaskFilter_Bit = 1 << 3,   //!< use this layer's maskfilter
35        kShader_Bit     = 1 << 4,   //!< use this layer's shader
36        kColorFilter_Bit = 1 << 5,  //!< use this layer's colorfilter
37        kXfermode_Bit   = 1 << 6,   //!< use this layer's xfermode
38
39        /**
40         *  Use the layer's paint entirely, with these exceptions:
41         *  - We never override the draw's paint's text_encoding, since that is
42         *    used to interpret the text/len parameters in draw[Pos]Text.
43         *  - Flags and Color are always computed using the LayerInfo's
44         *    fFlagsMask and fColorMode.
45         */
46        kEntirePaint_Bits = -1
47
48    };
49    typedef int32_t BitFlags;
50
51    /**
52     *  Info for how to apply the layer's paint and offset.
53     *
54     *  fFlagsMask selects which flags in the layer's paint should be applied.
55     *      result = (draw-flags & ~fFlagsMask) | (layer-flags & fFlagsMask)
56     *  In the extreme:
57     *      If fFlagsMask is 0, we ignore all of the layer's flags
58     *      If fFlagsMask is -1, we use all of the layer's flags
59     *
60     *  fColorMode controls how we compute the final color for the layer:
61     *      The layer's paint's color is treated as the SRC
62     *      The draw's paint's color is treated as the DST
63     *      final-color = Mode(layers-color, draws-color);
64     *  Any SkXfermode::Mode will work. Two common choices are:
65     *      kSrc_Mode: to use the layer's color, ignoring the draw's
66     *      kDst_Mode: to just keep the draw's color, ignoring the layer's
67     */
68    struct SK_API LayerInfo {
69        uint32_t            fFlagsMask; // SkPaint::Flags
70        BitFlags            fPaintBits;
71        SkXfermode::Mode    fColorMode;
72        SkVector            fOffset;
73        bool                fPostTranslate; //!< applies to fOffset
74
75        /**
76         *  Initial the LayerInfo. Defaults to settings that will draw the
77         *  layer with no changes: e.g.
78         *      fPaintBits == 0
79         *      fColorMode == kDst_Mode
80         *      fOffset == (0, 0)
81         */
82        LayerInfo();
83    };
84
85    /**
86     *  Call for each layer you want to add (from top to bottom).
87     *  This returns a paint you can modify, but that ptr is only valid until
88     *  the next call made to addLayer().
89     */
90    SkPaint* addLayer(const LayerInfo&);
91
92    /**
93     *  This layer will draw with the original paint, at the specified offset
94     */
95    void addLayer(SkScalar dx, SkScalar dy);
96
97    /**
98     *  This layer will with the original paint and no offset.
99     */
100    void addLayer() { this->addLayer(0, 0); }
101
102    /// Similar to addLayer, but adds a layer to the top.
103    SkPaint* addLayerOnTop(const LayerInfo&);
104
105    // overrides from SkDrawLooper
106    virtual void init(SkCanvas*);
107    virtual bool next(SkCanvas*, SkPaint* paint);
108
109    SK_DEVELOPER_TO_STRING()
110    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLayerDrawLooper)
111
112protected:
113    SkLayerDrawLooper(SkReadBuffer&);
114    virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
115
116private:
117    struct Rec {
118        Rec*    fNext;
119        SkPaint fPaint;
120        LayerInfo fInfo;
121    };
122    Rec*    fRecs;
123    Rec*    fTopRec;
124    int     fCount;
125
126    // state-machine during the init/next cycle
127    Rec* fCurrRec;
128
129    static void ApplyInfo(SkPaint* dst, const SkPaint& src, const LayerInfo&);
130
131    class MyRegistrar : public SkFlattenable::Registrar {
132    public:
133        MyRegistrar();
134    };
135
136    typedef SkDrawLooper INHERITED;
137};
138
139#endif
140