SkLayerDrawLooper.h revision 842292f10fc08bc8701114f7eec00944b6ea26d2 
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 for fColorMode, which is
28     *  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         *  - Color is always computed using the LayerInfo's fColorMode.
44         */
45        kEntirePaint_Bits = -1
46
47    };
48    typedef int32_t BitFlags;
49
50    /**
51     *  Info for how to apply the layer's paint and offset.
52     *
53     *  fColorMode controls how we compute the final color for the layer:
54     *      The layer's paint's color is treated as the SRC
55     *      The draw's paint's color is treated as the DST
56     *      final-color = Mode(layers-color, draws-color);
57     *  Any SkXfermode::Mode will work. Two common choices are:
58     *      kSrc_Mode: to use the layer's color, ignoring the draw's
59     *      kDst_Mode: to just keep the draw's color, ignoring the layer's
60     */
61    struct SK_API LayerInfo {
62        BitFlags            fPaintBits;
63        SkXfermode::Mode    fColorMode;
64        SkVector            fOffset;
65        bool                fPostTranslate; //!< applies to fOffset
66
67        /**
68         *  Initial the LayerInfo. Defaults to settings that will draw the
69         *  layer with no changes: e.g.
70         *      fPaintBits == 0
71         *      fColorMode == kDst_Mode
72         *      fOffset == (0, 0)
73         */
74        LayerInfo();
75    };
76
77    /**
78     *  Call for each layer you want to add (from top to bottom).
79     *  This returns a paint you can modify, but that ptr is only valid until
80     *  the next call made to addLayer().
81     */
82    SkPaint* addLayer(const LayerInfo&);
83
84    /**
85     *  This layer will draw with the original paint, at the specified offset
86     */
87    void addLayer(SkScalar dx, SkScalar dy);
88
89    /**
90     *  This layer will with the original paint and no offset.
91     */
92    void addLayer() { this->addLayer(0, 0); }
93
94    /// Similar to addLayer, but adds a layer to the top.
95    SkPaint* addLayerOnTop(const LayerInfo&);
96
97    // overrides from SkDrawLooper
98    virtual void init(SkCanvas*);
99    virtual bool next(SkCanvas*, SkPaint* paint);
100
101    SK_DEVELOPER_TO_STRING()
102
103    /// Implements Flattenable.
104    virtual Factory getFactory() const SK_OVERRIDE { return CreateProc; }
105    static SkFlattenable* CreateProc(SkReadBuffer& buffer);
106
107protected:
108    virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
109
110private:
111    struct Rec {
112        Rec*    fNext;
113        SkPaint fPaint;
114        LayerInfo fInfo;
115    };
116    Rec*    fRecs;
117    Rec*    fTopRec;
118    int     fCount;
119
120    // state-machine during the init/next cycle
121    Rec* fCurrRec;
122
123    static void ApplyInfo(SkPaint* dst, const SkPaint& src, const LayerInfo&);
124
125    class MyRegistrar : public SkFlattenable::Registrar {
126    public:
127        MyRegistrar();
128    };
129
130    typedef SkDrawLooper INHERITED;
131
132public:
133    class SK_API Builder {
134    public:
135        Builder();
136        ~Builder();
137
138        /**
139         *  Call for each layer you want to add (from top to bottom).
140         *  This returns a paint you can modify, but that ptr is only valid until
141         *  the next call made to addLayer().
142         */
143        SkPaint* addLayer(const LayerInfo&);
144
145        /**
146         *  This layer will draw with the original paint, at the specified offset
147         */
148        void addLayer(SkScalar dx, SkScalar dy);
149
150        /**
151         *  This layer will with the original paint and no offset.
152         */
153        void addLayer() { this->addLayer(0, 0); }
154
155        /// Similar to addLayer, but adds a layer to the top.
156        SkPaint* addLayerOnTop(const LayerInfo&);
157
158        /**
159          * Pass list of layers on to newly built looper and return it. This will
160          * also reset the builder, so it can be used to build another looper.
161          */
162        SkLayerDrawLooper* detachLooper();
163
164    private:
165        Rec* fRecs;
166        Rec* fTopRec;
167        int  fCount;
168    };
169};
170
171#endif
172