SkScalerContext.h revision 0910916c0f7b951ee55c4b7c6358295b9bca0565 
1/*
2 * Copyright (C) 2006 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef SkScalerContext_DEFINED
18#define SkScalerContext_DEFINED
19
20#include "SkMask.h"
21#include "SkMatrix.h"
22#include "SkPaint.h"
23#include "SkPath.h"
24#include "SkPoint.h"
25
26class SkDescriptor;
27class SkMaskFilter;
28class SkPathEffect;
29class SkRasterizer;
30
31// needs to be != to any valid SkMask::Format
32#define MASK_FORMAT_JUST_ADVANCE    (0xFF)
33
34struct SkGlyph {
35    void*       fImage;
36    SkPath*     fPath;
37    SkFixed     fAdvanceX, fAdvanceY;
38
39    uint32_t    fID;
40    uint16_t    fWidth, fHeight;
41    int16_t     fTop, fLeft;
42
43    uint8_t     fMaskFormat;
44    int8_t      fRsbDelta, fLsbDelta;  // used by auto-kerning
45
46    unsigned rowBytes() const {
47        unsigned rb = fWidth;
48        if (SkMask::kBW_Format == fMaskFormat) {
49            rb = (rb + 7) >> 3;
50        } else {
51            rb = SkAlign4(rb);
52        }
53        return rb;
54    }
55
56    bool isJustAdvance() const {
57        return MASK_FORMAT_JUST_ADVANCE == fMaskFormat;
58    }
59
60    bool isFullMetrics() const {
61        return MASK_FORMAT_JUST_ADVANCE != fMaskFormat;
62    }
63
64    uint16_t getGlyphID() const {
65        return ID2Code(fID);
66    }
67
68    unsigned getGlyphID(unsigned baseGlyphCount) const {
69        unsigned code = ID2Code(fID);
70        SkASSERT(code >= baseGlyphCount);
71        return code - baseGlyphCount;
72    }
73
74    unsigned getSubX() const {
75        return ID2SubX(fID);
76    }
77
78    SkFixed getSubXFixed() const {
79        return SubToFixed(ID2SubX(fID));
80    }
81
82    SkFixed getSubYFixed() const {
83        return SubToFixed(ID2SubY(fID));
84    }
85
86    size_t computeImageSize() const;
87
88    /** Call this to set all of the metrics fields to 0 (e.g. if the scaler
89        encounters an error measuring a glyph). Note: this does not alter the
90        fImage, fPath, fID, fMaskFormat fields.
91     */
92    void zeroMetrics();
93
94    enum {
95        kSubBits = 2,
96        kSubMask = ((1 << kSubBits) - 1),
97        kSubShift = 24, // must be large enough for glyphs and unichars
98        kCodeMask = ((1 << kSubShift) - 1),
99        // relative offsets for X and Y subpixel bits
100        kSubShiftX = kSubBits,
101        kSubShiftY = 0
102    };
103
104    static unsigned ID2Code(uint32_t id) {
105        return id & kCodeMask;
106    }
107
108    static unsigned ID2SubX(uint32_t id) {
109        return id >> (kSubShift + kSubShiftX);
110    }
111
112    static unsigned ID2SubY(uint32_t id) {
113        return (id >> (kSubShift + kSubShiftY)) & kSubMask;
114    }
115
116    static unsigned FixedToSub(SkFixed n) {
117        return (n >> (16 - kSubBits)) & kSubMask;
118    }
119
120    static SkFixed SubToFixed(unsigned sub) {
121        SkASSERT(sub <= kSubMask);
122        return sub << (16 - kSubBits);
123    }
124
125    static uint32_t MakeID(unsigned code) {
126        return code;
127    }
128
129    static uint32_t MakeID(unsigned code, SkFixed x, SkFixed y) {
130        SkASSERT(code <= kCodeMask);
131        x = FixedToSub(x);
132        y = FixedToSub(y);
133        return (x << (kSubShift + kSubShiftX)) |
134               (y << (kSubShift + kSubShiftY)) |
135               code;
136    }
137
138    void toMask(SkMask* mask) const;
139};
140
141class SkScalerContext {
142public:
143    enum Hints {
144        kNo_Hints,
145        kSubpixel_Hints,
146        kNormal_Hints
147    };
148    enum Flags {
149        kFrameAndFill_Flag  = 0x01,
150        kDevKernText_Flag   = 0x02,
151        kGammaForBlack_Flag = 0x04, // illegal to set both Gamma flags
152        kGammaForWhite_Flag = 0x08  // illegal to set both Gamma flags
153    };
154    struct Rec {
155        uint32_t    fFontID;
156        SkScalar    fTextSize, fPreScaleX, fPreSkewX;
157        SkScalar    fPost2x2[2][2];
158        SkScalar    fFrameWidth, fMiterLimit;
159        uint8_t     fHints;
160        uint8_t     fMaskFormat;
161        uint8_t     fStrokeJoin;
162        uint8_t     fFlags;
163
164        void    getMatrixFrom2x2(SkMatrix*) const;
165        void    getLocalMatrix(SkMatrix*) const;
166        void    getSingleMatrix(SkMatrix*) const;
167    };
168
169    SkScalerContext(const SkDescriptor* desc);
170    virtual ~SkScalerContext();
171
172    void setBaseGlyphCount(unsigned baseGlyphCount) {
173        fBaseGlyphCount = baseGlyphCount;
174    }
175
176    uint16_t    charToGlyphID(SkUnichar uni);
177
178    unsigned    getGlyphCount() const { return this->generateGlyphCount(); }
179    void        getAdvance(SkGlyph*);
180    void        getMetrics(SkGlyph*);
181    void        getImage(const SkGlyph&);
182    void        getPath(const SkGlyph&, SkPath*);
183    void        getFontMetrics(SkPaint::FontMetrics* mX,
184                               SkPaint::FontMetrics* mY);
185
186    static inline void MakeRec(const SkPaint&, const SkMatrix*, Rec* rec);
187    static SkScalerContext* Create(const SkDescriptor*);
188
189protected:
190    Rec         fRec;
191    unsigned    fBaseGlyphCount;
192
193    virtual unsigned generateGlyphCount() const = 0;
194    virtual uint16_t generateCharToGlyph(SkUnichar) = 0;
195    virtual void generateAdvance(SkGlyph*) = 0;
196    virtual void generateMetrics(SkGlyph*) = 0;
197    virtual void generateImage(const SkGlyph&) = 0;
198    virtual void generatePath(const SkGlyph&, SkPath*) = 0;
199    virtual void generateFontMetrics(SkPaint::FontMetrics* mX,
200                                     SkPaint::FontMetrics* mY) = 0;
201
202private:
203    SkPathEffect*   fPathEffect;
204    SkMaskFilter*   fMaskFilter;
205    SkRasterizer*   fRasterizer;
206    SkScalar        fDevFrameWidth;
207
208    void internalGetPath(const SkGlyph& glyph, SkPath* fillPath,
209                         SkPath* devPath, SkMatrix* fillToDevMatrix);
210
211    mutable SkScalerContext* fAuxScalerContext;
212
213    SkScalerContext* getGlyphContext(const SkGlyph& glyph) const;
214
215    // return loaded fAuxScalerContext or NULL
216    SkScalerContext* loadAuxContext() const;
217};
218
219#define kRec_SkDescriptorTag            SkSetFourByteTag('s', 'r', 'e', 'c')
220#define kPathEffect_SkDescriptorTag     SkSetFourByteTag('p', 't', 'h', 'e')
221#define kMaskFilter_SkDescriptorTag     SkSetFourByteTag('m', 's', 'k', 'f')
222#define kRasterizer_SkDescriptorTag     SkSetFourByteTag('r', 'a', 's', 't')
223
224#endif
225
226