SkScalerContext.h revision 0abbff9987b9452fd30cce198bea34fdb210ac41 
1/*
2 * Copyright 2006 The Android Open Source Project
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 SkScalerContext_DEFINED
9#define SkScalerContext_DEFINED
10
11#include "SkMask.h"
12#include "SkMaskGamma.h"
13#include "SkMatrix.h"
14#include "SkPaint.h"
15#include "SkTypeface.h"
16
17#ifdef SK_BUILD_FOR_ANDROID
18    #include "SkPaintOptionsAndroid.h"
19#endif
20
21struct SkGlyph;
22class SkDescriptor;
23class SkMaskFilter;
24class SkPathEffect;
25class SkRasterizer;
26
27/*
28 *  To allow this to be forward-declared, it must be its own typename, rather
29 *  than a nested struct inside SkScalerContext (where it started).
30 */
31struct SkScalerContextRec {
32    uint32_t    fOrigFontID;
33    uint32_t    fFontID;
34    SkScalar    fTextSize, fPreScaleX, fPreSkewX;
35    SkScalar    fPost2x2[2][2];
36    SkScalar    fFrameWidth, fMiterLimit;
37#ifdef SK_SUPPORT_HINTING_SCALE_FACTOR
38    SkScalar    fHintingScaleFactor;
39#endif
40
41    //These describe the parameters to create (uniquely identify) the pre-blend.
42    uint32_t    fLumBits;
43    uint8_t     fDeviceGamma; //2.6, (0.0, 4.0) gamma, 0.0 for sRGB
44    uint8_t     fPaintGamma;  //2.6, (0.0, 4.0) gamma, 0.0 for sRGB
45    uint8_t     fContrast;    //0.8+1, [0.0, 1.0] artificial contrast
46    uint8_t     fReservedAlign;
47
48    SkScalar getDeviceGamma() const {
49        return SkIntToScalar(fDeviceGamma) / (1 << 6);
50    }
51    void setDeviceGamma(SkScalar dg) {
52        SkASSERT(0 <= dg && dg < SkIntToScalar(4));
53        fDeviceGamma = SkScalarFloorToInt(dg * (1 << 6));
54    }
55
56    SkScalar getPaintGamma() const {
57        return SkIntToScalar(fPaintGamma) / (1 << 6);
58    }
59    void setPaintGamma(SkScalar pg) {
60        SkASSERT(0 <= pg && pg < SkIntToScalar(4));
61        fPaintGamma = SkScalarFloorToInt(pg * (1 << 6));
62    }
63
64    SkScalar getContrast() const {
65        return SkIntToScalar(fContrast) / ((1 << 8) - 1);
66    }
67    void setContrast(SkScalar c) {
68        SkASSERT(0 <= c && c <= SK_Scalar1);
69        fContrast = SkScalarRoundToInt(c * ((1 << 8) - 1));
70    }
71
72    /**
73     *  Causes the luminance color and contrast to be ignored, and the
74     *  paint and device gamma to be effectively 1.0.
75     */
76    void ignorePreBlend() {
77        setLuminanceColor(SK_ColorTRANSPARENT);
78        setPaintGamma(SK_Scalar1);
79        setDeviceGamma(SK_Scalar1);
80        setContrast(0);
81    }
82
83    uint8_t     fMaskFormat;
84    uint8_t     fStrokeJoin;
85    uint16_t    fFlags;
86    // Warning: when adding members note that the size of this structure
87    // must be a multiple of 4. SkDescriptor requires that its arguments be
88    // multiples of four and this structure is put in an SkDescriptor in
89    // SkPaint::MakeRec.
90
91    void    getMatrixFrom2x2(SkMatrix*) const;
92    void    getLocalMatrix(SkMatrix*) const;
93    void    getSingleMatrix(SkMatrix*) const;
94
95    inline SkPaint::Hinting getHinting() const;
96    inline void setHinting(SkPaint::Hinting);
97
98    SkMask::Format getFormat() const {
99        return static_cast<SkMask::Format>(fMaskFormat);
100    }
101
102    SkColor getLuminanceColor() const {
103        return fLumBits;
104    }
105
106    void setLuminanceColor(SkColor c) {
107        fLumBits = c;
108    }
109};
110
111//The following typedef hides from the rest of the implementation the number of
112//most significant bits to consider when creating mask gamma tables. Two bits
113//per channel was chosen as a balance between fidelity (more bits) and cache
114//sizes (fewer bits). Three bits per channel was chosen when #303942; (used by
115//the Chrome UI) turned out too green.
116typedef SkTMaskGamma<3, 3, 3> SkMaskGamma;
117
118class SkScalerContext {
119public:
120    typedef SkScalerContextRec Rec;
121
122    enum Flags {
123        kFrameAndFill_Flag        = 0x0001,
124        kDevKernText_Flag         = 0x0002,
125        kEmbeddedBitmapText_Flag  = 0x0004,
126        kEmbolden_Flag            = 0x0008,
127        kSubpixelPositioning_Flag = 0x0010,
128        kAutohinting_Flag         = 0x0020,
129        kVertical_Flag            = 0x0040,
130
131        // together, these two flags resulting in a two bit value which matches
132        // up with the SkPaint::Hinting enum.
133        kHinting_Shift            = 7, // to shift into the other flags above
134        kHintingBit1_Flag         = 0x0080,
135        kHintingBit2_Flag         = 0x0100,
136
137        // Pixel geometry information.
138        // only meaningful if fMaskFormat is LCD16 or LCD32
139        kLCD_Vertical_Flag        = 0x0200,    // else Horizontal
140        kLCD_BGROrder_Flag        = 0x0400,    // else RGB order
141
142        // Generate A8 from LCD source (for GDI and CoreGraphics).
143        // only meaningful if fMaskFormat is kA8
144        kGenA8FromLCD_Flag        = 0x0800, // could be 0x200 (bit meaning dependent on fMaskFormat)
145    };
146
147    // computed values
148    enum {
149        kHinting_Mask   = kHintingBit1_Flag | kHintingBit2_Flag,
150    };
151
152
153    SkScalerContext(SkTypeface*, const SkDescriptor*);
154    virtual ~SkScalerContext();
155
156    SkTypeface* getTypeface() const { return fTypeface.get(); }
157
158    SkMask::Format getMaskFormat() const {
159        return (SkMask::Format)fRec.fMaskFormat;
160    }
161
162    bool isSubpixel() const {
163        return SkToBool(fRec.fFlags & kSubpixelPositioning_Flag);
164    }
165
166    // remember our glyph offset/base
167    void setBaseGlyphCount(unsigned baseGlyphCount) {
168        fBaseGlyphCount = baseGlyphCount;
169    }
170
171    /** Return the corresponding glyph for the specified unichar. Since contexts
172        may be chained (under the hood), the glyphID that is returned may in
173        fact correspond to a different font/context. In that case, we use the
174        base-glyph-count to know how to translate back into local glyph space.
175     */
176    uint16_t charToGlyphID(SkUnichar uni);
177
178    /** Map the glyphID to its glyph index, and then to its char code. Unmapped
179        glyphs return zero.
180    */
181    SkUnichar glyphIDToChar(uint16_t glyphID);
182
183    unsigned    getGlyphCount() { return this->generateGlyphCount(); }
184    void        getAdvance(SkGlyph*);
185    void        getMetrics(SkGlyph*);
186    void        getImage(const SkGlyph&);
187    void        getPath(const SkGlyph&, SkPath*);
188    void        getFontMetrics(SkPaint::FontMetrics*);
189
190#ifdef SK_BUILD_FOR_ANDROID
191    unsigned getBaseGlyphCount(SkUnichar charCode);
192
193    // This function must be public for SkTypeface_android.h, but should not be
194    // called by other callers
195    SkFontID findTypefaceIdForChar(SkUnichar uni);
196#endif
197
198    static inline void MakeRec(const SkPaint&, const SkDeviceProperties* deviceProperties,
199                               const SkMatrix*, Rec* rec);
200    static inline void PostMakeRec(const SkPaint&, Rec*);
201
202    static SkMaskGamma::PreBlend GetMaskPreBlend(const Rec& rec);
203
204protected:
205    Rec         fRec;
206    unsigned    fBaseGlyphCount;
207
208    virtual unsigned generateGlyphCount() = 0;
209    virtual uint16_t generateCharToGlyph(SkUnichar) = 0;
210    virtual void generateAdvance(SkGlyph*) = 0;
211    virtual void generateMetrics(SkGlyph*) = 0;
212    virtual void generateImage(const SkGlyph&) = 0;
213    virtual void generatePath(const SkGlyph&, SkPath*) = 0;
214    virtual void generateFontMetrics(SkPaint::FontMetrics* mX,
215                                     SkPaint::FontMetrics* mY) = 0;
216    // default impl returns 0, indicating failure.
217    virtual SkUnichar generateGlyphToChar(uint16_t);
218
219    void forceGenerateImageFromPath() { fGenerateImageFromPath = true; }
220
221private:
222    // never null
223    SkAutoTUnref<SkTypeface> fTypeface;
224
225#ifdef SK_BUILD_FOR_ANDROID
226    SkPaintOptionsAndroid fPaintOptionsAndroid;
227#endif
228
229    // optional object, which may be null
230    SkPathEffect*   fPathEffect;
231    SkMaskFilter*   fMaskFilter;
232    SkRasterizer*   fRasterizer;
233
234    // if this is set, we draw the image from a path, rather than
235    // calling generateImage.
236    bool fGenerateImageFromPath;
237
238    void internalGetPath(const SkGlyph& glyph, SkPath* fillPath,
239                         SkPath* devPath, SkMatrix* fillToDevMatrix);
240
241    // Return the context associated with the next logical typeface, or NULL if
242    // there are no more entries in the fallback chain.
243    SkScalerContext* allocNextContext() const;
244
245    // return the next context, treating fNextContext as a cache of the answer
246    SkScalerContext* getNextContext();
247
248    // returns the right context from our link-list for this glyph. If no match
249    // is found, just returns the original context (this)
250    SkScalerContext* getGlyphContext(const SkGlyph& glyph);
251
252    // returns the right context from our link-list for this char. If no match
253    // is found it returns NULL. If a match is found then the glyphID param is
254    // set to the glyphID that maps to the provided char.
255    SkScalerContext* getContextFromChar(SkUnichar uni, uint16_t* glyphID);
256
257    // link-list of context, to handle missing chars. null-terminated.
258    SkScalerContext* fNextContext;
259
260    // SkMaskGamma::PreBlend converts linear masks to gamma correcting masks.
261protected:
262    // Visible to subclasses so that generateImage can apply the pre-blend directly.
263    const SkMaskGamma::PreBlend fPreBlend;
264private:
265    // When there is a filter, previous steps must create a linear mask
266    // and the pre-blend applied as a final step.
267    const SkMaskGamma::PreBlend fPreBlendForFilter;
268};
269
270#define kRec_SkDescriptorTag            SkSetFourByteTag('s', 'r', 'e', 'c')
271#define kPathEffect_SkDescriptorTag     SkSetFourByteTag('p', 't', 'h', 'e')
272#define kMaskFilter_SkDescriptorTag     SkSetFourByteTag('m', 's', 'k', 'f')
273#define kRasterizer_SkDescriptorTag     SkSetFourByteTag('r', 'a', 's', 't')
274#ifdef SK_BUILD_FOR_ANDROID
275#define kAndroidOpts_SkDescriptorTag    SkSetFourByteTag('a', 'n', 'd', 'r')
276#endif
277
278///////////////////////////////////////////////////////////////////////////////
279
280enum SkAxisAlignment {
281    kNone_SkAxisAlignment,
282    kX_SkAxisAlignment,
283    kY_SkAxisAlignment
284};
285
286/**
287 *  Return the axis (if any) that the baseline for horizontal text will land on
288 *  after running through the specified matrix.
289 *
290 *  As an example, the identity matrix will return kX_SkAxisAlignment
291 */
292SkAxisAlignment SkComputeAxisAlignmentForHText(const SkMatrix& matrix);
293
294///////////////////////////////////////////////////////////////////////////////
295
296SkPaint::Hinting SkScalerContextRec::getHinting() const {
297    unsigned hint = (fFlags & SkScalerContext::kHinting_Mask) >>
298                                            SkScalerContext::kHinting_Shift;
299    return static_cast<SkPaint::Hinting>(hint);
300}
301
302void SkScalerContextRec::setHinting(SkPaint::Hinting hinting) {
303    fFlags = (fFlags & ~SkScalerContext::kHinting_Mask) |
304                                (hinting << SkScalerContext::kHinting_Shift);
305}
306
307
308#endif
309