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 "SkGlyph.h"
12#include "SkMask.h"
13#include "SkMaskGamma.h"
14#include "SkMatrix.h"
15#include "SkPaint.h"
16#include "SkTypeface.h"
17
18class SkDescriptor;
19class SkMaskFilter;
20class SkPathEffect;
21class SkRasterizer;
22
23struct SkScalerContextEffects {
24    SkScalerContextEffects() : fPathEffect(nullptr), fMaskFilter(nullptr), fRasterizer(nullptr) {}
25    SkScalerContextEffects(SkPathEffect* pe, SkMaskFilter* mf, SkRasterizer* ra)
26        : fPathEffect(pe), fMaskFilter(mf), fRasterizer(ra) {}
27
28    SkPathEffect*   fPathEffect;
29    SkMaskFilter*   fMaskFilter;
30    SkRasterizer*   fRasterizer;
31};
32
33enum SkAxisAlignment {
34    kNone_SkAxisAlignment,
35    kX_SkAxisAlignment,
36    kY_SkAxisAlignment
37};
38
39/*
40 *  To allow this to be forward-declared, it must be its own typename, rather
41 *  than a nested struct inside SkScalerContext (where it started).
42 */
43struct SkScalerContextRec {
44    uint32_t    fFontID;
45    SkScalar    fTextSize, fPreScaleX, fPreSkewX;
46    SkScalar    fPost2x2[2][2];
47    SkScalar    fFrameWidth, fMiterLimit;
48
49    //These describe the parameters to create (uniquely identify) the pre-blend.
50    uint32_t    fLumBits;
51    uint8_t     fDeviceGamma; //2.6, (0.0, 4.0) gamma, 0.0 for sRGB
52    uint8_t     fPaintGamma;  //2.6, (0.0, 4.0) gamma, 0.0 for sRGB
53    uint8_t     fContrast;    //0.8+1, [0.0, 1.0] artificial contrast
54    uint8_t     fReservedAlign;
55
56    SkScalar getDeviceGamma() const {
57        return SkIntToScalar(fDeviceGamma) / (1 << 6);
58    }
59    void setDeviceGamma(SkScalar dg) {
60        SkASSERT(0 <= dg && dg < SkIntToScalar(4));
61        fDeviceGamma = SkScalarFloorToInt(dg * (1 << 6));
62    }
63
64    SkScalar getPaintGamma() const {
65        return SkIntToScalar(fPaintGamma) / (1 << 6);
66    }
67    void setPaintGamma(SkScalar pg) {
68        SkASSERT(0 <= pg && pg < SkIntToScalar(4));
69        fPaintGamma = SkScalarFloorToInt(pg * (1 << 6));
70    }
71
72    SkScalar getContrast() const {
73        return SkIntToScalar(fContrast) / ((1 << 8) - 1);
74    }
75    void setContrast(SkScalar c) {
76        SkASSERT(0 <= c && c <= SK_Scalar1);
77        fContrast = SkScalarRoundToInt(c * ((1 << 8) - 1));
78    }
79
80    /**
81     *  Causes the luminance color to be ignored, and the paint and device
82     *  gamma to be effectively 1.0
83     */
84    void ignoreGamma() {
85        setLuminanceColor(SK_ColorTRANSPARENT);
86        setPaintGamma(SK_Scalar1);
87        setDeviceGamma(SK_Scalar1);
88    }
89
90    /**
91     *  Causes the luminance color and contrast to be ignored, and the
92     *  paint and device gamma to be effectively 1.0.
93     */
94    void ignorePreBlend() {
95        ignoreGamma();
96        setContrast(0);
97    }
98
99    uint8_t     fMaskFormat;
100    uint8_t     fStrokeJoin : 4;
101    uint8_t     fStrokeCap : 4;
102    uint16_t    fFlags;
103    // Warning: when adding members note that the size of this structure
104    // must be a multiple of 4. SkDescriptor requires that its arguments be
105    // multiples of four and this structure is put in an SkDescriptor in
106    // SkPaint::MakeRec.
107
108    void    getMatrixFrom2x2(SkMatrix*) const;
109    void    getLocalMatrix(SkMatrix*) const;
110    void    getSingleMatrix(SkMatrix*) const;
111
112    /** The kind of scale which will be applied by the underlying port (pre-matrix). */
113    enum PreMatrixScale {
114        kFull_PreMatrixScale,  // The underlying port can apply both x and y scale.
115        kVertical_PreMatrixScale,  // The underlying port can only apply a y scale.
116        kVerticalInteger_PreMatrixScale  // The underlying port can only apply an integer y scale.
117    };
118    /**
119     *  Compute useful matrices for use with sizing in underlying libraries.
120     *
121     *  There are two kinds of text size, a 'requested/logical size' which is like asking for size
122     *  '12' and a 'real' size which is the size after the matrix is applied. The matrices produced
123     *  by this method are based on the 'real' size. This method effectively finds the total device
124     *  matrix and decomposes it in various ways.
125     *
126     *  The most useful decomposition is into 'scale' and 'remaining'. The 'scale' is applied first
127     *  and then the 'remaining' to fully apply the total matrix. This decomposition is useful when
128     *  the text size ('scale') may have meaning apart from the total matrix. This is true when
129     *  hinting, and sometimes true for other properties as well.
130     *
131     *  The second (optional) decomposition is of 'remaining' into a non-rotational part
132     *  'remainingWithoutRotation' and a rotational part 'remainingRotation'. The 'scale' is applied
133     *  first, then 'remainingWithoutRotation', then 'remainingRotation' to fully apply the total
134     *  matrix. This decomposition is helpful when only horizontal metrics can be trusted, so the
135     *  'scale' and 'remainingWithoutRotation' will be handled by the underlying library, but
136     *  the final rotation 'remainingRotation' will be handled manually.
137     *
138     *  The 'total' matrix is also (optionally) available. This is useful in cases where the
139     *  underlying library will not be used, often when working directly with font data.
140     *
141     *  The parameters 'scale' and 'remaining' are required, the other pointers may be nullptr.
142     *
143     *  @param preMatrixScale the kind of scale to extract from the total matrix.
144     *  @param scale the scale extracted from the total matrix (both values positive).
145     *  @param remaining apply after scale to apply the total matrix.
146     *  @param remainingWithoutRotation apply after scale to apply the total matrix sans rotation.
147     *  @param remainingRotation apply after remainingWithoutRotation to apply the total matrix.
148     *  @param total the total matrix.
149     *  @return false if the matrix was singular. The output will be valid but not invertible.
150     */
151    bool computeMatrices(PreMatrixScale preMatrixScale,
152                         SkVector* scale, SkMatrix* remaining,
153                         SkMatrix* remainingWithoutRotation = nullptr,
154                         SkMatrix* remainingRotation = nullptr,
155                         SkMatrix* total = nullptr);
156
157    inline SkPaint::Hinting getHinting() const;
158    inline void setHinting(SkPaint::Hinting);
159
160    SkMask::Format getFormat() const {
161        return static_cast<SkMask::Format>(fMaskFormat);
162    }
163
164    SkColor getLuminanceColor() const {
165        return fLumBits;
166    }
167
168    void setLuminanceColor(SkColor c) {
169        fLumBits = c;
170    }
171};
172
173//The following typedef hides from the rest of the implementation the number of
174//most significant bits to consider when creating mask gamma tables. Two bits
175//per channel was chosen as a balance between fidelity (more bits) and cache
176//sizes (fewer bits). Three bits per channel was chosen when #303942; (used by
177//the Chrome UI) turned out too green.
178typedef SkTMaskGamma<3, 3, 3> SkMaskGamma;
179
180class SkScalerContext {
181public:
182    typedef SkScalerContextRec Rec;
183
184    enum Flags {
185        kFrameAndFill_Flag        = 0x0001,
186        kDevKernText_Flag         = 0x0002,
187        kEmbeddedBitmapText_Flag  = 0x0004,
188        kEmbolden_Flag            = 0x0008,
189        kSubpixelPositioning_Flag = 0x0010,
190        kForceAutohinting_Flag    = 0x0020,  // Use auto instead of bytcode hinting if hinting.
191        kVertical_Flag            = 0x0040,
192
193        // together, these two flags resulting in a two bit value which matches
194        // up with the SkPaint::Hinting enum.
195        kHinting_Shift            = 7, // to shift into the other flags above
196        kHintingBit1_Flag         = 0x0080,
197        kHintingBit2_Flag         = 0x0100,
198
199        // Pixel geometry information.
200        // only meaningful if fMaskFormat is kLCD16
201        kLCD_Vertical_Flag        = 0x0200,    // else Horizontal
202        kLCD_BGROrder_Flag        = 0x0400,    // else RGB order
203
204        // Generate A8 from LCD source (for GDI and CoreGraphics).
205        // only meaningful if fMaskFormat is kA8
206        kGenA8FromLCD_Flag        = 0x0800, // could be 0x200 (bit meaning dependent on fMaskFormat)
207    };
208
209    // computed values
210    enum {
211        kHinting_Mask   = kHintingBit1_Flag | kHintingBit2_Flag,
212    };
213
214    SkScalerContext(sk_sp<SkTypeface>, const SkScalerContextEffects&, const SkDescriptor*);
215    virtual ~SkScalerContext();
216
217    SkTypeface* getTypeface() const { return fTypeface.get(); }
218
219    SkMask::Format getMaskFormat() const {
220        return (SkMask::Format)fRec.fMaskFormat;
221    }
222
223    bool isSubpixel() const {
224        return SkToBool(fRec.fFlags & kSubpixelPositioning_Flag);
225    }
226
227    bool isVertical() const {
228        return SkToBool(fRec.fFlags & kVertical_Flag);
229    }
230
231    /** Return the corresponding glyph for the specified unichar. Since contexts
232        may be chained (under the hood), the glyphID that is returned may in
233        fact correspond to a different font/context. In that case, we use the
234        base-glyph-count to know how to translate back into local glyph space.
235     */
236    uint16_t charToGlyphID(SkUnichar uni) {
237        return generateCharToGlyph(uni);
238    }
239
240    /** Map the glyphID to its glyph index, and then to its char code. Unmapped
241        glyphs return zero.
242    */
243    SkUnichar glyphIDToChar(uint16_t glyphID) {
244        return (glyphID < getGlyphCount()) ? generateGlyphToChar(glyphID) : 0;
245    }
246
247    unsigned    getGlyphCount() { return this->generateGlyphCount(); }
248    void        getAdvance(SkGlyph*);
249    void        getMetrics(SkGlyph*);
250    void        getImage(const SkGlyph&);
251    void        getPath(SkPackedGlyphID, SkPath*);
252    void        getFontMetrics(SkPaint::FontMetrics*);
253
254    /** Return the size in bytes of the associated gamma lookup table
255     */
256    static size_t GetGammaLUTSize(SkScalar contrast, SkScalar paintGamma, SkScalar deviceGamma,
257                                  int* width, int* height);
258
259    /** Get the associated gamma lookup table. The 'data' pointer must point to pre-allocated
260        memory, with size in bytes greater than or equal to the return value of getGammaLUTSize().
261     */
262    static void   GetGammaLUTData(SkScalar contrast, SkScalar paintGamma, SkScalar deviceGamma,
263                                  void* data);
264
265    static void MakeRec(const SkPaint&, const SkSurfaceProps* surfaceProps,
266                        const SkMatrix*, Rec* rec);
267    static inline void PostMakeRec(const SkPaint&, Rec*);
268
269    static SkMaskGamma::PreBlend GetMaskPreBlend(const Rec& rec);
270
271    const Rec& getRec() const { return fRec; }
272
273    SkScalerContextEffects getEffects() const {
274        return { fPathEffect.get(), fMaskFilter.get(), fRasterizer.get() };
275    }
276
277    /**
278    *  Return the axis (if any) that the baseline for horizontal text should land on.
279    *  As an example, the identity matrix will return kX_SkAxisAlignment
280    */
281    SkAxisAlignment computeAxisAlignmentForHText();
282
283protected:
284    Rec         fRec;
285
286    /** Generates the contents of glyph.fAdvanceX and glyph.fAdvanceY.
287     *  May call getMetrics if that would be just as fast.
288     */
289    virtual void generateAdvance(SkGlyph* glyph) = 0;
290
291    /** Generates the contents of glyph.fWidth, fHeight, fTop, fLeft,
292     *  as well as fAdvanceX and fAdvanceY if not already set.
293     *
294     *  TODO: fMaskFormat is set by getMetrics later; cannot be set here.
295     */
296    virtual void generateMetrics(SkGlyph* glyph) = 0;
297
298    /** Generates the contents of glyph.fImage.
299     *  When called, glyph.fImage will be pointing to a pre-allocated,
300     *  uninitialized region of memory of size glyph.computeImageSize().
301     *  This method may change glyph.fMaskFormat if the new image size is
302     *  less than or equal to the old image size.
303     *
304     *  Because glyph.computeImageSize() will determine the size of fImage,
305     *  generateMetrics will be called before generateImage.
306     */
307    virtual void generateImage(const SkGlyph& glyph) = 0;
308
309    /** Sets the passed path to the glyph outline.
310     *  If this cannot be done the path is set to empty;
311     *  this is indistinguishable from a glyph with an empty path.
312     */
313    virtual void generatePath(SkGlyphID glyphId, SkPath* path) = 0;
314
315    /** Retrieves font metrics. */
316    virtual void generateFontMetrics(SkPaint::FontMetrics*) = 0;
317
318    /** Returns the number of glyphs in the font. */
319    virtual unsigned generateGlyphCount() = 0;
320
321    /** Returns the glyph id for the given unichar.
322     *  If there is no 1:1 mapping from the unichar to a glyph id, returns 0.
323     */
324    virtual uint16_t generateCharToGlyph(SkUnichar unichar) = 0;
325
326    /** Returns the unichar for the given glyph id.
327     *  If there is no 1:1 mapping from the glyph id to a unichar, returns 0.
328     *  The default implementation always returns 0, indicating failure.
329     */
330    virtual SkUnichar generateGlyphToChar(uint16_t glyphId);
331
332    void forceGenerateImageFromPath() { fGenerateImageFromPath = true; }
333    void forceOffGenerateImageFromPath() { fGenerateImageFromPath = false; }
334
335private:
336    friend class SkRandomScalerContext; // For debug purposes
337
338    // never null
339    sk_sp<SkTypeface> fTypeface;
340
341    // optional objects, which may be null
342    sk_sp<SkPathEffect> fPathEffect;
343    sk_sp<SkMaskFilter> fMaskFilter;
344    sk_sp<SkRasterizer> fRasterizer;
345
346    // if this is set, we draw the image from a path, rather than
347    // calling generateImage.
348    bool fGenerateImageFromPath;
349
350    void internalGetPath(SkPackedGlyphID id, SkPath* fillPath,
351                         SkPath* devPath, SkMatrix* fillToDevMatrix);
352
353    // SkMaskGamma::PreBlend converts linear masks to gamma correcting masks.
354protected:
355    // Visible to subclasses so that generateImage can apply the pre-blend directly.
356    const SkMaskGamma::PreBlend fPreBlend;
357private:
358    // When there is a filter, previous steps must create a linear mask
359    // and the pre-blend applied as a final step.
360    const SkMaskGamma::PreBlend fPreBlendForFilter;
361};
362
363#define kRec_SkDescriptorTag            SkSetFourByteTag('s', 'r', 'e', 'c')
364#define kPathEffect_SkDescriptorTag     SkSetFourByteTag('p', 't', 'h', 'e')
365#define kMaskFilter_SkDescriptorTag     SkSetFourByteTag('m', 's', 'k', 'f')
366#define kRasterizer_SkDescriptorTag     SkSetFourByteTag('r', 'a', 's', 't')
367
368///////////////////////////////////////////////////////////////////////////////
369
370SkPaint::Hinting SkScalerContextRec::getHinting() const {
371    unsigned hint = (fFlags & SkScalerContext::kHinting_Mask) >>
372                                            SkScalerContext::kHinting_Shift;
373    return static_cast<SkPaint::Hinting>(hint);
374}
375
376void SkScalerContextRec::setHinting(SkPaint::Hinting hinting) {
377    fFlags = (fFlags & ~SkScalerContext::kHinting_Mask) |
378                                (hinting << SkScalerContext::kHinting_Shift);
379}
380
381
382#endif
383