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