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1 /*
2  * Copyright 2014 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 #include "SkDraw.h"
9 #include "SkFontPriv.h"
10 #include "SkPaint.h"
11 #include "SkPaintDefaults.h"
12 #include "SkPath.h"
13 #include "SkScalerContext.h"
14 #include "SkStrike.h"
15 #include "SkStrikeCache.h"
16 #include "SkTo.h"
17 #include "SkTLazy.h"
18 #include "SkTypeface.h"
19 #include "SkUTF.h"
20 #include "SkUtils.h"
21 
22 #define kDefault_Size       SkPaintDefaults_TextSize
23 #define kDefault_Flags      0
24 #define kDefault_Edging     SkFont::Edging::kAntiAlias
25 #define kDefault_Hinting    SkPaintDefaults_Hinting
26 
valid_size(SkScalar size)27 static inline SkScalar valid_size(SkScalar size) {
28     return SkTMax<SkScalar>(0, size);
29 }
30 
SkFont(sk_sp<SkTypeface> face,SkScalar size,SkScalar scaleX,SkScalar skewX)31 SkFont::SkFont(sk_sp<SkTypeface> face, SkScalar size, SkScalar scaleX, SkScalar skewX)
32     : fTypeface(std::move(face))
33     , fSize(valid_size(size))
34     , fScaleX(scaleX)
35     , fSkewX(skewX)
36     , fFlags(kDefault_Flags)
37     , fEdging(static_cast<unsigned>(kDefault_Edging))
38     , fHinting(static_cast<unsigned>(kDefault_Hinting))
39 {}
40 
SkFont(sk_sp<SkTypeface> face,SkScalar size)41 SkFont::SkFont(sk_sp<SkTypeface> face, SkScalar size) : SkFont(std::move(face), size, 1, 0) {}
42 
SkFont(sk_sp<SkTypeface> face)43 SkFont::SkFont(sk_sp<SkTypeface> face) : SkFont(std::move(face), kDefault_Size, 1, 0) {}
44 
SkFont()45 SkFont::SkFont() : SkFont(nullptr, kDefault_Size) {}
46 
operator ==(const SkFont & b) const47 bool SkFont::operator==(const SkFont& b) const {
48     return  fTypeface.get() == b.fTypeface.get() &&
49             fSize           == b.fSize &&
50             fScaleX         == b.fScaleX &&
51             fSkewX          == b.fSkewX &&
52             fFlags          == b.fFlags &&
53             fEdging         == b.fEdging &&
54             fHinting        == b.fHinting;
55 }
56 
dump() const57 void SkFont::dump() const {
58     SkDebugf("typeface %p\n", fTypeface.get());
59     SkDebugf("size %g\n", fSize);
60     SkDebugf("skewx %g\n", fSkewX);
61     SkDebugf("scalex %g\n", fScaleX);
62     SkDebugf("flags 0x%X\n", fFlags);
63     SkDebugf("edging %d\n", (unsigned)fEdging);
64     SkDebugf("hinting %d\n", (unsigned)fHinting);
65 }
66 
67 ///////////////////////////////////////////////////////////////////////////////////////////////////
68 
set_clear_mask(uint32_t bits,bool cond,uint32_t mask)69 static inline uint32_t set_clear_mask(uint32_t bits, bool cond, uint32_t mask) {
70     return cond ? bits | mask : bits & ~mask;
71 }
72 
setForceAutoHinting(bool predicate)73 void SkFont::setForceAutoHinting(bool predicate) {
74     fFlags = set_clear_mask(fFlags, predicate, kForceAutoHinting_PrivFlag);
75 }
setEmbeddedBitmaps(bool predicate)76 void SkFont::setEmbeddedBitmaps(bool predicate) {
77     fFlags = set_clear_mask(fFlags, predicate, kEmbeddedBitmaps_PrivFlag);
78 }
setSubpixel(bool predicate)79 void SkFont::setSubpixel(bool predicate) {
80     fFlags = set_clear_mask(fFlags, predicate, kSubpixel_PrivFlag);
81 }
setLinearMetrics(bool predicate)82 void SkFont::setLinearMetrics(bool predicate) {
83     fFlags = set_clear_mask(fFlags, predicate, kLinearMetrics_PrivFlag);
84 }
setEmbolden(bool predicate)85 void SkFont::setEmbolden(bool predicate) {
86     fFlags = set_clear_mask(fFlags, predicate, kEmbolden_PrivFlag);
87 }
88 
setEdging(Edging e)89 void SkFont::setEdging(Edging e) {
90     fEdging = SkToU8(e);
91 }
92 
setHinting(SkFontHinting h)93 void SkFont::setHinting(SkFontHinting h) {
94     fHinting = SkToU8(h);
95 }
96 
setSize(SkScalar size)97 void SkFont::setSize(SkScalar size) {
98     fSize = valid_size(size);
99 }
setScaleX(SkScalar scale)100 void SkFont::setScaleX(SkScalar scale) {
101     fScaleX = scale;
102 }
setSkewX(SkScalar skew)103 void SkFont::setSkewX(SkScalar skew) {
104     fSkewX = skew;
105 }
106 
makeWithSize(SkScalar newSize) const107 SkFont SkFont::makeWithSize(SkScalar newSize) const {
108     SkFont font = *this;
109     font.setSize(newSize);
110     return font;
111 }
112 
113 ///////////////////////////////////////////////////////////////////////////////////////////////////
114 
setupForAsPaths(SkPaint * paint)115 SkScalar SkFont::setupForAsPaths(SkPaint* paint) {
116     constexpr uint32_t flagsToIgnore = kLinearMetrics_PrivFlag        |
117                                        kEmbeddedBitmaps_PrivFlag      |
118                                        kForceAutoHinting_PrivFlag;
119 
120     fFlags = (fFlags & ~flagsToIgnore) | kSubpixel_PrivFlag;
121     this->setHinting(kNo_SkFontHinting);
122 
123     if (this->getEdging() == Edging::kSubpixelAntiAlias) {
124         this->setEdging(Edging::kAntiAlias);
125     }
126 
127     if (paint) {
128         paint->setStyle(SkPaint::kFill_Style);
129         paint->setPathEffect(nullptr);
130     }
131     SkScalar textSize = fSize;
132     this->setSize(SkIntToScalar(SkFontPriv::kCanonicalTextSizeForPaths));
133     return textSize / SkFontPriv::kCanonicalTextSizeForPaths;
134 }
135 
hasSomeAntiAliasing() const136 bool SkFont::hasSomeAntiAliasing() const {
137     Edging edging = this->getEdging();
138     return edging == SkFont::Edging::kAntiAlias
139         || edging == SkFont::Edging::kSubpixelAntiAlias;
140 }
141 
142 class SkCanonicalizeFont {
143 public:
SkCanonicalizeFont(const SkFont & font,const SkPaint * paint)144     SkCanonicalizeFont(const SkFont& font, const SkPaint* paint) : fFont(&font) {
145         if (paint) {
146             fPaint = *paint;
147         }
148         if (font.isLinearMetrics() ||
149             SkDraw::ShouldDrawTextAsPaths(font, fPaint, SkMatrix::I()))
150         {
151             SkFont* f = fLazyFont.set(font);
152             fScale = f->setupForAsPaths(nullptr);
153             fFont = f;
154             fPaint.reset();
155         }
156     }
157 
getFont() const158     const SkFont& getFont() const { return *fFont; }
getPaint() const159     const SkPaint& getPaint() const { return fPaint; }
getScale() const160     SkScalar getScale() const { return fScale; }
161 
162 private:
163     const SkFont*    fFont;
164     SkTLazy<SkFont>  fLazyFont;
165     SkPaint          fPaint;
166     SkScalar         fScale = 0;
167 };
168 
unicharToGlyph(SkUnichar uni) const169 SkGlyphID SkFont::unicharToGlyph(SkUnichar uni) const {
170     return this->getTypefaceOrDefault()->unicharToGlyph(uni);
171 }
172 
textToGlyphs(const void * text,size_t byteLength,SkTextEncoding encoding,uint16_t glyphs[],int maxGlyphCount) const173 int SkFont::textToGlyphs(const void* text, size_t byteLength, SkTextEncoding encoding,
174                          uint16_t glyphs[], int maxGlyphCount) const {
175     if (0 == byteLength) {
176         return 0;
177     }
178 
179     SkASSERT(text);
180 
181     int count = SkFontPriv::CountTextElements(text, byteLength, encoding);
182     if (!glyphs || count > maxGlyphCount) {
183         return count;
184     }
185 
186     // TODO: unify/eliminate SkTypeface::Encoding with SkTextEncoding
187     SkTypeface::Encoding typefaceEncoding;
188     switch (encoding) {
189         case kUTF8_SkTextEncoding:
190             typefaceEncoding = SkTypeface::kUTF8_Encoding;
191             break;
192         case kUTF16_SkTextEncoding:
193             typefaceEncoding = SkTypeface::kUTF16_Encoding;
194             break;
195         case kUTF32_SkTextEncoding:
196             typefaceEncoding = SkTypeface::kUTF32_Encoding;
197             break;
198         default:
199             SkASSERT(kGlyphID_SkTextEncoding == encoding);
200             // we can early exit, since we already have glyphIDs
201             memcpy(glyphs, text, count << 1);
202             return count;
203     }
204 
205     (void) this->getTypefaceOrDefault()->charsToGlyphs(text, typefaceEncoding, glyphs,count);
206     return count;
207 }
208 
glyphsToUnichars(const SkGlyphID glyphs[],int count,SkUnichar text[]) const209 void SkFont::glyphsToUnichars(const SkGlyphID glyphs[], int count, SkUnichar text[]) const {
210     if (count <= 0) {
211         return;
212     }
213 
214     auto typeface = this->getTypefaceOrDefault();
215     const unsigned numGlyphsInTypeface = typeface->countGlyphs();
216     SkAutoTArray<SkUnichar> unichars(numGlyphsInTypeface);
217     typeface->getGlyphToUnicodeMap(unichars.get());
218 
219     for (int i = 0; i < count; ++i) {
220         unsigned id = glyphs[i];
221         text[i] = (id < numGlyphsInTypeface) ? unichars[id] : 0xFFFD;
222     }
223 }
224 
set_bounds(const SkGlyph & g,SkRect * bounds)225 static void set_bounds(const SkGlyph& g, SkRect* bounds) {
226     bounds->set(SkIntToScalar(g.fLeft),
227                 SkIntToScalar(g.fTop),
228                 SkIntToScalar(g.fLeft + g.fWidth),
229                 SkIntToScalar(g.fTop + g.fHeight));
230 }
231 
join_bounds_x(const SkGlyph & g,SkRect * bounds,SkScalar dx)232 static void join_bounds_x(const SkGlyph& g, SkRect* bounds, SkScalar dx) {
233     bounds->join(SkIntToScalar(g.fLeft) + dx,
234                  SkIntToScalar(g.fTop),
235                  SkIntToScalar(g.fLeft + g.fWidth) + dx,
236                  SkIntToScalar(g.fTop + g.fHeight));
237 }
238 
measureText(const void * text,size_t length,SkTextEncoding encoding,SkRect * bounds,const SkPaint * paint) const239 SkScalar SkFont::measureText(const void* text, size_t length, SkTextEncoding encoding,
240                              SkRect* bounds, const SkPaint* paint) const {
241     SkCanonicalizeFont canon(*this, paint);
242     const SkFont& font = canon.getFont();
243     const SkScalar scale = canon.getScale();
244 
245     SkAutoToGlyphs atg(font, text, length, encoding);
246     const int count = atg.count();
247     if (count == 0) {
248         if (bounds) {
249             bounds->setEmpty();
250         }
251         return 0;
252     }
253     const uint16_t* glyphs = atg.glyphs();
254 
255     auto cache = SkStrikeCache::FindOrCreateStrikeWithNoDeviceExclusive(font, canon.getPaint());
256 
257     SkScalar width = 0;
258     if (bounds) {
259         const SkGlyph* g = &cache->getGlyphIDMetrics(glyphs[0]);
260         set_bounds(*g, bounds);
261         width = g->fAdvanceX;
262         for (int i = 1; i < count; ++i) {
263             g = &cache->getGlyphIDMetrics(glyphs[i]);
264             join_bounds_x(*g, bounds, width);
265             width += g->fAdvanceX;
266         }
267     } else {
268         for (int i = 0; i < count; ++i) {
269             width += cache->getGlyphIDAdvance(glyphs[i]).fAdvanceX;
270         }
271     }
272 
273     if (scale) {
274         width *= scale;
275         if (bounds) {
276             bounds->fLeft *= scale;
277             bounds->fTop *= scale;
278             bounds->fRight *= scale;
279             bounds->fBottom *= scale;
280         }
281     }
282 
283     return width;
284 }
285 
make_bounds(const SkGlyph & g,SkScalar scale)286 static SkRect make_bounds(const SkGlyph& g, SkScalar scale) {
287     return {
288         g.fLeft * scale,
289         g.fTop * scale,
290         (g.fLeft + g.fWidth) * scale,
291         (g.fTop + g.fHeight) * scale
292     };
293 }
294 
295 template <typename HANDLER>
VisitGlyphs(const SkFont & origFont,const SkPaint * paint,const uint16_t glyphs[],int count,HANDLER handler)296 void VisitGlyphs(const SkFont& origFont, const SkPaint* paint, const uint16_t glyphs[], int count,
297                  HANDLER handler) {
298     if (count <= 0) {
299         return;
300     }
301 
302     SkCanonicalizeFont canon(origFont, paint);
303     const SkFont& font = canon.getFont();
304     SkScalar scale = canon.getScale();
305     if (!scale) {
306         scale = 1;
307     }
308 
309     auto cache = SkStrikeCache::FindOrCreateStrikeWithNoDeviceExclusive(font, canon.getPaint());
310     handler(cache.get(), glyphs, count, scale);
311 }
312 
getWidthsBounds(const uint16_t glyphs[],int count,SkScalar widths[],SkRect bounds[],const SkPaint * paint) const313 void SkFont::getWidthsBounds(const uint16_t glyphs[], int count, SkScalar widths[], SkRect bounds[],
314                              const SkPaint* paint) const {
315     VisitGlyphs(*this, paint, glyphs, count, [widths, bounds]
316                 (SkStrike* cache, const uint16_t glyphs[], int count, SkScalar scale) {
317         for (int i = 0; i < count; ++i) {
318             const SkGlyph* g;
319             if (bounds) {
320                 g = &cache->getGlyphIDMetrics(glyphs[i]);
321                 bounds[i] = make_bounds(*g, scale);
322             } else {
323                 g = &cache->getGlyphIDAdvance(glyphs[i]);
324             }
325             if (widths) {
326                 widths[i] = g->fAdvanceX * scale;
327             }
328         }
329     });
330 }
331 
getPos(const uint16_t glyphs[],int count,SkPoint pos[],SkPoint origin) const332 void SkFont::getPos(const uint16_t glyphs[], int count, SkPoint pos[], SkPoint origin) const {
333     VisitGlyphs(*this, nullptr, glyphs, count, [pos, origin]
334                       (SkStrike* cache, const uint16_t glyphs[], int count, SkScalar scale) {
335         SkPoint loc = origin;
336         for (int i = 0; i < count; ++i) {
337             pos[i] = loc;
338             loc.fX += cache->getGlyphIDAdvance(glyphs[i]).fAdvanceX * scale;
339         }
340     });
341 }
342 
getXPos(const uint16_t glyphs[],int count,SkScalar xpos[],SkScalar origin) const343 void SkFont::getXPos(const uint16_t glyphs[], int count, SkScalar xpos[], SkScalar origin) const {
344     VisitGlyphs(*this, nullptr, glyphs, count, [xpos, origin]
345                       (SkStrike* cache, const uint16_t glyphs[], int count, SkScalar scale) {
346         SkScalar x = origin;
347         for (int i = 0; i < count; ++i) {
348             xpos[i] = x;
349             x += cache->getGlyphIDAdvance(glyphs[i]).fAdvanceX * scale;
350         }
351     });
352 }
353 
getPaths(const uint16_t glyphs[],int count,void (* proc)(const SkPath *,const SkMatrix &,void *),void * ctx) const354 void SkFont::getPaths(const uint16_t glyphs[], int count,
355                       void (*proc)(const SkPath*, const SkMatrix&, void*), void* ctx) const {
356     SkFont font(*this);
357     SkScalar scale = font.setupForAsPaths(nullptr);
358     if (!scale) {
359         scale = 1;
360     }
361     const SkMatrix mx = SkMatrix::MakeScale(scale, scale);
362 
363     auto exclusive = SkStrikeCache::FindOrCreateStrikeWithNoDeviceExclusive(font);
364     auto cache = exclusive.get();
365 
366     for (int i = 0; i < count; ++i) {
367         proc(cache->findPath(cache->getGlyphIDMetrics(glyphs[i])), mx, ctx);
368     }
369 }
370 
getPath(uint16_t glyphID,SkPath * path) const371 bool SkFont::getPath(uint16_t glyphID, SkPath* path) const {
372     struct Pair {
373         SkPath* fPath;
374         bool    fWasSet;
375     } pair = { path, false };
376 
377     this->getPaths(&glyphID, 1, [](const SkPath* orig, const SkMatrix& mx, void* ctx) {
378         Pair* pair = static_cast<Pair*>(ctx);
379         if (orig) {
380             orig->transform(mx, pair->fPath);
381             pair->fWasSet = true;
382         }
383     }, &pair);
384     return pair.fWasSet;
385 }
386 
getMetrics(SkFontMetrics * metrics) const387 SkScalar SkFont::getMetrics(SkFontMetrics* metrics) const {
388     SkCanonicalizeFont canon(*this, nullptr);
389     const SkFont& font = canon.getFont();
390     SkScalar scale = canon.getScale();
391 
392     SkFontMetrics storage;
393     if (nullptr == metrics) {
394         metrics = &storage;
395     }
396 
397     auto cache = SkStrikeCache::FindOrCreateStrikeWithNoDeviceExclusive(font);
398     *metrics = cache->getFontMetrics();
399 
400     if (scale) {
401         SkFontPriv::ScaleFontMetrics(metrics, scale);
402     }
403     return metrics->fDescent - metrics->fAscent + metrics->fLeading;
404 }
405 
getTypefaceOrDefault() const406 SkTypeface* SkFont::getTypefaceOrDefault() const {
407     return fTypeface ? fTypeface.get() : SkTypeface::GetDefaultTypeface();
408 }
409 
refTypefaceOrDefault() const410 sk_sp<SkTypeface> SkFont::refTypefaceOrDefault() const {
411     return fTypeface ? fTypeface : SkTypeface::MakeDefault();
412 }
413 
414 //////////////////////////////////////////////////////////////////////////////////////////////////
415 
ScaleFontMetrics(SkFontMetrics * metrics,SkScalar scale)416 void SkFontPriv::ScaleFontMetrics(SkFontMetrics* metrics, SkScalar scale) {
417     metrics->fTop *= scale;
418     metrics->fAscent *= scale;
419     metrics->fDescent *= scale;
420     metrics->fBottom *= scale;
421     metrics->fLeading *= scale;
422     metrics->fAvgCharWidth *= scale;
423     metrics->fMaxCharWidth *= scale;
424     metrics->fXMin *= scale;
425     metrics->fXMax *= scale;
426     metrics->fXHeight *= scale;
427     metrics->fCapHeight *= scale;
428     metrics->fUnderlineThickness *= scale;
429     metrics->fUnderlinePosition *= scale;
430     metrics->fStrikeoutThickness *= scale;
431     metrics->fStrikeoutPosition *= scale;
432 }
433 
GetFontBounds(const SkFont & font)434 SkRect SkFontPriv::GetFontBounds(const SkFont& font) {
435     SkMatrix m;
436     m.setScale(font.getSize() * font.getScaleX(), font.getSize());
437     m.postSkew(font.getSkewX(), 0);
438 
439     SkTypeface* typeface = font.getTypefaceOrDefault();
440 
441     SkRect bounds;
442     m.mapRect(&bounds, typeface->getBounds());
443     return bounds;
444 }
445 
CountTextElements(const void * text,size_t byteLength,SkTextEncoding encoding)446 int SkFontPriv::CountTextElements(const void* text, size_t byteLength, SkTextEncoding encoding) {
447     switch (encoding) {
448         case kUTF8_SkTextEncoding:
449             return SkUTF::CountUTF8(reinterpret_cast<const char*>(text), byteLength);
450         case kUTF16_SkTextEncoding:
451             return SkUTF::CountUTF16(reinterpret_cast<const uint16_t*>(text), byteLength);
452         case kUTF32_SkTextEncoding:
453             return byteLength >> 2;
454         case kGlyphID_SkTextEncoding:
455             return byteLength >> 1;
456     }
457     SkASSERT(false);
458     return 0;
459 }
460 
GlyphsToUnichars(const SkFont & font,const uint16_t glyphs[],int count,SkUnichar uni[])461 void SkFontPriv::GlyphsToUnichars(const SkFont& font, const uint16_t glyphs[], int count,
462                                   SkUnichar uni[]) {
463     font.glyphsToUnichars(glyphs, count, uni);
464 }
465 
466 ///////////////////////////////////////////////////////////////////////////////////////////////////
467 #include "SkReadBuffer.h"
468 #include "SkWriteBuffer.h"
469 
470 // packed int at the beginning of the serialized font:
471 //
472 //  control_bits:8 size_as_byte:8 flags:12 edging:2 hinting:2
473 
474 enum {
475     kSize_Is_Byte_Bit   = 1 << 31,
476     kHas_ScaleX_Bit     = 1 << 30,
477     kHas_SkewX_Bit      = 1 << 29,
478     kHas_Typeface_Bit   = 1 << 28,
479 
480     kShift_for_Size     = 16,
481     kMask_For_Size      = 0xFF,
482 
483     kShift_For_Flags    = 4,
484     kMask_For_Flags     = 0xFFF,
485 
486     kShift_For_Edging   = 2,
487     kMask_For_Edging    = 0x3,
488 
489     kShift_For_Hinting  = 0,
490     kMask_For_Hinting   = 0x3
491 };
492 
scalar_is_byte(SkScalar x)493 static bool scalar_is_byte(SkScalar x) {
494     int ix = (int)x;
495     return ix == x && ix >= 0 && ix <= kMask_For_Size;
496 }
497 
Flatten(const SkFont & font,SkWriteBuffer & buffer)498 void SkFontPriv::Flatten(const SkFont& font, SkWriteBuffer& buffer) {
499     SkASSERT((font.fFlags & ~kMask_For_Flags) == 0);
500     SkASSERT((font.fEdging & ~kMask_For_Edging) == 0);
501     SkASSERT((font.fHinting & ~kMask_For_Hinting) == 0);
502 
503     uint32_t packed = 0;
504     packed |= font.fFlags << kShift_For_Flags;
505     packed |= font.fEdging << kShift_For_Edging;
506     packed |= font.fHinting << kShift_For_Hinting;
507 
508     if (scalar_is_byte(font.fSize)) {
509         packed |= kSize_Is_Byte_Bit;
510         packed |= (int)font.fSize << kShift_for_Size;
511     }
512     if (font.fScaleX != 1) {
513         packed |= kHas_ScaleX_Bit;
514     }
515     if (font.fSkewX != 0) {
516         packed |= kHas_SkewX_Bit;
517     }
518     if (font.fTypeface) {
519         packed |= kHas_Typeface_Bit;
520     }
521 
522     buffer.write32(packed);
523     if (!(packed & kSize_Is_Byte_Bit)) {
524         buffer.writeScalar(font.fSize);
525     }
526     if (packed & kHas_ScaleX_Bit) {
527         buffer.writeScalar(font.fScaleX);
528     }
529     if (packed & kHas_SkewX_Bit) {
530         buffer.writeScalar(font.fSkewX);
531     }
532     if (packed & kHas_Typeface_Bit) {
533         buffer.writeTypeface(font.fTypeface.get());
534     }
535 }
536 
Unflatten(SkFont * font,SkReadBuffer & buffer)537 bool SkFontPriv::Unflatten(SkFont* font, SkReadBuffer& buffer) {
538     const uint32_t packed = buffer.read32();
539 
540     if (packed & kSize_Is_Byte_Bit) {
541         font->fSize = (packed >> kShift_for_Size) & kMask_For_Size;
542     } else {
543         font->fSize = buffer.readScalar();
544     }
545     if (packed & kHas_ScaleX_Bit) {
546         font->fScaleX = buffer.readScalar();
547     }
548     if (packed & kHas_SkewX_Bit) {
549         font->fSkewX = buffer.readScalar();
550     }
551     if (packed & kHas_Typeface_Bit) {
552         font->fTypeface = buffer.readTypeface();
553     }
554 
555     SkASSERT(SkFont::kAllFlags <= kMask_For_Flags);
556     // we & with kAllFlags, to clear out any unknown flag bits
557     font->fFlags = SkToU8((packed >> kShift_For_Flags) & SkFont::kAllFlags);
558 
559     unsigned edging = (packed >> kShift_For_Edging) & kMask_For_Edging;
560     if (edging > (unsigned)SkFont::Edging::kSubpixelAntiAlias) {
561         edging = 0;
562     }
563     font->fEdging = SkToU8(edging);
564 
565     unsigned hinting = (packed >> kShift_For_Hinting) & kMask_For_Hinting;
566     if (hinting > (unsigned)kFull_SkFontHinting) {
567         hinting = 0;
568     }
569     font->fHinting = SkToU8(hinting);
570 
571     return buffer.isValid();
572 }
573