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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=4 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#ifndef GFX_FONT_H
#define GFX_FONT_H
#include <new>
#include <utility>
#include <functional>
#include "PLDHashTable.h"
#include "ThebesRLBoxTypes.h"
#include "gfxFontVariations.h"
#include "gfxRect.h"
#include "gfxTypes.h"
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/Attributes.h"
#include "mozilla/FontPropertyTypes.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/MruCache.h"
#include "mozilla/Mutex.h"
#include "mozilla/RefPtr.h"
#include "mozilla/RWLock.h"
#include "mozilla/TypedEnumBits.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/gfx/MatrixFwd.h"
#include "mozilla/gfx/Point.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/intl/UnicodeScriptCodes.h"
#include "nsCOMPtr.h"
#include "nsColor.h"
#include "nsTHashMap.h"
#include "nsTHashSet.h"
#include "nsExpirationTracker.h"
#include "nsFontMetrics.h"
#include "nsHashKeys.h"
#include "nsIMemoryReporter.h"
#include "nsIObserver.h"
#include "nsISupports.h"
#include "nsString.h"
#include "nsTArray.h"
#include "nsTHashtable.h"
#include "nscore.h"
#include "DrawMode.h"
// Only required for function bodies
#include "gfxFontEntry.h"
#include "gfxFontFeatures.h"
class gfxContext;
class gfxGraphiteShaper;
class gfxHarfBuzzShaper;
class gfxGlyphExtents;
class gfxMathTable;
class gfxPattern;
class gfxShapedText;
class gfxShapedWord;
class gfxSkipChars;
class gfxTextRun;
class nsIEventTarget;
class nsITimer;
struct gfxTextRunDrawCallbacks;
namespace mozilla {
class SVGContextPaint;
namespace layout {
class TextDrawTarget;
} // namespace mozilla
typedef struct _cairo cairo_t;
typedef struct _cairo_scaled_font cairo_scaled_font_t;
#define FONT_MAX_SIZE 2000.0
// The skew factor used for synthetic-italic [oblique] fonts;
// we use a platform-dependent value to harmonize with the platform's own APIs.
#ifdef XP_WIN
#elif defined(MOZ_WIDGET_GTK)
# define OBLIQUE_SKEW_FACTOR 0.25f
struct gfxFontStyle {
using FontStretch = mozilla::FontStretch;
using FontSlantStyle = mozilla::FontSlantStyle;
using FontWeight = mozilla::FontWeight;
using FontSizeAdjust = mozilla::StyleFontSizeAdjust;
gfxFontStyle(FontSlantStyle aStyle, FontWeight aWeight, FontStretch aStretch,
gfxFloat aSize, const FontSizeAdjust& aSizeAdjust,
bool aSystemFont, bool aPrinterFont, bool aWeightSynthesis,
bool aStyleSynthesis, bool aSmallCapsSynthesis,
uint32_t aLanguageOverride);
// Features are composed of (1) features from style rules (2) features
// from feature settings rules and (3) family-specific features. (1) and
// (3) are guaranteed to be mutually exclusive
// custom opentype feature settings
CopyableTArray<gfxFontFeature> featureSettings;
// Some font-variant property values require font-specific settings
// defined via @font-feature-values rules. These are resolved after
// font matching occurs.
// -- list of value tags for specific alternate features
mozilla::StyleFontVariantAlternates variantAlternates;
// -- object used to look these up once the font is matched
RefPtr<gfxFontFeatureValueSet> featureValueLookup;
// opentype variation settings
CopyableTArray<gfxFontVariation> variationSettings;
// The logical size of the font, in pixels
gfxFloat size;
// The optical size value to apply (if supported); negative means none.
float autoOpticalSize = -1.0f;
// The aspect-value (ie., the ratio actualsize:actualxheight) that any
// actual physical font created from this font structure must have when
// rendering or measuring a string. A value of -1.0 means no adjustment
// needs to be done; otherwise the value must be nonnegative.
float sizeAdjust;
// baseline offset, used when simulating sub/superscript glyphs
float baselineOffset;
// Language system tag, to override document language;
// an OpenType "language system" tag represented as a 32-bit integer
// Normally 0, so font rendering will use the document or element language
// (see above) to control any language-specific rendering, but the author
// can override this for cases where the options implemented in the font
// do not directly match the actual language. (E.g. lang may be Macedonian,
// but the font in use does not explicitly support this; the author can
// use font-language-override to request the Serbian option in the font
// in order to get correct glyph shapes.)
uint32_t languageOverride;
// The estimated background color behind the text. Enables a special
// rendering mode when NS_GET_A(.) > 0. Only used for text in the chrome.
nscolor fontSmoothingBackgroundColor;
// The Font{Weight,Stretch,SlantStyle} fields are each a 16-bit type.
// The weight of the font: 100, 200, ... 900.
FontWeight weight;
// The stretch of the font
FontStretch stretch;
// The style of font
FontSlantStyle style;
// Whether face-selection properties weight/style/stretch are all 'normal'
bool IsNormalStyle() const {
return weight.IsNormal() && style.IsNormal() && stretch.IsNormal();
// We pack these three small-integer fields into a single byte to avoid
// overflowing an 8-byte boundary [in a 64-bit build] and ending up with
// 7 bytes of padding at the end of the struct.
// caps variant (small-caps, petite-caps, etc.)
uint8_t variantCaps : 3; // uses range 0..6
// sub/superscript variant
uint8_t variantSubSuper : 2; // uses range 0..2
// font metric used as basis of font-size-adjust
uint8_t sizeAdjustBasis : 3; // uses range 0..4
// Say that this font is a system font and therefore does not
// require certain fixup that we do for fonts from untrusted
// sources.
bool systemFont : 1;
// Say that this font is used for print or print preview.
bool printerFont : 1;
// Used to imitate -webkit-font-smoothing: antialiased
bool useGrayscaleAntialiasing : 1;
// Whether synthetic styles are allowed
bool allowSyntheticWeight : 1;
bool allowSyntheticStyle : 1;
bool allowSyntheticSmallCaps : 1;
// some variant features require fallback which complicates the shaping
// code, so set up a bool to indicate when shaping with fallback is needed
bool noFallbackVariantFeatures : 1;
// Return the final adjusted font size for the given aspect ratio.
// Not meant to be called when sizeAdjustBasis is NONE.
gfxFloat GetAdjustedSize(gfxFloat aspect) const {
FontSizeAdjust::Tag(sizeAdjustBasis) != FontSizeAdjust::Tag::None,
"Not meant to be called when sizeAdjustBasis is none");
gfxFloat adjustedSize =
std::max(NS_round(size * (sizeAdjust / aspect)), 1.0);
return std::min(adjustedSize, FONT_MAX_SIZE);
// Some callers want to take a short-circuit path if they can be sure the
// adjusted size will be zero.
bool AdjustedSizeMustBeZero() const {
return size == 0.0 ||
(FontSizeAdjust::Tag(sizeAdjustBasis) != FontSizeAdjust::Tag::None &&
sizeAdjust == 0.0);
PLDHashNumber Hash() const;
// Adjust this style to simulate sub/superscript (as requested in the
// variantSubSuper field) using size and baselineOffset instead.
void AdjustForSubSuperscript(int32_t aAppUnitsPerDevPixel);
// Should this style cause the given font entry to use synthetic bold?
bool NeedsSyntheticBold(gfxFontEntry* aFontEntry) const {
return weight.IsBold() && allowSyntheticWeight &&
bool Equals(const gfxFontStyle& other) const {
return mozilla::NumbersAreBitwiseIdentical(size, other.size) &&
(style == && (weight == other.weight) &&
(stretch == other.stretch) && (variantCaps == other.variantCaps) &&
(variantSubSuper == other.variantSubSuper) &&
(allowSyntheticWeight == other.allowSyntheticWeight) &&
(allowSyntheticStyle == other.allowSyntheticStyle) &&
(systemFont == other.systemFont) &&
(printerFont == other.printerFont) &&
(useGrayscaleAntialiasing == other.useGrayscaleAntialiasing) &&
(baselineOffset == other.baselineOffset) &&
mozilla::NumbersAreBitwiseIdentical(sizeAdjust, other.sizeAdjust) &&
(sizeAdjustBasis == other.sizeAdjustBasis) &&
(featureSettings == other.featureSettings) &&
(variantAlternates == other.variantAlternates) &&
(featureValueLookup == other.featureValueLookup) &&
(variationSettings == other.variationSettings) &&
(languageOverride == other.languageOverride) &&
other.autoOpticalSize) &&
(fontSmoothingBackgroundColor == other.fontSmoothingBackgroundColor);
* Font cache design:
* The mFonts hashtable contains most fonts, indexed by (gfxFontEntry*, style).
* It maintains a strong reference to the fonts it contains.
* Whenever a font is accessed, it is marked as used to move it to a new
* generation in the tracker to avoid expiration.
* The expiration tracker will only expire fonts with a single reference, the
* cache itself. Fonts with more than one reference are marked as used.
* We're using 3 generations with a ten-second generation interval, so
* zero-refcount fonts will be deleted 20-30 seconds after their refcount
* goes to zero, if timer events fire in a timely manner.
* The font cache also handles timed expiration of cached ShapedWords
* for "persistent" fonts: it has a repeating timer, and notifies
* each cached font to "age" its shaped words. The words will be released
* by the fonts if they get aged three times without being re-used in the
* meantime.
* Note that the ShapedWord timeout is much larger than the font timeout,
* so that in the case of a short-lived font, we'll discard the gfxFont
* completely, with all its words, and avoid the cost of aging the words
* individually. That only happens with longer-lived fonts.
struct FontCacheSizes {
FontCacheSizes() : mFontInstances(0), mShapedWords(0) {}
size_t mFontInstances; // memory used by instances of gfxFont subclasses
size_t mShapedWords; // memory used by the per-font shapedWord caches
class gfxFontCache final
: public ExpirationTrackerImpl<gfxFont, 3, mozilla::Mutex,
mozilla::MutexAutoLock> {
// Expiration tracker implementation.
typedef mozilla::Mutex Lock;
typedef mozilla::MutexAutoLock AutoLock;
// This protects the ExpirationTracker tables.
Lock mMutex = Lock("fontCacheExpirationMutex");
Lock& GetMutex() override { return mMutex; }
explicit gfxFontCache(nsIEventTarget* aEventTarget);
* Get the global gfxFontCache. You must call Init() before
* calling this method --- the result will not be null.
static gfxFontCache* GetCache() { return gGlobalCache; }
static nsresult Init();
// It's OK to call this even if Init() has not been called.
static void Shutdown();
// Look up a font in the cache. Returns null if there's nothing matching
// in the cache
already_AddRefed<gfxFont> Lookup(const gfxFontEntry* aFontEntry,
const gfxFontStyle* aStyle,
const gfxCharacterMap* aUnicodeRangeMap);
// We created a new font (presumably because Lookup returned null);
// put it in the cache. The font's refcount should be nonzero. It is
// allowable to add a new font even if there is one already in the
// cache with the same key, as we may race with other threads to do
// the insertion -- in that case we will return the original font,
// and destroy the new one.
already_AddRefed<gfxFont> MaybeInsert(gfxFont* aFont);
bool MaybeDestroy(gfxFont* aFont);
// Cleans out the hashtable and removes expired fonts waiting for cleanup.
// Other gfxFont objects may be still in use but they will be pushed
// into the expiration queues and removed.
void Flush();
void FlushShapedWordCaches();
void NotifyGlyphsChanged();
void AgeCachedWords();
void RunWordCacheExpirationTimer() {
if (!mTimerRunning) {
mozilla::MutexAutoLock lock(mMutex);
if (!mTimerRunning && mWordCacheExpirationTimer) {
WordCacheExpirationTimerCallback, this,
mTimerRunning = true;
void PauseWordCacheExpirationTimer() {
if (mTimerRunning) {
mozilla::MutexAutoLock lock(mMutex);
if (mTimerRunning && mWordCacheExpirationTimer) {
mTimerRunning = false;
void AddSizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf,
FontCacheSizes* aSizes) const;
void AddSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf,
FontCacheSizes* aSizes) const;
class MemoryReporter final : public nsIMemoryReporter {
~MemoryReporter() = default;
// Observer for notifications that the font cache cares about
class Observer final : public nsIObserver {
~Observer() = default;
nsresult AddObject(gfxFont* aFont) {
AutoLock lock(mMutex);
return AddObjectLocked(aFont, lock);
// This gets called when the timeout has expired on a single-refcount
// font; we just delete it.
void NotifyExpiredLocked(gfxFont* aFont, const AutoLock&)
MOZ_REQUIRES(mMutex) override;
void NotifyHandlerEnd() override;
void DestroyDiscard(nsTArray<gfxFont*>& aDiscard);
static gfxFontCache* gGlobalCache;
struct MOZ_STACK_CLASS Key {
const gfxFontEntry* mFontEntry;
const gfxFontStyle* mStyle;
const gfxCharacterMap* mUnicodeRangeMap;
Key(const gfxFontEntry* aFontEntry, const gfxFontStyle* aStyle,
const gfxCharacterMap* aUnicodeRangeMap)
: mFontEntry(aFontEntry),
mUnicodeRangeMap(aUnicodeRangeMap) {}
class HashEntry : public PLDHashEntryHdr {
typedef const Key& KeyType;
typedef const Key* KeyTypePointer;
// When constructing a new entry in the hashtable, we'll leave this
// blank. The caller of Put() will fill this in.
explicit HashEntry(KeyTypePointer aStr) {}
bool KeyEquals(const KeyTypePointer aKey) const;
static KeyTypePointer KeyToPointer(KeyType aKey) { return &aKey; }
static PLDHashNumber HashKey(const KeyTypePointer aKey) {
return mozilla::HashGeneric(aKey->mStyle->Hash(), aKey->mFontEntry,
enum { ALLOW_MEMMOVE = true };
gfxFont* MOZ_UNSAFE_REF("tracking for deferred deletion") mFont = nullptr;
nsTHashtable<HashEntry> mFonts MOZ_GUARDED_BY(mMutex);
nsTArray<gfxFont*> mTrackerDiscard MOZ_GUARDED_BY(mMutex);
static void WordCacheExpirationTimerCallback(nsITimer* aTimer, void* aCache);
nsCOMPtr<nsITimer> mWordCacheExpirationTimer MOZ_GUARDED_BY(mMutex);
std::atomic<bool> mTimerRunning = false;
class gfxTextPerfMetrics {
struct TextCounts {
uint32_t numContentTextRuns;
uint32_t numChromeTextRuns;
uint32_t numChars;
uint32_t maxTextRunLen;
uint32_t wordCacheSpaceRules;
uint32_t wordCacheLong;
uint32_t wordCacheHit;
uint32_t wordCacheMiss;
uint32_t fallbackPrefs;
uint32_t fallbackSystem;
uint32_t textrunConst;
uint32_t textrunDestr;
uint32_t genericLookups;
uint32_t reflowCount;
// counts per reflow operation
TextCounts current;
// totals for the lifetime of a document
TextCounts cumulative;
gfxTextPerfMetrics() { memset(this, 0, sizeof(gfxTextPerfMetrics)); }
// add current totals to cumulative ones
void Accumulate() {
if (current.numChars == 0) {
cumulative.numContentTextRuns += current.numContentTextRuns;
cumulative.numChromeTextRuns += current.numChromeTextRuns;
cumulative.numChars += current.numChars;
if (current.maxTextRunLen > cumulative.maxTextRunLen) {
cumulative.maxTextRunLen = current.maxTextRunLen;
cumulative.wordCacheSpaceRules += current.wordCacheSpaceRules;
cumulative.wordCacheLong += current.wordCacheLong;
cumulative.wordCacheHit += current.wordCacheHit;
cumulative.wordCacheMiss += current.wordCacheMiss;
cumulative.fallbackPrefs += current.fallbackPrefs;
cumulative.fallbackSystem += current.fallbackSystem;
cumulative.textrunConst += current.textrunConst;
cumulative.textrunDestr += current.textrunDestr;
cumulative.genericLookups += current.genericLookups;
memset(&current, 0, sizeof(current));
namespace mozilla {
namespace gfx {
class UnscaledFont;
// Flags that live in the gfxShapedText::mFlags field.
// (Note that gfxTextRun has an additional mFlags2 field for use
// by textrun clients like nsTextFrame.)
// If you add a flag, please add support for it in gfxTextRun::Dump.
enum class ShapedTextFlags : uint16_t {
* When set, the text is RTL.
TEXT_IS_RTL = 0x0001,
* When set, spacing is enabled and the textrun needs to call GetSpacing
* on the spacing provider.
* When set, the text has no characters above 255 and it is stored
* in the textrun in 8-bit format.
TEXT_IS_8BIT = 0x0004,
* When set, GetHyphenationBreaks may return true for some character
* positions, otherwise it will always return false for all characters.
* When set, the RunMetrics::mBoundingBox field will be initialized
* properly based on glyph extents, in particular, glyph extents that
* overflow the standard font-box (the box defined by the ascent, descent
* and advance width of the glyph). When not set, it may just be the
* standard font-box even if glyphs overflow.
* When set, optional ligatures are disabled. Ligatures that are
* required for legible text should still be enabled.
* When set, the textrun should favour speed of construction over
* quality. This may involve disabling ligatures and/or kerning or
* other effects.
* When set, the textrun should discard control characters instead of
* turning them into hexboxes.
* nsTextFrameThebes sets these, but they're defined here rather than
* in nsTextFrameUtils.h because ShapedWord creation/caching also needs
* to check the _INCOMING flag
* When set, the previous character for this textrun was an Arabic
* character. This is used for the context detection necessary for
* bidi.numeral implementation.
* Set if the textrun should use the OpenType 'math' script.
* Bit 0x0800 is currently unused.
* Field for orientation of the textrun and glyphs within it.
* Possible values of the TEXT_ORIENT_MASK field:
* For all VERTICAL settings, the x and y coordinates of glyph
* positions are exchanged, so that simple advances are vertical.
* The MIXED value indicates vertical textRuns for which the CSS
* text-orientation property is 'mixed', but is never used for
* individual glyphRuns; it will be resolved to either UPRIGHT
* or SIDEWAYS_RIGHT according to the UTR50 properties of the
* characters, and separate glyphRuns created for the resulting
* glyph orientations.
} // namespace gfx
} // namespace mozilla
class gfxTextRunFactory {
// Used by stylo
typedef mozilla::gfx::DrawTarget DrawTarget;
* This record contains all the parameters needed to initialize a textrun.
struct MOZ_STACK_CLASS Parameters {
// Shape text params suggesting where the textrun will be rendered
DrawTarget* mDrawTarget;
// Pointer to arbitrary user data (which should outlive the textrun)
void* mUserData;
// A description of which characters have been stripped from the original
// DOM string to produce the characters in the textrun. May be null
// if that information is not relevant.
gfxSkipChars* mSkipChars;
// A list of where linebreaks are currently placed in the textrun. May
// be null if mInitialBreakCount is zero.
uint32_t* mInitialBreaks;
uint32_t mInitialBreakCount;
// The ratio to use to convert device pixels to application layout units
int32_t mAppUnitsPerDevUnit;
// Protected destructor, to discourage deletion outside of Release():
virtual ~gfxTextRunFactory();
* gfxFontShaper
* This class implements text shaping (character to glyph mapping and
* glyph layout). There is a gfxFontShaper subclass for each text layout
* technology (uniscribe, core text, harfbuzz,....) we support.
* The shaper is responsible for setting up glyph data in gfxTextRuns.
* A generic, platform-independent shaper relies only on the standard
* gfxFont interface and can work with any concrete subclass of gfxFont.
* Platform-specific implementations designed to interface to platform
* shaping APIs such as Uniscribe or CoreText may rely on features of a
* specific font subclass to access native font references
* (such as CTFont, HFONT, DWriteFont, etc).
class gfxFontShaper {
typedef mozilla::gfx::DrawTarget DrawTarget;
typedef mozilla::intl::Script Script;
enum class RoundingFlags : uint8_t { kRoundX = 0x01, kRoundY = 0x02 };
explicit gfxFontShaper(gfxFont* aFont) : mFont(aFont) {
NS_ASSERTION(aFont, "shaper requires a valid font!");
virtual ~gfxFontShaper() = default;
// Shape a piece of text and store the resulting glyph data into
// aShapedText. Parameters aOffset/aLength indicate the range of
// aShapedText to be updated; aLength is also the length of aText.
virtual bool ShapeText(DrawTarget* aDrawTarget, const char16_t* aText,
uint32_t aOffset, uint32_t aLength, Script aScript,
nsAtom* aLanguage, // may be null, indicating no
// lang-specific shaping to be
// applied
bool aVertical, RoundingFlags aRounding,
gfxShapedText* aShapedText) = 0;
gfxFont* GetFont() const { return mFont; }
static void MergeFontFeatures(
const gfxFontStyle* aStyle, const nsTArray<gfxFontFeature>& aFontFeatures,
bool aDisableLigatures, const nsACString& aFamilyName, bool aAddSmallCaps,
void (*aHandleFeature)(const uint32_t&, uint32_t&, void*),
void* aHandleFeatureData);
// the font this shaper is working with. The font owns a UniquePtr reference
// to this object, and will destroy it before it dies. Thus, mFont will always
// be valid.
gfxFont* MOZ_NON_OWNING_REF mFont;
* gfxShapedText is an abstract superclass for gfxShapedWord and gfxTextRun.
* These are objects that store a list of zero or more glyphs for each
* character. For each glyph we store the glyph ID, the advance, and possibly
* x/y-offsets. The idea is that a string is rendered by a loop that draws each
* glyph at its designated offset from the current point, then advances the
* current point by the glyph's advance in the direction of the textrun (LTR or
* RTL). Each glyph advance is always rounded to the nearest appunit; this
* ensures consistent results when dividing the text in a textrun into multiple
* text frames (frame boundaries are always aligned to appunits). We optimize
* for the case where a character has a single glyph and zero xoffset and
* yoffset, and the glyph ID and advance are in a reasonable range so we can
* pack all necessary data into 32 bits.
* gfxFontShaper can shape text into either a gfxShapedWord (cached by a
* gfxFont) or directly into a gfxTextRun (for cases where we want to shape
* textruns in their entirety rather than using cached words, because there may
* be layout features that depend on the inter-word spaces).
class gfxShapedText {
typedef mozilla::intl::Script Script;
gfxShapedText(uint32_t aLength, mozilla::gfx::ShapedTextFlags aFlags,
uint16_t aAppUnitsPerDevUnit)
: mLength(aLength),
mAppUnitsPerDevUnit(aAppUnitsPerDevUnit) {}
virtual ~gfxShapedText() = default;
* This class records the information associated with a character in the
* input string. It's optimized for the case where there is one glyph
* representing that character alone.
* A character can have zero or more associated glyphs. Each glyph
* has an advance width and an x and y offset.
* A character may be the start of a cluster.
* A character may be the start of a ligature group.
* A character can be "missing", indicating that the system is unable
* to render the character.
* All characters in a ligature group conceptually share all the glyphs
* associated with the characters in a group.
class CompressedGlyph {
enum {
// Indicates that a cluster and ligature group starts at this
// character; this character has a single glyph with a reasonable
// advance and zero offsets. A "reasonable" advance
// is one that fits in the available bits (currently 12) (specified
// in appunits).
// These flags are applicable to both "simple" and "complex" records.
COMMON_FLAGS_MASK = 0x70000000U,
// Indicates whether a linebreak is allowed before this character;
// this is a two-bit field that holds a FLAG_BREAK_TYPE_xxx value
// indicating the kind of linebreak (if any) allowed here.
FLAG_CHAR_IS_SPACE = 0x10000000U,
// Fields present only when FLAG_IS_SIMPLE_GLYPH is /true/.
// The advance is stored in appunits as a 12-bit field:
// and the glyph ID is stored in the low 16 bits.
// Fields present only when FLAG_IS_SIMPLE_GLYPH is /false/.
// Non-simple glyphs may or may not have glyph data in the
// corresponding mDetailedGlyphs entry. They have a glyph count
// stored in the low 16 bits, and the following flag bits:
// When NOT set, indicates that this character corresponds to a
// missing glyph and should be skipped (or possibly, render the character
// Unicode value in some special way). If there are glyphs,
// the mGlyphID is actually the UTF16 character code. The bit is
// inverted so we can memset the array to zero to indicate all missing.
FLAG_NOT_MISSING = 0x010000,
// Flag bit 0x080000 is currently unused.
// Certain types of characters are marked so that they can be given
// special treatment in rendering. This may require use of a "complex"
// CompressedGlyph record even for a character that would otherwise be
// treated as "simple".
FLAG_CHAR_IS_TAB = 0x100000,
// Per CSS Text Decoration Module Level 3, emphasis marks are not
// drawn for any character in Unicode categories Z*, Cc, Cf, and Cn
// which is not combined with any combining characters. This flag is
// set for all those characters except 0x20 whitespace.
// Per CSS Text, letter-spacing is not applied to formatting chars
// (category Cf). We mark those in the textrun so as to be able to
// skip them when setting up spacing in nsTextFrame.
// The bits 0x0F000000 are currently unused in non-simple glyphs.
// "Simple glyphs" have a simple glyph ID, simple advance and their
// x and y offsets are zero. Also the glyph extents do not overflow
// the font-box defined by the font ascent, descent and glyph advance width.
// These case is optimized to avoid storing DetailedGlyphs.
// Returns true if the glyph ID aGlyph fits into the compressed
// representation
static bool IsSimpleGlyphID(uint32_t aGlyph) {
return (aGlyph & GLYPH_MASK) == aGlyph;
// Returns true if the advance aAdvance fits into the compressed
// representation. aAdvance is in appunits.
static bool IsSimpleAdvance(uint32_t aAdvance) {
return (aAdvance & (ADVANCE_MASK >> ADVANCE_SHIFT)) == aAdvance;
bool IsSimpleGlyph() const { return mValue & FLAG_IS_SIMPLE_GLYPH; }
uint32_t GetSimpleAdvance() const {
return (mValue & ADVANCE_MASK) >> ADVANCE_SHIFT;
uint32_t GetSimpleGlyph() const {
return mValue & GLYPH_MASK;
bool IsMissing() const {
bool IsClusterStart() const {
return IsSimpleGlyph() || !(mValue & FLAG_NOT_CLUSTER_START);
bool IsLigatureGroupStart() const {
return IsSimpleGlyph() || !(mValue & FLAG_NOT_LIGATURE_GROUP_START);
bool IsLigatureContinuation() const {
return !IsSimpleGlyph() &&
// Return true if the original character was a normal (breakable,
// trimmable) space (U+0020). Not true for other characters that
// may happen to map to the space glyph (U+00A0).
bool CharIsSpace() const { return mValue & FLAG_CHAR_IS_SPACE; }
bool CharIsTab() const {
return !IsSimpleGlyph() && (mValue & FLAG_CHAR_IS_TAB);
bool CharIsNewline() const {
return !IsSimpleGlyph() && (mValue & FLAG_CHAR_IS_NEWLINE);
bool CharMayHaveEmphasisMark() const {
return !CharIsSpace() &&
(IsSimpleGlyph() || !(mValue & FLAG_CHAR_NO_EMPHASIS_MARK));
bool CharIsFormattingControl() const {
return !IsSimpleGlyph() && (mValue & FLAG_CHAR_IS_FORMATTING_CONTROL);
uint32_t CharTypeFlags() const {
return IsSimpleGlyph() ? 0 : (mValue & CHAR_TYPE_FLAGS_MASK);
void SetClusterStart(bool aIsClusterStart) {
if (aIsClusterStart) {
} else {
uint8_t CanBreakBefore() const {
// Returns FLAGS_CAN_BREAK_BEFORE if the setting changed, 0 otherwise
uint32_t SetCanBreakBefore(uint8_t aCanBreakBefore) {
MOZ_ASSERT(aCanBreakBefore <= 2, "Bogus break-before value!");
uint32_t breakMask = (uint32_t(aCanBreakBefore) << FLAGS_CAN_BREAK_SHIFT);
uint32_t toggle = breakMask ^ (mValue & FLAGS_CAN_BREAK_BEFORE);
mValue ^= toggle;
return toggle;
// Create a CompressedGlyph value representing a simple glyph with
// no extra flags (line-break or is_space) set.
static CompressedGlyph MakeSimpleGlyph(uint32_t aAdvanceAppUnits,
uint32_t aGlyph) {
CompressedGlyph g;
g.mValue =
FLAG_IS_SIMPLE_GLYPH | (aAdvanceAppUnits << ADVANCE_SHIFT) | aGlyph;
return g;
// Assign a simple glyph value to an existing CompressedGlyph record,
// preserving line-break/is-space flags if present.
CompressedGlyph& SetSimpleGlyph(uint32_t aAdvanceAppUnits,
uint32_t aGlyph) {
MOZ_ASSERT(!CharTypeFlags(), "Char type flags lost");
mValue = (mValue & COMMON_FLAGS_MASK) |
MakeSimpleGlyph(aAdvanceAppUnits, aGlyph).mValue;
return *this;
// Create a CompressedGlyph value representing a complex glyph record,
// without any line-break or char-type flags.
static CompressedGlyph MakeComplex(bool aClusterStart,
bool aLigatureStart) {
CompressedGlyph g;
(aClusterStart ? 0 : FLAG_NOT_CLUSTER_START) |
return g;
// Assign a complex glyph value to an existing CompressedGlyph record,
// preserving line-break/char-type flags if present.
// This sets the glyphCount to zero; it will be updated when we call
// gfxShapedText::SetDetailedGlyphs.
CompressedGlyph& SetComplex(bool aClusterStart, bool aLigatureStart) {
mValue = (mValue & COMMON_FLAGS_MASK) | CharTypeFlags() |
MakeComplex(aClusterStart, aLigatureStart).mValue;
return *this;
* Mark a glyph record as being a missing-glyph.
* Missing glyphs are treated as ligature group starts; don't mess with
* the cluster-start flag (see bugs 618870 and 619286).
* We also preserve the glyph count here, as this is used after any
* required DetailedGlyphs (to store the char code for a hexbox) has been
* set up.
* This must be called *after* SetDetailedGlyphs is used for the relevant
* offset in the shaped-word, because that will mark it as not-missing.
CompressedGlyph& SetMissing() {
return *this;
uint32_t GetGlyphCount() const {
return mValue & GLYPH_COUNT_MASK;
void SetGlyphCount(uint32_t aGlyphCount) {
MOZ_ASSERT(GetGlyphCount() == 0, "Glyph count already set");
MOZ_ASSERT(aGlyphCount <= 0xffff, "Glyph count out of range");
mValue |= FLAG_NOT_MISSING | aGlyphCount;
void SetIsSpace() { mValue |= FLAG_CHAR_IS_SPACE; }
void SetIsTab() {
void SetIsNewline() {
void SetNoEmphasisMark() {
void SetIsFormattingControl() {
uint32_t mValue;
// Accessor for the array of CompressedGlyph records, which will be in
// a different place in gfxShapedWord vs gfxTextRun
virtual const CompressedGlyph* GetCharacterGlyphs() const = 0;
virtual CompressedGlyph* GetCharacterGlyphs() = 0;
* When the glyphs for a character don't fit into a CompressedGlyph record
* in SimpleGlyph format, we use an array of DetailedGlyphs instead.
struct DetailedGlyph {
// The glyphID, or the Unicode character if this is a missing glyph
uint32_t mGlyphID;
// The advance of the glyph, in appunits.
// mAdvance is in the text direction (RTL or LTR),
// and will normally be non-negative (although this is not guaranteed)
int32_t mAdvance;
// The offset from the glyph's default position, in line-relative
// coordinates (so mOffset.x is an offset in the line-right direction,
// and mOffset.y is an offset in line-downwards direction).
// These values are in floating-point appUnits.
mozilla::gfx::Point mOffset;
// Store DetailedGlyph records for the given index. (This does not modify
// the associated CompressedGlyph character-type or break flags.)
void SetDetailedGlyphs(uint32_t aIndex, uint32_t aGlyphCount,
const DetailedGlyph* aGlyphs);
void SetMissingGlyph(uint32_t aIndex, uint32_t aChar, gfxFont* aFont);
void SetIsSpace(uint32_t aIndex) {
bool HasDetailedGlyphs() const { return mDetailedGlyphs != nullptr; }
bool IsLigatureGroupStart(uint32_t aPos) {
NS_ASSERTION(aPos < GetLength(), "aPos out of range");
return GetCharacterGlyphs()[aPos].IsLigatureGroupStart();
// NOTE that this must not be called for a character offset that does
// not have any DetailedGlyph records; callers must have verified that
// GetCharacterGlyphs()[aCharIndex].GetGlyphCount() is greater than zero.
DetailedGlyph* GetDetailedGlyphs(uint32_t aCharIndex) const {
NS_ASSERTION(GetCharacterGlyphs() && HasDetailedGlyphs() &&
!GetCharacterGlyphs()[aCharIndex].IsSimpleGlyph() &&
GetCharacterGlyphs()[aCharIndex].GetGlyphCount() > 0,
"invalid use of GetDetailedGlyphs; check the caller!");
return mDetailedGlyphs->Get(aCharIndex);
void AdjustAdvancesForSyntheticBold(float aSynBoldOffset, uint32_t aOffset,
uint32_t aLength);
// Mark clusters in the CompressedGlyph records, starting at aOffset,
// based on the Unicode properties of the text in aString.
// This is also responsible to set the IsSpace flag for space characters.
void SetupClusterBoundaries(uint32_t aOffset, const char16_t* aString,
uint32_t aLength);
// In 8-bit text, there won't actually be any clusters, but we still need
// the space-marking functionality.
void SetupClusterBoundaries(uint32_t aOffset, const uint8_t* aString,
uint32_t aLength);
mozilla::gfx::ShapedTextFlags GetFlags() const { return mFlags; }
bool IsVertical() const {
return (GetFlags() & mozilla::gfx::ShapedTextFlags::TEXT_ORIENT_MASK) !=
bool UseCenterBaseline() const {
mozilla::gfx::ShapedTextFlags orient =
GetFlags() & mozilla::gfx::ShapedTextFlags::TEXT_ORIENT_MASK;
return orient ==
mozilla::gfx::ShapedTextFlags::TEXT_ORIENT_VERTICAL_MIXED ||
orient ==
bool IsRightToLeft() const {
return (GetFlags() & mozilla::gfx::ShapedTextFlags::TEXT_IS_RTL) ==
bool IsSidewaysLeft() const {
return (GetFlags() & mozilla::gfx::ShapedTextFlags::TEXT_ORIENT_MASK) ==
// Return true if the logical inline direction is reversed compared to
// normal physical coordinates (i.e. if it is leftwards or upwards)
bool IsInlineReversed() const { return IsSidewaysLeft() != IsRightToLeft(); }
gfxFloat GetDirection() const { return IsInlineReversed() ? -1.0f : 1.0f; }
bool DisableLigatures() const {
return (GetFlags() &
mozilla::gfx::ShapedTextFlags::TEXT_DISABLE_OPTIONAL_LIGATURES) ==
bool TextIs8Bit() const {
return (GetFlags() & mozilla::gfx::ShapedTextFlags::TEXT_IS_8BIT) ==
int32_t GetAppUnitsPerDevUnit() const { return mAppUnitsPerDevUnit; }
uint32_t GetLength() const { return mLength; }
bool FilterIfIgnorable(uint32_t aIndex, uint32_t aCh);
// Allocate aCount DetailedGlyphs for the given index
DetailedGlyph* AllocateDetailedGlyphs(uint32_t aCharIndex, uint32_t aCount);
// Ensure the glyph on the given index is complex glyph so that we can use
// it to record specific characters that layout may need to detect.
void EnsureComplexGlyph(uint32_t aIndex, CompressedGlyph& aGlyph) {
MOZ_ASSERT(GetCharacterGlyphs() + aIndex == &aGlyph);
if (aGlyph.IsSimpleGlyph()) {
DetailedGlyph details = {aGlyph.GetSimpleGlyph(),
aGlyph.SetComplex(true, true);
SetDetailedGlyphs(aIndex, 1, &details);
// For characters whose glyph data does not fit the "simple" glyph criteria
// in CompressedGlyph, we use a sorted array to store the association
// between the source character offset and an index into an array
// DetailedGlyphs. The CompressedGlyph record includes a count of
// the number of DetailedGlyph records that belong to the character,
// starting at the given index.
class DetailedGlyphStore {
DetailedGlyphStore() = default;
// This is optimized for the most common calling patterns:
// we rarely need random access to the records, access is most commonly
// sequential through the textRun, so we record the last-used index
// and check whether the caller wants the same record again, or the
// next; if not, it's most likely we're starting over from the start
// of the run, so we check the first entry before resorting to binary
// search as a last resort.
// NOTE that this must not be called for a character offset that does
// not have any DetailedGlyph records; callers must have verified that
// mCharacterGlyphs[aOffset].GetGlyphCount() is greater than zero
// before calling this, otherwise the assertions here will fire (in a
// debug build), and we'll probably crash.
DetailedGlyph* Get(uint32_t aOffset) {
NS_ASSERTION(mOffsetToIndex.Length() > 0, "no detailed glyph records!");
DetailedGlyph* details = mDetails.Elements();
// check common cases (fwd iteration, initial entry, etc) first
if (mLastUsed < mOffsetToIndex.Length() - 1 &&
aOffset == mOffsetToIndex[mLastUsed + 1].mOffset) {
} else if (aOffset == mOffsetToIndex[0].mOffset) {
mLastUsed = 0;
} else if (aOffset == mOffsetToIndex[mLastUsed].mOffset) {
// do nothing
} else if (mLastUsed > 0 &&
aOffset == mOffsetToIndex[mLastUsed - 1].mOffset) {
} else {
mLastUsed = mOffsetToIndex.BinaryIndexOf(aOffset, CompareToOffset());
NS_ASSERTION(mLastUsed != nsTArray<DGRec>::NoIndex,
"detailed glyph record missing!");
return details + mOffsetToIndex[mLastUsed].mIndex;
DetailedGlyph* Allocate(uint32_t aOffset, uint32_t aCount) {
uint32_t detailIndex = mDetails.Length();
DetailedGlyph* details = mDetails.AppendElements(aCount);
// We normally set up glyph records sequentially, so the common case
// here is to append new records to the mOffsetToIndex array;
// test for that before falling back to the InsertElementSorted
// method.
if (mOffsetToIndex.Length() == 0 ||
aOffset > mOffsetToIndex[mOffsetToIndex.Length() - 1].mOffset) {
mOffsetToIndex.AppendElement(DGRec(aOffset, detailIndex));
} else {
mOffsetToIndex.InsertElementSorted(DGRec(aOffset, detailIndex),
return details;
size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) {
return aMallocSizeOf(this) +
mDetails.ShallowSizeOfExcludingThis(aMallocSizeOf) +
struct DGRec {
DGRec(const uint32_t& aOffset, const uint32_t& aIndex)
: mOffset(aOffset), mIndex(aIndex) {}
uint32_t mOffset; // source character offset in the textrun
uint32_t mIndex; // index where this char's DetailedGlyphs begin
struct CompareToOffset {
bool Equals(const DGRec& a, const uint32_t& b) const {
return a.mOffset == b;
bool LessThan(const DGRec& a, const uint32_t& b) const {
return a.mOffset < b;
struct CompareRecordOffsets {
bool Equals(const DGRec& a, const DGRec& b) const {
return a.mOffset == b.mOffset;
bool LessThan(const DGRec& a, const DGRec& b) const {
return a.mOffset < b.mOffset;
// Concatenated array of all the DetailedGlyph records needed for the
// textRun; individual character offsets are associated with indexes
// into this array via the mOffsetToIndex table.
nsTArray<DetailedGlyph> mDetails;
// For each character offset that needs DetailedGlyphs, we record the
// index in mDetails where the list of glyphs begins. This array is
// sorted by mOffset.
nsTArray<DGRec> mOffsetToIndex;
// Records the most recently used index into mOffsetToIndex, so that
// we can support sequential access more quickly than just doing
// a binary search each time.
nsTArray<DGRec>::index_type mLastUsed = 0;
mozilla::UniquePtr<DetailedGlyphStore> mDetailedGlyphs;
// Number of char16_t characters and CompressedGlyph glyph records
uint32_t mLength;
// Shaping flags (direction, ligature-suppression)
mozilla::gfx::ShapedTextFlags mFlags;
uint16_t mAppUnitsPerDevUnit;
* gfxShapedWord: an individual (space-delimited) run of text shaped with a
* particular font, without regard to external context.
* The glyph data is copied into gfxTextRuns as needed from the cache of
* ShapedWords associated with each gfxFont instance.
class gfxShapedWord final : public gfxShapedText {
typedef mozilla::intl::Script Script;
// Create a ShapedWord that can hold glyphs for aLength characters,
// with mCharacterGlyphs sized appropriately.
// Returns null on allocation failure (does NOT use infallible alloc)
// so caller must check for success.
// This does NOT perform shaping, so the returned word contains no
// glyph data; the caller must call gfxFont::ShapeText() with appropriate
// parameters to set up the glyphs.
static gfxShapedWord* Create(const uint8_t* aText, uint32_t aLength,
Script aRunScript, nsAtom* aLanguage,
uint16_t aAppUnitsPerDevUnit,
mozilla::gfx::ShapedTextFlags aFlags,
gfxFontShaper::RoundingFlags aRounding) {
NS_ASSERTION(aLength <= gfxPlatform::GetPlatform()->WordCacheCharLimit(),
"excessive length for gfxShapedWord!");
// Compute size needed including the mCharacterGlyphs array
// and a copy of the original text
uint32_t size = offsetof(gfxShapedWord, mCharGlyphsStorage) +
aLength * (sizeof(CompressedGlyph) + sizeof(uint8_t));
void* storage = malloc(size);
if (!storage) {
return nullptr;
// Construct in the pre-allocated storage, using placement new
return new (storage) gfxShapedWord(aText, aLength, aRunScript, aLanguage,
aAppUnitsPerDevUnit, aFlags, aRounding);
static gfxShapedWord* Create(const char16_t* aText, uint32_t aLength,
Script aRunScript, nsAtom* aLanguage,
uint16_t aAppUnitsPerDevUnit,
mozilla::gfx::ShapedTextFlags aFlags,
gfxFontShaper::RoundingFlags aRounding) {
NS_ASSERTION(aLength <= gfxPlatform::GetPlatform()->WordCacheCharLimit(),
"excessive length for gfxShapedWord!");
// In the 16-bit version of Create, if the TEXT_IS_8BIT flag is set,
// then we convert the text to an 8-bit version and call the 8-bit
// Create function instead.
if (aFlags & mozilla::gfx::ShapedTextFlags::TEXT_IS_8BIT) {
nsAutoCString narrowText;
LossyAppendUTF16toASCII(nsDependentSubstring(aText, aLength), narrowText);
return Create((const uint8_t*)(narrowText.BeginReading()), aLength,
aRunScript, aLanguage, aAppUnitsPerDevUnit, aFlags,
uint32_t size = offsetof(gfxShapedWord, mCharGlyphsStorage) +
aLength * (sizeof(CompressedGlyph) + sizeof(char16_t));
void* storage = malloc(size);
if (!storage) {
return nullptr;
return new (storage) gfxShapedWord(aText, aLength, aRunScript, aLanguage,
aAppUnitsPerDevUnit, aFlags, aRounding);
// Override operator delete to properly free the object that was
// allocated via malloc.
void operator delete(void* p) { free(p); }
const CompressedGlyph* GetCharacterGlyphs() const override {
return &mCharGlyphsStorage[0];
CompressedGlyph* GetCharacterGlyphs() override {
return &mCharGlyphsStorage[0];
const uint8_t* Text8Bit() const {
NS_ASSERTION(TextIs8Bit(), "invalid use of Text8Bit()");
return reinterpret_cast<const uint8_t*>(mCharGlyphsStorage + GetLength());
const char16_t* TextUnicode() const {
NS_ASSERTION(!TextIs8Bit(), "invalid use of TextUnicode()");
return reinterpret_cast<const char16_t*>(mCharGlyphsStorage + GetLength());
char16_t GetCharAt(uint32_t aOffset) const {
NS_ASSERTION(aOffset < GetLength(), "aOffset out of range");
return TextIs8Bit() ? char16_t(Text8Bit()[aOffset])
: TextUnicode()[aOffset];
Script GetScript() const { return mScript; }
nsAtom* GetLanguage() const { return mLanguage.get(); }
gfxFontShaper::RoundingFlags GetRounding() const { return mRounding; }
void ResetAge() { mAgeCounter = 0; }
uint32_t IncrementAge() { return ++mAgeCounter; }
// Helper used when hashing a word for the shaped-word caches
static uint32_t HashMix(uint32_t aHash, char16_t aCh) {
return (aHash >> 28) ^ (aHash << 4) ^ aCh;
// so that gfxTextRun can share our DetailedGlyphStore class
friend class gfxTextRun;
// Construct storage for a ShapedWord, ready to receive glyph data
gfxShapedWord(const uint8_t* aText, uint32_t aLength, Script aRunScript,
nsAtom* aLanguage, uint16_t aAppUnitsPerDevUnit,
mozilla::gfx::ShapedTextFlags aFlags,
gfxFontShaper::RoundingFlags aRounding)
: gfxShapedText(aLength,
aFlags | mozilla::gfx::ShapedTextFlags::TEXT_IS_8BIT,
mAgeCounter(0) {
memset(mCharGlyphsStorage, 0, aLength * sizeof(CompressedGlyph));
uint8_t* text = reinterpret_cast<uint8_t*>(&mCharGlyphsStorage[aLength]);
memcpy(text, aText, aLength * sizeof(uint8_t));
gfxShapedWord(const char16_t* aText, uint32_t aLength, Script aRunScript,
nsAtom* aLanguage, uint16_t aAppUnitsPerDevUnit,
mozilla::gfx::ShapedTextFlags aFlags,
gfxFontShaper::RoundingFlags aRounding)
: gfxShapedText(aLength, aFlags, aAppUnitsPerDevUnit),
mAgeCounter(0) {
memset(mCharGlyphsStorage, 0, aLength * sizeof(CompressedGlyph));
char16_t* text = reinterpret_cast<char16_t*>(&mCharGlyphsStorage[aLength]);
memcpy(text, aText, aLength * sizeof(char16_t));
SetupClusterBoundaries(0, aText, aLength);
RefPtr<nsAtom> mLanguage;
Script mScript;
gfxFontShaper::RoundingFlags mRounding;
// With multithreaded shaping, this may be updated by any thread.
std::atomic<uint32_t> mAgeCounter;
// The mCharGlyphsStorage array is actually a variable-size member;
// when the ShapedWord is created, its size will be increased as necessary
// to allow the proper number of glyphs to be stored.
// The original text, in either 8-bit or 16-bit form, will be stored
// immediately following the CompressedGlyphs.
CompressedGlyph mCharGlyphsStorage[1];
class GlyphBufferAzure;
struct TextRunDrawParams;
struct FontDrawParams;
struct EmphasisMarkDrawParams;
class gfxFont {
friend class gfxHarfBuzzShaper;
friend class gfxGraphiteShaper;
using DrawTarget = mozilla::gfx::DrawTarget;
using Script = mozilla::intl::Script;
using SVGContextPaint = mozilla::SVGContextPaint;
using RoundingFlags = gfxFontShaper::RoundingFlags;
using FontSlantStyle = mozilla::FontSlantStyle;
using FontSizeAdjust = mozilla::StyleFontSizeAdjust;
int32_t GetRefCount() { return int32_t(mRefCnt); }
// options to specify the kind of AA to be used when creating a font
typedef enum : uint8_t {
} AntialiasOption;
gfxFont(const RefPtr<mozilla::gfx::UnscaledFont>& aUnscaledFont,
gfxFontEntry* aFontEntry, const gfxFontStyle* aFontStyle,
AntialiasOption anAAOption = kAntialiasDefault);
virtual ~gfxFont();
void MaybeDestroy() {
bool destroy = true;
if (gfxFontCache* fc = gfxFontCache::GetCache()) {
destroy = fc->MaybeDestroy(this);
if (destroy) {
void Destroy() {
MOZ_ASSERT(GetRefCount() == 0);
delete this;
bool Valid() const { return mIsValid; }
// options for the kind of bounding box to return from measurement
typedef enum {
// A box that encloses all the painted pixels, and may
// include sidebearings and/or additional ascent/descent
// within the glyph cell even if the ink is smaller.
// A box that tightly encloses all the painted pixels
// (although actually on Windows, at least, it may be
// slightly larger than strictly necessary because
// we can't get precise extents with ClearType).
// A box that tightly encloses the glyph outline,
// ignoring possible antialiasing pixels that extend
// beyond this.
// NOTE: The default implementation of gfxFont::Measure(),
// which works with the glyph extents cache, does not
// differentiate between this and TIGHT_INK_EXTENTS.
// Whether the distinction is important depends on the
// antialiasing behavior of the platform; currently the
// distinction is only implemented in the gfxWindowsFont
// subclass, because of ClearType's tendency to paint
// outside the hinted outline.
// Also NOTE: it is relatively expensive to request this,
// as it does not use cached glyph extents in the font.
} BoundingBoxType;
const nsCString& GetName() const { return mFontEntry->Name(); }
const gfxFontStyle* GetStyle() const { return &mStyle; }
virtual gfxFont* CopyWithAntialiasOption(AntialiasOption anAAOption) const {
// platforms where this actually matters should override
return nullptr;
gfxFloat GetAdjustedSize() const {
// mAdjustedSize is cached here if not already set to a non-zero value;
// but it may be overridden by a value computed in metrics initialization
// from font-size-adjust.
if (mAdjustedSize < 0.0) {
mAdjustedSize = mStyle.AdjustedSizeMustBeZero()
? 0.0
: mStyle.size * mFontEntry->mSizeAdjust;
return mAdjustedSize;
float FUnitsToDevUnitsFactor() const {
// check this was set up during font initialization
NS_ASSERTION(mFUnitsConvFactor >= 0.0f, "mFUnitsConvFactor not valid");
return mFUnitsConvFactor;
// check whether this is an sfnt we can potentially use with harfbuzz
bool FontCanSupportHarfBuzz() const { return mFontEntry->HasCmapTable(); }
// check whether this is an sfnt we can potentially use with Graphite
bool FontCanSupportGraphite() const {
return mFontEntry->HasGraphiteTables();
// Whether this is a font that may be doing full-color rendering,
// and therefore needs us to use a mask for text-shadow even when
// we're not actually blurring.
bool AlwaysNeedsMaskForShadow() const {
return mFontEntry->TryGetColorGlyphs() || mFontEntry->TryGetSVGData(this) ||
mFontEntry->HasFontTable(TRUETYPE_TAG('C', 'B', 'D', 'T')) ||
mFontEntry->HasFontTable(TRUETYPE_TAG('s', 'b', 'i', 'x'));
// whether a feature is supported by the font (limited to a small set
// of features for which some form of fallback needs to be implemented)
bool SupportsFeature(Script aScript, uint32_t aFeatureTag);
// whether the font supports "real" small caps, petite caps etc.
// aFallbackToSmallCaps true when petite caps should fallback to small caps
bool SupportsVariantCaps(Script aScript, uint32_t aVariantCaps,
bool& aFallbackToSmallCaps,
bool& aSyntheticLowerToSmallCaps,
bool& aSyntheticUpperToSmallCaps);
// whether the font supports subscript/superscript feature
// for fallback, need to verify that all characters in the run
// have variant substitutions
bool SupportsSubSuperscript(uint32_t aSubSuperscript, const uint8_t* aString,
uint32_t aLength, Script aRunScript);
bool SupportsSubSuperscript(uint32_t aSubSuperscript, const char16_t* aString,
uint32_t aLength, Script aRunScript);
// whether the specified feature will apply to the given character
bool FeatureWillHandleChar(Script aRunScript, uint32_t aFeature,
uint32_t aUnicode);
// Subclasses may choose to look up glyph ids for characters.
// If they do not override this, gfxHarfBuzzShaper will fetch the cmap
// table and use that.
virtual bool ProvidesGetGlyph() const { return false; }
// Map unicode character to glyph ID.
// Only used if ProvidesGetGlyph() returns true.
virtual uint32_t GetGlyph(uint32_t unicode, uint32_t variation_selector) {
return 0;
// Return the advance of a glyph.
gfxFloat GetGlyphAdvance(uint16_t aGID, bool aVertical = false);
// Return the advance of a given Unicode char in isolation.
// Returns -1.0 if the char is not supported.
gfxFloat GetCharAdvance(uint32_t aUnicode, bool aVertical = false);
gfxFloat SynthesizeSpaceWidth(uint32_t aCh);
// Work out whether cairo will snap inter-glyph spacing to pixels
// when rendering to the given drawTarget.
RoundingFlags GetRoundOffsetsToPixels(DrawTarget* aDrawTarget);
virtual bool ShouldHintMetrics() const { return true; }
virtual bool ShouldRoundXOffset(cairo_t* aCairo) const { return true; }
// Return the font's owned harfbuzz shaper, creating and initializing it if
// necessary; returns null if shaper initialization has failed.
gfxHarfBuzzShaper* GetHarfBuzzShaper();
// Font metrics
struct Metrics {
gfxFloat capHeight;
gfxFloat xHeight;
gfxFloat strikeoutSize;
gfxFloat strikeoutOffset;
gfxFloat underlineSize;
gfxFloat underlineOffset;
gfxFloat internalLeading;
gfxFloat externalLeading;
gfxFloat emHeight;
gfxFloat emAscent;
gfxFloat emDescent;
gfxFloat maxHeight;
gfxFloat maxAscent;
gfxFloat maxDescent;
gfxFloat maxAdvance;
gfxFloat aveCharWidth;
gfxFloat spaceWidth;
gfxFloat zeroWidth; // -1 if there was no zero glyph
gfxFloat ideographicWidth; // -1 if kWaterIdeograph is not supported
gfxFloat ZeroOrAveCharWidth() const {
return zeroWidth >= 0 ? zeroWidth : aveCharWidth;
// Unicode character used as basis for 'ic' unit:
static constexpr uint32_t kWaterIdeograph = 0x6C34;
typedef nsFontMetrics::FontOrientation Orientation;
const Metrics& GetMetrics(Orientation aOrientation) {
if (aOrientation ==