Add m-esr52 at 52.6.0

1 files changed, 1818 insertions, 0 deletions

diff --git a/gfx/thebes/gfxHarfBuzzShaper.cpp b/gfx/thebes/gfxHarfBuzzShaper.cpp
new file mode 100644
index 000000000..1f472f88d
--- /dev/null
+++ b/gfx/thebes/gfxHarfBuzzShaper.cpp
@@ -0,0 +1,1818 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+#include "nsString.h"
+#include "gfxContext.h"
+#include "gfxFontConstants.h"
+#include "gfxHarfBuzzShaper.h"
+#include "gfxFontUtils.h"
+#include "gfxTextRun.h"
+#include "mozilla/Sprintf.h"
+#include "nsUnicodeProperties.h"
+#include "nsUnicodeScriptCodes.h"
+#include "nsUnicodeNormalizer.h"
+
+#include "harfbuzz/hb.h"
+#include "harfbuzz/hb-ot.h"
+
+#if ENABLE_INTL_API // ICU is available: we'll use it for Unicode composition
+                    // and decomposition in preference to nsUnicodeNormalizer.
+#include "unicode/unorm.h"
+#include "unicode/utext.h"
+#define MOZ_HB_SHAPER_USE_ICU_NORMALIZATION 1
+static const UNormalizer2 * sNormalizer = nullptr;
+#else
+#undef MOZ_HB_SHAPER_USE_ICU_NORMALIZATION
+#endif
+
+#include <algorithm>
+
+#define FloatToFixed(f) (65536 * (f))
+#define FixedToFloat(f) ((f) * (1.0 / 65536.0))
+// Right shifts of negative (signed) integers are undefined, as are overflows
+// when converting unsigned to negative signed integers.
+// (If speed were an issue we could make some 2's complement assumptions.)
+#define FixedToIntRound(f) ((f) > 0 ?  ((32768 + (f)) >> 16) \
+                                    : -((32767 - (f)) >> 16))
+
+using namespace mozilla; // for AutoSwap_* types
+using namespace mozilla::unicode; // for Unicode property lookup
+
+/*
+ * Creation and destruction; on deletion, release any font tables we're holding
+ */
+
+gfxHarfBuzzShaper::gfxHarfBuzzShaper(gfxFont *aFont)
+    : gfxFontShaper(aFont),
+      mHBFace(aFont->GetFontEntry()->GetHBFace()),
+      mHBFont(nullptr),
+      mKernTable(nullptr),
+      mHmtxTable(nullptr),
+      mVmtxTable(nullptr),
+      mVORGTable(nullptr),
+      mLocaTable(nullptr),
+      mGlyfTable(nullptr),
+      mCmapTable(nullptr),
+      mCmapFormat(-1),
+      mSubtableOffset(0),
+      mUVSTableOffset(0),
+      mNumLongHMetrics(0),
+      mNumLongVMetrics(0),
+      mUseFontGetGlyph(aFont->ProvidesGetGlyph()),
+      mUseFontGlyphWidths(false),
+      mInitialized(false),
+      mVerticalInitialized(false),
+      mLoadedLocaGlyf(false),
+      mLocaLongOffsets(false)
+{
+}
+
+gfxHarfBuzzShaper::~gfxHarfBuzzShaper()
+{
+    if (mCmapTable) {
+        hb_blob_destroy(mCmapTable);
+    }
+    if (mHmtxTable) {
+        hb_blob_destroy(mHmtxTable);
+    }
+    if (mKernTable) {
+        hb_blob_destroy(mKernTable);
+    }
+    if (mVmtxTable) {
+        hb_blob_destroy(mVmtxTable);
+    }
+    if (mVORGTable) {
+        hb_blob_destroy(mVORGTable);
+    }
+    if (mLocaTable) {
+        hb_blob_destroy(mLocaTable);
+    }
+    if (mGlyfTable) {
+        hb_blob_destroy(mGlyfTable);
+    }
+    if (mHBFont) {
+        hb_font_destroy(mHBFont);
+    }
+    if (mHBFace) {
+        hb_face_destroy(mHBFace);
+    }
+}
+
+#define UNICODE_BMP_LIMIT 0x10000
+
+hb_codepoint_t
+gfxHarfBuzzShaper::GetNominalGlyph(hb_codepoint_t unicode) const
+{
+    hb_codepoint_t gid = 0;
+
+    if (mUseFontGetGlyph) {
+        gid = mFont->GetGlyph(unicode, 0);
+    } else {
+        // we only instantiate a harfbuzz shaper if there's a cmap available
+        NS_ASSERTION(mFont->GetFontEntry()->HasCmapTable(),
+                     "we cannot be using this font!");
+
+        NS_ASSERTION(mCmapTable && (mCmapFormat > 0) && (mSubtableOffset > 0),
+                     "cmap data not correctly set up, expect disaster");
+
+        const uint8_t* data =
+            (const uint8_t*)hb_blob_get_data(mCmapTable, nullptr);
+
+        switch (mCmapFormat) {
+        case 4:
+            gid = unicode < UNICODE_BMP_LIMIT ?
+                gfxFontUtils::MapCharToGlyphFormat4(data + mSubtableOffset,
+                                                    unicode) : 0;
+            break;
+        case 10:
+            gid = gfxFontUtils::MapCharToGlyphFormat10(data + mSubtableOffset,
+                                                       unicode);
+            break;
+        case 12:
+            gid = gfxFontUtils::MapCharToGlyphFormat12(data + mSubtableOffset,
+                                                       unicode);
+            break;
+        default:
+            NS_WARNING("unsupported cmap format, glyphs will be missing");
+            break;
+        }
+    }
+
+    if (!gid) {
+        // if there's no glyph for &nbsp;, just use the space glyph instead
+        if (unicode == 0xA0) {
+            gid = mFont->GetSpaceGlyph();
+        }
+    }
+
+    return gid;
+}
+
+hb_codepoint_t
+gfxHarfBuzzShaper::GetVariationGlyph(hb_codepoint_t unicode,
+                                     hb_codepoint_t variation_selector) const
+{
+    if (mUseFontGetGlyph) {
+        return mFont->GetGlyph(unicode, variation_selector);
+    }
+
+    NS_ASSERTION(mFont->GetFontEntry()->HasCmapTable(),
+                 "we cannot be using this font!");
+    NS_ASSERTION(mCmapTable && (mCmapFormat > 0) && (mSubtableOffset > 0),
+                 "cmap data not correctly set up, expect disaster");
+
+    const uint8_t* data =
+        (const uint8_t*)hb_blob_get_data(mCmapTable, nullptr);
+
+    if (mUVSTableOffset) {
+        hb_codepoint_t gid =
+            gfxFontUtils::MapUVSToGlyphFormat14(data + mUVSTableOffset,
+                                                unicode, variation_selector);
+        if (gid) {
+            return gid;
+        }
+    }
+
+    uint32_t compat =
+        gfxFontUtils::GetUVSFallback(unicode, variation_selector);
+    if (compat) {
+        switch (mCmapFormat) {
+        case 4:
+            if (compat < UNICODE_BMP_LIMIT) {
+                return gfxFontUtils::MapCharToGlyphFormat4(data + mSubtableOffset,
+                                                           compat);
+            }
+            break;
+        case 10:
+            return gfxFontUtils::MapCharToGlyphFormat10(data + mSubtableOffset,
+                                                        compat);
+            break;
+        case 12:
+            return gfxFontUtils::MapCharToGlyphFormat12(data + mSubtableOffset,
+                                                        compat);
+            break;
+        }
+    }
+
+    return 0;
+}
+
+static int
+VertFormsGlyphCompare(const void* aKey, const void* aElem)
+{
+    return int(*((hb_codepoint_t*)(aKey))) - int(*((uint16_t*)(aElem)));
+}
+
+// Return a vertical presentation-form codepoint corresponding to the
+// given Unicode value, or 0 if no such form is available.
+static hb_codepoint_t
+GetVerticalPresentationForm(hb_codepoint_t unicode)
+{
+    static const uint16_t sVerticalForms[][2] = {
+        { 0x2013, 0xfe32 }, // EN DASH
+        { 0x2014, 0xfe31 }, // EM DASH
+        { 0x2025, 0xfe30 }, // TWO DOT LEADER
+        { 0x2026, 0xfe19 }, // HORIZONTAL ELLIPSIS
+        { 0x3001, 0xfe11 }, // IDEOGRAPHIC COMMA
+        { 0x3002, 0xfe12 }, // IDEOGRAPHIC FULL STOP
+        { 0x3008, 0xfe3f }, // LEFT ANGLE BRACKET
+        { 0x3009, 0xfe40 }, // RIGHT ANGLE BRACKET
+        { 0x300a, 0xfe3d }, // LEFT DOUBLE ANGLE BRACKET
+        { 0x300b, 0xfe3e }, // RIGHT DOUBLE ANGLE BRACKET
+        { 0x300c, 0xfe41 }, // LEFT CORNER BRACKET
+        { 0x300d, 0xfe42 }, // RIGHT CORNER BRACKET
+        { 0x300e, 0xfe43 }, // LEFT WHITE CORNER BRACKET
+        { 0x300f, 0xfe44 }, // RIGHT WHITE CORNER BRACKET
+        { 0x3010, 0xfe3b }, // LEFT BLACK LENTICULAR BRACKET
+        { 0x3011, 0xfe3c }, // RIGHT BLACK LENTICULAR BRACKET
+        { 0x3014, 0xfe39 }, // LEFT TORTOISE SHELL BRACKET
+        { 0x3015, 0xfe3a }, // RIGHT TORTOISE SHELL BRACKET
+        { 0x3016, 0xfe17 }, // LEFT WHITE LENTICULAR BRACKET
+        { 0x3017, 0xfe18 }, // RIGHT WHITE LENTICULAR BRACKET
+        { 0xfe4f, 0xfe34 }, // WAVY LOW LINE
+        { 0xff01, 0xfe15 }, // FULLWIDTH EXCLAMATION MARK
+        { 0xff08, 0xfe35 }, // FULLWIDTH LEFT PARENTHESIS
+        { 0xff09, 0xfe36 }, // FULLWIDTH RIGHT PARENTHESIS
+        { 0xff0c, 0xfe10 }, // FULLWIDTH COMMA
+        { 0xff1a, 0xfe13 }, // FULLWIDTH COLON
+        { 0xff1b, 0xfe14 }, // FULLWIDTH SEMICOLON
+        { 0xff1f, 0xfe16 }, // FULLWIDTH QUESTION MARK
+        { 0xff3b, 0xfe47 }, // FULLWIDTH LEFT SQUARE BRACKET
+        { 0xff3d, 0xfe48 }, // FULLWIDTH RIGHT SQUARE BRACKET
+        { 0xff3f, 0xfe33 }, // FULLWIDTH LOW LINE
+        { 0xff5b, 0xfe37 }, // FULLWIDTH LEFT CURLY BRACKET
+        { 0xff5d, 0xfe38 }  // FULLWIDTH RIGHT CURLY BRACKET
+    };
+    const uint16_t* charPair =
+        static_cast<const uint16_t*>(bsearch(&unicode,
+                                             sVerticalForms,
+                                             ArrayLength(sVerticalForms),
+                                             sizeof(sVerticalForms[0]),
+                                             VertFormsGlyphCompare));
+    return charPair ? charPair[1] : 0;
+}
+
+static hb_bool_t
+HBGetNominalGlyph(hb_font_t *font, void *font_data,
+                  hb_codepoint_t unicode,
+                  hb_codepoint_t *glyph,
+                  void *user_data)
+{
+    const gfxHarfBuzzShaper::FontCallbackData *fcd =
+        static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
+
+    if (fcd->mShaper->UseVerticalPresentationForms()) {
+        hb_codepoint_t verticalForm = GetVerticalPresentationForm(unicode);
+        if (verticalForm) {
+            *glyph = fcd->mShaper->GetNominalGlyph(verticalForm);
+            if (*glyph != 0) {
+                return true;
+            }
+        }
+        // fall back to the non-vertical form if we didn't find an alternate
+    }
+
+    *glyph = fcd->mShaper->GetNominalGlyph(unicode);
+    return *glyph != 0;
+}
+
+static hb_bool_t
+HBGetVariationGlyph(hb_font_t *font, void *font_data,
+                    hb_codepoint_t unicode, hb_codepoint_t variation_selector,
+                    hb_codepoint_t *glyph,
+                    void *user_data)
+{
+    const gfxHarfBuzzShaper::FontCallbackData *fcd =
+        static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
+
+    if (fcd->mShaper->UseVerticalPresentationForms()) {
+        hb_codepoint_t verticalForm = GetVerticalPresentationForm(unicode);
+        if (verticalForm) {
+            *glyph = fcd->mShaper->GetVariationGlyph(verticalForm,
+                                                     variation_selector);
+            if (*glyph != 0) {
+                return true;
+            }
+        }
+        // fall back to the non-vertical form if we didn't find an alternate
+    }
+
+    *glyph = fcd->mShaper->GetVariationGlyph(unicode, variation_selector);
+    return *glyph != 0;
+}
+
+// Glyph metrics structures, shared (with appropriate reinterpretation of
+// field names) by horizontal and vertical metrics tables.
+struct LongMetric {
+    AutoSwap_PRUint16    advanceWidth; // or advanceHeight, when vertical
+    AutoSwap_PRInt16     lsb;          // or tsb, when vertical
+};
+
+struct GlyphMetrics {
+    LongMetric           metrics[1]; // actually numberOfLongMetrics
+// the variable-length metrics[] array is immediately followed by:
+//  AutoSwap_PRUint16    leftSideBearing[];
+};
+
+hb_position_t
+gfxHarfBuzzShaper::GetGlyphHAdvance(hb_codepoint_t glyph) const
+{
+    // font did not implement GetGlyphWidth, so get an unhinted value
+    // directly from the font tables
+
+    NS_ASSERTION((mNumLongHMetrics > 0) && mHmtxTable != nullptr,
+                 "font is lacking metrics, we shouldn't be here");
+
+    if (glyph >= uint32_t(mNumLongHMetrics)) {
+        glyph = mNumLongHMetrics - 1;
+    }
+
+    // glyph must be valid now, because we checked during initialization
+    // that mNumLongHMetrics is > 0, and that the metrics table is large enough
+    // to contain mNumLongHMetrics records
+    const GlyphMetrics* metrics =
+        reinterpret_cast<const GlyphMetrics*>(hb_blob_get_data(mHmtxTable,
+                                                               nullptr));
+    return FloatToFixed(mFont->FUnitsToDevUnitsFactor() *
+                        uint16_t(metrics->metrics[glyph].advanceWidth));
+}
+
+hb_position_t
+gfxHarfBuzzShaper::GetGlyphVAdvance(hb_codepoint_t glyph) const
+{
+    if (!mVmtxTable) {
+        // Must be a "vertical" font that doesn't actually have vertical metrics;
+        // use a fixed advance.
+        return FloatToFixed(mFont->GetMetrics(gfxFont::eVertical).aveCharWidth);
+    }
+
+    NS_ASSERTION(mNumLongVMetrics > 0,
+                 "font is lacking metrics, we shouldn't be here");
+
+    if (glyph >= uint32_t(mNumLongVMetrics)) {
+        glyph = mNumLongVMetrics - 1;
+    }
+
+    // glyph must be valid now, because we checked during initialization
+    // that mNumLongVMetrics is > 0, and that the metrics table is large enough
+    // to contain mNumLongVMetrics records
+    const GlyphMetrics* metrics =
+        reinterpret_cast<const GlyphMetrics*>(hb_blob_get_data(mVmtxTable,
+                                                               nullptr));
+    return FloatToFixed(mFont->FUnitsToDevUnitsFactor() *
+                        uint16_t(metrics->metrics[glyph].advanceWidth));
+}
+
+/* static */
+hb_position_t
+gfxHarfBuzzShaper::HBGetGlyphHAdvance(hb_font_t *font, void *font_data,
+                                      hb_codepoint_t glyph, void *user_data)
+{
+    const gfxHarfBuzzShaper::FontCallbackData *fcd =
+        static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
+    gfxFont *gfxfont = fcd->mShaper->GetFont();
+    if (gfxfont->ProvidesGlyphWidths()) {
+        return gfxfont->GetGlyphWidth(*fcd->mDrawTarget, glyph);
+    }
+    return fcd->mShaper->GetGlyphHAdvance(glyph);
+}
+
+/* static */
+hb_position_t
+gfxHarfBuzzShaper::HBGetGlyphVAdvance(hb_font_t *font, void *font_data,
+                                      hb_codepoint_t glyph, void *user_data)
+{
+    const gfxHarfBuzzShaper::FontCallbackData *fcd =
+        static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
+    // Currently, we don't offer gfxFont subclasses a method to override this
+    // and provide hinted platform-specific vertical advances (analogous to the
+    // GetGlyphWidth method for horizontal advances). If that proves necessary,
+    // we'll add a new gfxFont method and call it from here.
+    return fcd->mShaper->GetGlyphVAdvance(glyph);
+}
+
+struct VORG {
+    AutoSwap_PRUint16 majorVersion;
+    AutoSwap_PRUint16 minorVersion;
+    AutoSwap_PRInt16  defaultVertOriginY;
+    AutoSwap_PRUint16 numVertOriginYMetrics;
+};
+
+struct VORGrec {
+    AutoSwap_PRUint16 glyphIndex;
+    AutoSwap_PRInt16  vertOriginY;
+};
+
+/* static */
+hb_bool_t
+gfxHarfBuzzShaper::HBGetGlyphVOrigin(hb_font_t *font, void *font_data,
+                                     hb_codepoint_t glyph,
+                                     hb_position_t *x, hb_position_t *y,
+                                     void *user_data)
+{
+    const gfxHarfBuzzShaper::FontCallbackData *fcd =
+        static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
+    fcd->mShaper->GetGlyphVOrigin(glyph, x, y);
+    return true;
+}
+
+void
+gfxHarfBuzzShaper::GetGlyphVOrigin(hb_codepoint_t aGlyph,
+                                   hb_position_t *aX, hb_position_t *aY) const
+{
+    *aX = -0.5 * GetGlyphHAdvance(aGlyph);
+
+    if (mVORGTable) {
+        // We checked in Initialize() that the VORG table is safely readable,
+        // so no length/bounds-check needed here.
+        const VORG* vorg =
+            reinterpret_cast<const VORG*>(hb_blob_get_data(mVORGTable, nullptr));
+
+        const VORGrec *lo = reinterpret_cast<const VORGrec*>(vorg + 1);
+        const VORGrec *hi = lo + uint16_t(vorg->numVertOriginYMetrics);
+        const VORGrec *limit = hi;
+        while (lo < hi) {
+            const VORGrec *mid = lo + (hi - lo) / 2;
+            if (uint16_t(mid->glyphIndex) < aGlyph) {
+                lo = mid + 1;
+            } else {
+                hi = mid;
+            }
+        }
+
+        if (lo < limit && uint16_t(lo->glyphIndex) == aGlyph) {
+            *aY = -FloatToFixed(GetFont()->FUnitsToDevUnitsFactor() *
+                                int16_t(lo->vertOriginY));
+        } else {
+            *aY = -FloatToFixed(GetFont()->FUnitsToDevUnitsFactor() *
+                                int16_t(vorg->defaultVertOriginY));
+        }
+        return;
+    }
+
+    if (mVmtxTable) {
+        bool emptyGlyf;
+        const Glyf *glyf = FindGlyf(aGlyph, &emptyGlyf);
+        if (glyf) {
+            if (emptyGlyf) {
+                *aY = 0;
+                return;
+            }
+
+            const GlyphMetrics* metrics =
+                reinterpret_cast<const GlyphMetrics*>
+                    (hb_blob_get_data(mVmtxTable, nullptr));
+            int16_t lsb;
+            if (aGlyph < hb_codepoint_t(mNumLongVMetrics)) {
+                // Glyph is covered by the first (advance & sidebearing) array
+                lsb = int16_t(metrics->metrics[aGlyph].lsb);
+            } else {
+                // Glyph is covered by the second (sidebearing-only) array
+                const AutoSwap_PRInt16* sidebearings =
+                    reinterpret_cast<const AutoSwap_PRInt16*>
+                        (&metrics->metrics[mNumLongVMetrics]);
+                lsb = int16_t(sidebearings[aGlyph - mNumLongVMetrics]);
+            }
+            *aY = -FloatToFixed(mFont->FUnitsToDevUnitsFactor() *
+                                (lsb + int16_t(glyf->yMax)));
+            return;
+        } else {
+            // XXX TODO: not a truetype font; need to get glyph extents
+            // via some other API?
+            // For now, fall through to default code below.
+        }
+    }
+
+    // XXX should we consider using OS/2 sTypo* metrics if available?
+
+    gfxFontEntry::AutoTable hheaTable(GetFont()->GetFontEntry(),
+                                      TRUETYPE_TAG('h','h','e','a'));
+    if (hheaTable) {
+        uint32_t len;
+        const MetricsHeader* hhea =
+            reinterpret_cast<const MetricsHeader*>(hb_blob_get_data(hheaTable,
+                                                                    &len));
+        if (len >= sizeof(MetricsHeader)) {
+            // divide up the default advance we're using (1em) in proportion
+            // to ascender:descender from the hhea table
+            int16_t a = int16_t(hhea->ascender);
+            int16_t d = int16_t(hhea->descender);
+            *aY = -FloatToFixed(GetFont()->GetAdjustedSize() * a / (a - d));
+            return;
+        }
+    }
+
+    NS_NOTREACHED("we shouldn't be here!");
+    *aY = -FloatToFixed(GetFont()->GetAdjustedSize() / 2);
+}
+
+static hb_bool_t
+HBGetGlyphExtents(hb_font_t *font, void *font_data,
+                  hb_codepoint_t glyph,
+                  hb_glyph_extents_t *extents,
+                  void *user_data)
+{
+    const gfxHarfBuzzShaper::FontCallbackData *fcd =
+        static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
+    return fcd->mShaper->GetGlyphExtents(glyph, extents);
+}
+
+// Find the data for glyph ID |aGlyph| in the 'glyf' table, if present.
+// Returns null if not found, otherwise pointer to the beginning of the
+// glyph's data. Sets aEmptyGlyf true if there is no actual data;
+// otherwise, it's guaranteed that we can read at least the bounding box.
+const gfxHarfBuzzShaper::Glyf*
+gfxHarfBuzzShaper::FindGlyf(hb_codepoint_t aGlyph, bool *aEmptyGlyf) const
+{
+    if (!mLoadedLocaGlyf) {
+        mLoadedLocaGlyf = true; // only try this once; if it fails, this
+                                // isn't a truetype font
+        gfxFontEntry *entry = mFont->GetFontEntry();
+        uint32_t len;
+        gfxFontEntry::AutoTable headTable(entry,
+                                          TRUETYPE_TAG('h','e','a','d'));
+        if (!headTable) {
+            return nullptr;
+        }
+        const HeadTable* head =
+            reinterpret_cast<const HeadTable*>(hb_blob_get_data(headTable,
+                                                                &len));
+        if (len < sizeof(HeadTable)) {
+            return nullptr;
+        }
+        mLocaLongOffsets = int16_t(head->indexToLocFormat) > 0;
+        mLocaTable = entry->GetFontTable(TRUETYPE_TAG('l','o','c','a'));
+        mGlyfTable = entry->GetFontTable(TRUETYPE_TAG('g','l','y','f'));
+    }
+
+    if (!mLocaTable || !mGlyfTable) {
+        // it's not a truetype font
+        return nullptr;
+    }
+
+    uint32_t offset; // offset of glyph record in the 'glyf' table
+    uint32_t len;
+    const char* data = hb_blob_get_data(mLocaTable, &len);
+    if (mLocaLongOffsets) {
+        if ((aGlyph + 1) * sizeof(AutoSwap_PRUint32) > len) {
+            return nullptr;
+        }
+        const AutoSwap_PRUint32* offsets =
+            reinterpret_cast<const AutoSwap_PRUint32*>(data);
+        offset = offsets[aGlyph];
+        *aEmptyGlyf = (offset == uint16_t(offsets[aGlyph + 1]));
+    } else {
+        if ((aGlyph + 1) * sizeof(AutoSwap_PRUint16) > len) {
+            return nullptr;
+        }
+        const AutoSwap_PRUint16* offsets =
+            reinterpret_cast<const AutoSwap_PRUint16*>(data);
+        offset = uint16_t(offsets[aGlyph]);
+        *aEmptyGlyf = (offset == uint16_t(offsets[aGlyph + 1]));
+        offset *= 2;
+    }
+
+    data = hb_blob_get_data(mGlyfTable, &len);
+    if (offset + sizeof(Glyf) > len) {
+        return nullptr;
+    }
+
+    return reinterpret_cast<const Glyf*>(data + offset);
+}
+
+hb_bool_t
+gfxHarfBuzzShaper::GetGlyphExtents(hb_codepoint_t aGlyph,
+                                   hb_glyph_extents_t *aExtents) const
+{
+    bool emptyGlyf;
+    const Glyf *glyf = FindGlyf(aGlyph, &emptyGlyf);
+    if (!glyf) {
+        // TODO: for non-truetype fonts, get extents some other way?
+        return false;
+    }
+
+    if (emptyGlyf) {
+        aExtents->x_bearing = 0;
+        aExtents->y_bearing = 0;
+        aExtents->width = 0;
+        aExtents->height = 0;
+        return true;
+    }
+
+    double f = mFont->FUnitsToDevUnitsFactor();
+    aExtents->x_bearing = FloatToFixed(int16_t(glyf->xMin) * f);
+    aExtents->width =
+        FloatToFixed((int16_t(glyf->xMax) - int16_t(glyf->xMin)) * f);
+
+    // Our y-coordinates are positive-downwards, whereas harfbuzz assumes
+    // positive-upwards; hence the apparently-reversed subtractions here.
+    aExtents->y_bearing =
+        FloatToFixed(int16_t(glyf->yMax) * f -
+                     mFont->GetHorizontalMetrics().emAscent);
+    aExtents->height =
+        FloatToFixed((int16_t(glyf->yMin) - int16_t(glyf->yMax)) * f);
+
+    return true;
+}
+
+static hb_bool_t
+HBGetContourPoint(hb_font_t *font, void *font_data,
+                  unsigned int point_index, hb_codepoint_t glyph,
+                  hb_position_t *x, hb_position_t *y,
+                  void *user_data)
+{
+    /* not yet implemented - no support for used of hinted contour points
+       to fine-tune anchor positions in GPOS AnchorFormat2 */
+    return false;
+}
+
+struct KernHeaderFmt0 {
+    AutoSwap_PRUint16 nPairs;
+    AutoSwap_PRUint16 searchRange;
+    AutoSwap_PRUint16 entrySelector;
+    AutoSwap_PRUint16 rangeShift;
+};
+
+struct KernPair {
+    AutoSwap_PRUint16 left;
+    AutoSwap_PRUint16 right;
+    AutoSwap_PRInt16  value;
+};
+
+// Find a kern pair in a Format 0 subtable.
+// The aSubtable parameter points to the subtable itself, NOT its header,
+// as the header structure differs between Windows and Mac (v0 and v1.0)
+// versions of the 'kern' table.
+// aSubtableLen is the length of the subtable EXCLUDING its header.
+// If the pair <aFirstGlyph,aSecondGlyph> is found, the kerning value is
+// added to aValue, so that multiple subtables can accumulate a total
+// kerning value for a given pair.
+static void
+GetKernValueFmt0(const void* aSubtable,
+                 uint32_t aSubtableLen,
+                 uint16_t aFirstGlyph,
+                 uint16_t aSecondGlyph,
+                 int32_t& aValue,
+                 bool     aIsOverride = false,
+                 bool     aIsMinimum = false)
+{
+    const KernHeaderFmt0* hdr =
+        reinterpret_cast<const KernHeaderFmt0*>(aSubtable);
+
+    const KernPair *lo = reinterpret_cast<const KernPair*>(hdr + 1);
+    const KernPair *hi = lo + uint16_t(hdr->nPairs);
+    const KernPair *limit = hi;
+
+    if (reinterpret_cast<const char*>(aSubtable) + aSubtableLen <
+        reinterpret_cast<const char*>(hi)) {
+        // subtable is not large enough to contain the claimed number
+        // of kern pairs, so just ignore it
+        return;
+    }
+
+#define KERN_PAIR_KEY(l,r) (uint32_t((uint16_t(l) << 16) + uint16_t(r)))
+
+    uint32_t key = KERN_PAIR_KEY(aFirstGlyph, aSecondGlyph);
+    while (lo < hi) {
+        const KernPair *mid = lo + (hi - lo) / 2;
+        if (KERN_PAIR_KEY(mid->left, mid->right) < key) {
+            lo = mid + 1;
+        } else {
+            hi = mid;
+        }
+    }
+
+    if (lo < limit && KERN_PAIR_KEY(lo->left, lo->right) == key) {
+        if (aIsOverride) {
+            aValue = int16_t(lo->value);
+        } else if (aIsMinimum) {
+            aValue = std::max(aValue, int32_t(lo->value));
+        } else {
+            aValue += int16_t(lo->value);
+        }
+    }
+}
+
+// Get kerning value from Apple (version 1.0) kern table,
+// subtable format 2 (simple N x M array of kerning values)
+
+// See http://developer.apple.com/fonts/TTRefMan/RM06/Chap6kern.html
+// for details of version 1.0 format 2 subtable.
+
+struct KernHeaderVersion1Fmt2 {
+    KernTableSubtableHeaderVersion1 header;
+    AutoSwap_PRUint16 rowWidth;
+    AutoSwap_PRUint16 leftOffsetTable;
+    AutoSwap_PRUint16 rightOffsetTable;
+    AutoSwap_PRUint16 array;
+};
+
+struct KernClassTableHdr {
+    AutoSwap_PRUint16 firstGlyph;
+    AutoSwap_PRUint16 nGlyphs;
+    AutoSwap_PRUint16 offsets[1]; // actually an array of nGlyphs entries
+};
+
+static int16_t
+GetKernValueVersion1Fmt2(const void* aSubtable,
+                         uint32_t aSubtableLen,
+                         uint16_t aFirstGlyph,
+                         uint16_t aSecondGlyph)
+{
+    if (aSubtableLen < sizeof(KernHeaderVersion1Fmt2)) {
+        return 0;
+    }
+
+    const char* base = reinterpret_cast<const char*>(aSubtable);
+    const char* subtableEnd = base + aSubtableLen;
+
+    const KernHeaderVersion1Fmt2* h =
+        reinterpret_cast<const KernHeaderVersion1Fmt2*>(aSubtable);
+    uint32_t offset = h->array;
+
+    const KernClassTableHdr* leftClassTable =
+        reinterpret_cast<const KernClassTableHdr*>(base +
+                                                   uint16_t(h->leftOffsetTable));
+    if (reinterpret_cast<const char*>(leftClassTable) +
+        sizeof(KernClassTableHdr) > subtableEnd) {
+        return 0;
+    }
+    if (aFirstGlyph >= uint16_t(leftClassTable->firstGlyph)) {
+        aFirstGlyph -= uint16_t(leftClassTable->firstGlyph);
+        if (aFirstGlyph < uint16_t(leftClassTable->nGlyphs)) {
+            if (reinterpret_cast<const char*>(leftClassTable) +
+                sizeof(KernClassTableHdr) +
+                aFirstGlyph * sizeof(uint16_t) >= subtableEnd) {
+                return 0;
+            }
+            offset = uint16_t(leftClassTable->offsets[aFirstGlyph]);
+        }
+    }
+
+    const KernClassTableHdr* rightClassTable =
+        reinterpret_cast<const KernClassTableHdr*>(base +
+                                                   uint16_t(h->rightOffsetTable));
+    if (reinterpret_cast<const char*>(rightClassTable) +
+        sizeof(KernClassTableHdr) > subtableEnd) {
+        return 0;
+    }
+    if (aSecondGlyph >= uint16_t(rightClassTable->firstGlyph)) {
+        aSecondGlyph -= uint16_t(rightClassTable->firstGlyph);
+        if (aSecondGlyph < uint16_t(rightClassTable->nGlyphs)) {
+            if (reinterpret_cast<const char*>(rightClassTable) +
+                sizeof(KernClassTableHdr) +
+                aSecondGlyph * sizeof(uint16_t) >= subtableEnd) {
+                return 0;
+            }
+            offset += uint16_t(rightClassTable->offsets[aSecondGlyph]);
+        }
+    }
+
+    const AutoSwap_PRInt16* pval =
+        reinterpret_cast<const AutoSwap_PRInt16*>(base + offset);
+    if (reinterpret_cast<const char*>(pval + 1) >= subtableEnd) {
+        return 0;
+    }
+    return *pval;
+}
+
+// Get kerning value from Apple (version 1.0) kern table,
+// subtable format 3 (simple N x M array of kerning values)
+
+// See http://developer.apple.com/fonts/TTRefMan/RM06/Chap6kern.html
+// for details of version 1.0 format 3 subtable.
+
+struct KernHeaderVersion1Fmt3 {
+    KernTableSubtableHeaderVersion1 header;
+    AutoSwap_PRUint16 glyphCount;
+    uint8_t kernValueCount;
+    uint8_t leftClassCount;
+    uint8_t rightClassCount;
+    uint8_t flags;
+};
+
+static int16_t
+GetKernValueVersion1Fmt3(const void* aSubtable,
+                         uint32_t aSubtableLen,
+                         uint16_t aFirstGlyph,
+                         uint16_t aSecondGlyph)
+{
+    // check that we can safely read the header fields
+    if (aSubtableLen < sizeof(KernHeaderVersion1Fmt3)) {
+        return 0;
+    }
+
+    const KernHeaderVersion1Fmt3* hdr =
+        reinterpret_cast<const KernHeaderVersion1Fmt3*>(aSubtable);
+    if (hdr->flags != 0) {
+        return 0;
+    }
+
+    uint16_t glyphCount = hdr->glyphCount;
+
+    // check that table is large enough for the arrays
+    if (sizeof(KernHeaderVersion1Fmt3) +
+        hdr->kernValueCount * sizeof(int16_t) +
+        glyphCount + glyphCount +
+        hdr->leftClassCount * hdr->rightClassCount > aSubtableLen) {
+        return 0;
+    }
+        
+    if (aFirstGlyph >= glyphCount || aSecondGlyph >= glyphCount) {
+        // glyphs are out of range for the class tables
+        return 0;
+    }
+
+    // get pointers to the four arrays within the subtable
+    const AutoSwap_PRInt16* kernValue =
+        reinterpret_cast<const AutoSwap_PRInt16*>(hdr + 1);
+    const uint8_t* leftClass =
+        reinterpret_cast<const uint8_t*>(kernValue + hdr->kernValueCount);
+    const uint8_t* rightClass = leftClass + glyphCount;
+    const uint8_t* kernIndex = rightClass + glyphCount;
+
+    uint8_t lc = leftClass[aFirstGlyph];
+    uint8_t rc = rightClass[aSecondGlyph];
+    if (lc >= hdr->leftClassCount || rc >= hdr->rightClassCount) {
+        return 0;
+    }
+
+    uint8_t ki = kernIndex[leftClass[aFirstGlyph] * hdr->rightClassCount +
+                           rightClass[aSecondGlyph]];
+    if (ki >= hdr->kernValueCount) {
+        return 0;
+    }
+
+    return kernValue[ki];
+}
+
+#define KERN0_COVERAGE_HORIZONTAL   0x0001
+#define KERN0_COVERAGE_MINIMUM      0x0002
+#define KERN0_COVERAGE_CROSS_STREAM 0x0004
+#define KERN0_COVERAGE_OVERRIDE     0x0008
+#define KERN0_COVERAGE_RESERVED     0x00F0
+
+#define KERN1_COVERAGE_VERTICAL     0x8000
+#define KERN1_COVERAGE_CROSS_STREAM 0x4000
+#define KERN1_COVERAGE_VARIATION    0x2000
+#define KERN1_COVERAGE_RESERVED     0x1F00
+
+hb_position_t
+gfxHarfBuzzShaper::GetHKerning(uint16_t aFirstGlyph,
+                               uint16_t aSecondGlyph) const
+{
+    // We want to ignore any kern pairs involving <space>, because we are
+    // handling words in isolation, the only space characters seen here are
+    // the ones artificially added by the textRun code.
+    uint32_t spaceGlyph = mFont->GetSpaceGlyph();
+    if (aFirstGlyph == spaceGlyph || aSecondGlyph == spaceGlyph) {
+        return 0;
+    }
+
+    if (!mKernTable) {
+        mKernTable = mFont->GetFontEntry()->GetFontTable(TRUETYPE_TAG('k','e','r','n'));
+        if (!mKernTable) {
+            mKernTable = hb_blob_get_empty();
+        }
+    }
+
+    uint32_t len;
+    const char* base = hb_blob_get_data(mKernTable, &len);
+    if (len < sizeof(KernTableVersion0)) {
+        return 0;
+    }
+    int32_t value = 0;
+
+    // First try to interpret as "version 0" kern table
+    // (see http://www.microsoft.com/typography/otspec/kern.htm)
+    const KernTableVersion0* kern0 =
+        reinterpret_cast<const KernTableVersion0*>(base);
+    if (uint16_t(kern0->version) == 0) {
+        uint16_t nTables = kern0->nTables;
+        uint32_t offs = sizeof(KernTableVersion0);
+        for (uint16_t i = 0; i < nTables; ++i) {
+            if (offs + sizeof(KernTableSubtableHeaderVersion0) > len) {
+                break;
+            }
+            const KernTableSubtableHeaderVersion0* st0 =
+                reinterpret_cast<const KernTableSubtableHeaderVersion0*>
+                                (base + offs);
+            uint16_t subtableLen = uint16_t(st0->length);
+            if (offs + subtableLen > len) {
+                break;
+            }
+            offs += subtableLen;
+            uint16_t coverage = st0->coverage;
+            if (!(coverage & KERN0_COVERAGE_HORIZONTAL)) {
+                // we only care about horizontal kerning (for now)
+                continue;
+            }
+            if (coverage &
+                (KERN0_COVERAGE_CROSS_STREAM | KERN0_COVERAGE_RESERVED)) {
+                // we don't support cross-stream kerning, and
+                // reserved bits should be zero;
+                // ignore the subtable if not
+                continue;
+            }
+            uint8_t format = (coverage >> 8);
+            switch (format) {
+            case 0:
+                GetKernValueFmt0(st0 + 1, subtableLen - sizeof(*st0),
+                                 aFirstGlyph, aSecondGlyph, value,
+                                 (coverage & KERN0_COVERAGE_OVERRIDE) != 0,
+                                 (coverage & KERN0_COVERAGE_MINIMUM) != 0);
+                break;
+            default:
+                // TODO: implement support for other formats,
+                // if they're ever used in practice
+#if DEBUG
+                {
+                    char buf[1024];
+                    SprintfLiteral(buf, "unknown kern subtable in %s: "
+                                        "ver 0 format %d\n",
+                                   NS_ConvertUTF16toUTF8(mFont->GetName()).get(),
+                                   format);
+                    NS_WARNING(buf);
+                }
+#endif
+                break;
+            }
+        }
+    } else {
+        // It wasn't a "version 0" table; check if it is Apple version 1.0
+        // (see http://developer.apple.com/fonts/TTRefMan/RM06/Chap6kern.html)
+        const KernTableVersion1* kern1 =
+            reinterpret_cast<const KernTableVersion1*>(base);
+        if (uint32_t(kern1->version) == 0x00010000) {
+            uint32_t nTables = kern1->nTables;
+            uint32_t offs = sizeof(KernTableVersion1);
+            for (uint32_t i = 0; i < nTables; ++i) {
+                if (offs + sizeof(KernTableSubtableHeaderVersion1) > len) {
+                    break;
+                }
+                const KernTableSubtableHeaderVersion1* st1 =
+                    reinterpret_cast<const KernTableSubtableHeaderVersion1*>
+                                    (base + offs);
+                uint32_t subtableLen = uint32_t(st1->length);
+                offs += subtableLen;
+                uint16_t coverage = st1->coverage;
+                if (coverage &
+                    (KERN1_COVERAGE_VERTICAL     |
+                     KERN1_COVERAGE_CROSS_STREAM |
+                     KERN1_COVERAGE_VARIATION    |
+                     KERN1_COVERAGE_RESERVED)) {
+                    // we only care about horizontal kerning (for now),
+                    // we don't support cross-stream kerning,
+                    // we don't support variations,
+                    // reserved bits should be zero;
+                    // ignore the subtable if not
+                    continue;
+                }
+                uint8_t format = (coverage & 0xff);
+                switch (format) {
+                case 0:
+                    GetKernValueFmt0(st1 + 1, subtableLen - sizeof(*st1),
+                                     aFirstGlyph, aSecondGlyph, value);
+                    break;
+                case 2:
+                    value = GetKernValueVersion1Fmt2(st1, subtableLen,
+                                                     aFirstGlyph, aSecondGlyph);
+                    break;
+                case 3:
+                    value = GetKernValueVersion1Fmt3(st1, subtableLen,
+                                                     aFirstGlyph, aSecondGlyph);
+                    break;
+                default:
+                    // TODO: implement support for other formats.
+                    // Note that format 1 cannot be supported here,
+                    // as it requires the full glyph array to run the FSM,
+                    // not just the current glyph pair.
+#if DEBUG
+                    {
+                        char buf[1024];
+                        SprintfLiteral(buf, "unknown kern subtable in %s: "
+                                            "ver 0 format %d\n",
+                                       NS_ConvertUTF16toUTF8(mFont->GetName()).get(),
+                                       format);
+                        NS_WARNING(buf);
+                    }
+#endif
+                    break;
+                }
+            }
+        }
+    }
+
+    if (value != 0) {
+        return FloatToFixed(mFont->FUnitsToDevUnitsFactor() * value);
+    }
+    return 0;
+}
+
+static hb_position_t
+HBGetHKerning(hb_font_t *font, void *font_data,
+              hb_codepoint_t first_glyph, hb_codepoint_t second_glyph,
+              void *user_data)
+{
+    const gfxHarfBuzzShaper::FontCallbackData *fcd =
+        static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
+    return fcd->mShaper->GetHKerning(first_glyph, second_glyph);
+}
+
+/*
+ * HarfBuzz unicode property callbacks
+ */
+
+static hb_codepoint_t
+HBGetMirroring(hb_unicode_funcs_t *ufuncs, hb_codepoint_t aCh,
+               void *user_data)
+{
+    return GetMirroredChar(aCh);
+}
+
+static hb_unicode_general_category_t
+HBGetGeneralCategory(hb_unicode_funcs_t *ufuncs, hb_codepoint_t aCh,
+                     void *user_data)
+{
+    return hb_unicode_general_category_t(GetGeneralCategory(aCh));
+}
+
+static hb_script_t
+HBGetScript(hb_unicode_funcs_t *ufuncs, hb_codepoint_t aCh, void *user_data)
+{
+    return hb_script_t(GetScriptTagForCode(GetScriptCode(aCh)));
+}
+
+static hb_unicode_combining_class_t
+HBGetCombiningClass(hb_unicode_funcs_t *ufuncs, hb_codepoint_t aCh,
+                    void *user_data)
+{
+    return hb_unicode_combining_class_t(GetCombiningClass(aCh));
+}
+
+// Hebrew presentation forms with dagesh, for characters 0x05D0..0x05EA;
+// note that some letters do not have a dagesh presForm encoded
+static const char16_t sDageshForms[0x05EA - 0x05D0 + 1] = {
+    0xFB30, // ALEF
+    0xFB31, // BET
+    0xFB32, // GIMEL
+    0xFB33, // DALET
+    0xFB34, // HE
+    0xFB35, // VAV
+    0xFB36, // ZAYIN
+    0, // HET
+    0xFB38, // TET
+    0xFB39, // YOD
+    0xFB3A, // FINAL KAF
+    0xFB3B, // KAF
+    0xFB3C, // LAMED
+    0, // FINAL MEM
+    0xFB3E, // MEM
+    0, // FINAL NUN
+    0xFB40, // NUN
+    0xFB41, // SAMEKH
+    0, // AYIN
+    0xFB43, // FINAL PE
+    0xFB44, // PE
+    0, // FINAL TSADI
+    0xFB46, // TSADI
+    0xFB47, // QOF
+    0xFB48, // RESH
+    0xFB49, // SHIN
+    0xFB4A // TAV
+};
+
+static hb_bool_t
+HBUnicodeCompose(hb_unicode_funcs_t *ufuncs,
+                 hb_codepoint_t      a,
+                 hb_codepoint_t      b,
+                 hb_codepoint_t     *ab,
+                 void               *user_data)
+{
+#if MOZ_HB_SHAPER_USE_ICU_NORMALIZATION
+
+    if (sNormalizer) {
+        UChar32 ch = unorm2_composePair(sNormalizer, a, b);
+        if (ch >= 0) {
+            *ab = ch;
+            return true;
+        }
+    }
+
+#else // no ICU available, use the old nsUnicodeNormalizer
+
+    if (nsUnicodeNormalizer::Compose(a, b, ab)) {
+        return true;
+    }
+
+#endif
+
+    return false;
+}
+
+static hb_bool_t
+HBUnicodeDecompose(hb_unicode_funcs_t *ufuncs,
+                   hb_codepoint_t      ab,
+                   hb_codepoint_t     *a,
+                   hb_codepoint_t     *b,
+                   void               *user_data)
+{
+#ifdef MOZ_WIDGET_ANDROID
+    // Hack for the SamsungDevanagari font, bug 1012365:
+    // support U+0972 by decomposing it.
+    if (ab == 0x0972) {
+        *a = 0x0905;
+        *b = 0x0945;
+        return true;
+    }
+#endif
+
+#if MOZ_HB_SHAPER_USE_ICU_NORMALIZATION
+
+    if (!sNormalizer) {
+        return false;
+    }
+
+    // Canonical decompositions are never more than two characters,
+    // or a maximum of 4 utf-16 code units.
+    const unsigned MAX_DECOMP_LENGTH = 4;
+
+    UErrorCode error = U_ZERO_ERROR;
+    UChar decomp[MAX_DECOMP_LENGTH];
+    int32_t len = unorm2_getRawDecomposition(sNormalizer, ab, decomp,
+                                             MAX_DECOMP_LENGTH, &error);
+    if (U_FAILURE(error) || len < 0) {
+        return false;
+    }
+
+    UText text = UTEXT_INITIALIZER;
+    utext_openUChars(&text, decomp, len, &error);
+    NS_ASSERTION(U_SUCCESS(error), "UText failure?");
+
+    UChar32 ch = UTEXT_NEXT32(&text);
+    if (ch != U_SENTINEL) {
+        *a = ch;
+    }
+    ch = UTEXT_NEXT32(&text);
+    if (ch != U_SENTINEL) {
+        *b = ch;
+    }
+    utext_close(&text);
+
+    return *b != 0 || *a != ab;
+
+#else // no ICU available, use the old nsUnicodeNormalizer
+
+    return nsUnicodeNormalizer::DecomposeNonRecursively(ab, a, b);
+
+#endif
+}
+
+static void
+AddOpenTypeFeature(const uint32_t& aTag, uint32_t& aValue, void *aUserArg)
+{
+    nsTArray<hb_feature_t>* features = static_cast<nsTArray<hb_feature_t>*> (aUserArg);
+
+    hb_feature_t feat = { 0, 0, 0, UINT_MAX };
+    feat.tag = aTag;
+    feat.value = aValue;
+    features->AppendElement(feat);
+}
+
+/*
+ * gfxFontShaper override to initialize the text run using HarfBuzz
+ */
+
+static hb_font_funcs_t * sHBFontFuncs = nullptr;
+static hb_unicode_funcs_t * sHBUnicodeFuncs = nullptr;
+static const hb_script_t sMathScript =
+    hb_ot_tag_to_script(HB_TAG('m','a','t','h'));
+
+bool
+gfxHarfBuzzShaper::Initialize()
+{
+    if (mInitialized) {
+        return mHBFont != nullptr;
+    }
+    mInitialized = true;
+    mCallbackData.mShaper = this;
+
+    mUseFontGlyphWidths = mFont->ProvidesGlyphWidths();
+
+    if (!sHBFontFuncs) {
+        // static function callback pointers, initialized by the first
+        // harfbuzz shaper used
+        sHBFontFuncs = hb_font_funcs_create();
+        hb_font_funcs_set_nominal_glyph_func(sHBFontFuncs,
+                                             HBGetNominalGlyph,
+                                             nullptr, nullptr);
+        hb_font_funcs_set_variation_glyph_func(sHBFontFuncs,
+                                               HBGetVariationGlyph,
+                                               nullptr, nullptr);
+        hb_font_funcs_set_glyph_h_advance_func(sHBFontFuncs,
+                                               HBGetGlyphHAdvance,
+                                               nullptr, nullptr);
+        hb_font_funcs_set_glyph_v_advance_func(sHBFontFuncs,
+                                               HBGetGlyphVAdvance,
+                                               nullptr, nullptr);
+        hb_font_funcs_set_glyph_v_origin_func(sHBFontFuncs,
+                                              HBGetGlyphVOrigin,
+                                              nullptr, nullptr);
+        hb_font_funcs_set_glyph_extents_func(sHBFontFuncs,
+                                             HBGetGlyphExtents,
+                                             nullptr, nullptr);
+        hb_font_funcs_set_glyph_contour_point_func(sHBFontFuncs,
+                                                   HBGetContourPoint,
+                                                   nullptr, nullptr);
+        hb_font_funcs_set_glyph_h_kerning_func(sHBFontFuncs,
+                                               HBGetHKerning,
+                                               nullptr, nullptr);
+
+        sHBUnicodeFuncs =
+            hb_unicode_funcs_create(hb_unicode_funcs_get_empty());
+        hb_unicode_funcs_set_mirroring_func(sHBUnicodeFuncs,
+                                            HBGetMirroring,
+                                            nullptr, nullptr);
+        hb_unicode_funcs_set_script_func(sHBUnicodeFuncs, HBGetScript,
+                                         nullptr, nullptr);
+        hb_unicode_funcs_set_general_category_func(sHBUnicodeFuncs,
+                                                   HBGetGeneralCategory,
+                                                   nullptr, nullptr);
+        hb_unicode_funcs_set_combining_class_func(sHBUnicodeFuncs,
+                                                  HBGetCombiningClass,
+                                                  nullptr, nullptr);
+        hb_unicode_funcs_set_compose_func(sHBUnicodeFuncs,
+                                          HBUnicodeCompose,
+                                          nullptr, nullptr);
+        hb_unicode_funcs_set_decompose_func(sHBUnicodeFuncs,
+                                            HBUnicodeDecompose,
+                                            nullptr, nullptr);
+
+#if MOZ_HB_SHAPER_USE_ICU_NORMALIZATION
+        UErrorCode error = U_ZERO_ERROR;
+        sNormalizer = unorm2_getNFCInstance(&error);
+        NS_ASSERTION(U_SUCCESS(error), "failed to get ICU normalizer");
+#endif
+    }
+
+    gfxFontEntry *entry = mFont->GetFontEntry();
+    if (!mUseFontGetGlyph) {
+        // get the cmap table and find offset to our subtable
+        mCmapTable = entry->GetFontTable(TRUETYPE_TAG('c','m','a','p'));
+        if (!mCmapTable) {
+            NS_WARNING("failed to load cmap, glyphs will be missing");
+            return false;
+        }
+        uint32_t len;
+        const uint8_t* data = (const uint8_t*)hb_blob_get_data(mCmapTable, &len);
+        bool symbol;
+        mCmapFormat = gfxFontUtils::
+            FindPreferredSubtable(data, len,
+                                  &mSubtableOffset, &mUVSTableOffset,
+                                  &symbol);
+        if (mCmapFormat <= 0) {
+            return false;
+        }
+    }
+
+    if (!mUseFontGlyphWidths) {
+        // If font doesn't implement GetGlyphWidth, we will be reading
+        // the metrics table directly, so make sure we can load it.
+        if (!LoadHmtxTable()) {
+            return false;
+        }
+    }
+
+    mHBFont = hb_font_create(mHBFace);
+    hb_font_set_funcs(mHBFont, sHBFontFuncs, &mCallbackData, nullptr);
+    hb_font_set_ppem(mHBFont, mFont->GetAdjustedSize(), mFont->GetAdjustedSize());
+    uint32_t scale = FloatToFixed(mFont->GetAdjustedSize()); // 16.16 fixed-point
+    hb_font_set_scale(mHBFont, scale, scale);
+
+    return true;
+}
+
+bool
+gfxHarfBuzzShaper::LoadHmtxTable()
+{
+    // Read mNumLongHMetrics from metrics-head table without caching its
+    // blob, and preload/cache the metrics table.
+    gfxFontEntry *entry = mFont->GetFontEntry();
+    gfxFontEntry::AutoTable hheaTable(entry, TRUETYPE_TAG('h','h','e','a'));
+    if (hheaTable) {
+        uint32_t len;
+        const MetricsHeader* hhea =
+            reinterpret_cast<const MetricsHeader*>
+            (hb_blob_get_data(hheaTable, &len));
+        if (len >= sizeof(MetricsHeader)) {
+            mNumLongHMetrics = hhea->numOfLongMetrics;
+            if (mNumLongHMetrics > 0 &&
+                int16_t(hhea->metricDataFormat) == 0) {
+                // no point reading metrics if number of entries is zero!
+                // in that case, we won't be able to use this font
+                // (this method will return FALSE below if mHmtxTable
+                // is null)
+                mHmtxTable = entry->GetFontTable(TRUETYPE_TAG('h','m','t','x'));
+                if (mHmtxTable && hb_blob_get_length(mHmtxTable) <
+                    mNumLongHMetrics * sizeof(LongMetric)) {
+                    // metrics table is not large enough for the claimed
+                    // number of entries: invalid, do not use.
+                    hb_blob_destroy(mHmtxTable);
+                    mHmtxTable = nullptr;
+                }
+            }
+        }
+    }
+    if (!mHmtxTable) {
+        return false;
+    }
+    return true;
+}
+
+bool
+gfxHarfBuzzShaper::InitializeVertical()
+{
+    // We only try this once. If we don't have a mHmtxTable after that,
+    // this font can't handle vertical shaping, so return false.
+    if (mVerticalInitialized) {
+        return mHmtxTable != nullptr;
+    }
+    mVerticalInitialized = true;
+
+    if (!mHmtxTable) {
+        if (!LoadHmtxTable()) {
+            return false;
+        }
+    }
+
+    // Load vertical metrics if present in the font; if not, we'll synthesize
+    // vertical glyph advances based on (horizontal) ascent/descent metrics.
+    gfxFontEntry *entry = mFont->GetFontEntry();
+    gfxFontEntry::AutoTable vheaTable(entry, TRUETYPE_TAG('v','h','e','a'));
+    if (vheaTable) {
+        uint32_t len;
+        const MetricsHeader* vhea =
+            reinterpret_cast<const MetricsHeader*>
+            (hb_blob_get_data(vheaTable, &len));
+        if (len >= sizeof(MetricsHeader)) {
+            mNumLongVMetrics = vhea->numOfLongMetrics;
+            gfxFontEntry::AutoTable
+                maxpTable(entry, TRUETYPE_TAG('m','a','x','p'));
+            int numGlyphs = -1; // invalid if we fail to read 'maxp'
+            if (maxpTable &&
+                hb_blob_get_length(maxpTable) >= sizeof(MaxpTableHeader)) {
+                const MaxpTableHeader* maxp =
+                    reinterpret_cast<const MaxpTableHeader*>
+                    (hb_blob_get_data(maxpTable, nullptr));
+                numGlyphs = uint16_t(maxp->numGlyphs);
+            }
+            if (mNumLongVMetrics > 0 && mNumLongVMetrics <= numGlyphs &&
+                int16_t(vhea->metricDataFormat) == 0) {
+                mVmtxTable = entry->GetFontTable(TRUETYPE_TAG('v','m','t','x'));
+                if (mVmtxTable && hb_blob_get_length(mVmtxTable) <
+                    mNumLongVMetrics * sizeof(LongMetric) +
+                    (numGlyphs - mNumLongVMetrics) * sizeof(int16_t)) {
+                    // metrics table is not large enough for the claimed
+                    // number of entries: invalid, do not use.
+                    hb_blob_destroy(mVmtxTable);
+                    mVmtxTable = nullptr;
+                }
+            }
+        }
+    }
+
+    // For CFF fonts only, load a VORG table if present.
+    if (entry->HasFontTable(TRUETYPE_TAG('C','F','F',' '))) {
+        mVORGTable = entry->GetFontTable(TRUETYPE_TAG('V','O','R','G'));
+        if (mVORGTable) {
+            uint32_t len;
+            const VORG* vorg =
+                reinterpret_cast<const VORG*>(hb_blob_get_data(mVORGTable,
+                                                               &len));
+            if (len < sizeof(VORG) ||
+                uint16_t(vorg->majorVersion) != 1 ||
+                uint16_t(vorg->minorVersion) != 0 ||
+                len < sizeof(VORG) + uint16_t(vorg->numVertOriginYMetrics) *
+                              sizeof(VORGrec)) {
+                // VORG table is an unknown version, or not large enough
+                // to be valid -- discard it.
+                NS_WARNING("discarding invalid VORG table");
+                hb_blob_destroy(mVORGTable);
+                mVORGTable = nullptr;
+            }
+        }
+    }
+
+    return true;
+}
+
+bool
+gfxHarfBuzzShaper::ShapeText(DrawTarget      *aDrawTarget,
+                             const char16_t *aText,
+                             uint32_t         aOffset,
+                             uint32_t         aLength,
+                             Script           aScript,
+                             bool             aVertical,
+                             gfxShapedText   *aShapedText)
+{
+    // some font back-ends require this in order to get proper hinted metrics
+    if (!mFont->SetupCairoFont(aDrawTarget)) {
+        return false;
+    }
+
+    mCallbackData.mDrawTarget = aDrawTarget;
+    mUseVerticalPresentationForms = false;
+
+    if (!Initialize()) {
+        return false;
+    }
+
+    if (aVertical) {
+        if (!InitializeVertical()) {
+            return false;
+        }
+        if (!mFont->GetFontEntry()->
+            SupportsOpenTypeFeature(aScript, HB_TAG('v','e','r','t'))) {
+            mUseVerticalPresentationForms = true;
+        }
+    }
+
+    const gfxFontStyle *style = mFont->GetStyle();
+
+    // determine whether petite-caps falls back to small-caps
+    bool addSmallCaps = false;
+    if (style->variantCaps != NS_FONT_VARIANT_CAPS_NORMAL) {
+        switch (style->variantCaps) {
+            case NS_FONT_VARIANT_CAPS_ALLPETITE:
+            case NS_FONT_VARIANT_CAPS_PETITECAPS:
+                bool synLower, synUpper;
+                mFont->SupportsVariantCaps(aScript, style->variantCaps,
+                                           addSmallCaps, synLower, synUpper);
+                break;
+            default:
+                break;
+        }
+    }
+
+    gfxFontEntry *entry = mFont->GetFontEntry();
+
+    // insert any merged features into hb_feature array
+    AutoTArray<hb_feature_t,20> features;
+    MergeFontFeatures(style,
+                      entry->mFeatureSettings,
+                      aShapedText->DisableLigatures(),
+                      entry->FamilyName(),
+                      addSmallCaps,
+                      AddOpenTypeFeature,
+                      &features);
+
+    bool isRightToLeft = aShapedText->IsRightToLeft();
+    hb_buffer_t *buffer = hb_buffer_create();
+    hb_buffer_set_unicode_funcs(buffer, sHBUnicodeFuncs);
+
+    hb_buffer_set_direction(buffer,
+                            aVertical ? HB_DIRECTION_TTB :
+                                        (isRightToLeft ? HB_DIRECTION_RTL :
+                                                         HB_DIRECTION_LTR));
+    hb_script_t scriptTag;
+    if (aShapedText->GetFlags() & gfxTextRunFactory::TEXT_USE_MATH_SCRIPT) {
+        scriptTag = sMathScript;
+    } else {
+        scriptTag = GetHBScriptUsedForShaping(aScript);
+    }
+    hb_buffer_set_script(buffer, scriptTag);
+
+    hb_language_t language;
+    if (style->languageOverride) {
+        language = hb_ot_tag_to_language(style->languageOverride);
+    } else if (entry->mLanguageOverride) {
+        language = hb_ot_tag_to_language(entry->mLanguageOverride);
+    } else if (style->explicitLanguage) {
+        nsCString langString;
+        style->language->ToUTF8String(langString);
+        language =
+            hb_language_from_string(langString.get(), langString.Length());
+    } else {
+        language = hb_ot_tag_to_language(HB_OT_TAG_DEFAULT_LANGUAGE);
+    }
+    hb_buffer_set_language(buffer, language);
+
+    uint32_t length = aLength;
+    hb_buffer_add_utf16(buffer,
+                        reinterpret_cast<const uint16_t*>(aText),
+                        length, 0, length);
+
+    hb_buffer_set_cluster_level(buffer, HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS);
+
+    hb_shape(mHBFont, buffer, features.Elements(), features.Length());
+
+    if (isRightToLeft) {
+        hb_buffer_reverse(buffer);
+    }
+
+    nsresult rv = SetGlyphsFromRun(aDrawTarget, aShapedText, aOffset, aLength,
+                                   aText, buffer, aVertical);
+
+    NS_WARNING_ASSERTION(NS_SUCCEEDED(rv),
+                         "failed to store glyphs into gfxShapedWord");
+    hb_buffer_destroy(buffer);
+
+    return NS_SUCCEEDED(rv);
+}
+
+#define SMALL_GLYPH_RUN 128 // some testing indicates that 90%+ of text runs
+                            // will fit without requiring separate allocation
+                            // for charToGlyphArray
+
+nsresult
+gfxHarfBuzzShaper::SetGlyphsFromRun(DrawTarget     *aDrawTarget,
+                                    gfxShapedText  *aShapedText,
+                                    uint32_t        aOffset,
+                                    uint32_t        aLength,
+                                    const char16_t *aText,
+                                    hb_buffer_t    *aBuffer,
+                                    bool            aVertical)
+{
+    uint32_t numGlyphs;
+    const hb_glyph_info_t *ginfo = hb_buffer_get_glyph_infos(aBuffer, &numGlyphs);
+    if (numGlyphs == 0) {
+        return NS_OK;
+    }
+
+    AutoTArray<gfxTextRun::DetailedGlyph,1> detailedGlyphs;
+
+    uint32_t wordLength = aLength;
+    static const int32_t NO_GLYPH = -1;
+    AutoTArray<int32_t,SMALL_GLYPH_RUN> charToGlyphArray;
+    if (!charToGlyphArray.SetLength(wordLength, fallible)) {
+        return NS_ERROR_OUT_OF_MEMORY;
+    }
+
+    int32_t *charToGlyph = charToGlyphArray.Elements();
+    for (uint32_t offset = 0; offset < wordLength; ++offset) {
+        charToGlyph[offset] = NO_GLYPH;
+    }
+
+    for (uint32_t i = 0; i < numGlyphs; ++i) {
+        uint32_t loc = ginfo[i].cluster;
+        if (loc < wordLength) {
+            charToGlyph[loc] = i;
+        }
+    }
+
+    int32_t glyphStart = 0; // looking for a clump that starts at this glyph
+    int32_t charStart = 0; // and this char index within the range of the run
+
+    bool roundI, roundB;
+    if (aVertical) {
+        GetRoundOffsetsToPixels(aDrawTarget, &roundB, &roundI);
+    } else {
+        GetRoundOffsetsToPixels(aDrawTarget, &roundI, &roundB);
+    }
+
+    int32_t appUnitsPerDevUnit = aShapedText->GetAppUnitsPerDevUnit();
+    gfxShapedText::CompressedGlyph *charGlyphs =
+        aShapedText->GetCharacterGlyphs() + aOffset;
+
+    // factor to convert 16.16 fixed-point pixels to app units
+    // (only used if not rounding)
+    double hb2appUnits = FixedToFloat(aShapedText->GetAppUnitsPerDevUnit());
+
+    // Residual from rounding of previous advance, for use in rounding the
+    // subsequent offset or advance appropriately.  16.16 fixed-point
+    //
+    // When rounding, the goal is to make the distance between glyphs and
+    // their base glyph equal to the integral number of pixels closest to that
+    // suggested by that shaper.
+    // i.e. posInfo[n].x_advance - posInfo[n].x_offset + posInfo[n+1].x_offset
+    //
+    // The value of the residual is the part of the desired distance that has
+    // not been included in integer offsets.
+    hb_position_t residual = 0;
+
+    // keep track of y-position to set glyph offsets if needed
+    nscoord bPos = 0;
+
+    const hb_glyph_position_t *posInfo =
+        hb_buffer_get_glyph_positions(aBuffer, nullptr);
+
+    while (glyphStart < int32_t(numGlyphs)) {
+
+        int32_t charEnd = ginfo[glyphStart].cluster;
+        int32_t glyphEnd = glyphStart;
+        int32_t charLimit = wordLength;
+        while (charEnd < charLimit) {
+            // This is normally executed once for each iteration of the outer loop,
+            // but in unusual cases where the character/glyph association is complex,
+            // the initial character range might correspond to a non-contiguous
+            // glyph range with "holes" in it. If so, we will repeat this loop to
+            // extend the character range until we have a contiguous glyph sequence.
+            charEnd += 1;
+            while (charEnd != charLimit && charToGlyph[charEnd] == NO_GLYPH) {
+                charEnd += 1;
+            }
+
+            // find the maximum glyph index covered by the clump so far
+            for (int32_t i = charStart; i < charEnd; ++i) {
+                if (charToGlyph[i] != NO_GLYPH) {
+                    glyphEnd = std::max(glyphEnd, charToGlyph[i] + 1);
+                    // update extent of glyph range
+                }
+            }
+
+            if (glyphEnd == glyphStart + 1) {
+                // for the common case of a single-glyph clump,
+                // we can skip the following checks
+                break;
+            }
+
+            if (glyphEnd == glyphStart) {
+                // no glyphs, try to extend the clump
+                continue;
+            }
+
+            // check whether all glyphs in the range are associated with the characters
+            // in our clump; if not, we have a discontinuous range, and should extend it
+            // unless we've reached the end of the text
+            bool allGlyphsAreWithinCluster = true;
+            for (int32_t i = glyphStart; i < glyphEnd; ++i) {
+                int32_t glyphCharIndex = ginfo[i].cluster;
+                if (glyphCharIndex < charStart || glyphCharIndex >= charEnd) {
+                    allGlyphsAreWithinCluster = false;
+                    break;
+                }
+            }
+            if (allGlyphsAreWithinCluster) {
+                break;
+            }
+        }
+
+        NS_ASSERTION(glyphStart < glyphEnd,
+                     "character/glyph clump contains no glyphs!");
+        NS_ASSERTION(charStart != charEnd,
+                     "character/glyph clump contains no characters!");
+
+        // Now charStart..charEnd is a ligature clump, corresponding to glyphStart..glyphEnd;
+        // Set baseCharIndex to the char we'll actually attach the glyphs to (1st of ligature),
+        // and endCharIndex to the limit (position beyond the last char),
+        // adjusting for the offset of the stringRange relative to the textRun.
+        int32_t baseCharIndex, endCharIndex;
+        while (charEnd < int32_t(wordLength) && charToGlyph[charEnd] == NO_GLYPH)
+            charEnd++;
+        baseCharIndex = charStart;
+        endCharIndex = charEnd;
+
+        // Then we check if the clump falls outside our actual string range;
+        // if so, just go to the next.
+        if (baseCharIndex >= int32_t(wordLength)) {
+            glyphStart = glyphEnd;
+            charStart = charEnd;
+            continue;
+        }
+        // Ensure we won't try to go beyond the valid length of the textRun's text
+        endCharIndex = std::min<int32_t>(endCharIndex, wordLength);
+
+        // Now we're ready to set the glyph info in the textRun
+        int32_t glyphsInClump = glyphEnd - glyphStart;
+
+        // Check for default-ignorable char that didn't get filtered, combined,
+        // etc by the shaping process, and remove from the run.
+        // (This may be done within harfbuzz eventually.)
+        if (glyphsInClump == 1 && baseCharIndex + 1 == endCharIndex &&
+            aShapedText->FilterIfIgnorable(aOffset + baseCharIndex,
+                                           aText[baseCharIndex])) {
+            glyphStart = glyphEnd;
+            charStart = charEnd;
+            continue;
+        }
+
+        // HarfBuzz gives us physical x- and y-coordinates, but we will store
+        // them as logical inline- and block-direction values in the textrun.
+
+        hb_position_t i_offset, i_advance; // inline-direction offset/advance
+        hb_position_t b_offset, b_advance; // block-direction offset/advance
+        if (aVertical) {
+            i_offset = posInfo[glyphStart].y_offset;
+            i_advance = posInfo[glyphStart].y_advance;
+            b_offset = posInfo[glyphStart].x_offset;
+            b_advance = posInfo[glyphStart].x_advance;
+        } else {
+            i_offset = posInfo[glyphStart].x_offset;
+            i_advance = posInfo[glyphStart].x_advance;
+            b_offset = posInfo[glyphStart].y_offset;
+            b_advance = posInfo[glyphStart].y_advance;
+        }
+
+        nscoord iOffset, advance;
+        if (roundI) {
+            iOffset =
+                appUnitsPerDevUnit * FixedToIntRound(i_offset + residual);
+            // Desired distance from the base glyph to the next reference point.
+            hb_position_t width = i_advance - i_offset;
+            int intWidth = FixedToIntRound(width);
+            residual = width - FloatToFixed(intWidth);
+            advance = appUnitsPerDevUnit * intWidth + iOffset;
+        } else {
+            iOffset = floor(hb2appUnits * i_offset + 0.5);
+            advance = floor(hb2appUnits * i_advance + 0.5);
+        }
+        // Check if it's a simple one-to-one mapping
+        if (glyphsInClump == 1 &&
+            gfxTextRun::CompressedGlyph::IsSimpleGlyphID(ginfo[glyphStart].codepoint) &&
+            gfxTextRun::CompressedGlyph::IsSimpleAdvance(advance) &&
+            charGlyphs[baseCharIndex].IsClusterStart() &&
+            iOffset == 0 && b_offset == 0 &&
+            b_advance == 0 && bPos == 0)
+        {
+            charGlyphs[baseCharIndex].SetSimpleGlyph(advance,
+                                                     ginfo[glyphStart].codepoint);
+        } else {
+            // Collect all glyphs in a list to be assigned to the first char;
+            // there must be at least one in the clump, and we already measured
+            // its advance, hence the placement of the loop-exit test and the
+            // measurement of the next glyph.
+            // For vertical orientation, we add a "base offset" to compensate
+            // for the positioning within the cluster being based on horizontal
+            // glyph origin/offset.
+            hb_position_t baseIOffset, baseBOffset;
+            if (aVertical) {
+                baseIOffset = 2 * (i_offset - i_advance);
+                baseBOffset = GetGlyphHAdvance(ginfo[glyphStart].codepoint);
+            }
+            while (1) {
+                gfxTextRun::DetailedGlyph* details =
+                    detailedGlyphs.AppendElement();
+                details->mGlyphID = ginfo[glyphStart].codepoint;
+
+                details->mXOffset = iOffset;
+                details->mAdvance = advance;
+
+                details->mYOffset = bPos -
+                    (roundB ? appUnitsPerDevUnit * FixedToIntRound(b_offset)
+                     : floor(hb2appUnits * b_offset + 0.5));
+
+                if (b_advance != 0) {
+                    bPos -=
+                        roundB ? appUnitsPerDevUnit * FixedToIntRound(b_advance)
+                        : floor(hb2appUnits * b_advance + 0.5);
+                }
+                if (++glyphStart >= glyphEnd) {
+                    break;
+                }
+
+                if (aVertical) {
+                    i_offset = baseIOffset - posInfo[glyphStart].y_offset;
+                    i_advance = posInfo[glyphStart].y_advance;
+                    b_offset = baseBOffset - posInfo[glyphStart].x_offset;
+                    b_advance = posInfo[glyphStart].x_advance;
+                } else {
+                    i_offset = posInfo[glyphStart].x_offset;
+                    i_advance = posInfo[glyphStart].x_advance;
+                    b_offset = posInfo[glyphStart].y_offset;
+                    b_advance = posInfo[glyphStart].y_advance;
+                }
+
+                if (roundI) {
+                    iOffset = appUnitsPerDevUnit *
+                        FixedToIntRound(i_offset + residual);
+                    // Desired distance to the next reference point.  The
+                    // residual is considered here, and includes the residual
+                    // from the base glyph offset and subsequent advances, so
+                    // that the distance from the base glyph is optimized
+                    // rather than the distance from combining marks.
+                    i_advance += residual;
+                    int intAdvance = FixedToIntRound(i_advance);
+                    residual = i_advance - FloatToFixed(intAdvance);
+                    advance = appUnitsPerDevUnit * intAdvance;
+                } else {
+                    iOffset = floor(hb2appUnits * i_offset + 0.5);
+                    advance = floor(hb2appUnits * i_advance + 0.5);
+                }
+            }
+
+            gfxShapedText::CompressedGlyph g;
+            g.SetComplex(charGlyphs[baseCharIndex].IsClusterStart(),
+                         true, detailedGlyphs.Length());
+            aShapedText->SetGlyphs(aOffset + baseCharIndex,
+                                   g, detailedGlyphs.Elements());
+
+            detailedGlyphs.Clear();
+        }
+
+        // the rest of the chars in the group are ligature continuations,
+        // no associated glyphs
+        while (++baseCharIndex != endCharIndex &&
+               baseCharIndex < int32_t(wordLength)) {
+            gfxShapedText::CompressedGlyph &g = charGlyphs[baseCharIndex];
+            NS_ASSERTION(!g.IsSimpleGlyph(), "overwriting a simple glyph");
+            g.SetComplex(g.IsClusterStart(), false, 0);
+        }
+
+        glyphStart = glyphEnd;
+        charStart = charEnd;
+    }
+
+    return NS_OK;
+}