gecko-dev/gfx/thebes/src/gfxPangoFonts.cpp

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Foundation code.
 *
 * The Initial Developer of the Original Code is Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2005
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Vladimir Vukicevic <vladimir@mozilla.com>
 *   Masayuki Nakano <masayuki@d-toybox.com>
 *   Behdad Esfahbod <behdad@gnome.org>
 *   Mats Palmgren <mats.palmgren@bredband.net>
 *   Karl Tomlinson <karlt+@karlt.net>, Mozilla Corporation
 *
 * based on nsFontMetricsPango.cpp by
 *   Christopher Blizzard <blizzard@mozilla.org>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#define PANGO_ENABLE_BACKEND

#include "prtypes.h"
#include "prlink.h"
#include "gfxTypes.h"

#include "nsMathUtils.h"

#include "gfxContext.h"
#include "gfxPlatformGtk.h"
#include "gfxPangoFonts.h"
#include "gfxFontconfigUtils.h"

#include <freetype/tttables.h>

#include <cairo.h>
#include <cairo-ft.h>

#include <fontconfig/fcfreetype.h>
#include <pango/pango.h>
#include <pango/pangofc-fontmap.h>

#include <gdk/gdkscreen.h>

#include <math.h>

#define FLOAT_PANGO_SCALE ((gfxFloat)PANGO_SCALE)

#ifndef PANGO_VERSION_CHECK
#define PANGO_VERSION_CHECK(x,y,z) 0
#endif
#ifndef PANGO_GLYPH_UNKNOWN_FLAG
#define PANGO_GLYPH_UNKNOWN_FLAG ((PangoGlyph)0x10000000)
#endif
#ifndef PANGO_GLYPH_EMPTY
#define PANGO_GLYPH_EMPTY           ((PangoGlyph)0)
#endif
// For g a PangoGlyph,
#define IS_MISSING_GLYPH(g) ((g) & PANGO_GLYPH_UNKNOWN_FLAG)
#define IS_EMPTY_GLYPH(g) ((g) == PANGO_GLYPH_EMPTY)

// Same as pango_units_from_double from Pango 1.16 (but not in older versions)
int moz_pango_units_from_double(double d) {
    return NS_lround(d * FLOAT_PANGO_SCALE);
}

static PangoLanguage *GetPangoLanguage(const nsACString& aLangGroup);

static cairo_scaled_font_t *CreateScaledFont(FcPattern *aPattern);

/* static */ gfxPangoFontCache* gfxPangoFontCache::sPangoFontCache = nsnull;

static PangoFontMap *gPangoFontMap;

/*
 * gfxFcFont
 *
 * This is a gfxFont implementation using a CAIRO_FONT_TYPE_FT
 * cairo_scaled_font created from an FcPattern.
 */

class gfxFcFont : public gfxFont {
public:
    virtual ~gfxFcFont ();
    static already_AddRefed<gfxFcFont> GetOrMakeFont(FcPattern *aPattern);

    virtual const gfxFont::Metrics& GetMetrics();

    virtual nsString GetUniqueName();

    // Get the glyphID of a space
    virtual PRUint32 GetSpaceGlyph() {
        NS_ASSERTION(GetStyle()->size != 0,
                     "forgot to short-circuit a text run with zero-sized font?");
        GetMetrics();
        return mSpaceGlyph;
    }

    cairo_scaled_font_t *CairoScaledFont() { return mCairoFont; }
    void GetGlyphExtents(PRUint32 aGlyph, cairo_text_extents_t* aExtents);

protected:
    cairo_scaled_font_t *mCairoFont;

    PRUint32 mSpaceGlyph;
    Metrics mMetrics;
    PRPackedBool mHasMetrics;

    gfxFcFont(cairo_scaled_font_t *aCairoFont,
              gfxPangoFontEntry *aFontEntry, const gfxFontStyle *aFontStyle);

    virtual PRBool SetupCairoFont(gfxContext *aContext);

    // key for locating a gfxFcFont corresponding to a cairo_scaled_font
    static cairo_user_data_key_t sGfxFontKey;
};

class LockedFTFace {
public:
    LockedFTFace(gfxFcFont *aFont)
        : mGfxFont(aFont),
          mFace(cairo_ft_scaled_font_lock_face(aFont->CairoScaledFont()))
    {
    }

    ~LockedFTFace()
    {
        if (mFace) {
            cairo_ft_scaled_font_unlock_face(mGfxFont->CairoScaledFont());
        }
    }

    /**
     * Get extents for a simple character representable by a single glyph.
     * The return value is the glyph id of that glyph or zero if no such glyph
     * exists.  aExtents is only set when this returns a non-zero glyph id.
     */
    PRUint32 GetCharExtents(char aChar, cairo_text_extents_t* aExtents);

    void GetMetrics(gfxFont::Metrics* aMetrics, PRUint32* aSpaceGlyph);

private:
    nsRefPtr<gfxFcFont> mGfxFont;
    FT_Face mFace;
};

/**
 * gfxPangoFcFont:
 *
 * An implementation of PangoFcFont that wraps a gfxFont so that it can be
 * passed to PangoRenderFc shapers.
 */

#define GFX_TYPE_PANGO_FC_FONT              (gfx_pango_fc_font_get_type())
#define GFX_PANGO_FC_FONT(object)           (G_TYPE_CHECK_INSTANCE_CAST ((object), GFX_TYPE_PANGO_FC_FONT, gfxPangoFcFont))
#define GFX_IS_PANGO_FC_FONT(object)        (G_TYPE_CHECK_INSTANCE_TYPE ((object), GFX_TYPE_PANGO_FC_FONT))

/* static */
GType gfx_pango_fc_font_get_type (void);

#define GFX_PANGO_FC_FONT_CLASS(klass)      (G_TYPE_CHECK_CLASS_CAST ((klass), GFX_TYPE_PANGO_FC_FONT, gfxPangoFcFontClass))
#define GFX_IS_PANGO_FC_FONT_CLASS(klass)   (G_TYPE_CHECK_CLASS_TYPE ((klass), GFX_TYPE_PANGO_FC_FONT))
#define GFX_PANGO_FC_FONT_GET_CLASS(obj)    (G_TYPE_INSTANCE_GET_CLASS ((obj), GFX_TYPE_PANGO_FC_FONT, gfxPangoFcFontClass))

// This struct is POD so that it can be used as a GObject.
struct gfxPangoFcFont {
    PangoFcFont parent_instance;

    gfxFcFont *mGfxFont;

    static gfxFcFont *GfxFont(gfxPangoFcFont *self)
    {
        if (!self->mGfxFont) {
            FcPattern *pattern = PANGO_FC_FONT(self)->font_pattern;
            self->mGfxFont = gfxFcFont::GetOrMakeFont(pattern).get();
        }
        return self->mGfxFont;
    }

    static cairo_scaled_font_t *CairoFont(gfxPangoFcFont *self)
    {
        return gfxPangoFcFont::GfxFont(self)->CairoScaledFont();
    }
};

struct gfxPangoFcFontClass {
    PangoFcFontClass parent_class;
};

G_DEFINE_TYPE (gfxPangoFcFont, gfx_pango_fc_font, PANGO_TYPE_FC_FONT)

static void
gfx_pango_fc_font_init(gfxPangoFcFont *fontset)
{
}


static void
gfx_pango_fc_font_finalize(GObject *object)
{
    gfxPangoFcFont *self = GFX_PANGO_FC_FONT(object);

    if (self->mGfxFont)
        self->mGfxFont->Release();

    G_OBJECT_CLASS(gfx_pango_fc_font_parent_class)->finalize(object);
}

static void
gfx_pango_fc_font_get_glyph_extents(PangoFont *font, PangoGlyph glyph,
                                    PangoRectangle *ink_rect,
                                    PangoRectangle *logical_rect)
{
    gfxPangoFcFont *self = GFX_PANGO_FC_FONT(font);
    gfxFcFont *gfxFont = gfxPangoFcFont::GfxFont(self);

    if (IS_MISSING_GLYPH(glyph)) {
        const gfxFont::Metrics& metrics = gfxFont->GetMetrics();

        PangoRectangle rect;
        rect.x = 0;
        rect.y = moz_pango_units_from_double(-metrics.maxAscent);
        rect.width = moz_pango_units_from_double(metrics.aveCharWidth);
        rect.height = moz_pango_units_from_double(metrics.maxHeight);
        if (ink_rect) {
            *ink_rect = rect;
        }
        if (logical_rect) {
            *logical_rect = rect;
        }
        return;
    }

    if (logical_rect) {
        // logical_rect.width is possibly used by pango_ot_buffer_output (used
        // by many shapers) and used by fallback_engine_shape (possibly used
        // by pango_shape and pango_itemize when no glyphs are found).  I
        // doubt the other fields will be used but we won't have any way to
        // detecting if they are so we'd better set them.
        const gfxFont::Metrics& metrics = gfxFont->GetMetrics();
        logical_rect->y = moz_pango_units_from_double(-metrics.maxAscent);
        logical_rect->height = moz_pango_units_from_double(metrics.maxHeight);
    }

    cairo_text_extents_t extents;
    if (IS_EMPTY_GLYPH(glyph)) {
        new (&extents) cairo_text_extents_t(); // zero
    } else {
        gfxFont->GetGlyphExtents(glyph, &extents);
    }

    if (ink_rect) {
        ink_rect->x = moz_pango_units_from_double(extents.x_bearing);
        ink_rect->y = moz_pango_units_from_double(extents.y_bearing);
        ink_rect->width = moz_pango_units_from_double(extents.width);
        ink_rect->height = moz_pango_units_from_double(extents.height);
    }
    if (logical_rect) {
        logical_rect->x = 0;
        logical_rect->width = moz_pango_units_from_double(extents.x_advance);
    }
}

#ifdef DEBUG
static PangoFontMetrics *
gfx_pango_fc_font_get_metrics(PangoFont *font, PangoLanguage *language)
{
    NS_WARNING("Using PangoFcFont::get_metrics");

    return PANGO_FONT_CLASS(gfx_pango_fc_font_parent_class)->
        get_metrics(font, language);
}
#endif

static FT_Face
gfx_pango_fc_font_lock_face(PangoFcFont *font)
{
    gfxPangoFcFont *self = GFX_PANGO_FC_FONT(font);
    return cairo_ft_scaled_font_lock_face(gfxPangoFcFont::CairoFont(self));
}

static void
gfx_pango_fc_font_unlock_face(PangoFcFont *font)
{
    gfxPangoFcFont *self = GFX_PANGO_FC_FONT(font);
    cairo_ft_scaled_font_unlock_face(gfxPangoFcFont::CairoFont(self));
}

static void
gfx_pango_fc_font_class_init (gfxPangoFcFontClass *klass)
{
    GObjectClass *object_class = G_OBJECT_CLASS (klass);
    PangoFontClass *font_class = PANGO_FONT_CLASS (klass);
    PangoFcFontClass *fc_font_class = PANGO_FC_FONT_CLASS (klass);

    object_class->finalize = gfx_pango_fc_font_finalize;

#if 0
    // This will need overriding for user fonts to defeat the PangoFcFontMap
    // caching, unless each user font is guaranteed to have a unique filename.
    font_class->get_coverage =
#endif
    font_class->get_glyph_extents = gfx_pango_fc_font_get_glyph_extents;
#ifdef DEBUG
    // non-DEBUG inherits from fc_font_class as this won't be used anyway.
    font_class->get_metrics = gfx_pango_fc_font_get_metrics;
#endif
    // fc_font_class->has_char,get_glyph are inherited
    fc_font_class->lock_face = gfx_pango_fc_font_lock_face;
    fc_font_class->unlock_face = gfx_pango_fc_font_unlock_face;
}

/**
 * Recording a base PangoFont on a PangoContext
 */

static GQuark GetBaseFontQuark()
{
    // Not using g_quark_from_static_string() because this module may be
    // unloaded (which would leave a dangling pointer).  Using
    // g_quark_from_string() instead, which creates a small shutdown leak.
    static GQuark quark = g_quark_from_string("moz-base-font");
    return quark;
}

static PangoFont *
GetBaseFont(PangoContext *aContext)
{
    return static_cast<PangoFont*>
        (g_object_get_qdata(G_OBJECT(aContext), GetBaseFontQuark()));
}

static void
SetBaseFont(PangoContext *aContext, PangoFont *aBaseFont)
{
    g_object_ref(aBaseFont);
    g_object_set_qdata_full(G_OBJECT(aContext), GetBaseFontQuark(),
                            aBaseFont, g_object_unref);
}

/**
 * gfxPangoFontset: An implementation of a PangoFontset for gfxPangoFontMap
 */

#define GFX_TYPE_PANGO_FONTSET              (gfx_pango_fontset_get_type())
#define GFX_PANGO_FONTSET(object)           (G_TYPE_CHECK_INSTANCE_CAST ((object), GFX_TYPE_PANGO_FONTSET, gfxPangoFontset))
#define GFX_IS_PANGO_FONTSET(object)        (G_TYPE_CHECK_INSTANCE_TYPE ((object), GFX_TYPE_PANGO_FONTSET))

/* static */
GType gfx_pango_fontset_get_type (void);

#define GFX_PANGO_FONTSET_CLASS(klass)      (G_TYPE_CHECK_CLASS_CAST ((klass), GFX_TYPE_PANGO_FONTSET, gfxPangoFontsetClass))
#define GFX_IS_PANGO_FONTSET_CLASS(klass)   (G_TYPE_CHECK_CLASS_TYPE ((klass), GFX_TYPE_PANGO_FONTSET))
#define GFX_PANGO_FONTSET_GET_CLASS(obj)    (G_TYPE_INSTANCE_GET_CLASS ((obj), GFX_TYPE_PANGO_FONTSET, gfxPangoFontsetClass))

// This struct is POD so that it can be used as a GObject.
struct gfxPangoFontset {
    PangoFontset parent_instance;

    PangoFontMap *mFontMap;
    PangoContext *mContext;
    PangoFontDescription *mFontDesc;
    PangoLanguage *mLanguage;
    PangoFont *mBaseFont;
    PangoFontset *mFallbackFontset;

    static PangoFontset *
    NewFontset(PangoFontMap *aFontMap,
               PangoContext *aContext,
               const PangoFontDescription *aFontDesc,
               PangoLanguage *aLanguage)
    {
        gfxPangoFontset *fontset = static_cast<gfxPangoFontset *>
            (g_object_new(GFX_TYPE_PANGO_FONTSET, NULL));

        fontset->mFontMap = aFontMap;
        g_object_ref(aFontMap);

        fontset->mContext = aContext;
        g_object_ref(aContext);

        fontset->mFontDesc = pango_font_description_copy(aFontDesc);
        fontset->mLanguage = aLanguage;

        fontset->mBaseFont = GetBaseFont(aContext);
        if(fontset->mBaseFont)
            g_object_ref(fontset->mBaseFont);

        return PANGO_FONTSET(fontset);
    }
};

struct gfxPangoFontsetClass {
    PangoFontsetClass parent_class;
};

G_DEFINE_TYPE (gfxPangoFontset, gfx_pango_fontset, PANGO_TYPE_FONTSET)

static void
gfx_pango_fontset_init(gfxPangoFontset *fontset)
{
}


static void
gfx_pango_fontset_finalize(GObject *object)
{
    gfxPangoFontset *self = GFX_PANGO_FONTSET(object);

    if (self->mContext)
        g_object_unref(self->mContext);
    if (self->mFontDesc)
        pango_font_description_free(self->mFontDesc);
    if (self->mBaseFont)
        g_object_unref(self->mBaseFont);
    if (self->mFontMap)
        g_object_unref(self->mFontMap);
    if (self->mFallbackFontset)
        g_object_unref(self->mFallbackFontset);

    G_OBJECT_CLASS(gfx_pango_fontset_parent_class)->finalize(object);
}

static PangoLanguage *
gfx_pango_fontset_get_language(PangoFontset *fontset)
{
    gfxPangoFontset *self = GFX_PANGO_FONTSET(fontset);
    return self->mLanguage;
}

struct ForeachExceptBaseData {
    PangoFont *mBaseFont;
    PangoFontset *mFontset;
    PangoFontsetForeachFunc mFunc;
    gpointer mData;
};

static gboolean
foreach_except_base_cb(PangoFontset *fontset, PangoFont *font, gpointer data)
{
    ForeachExceptBaseData *baseData =
        static_cast<ForeachExceptBaseData *>(data);
    
    // returning false means continue with the other fonts in the set
    return font != baseData->mBaseFont &&
        (*baseData->mFunc)(baseData->mFontset, font, baseData->mData);
}

static PangoFontset *
gfx_pango_font_map_load_fallback_fontset(PangoFontMap *fontmap,
                                         PangoContext *context,
                                         const PangoFontDescription *desc,
                                         PangoLanguage *language);

static PangoFontset *
EnsureFallbackFontset(gfxPangoFontset *self)
{
    if (!self->mFallbackFontset) {
        // To consider:
        //
        // * If this is happening often (e.g. Chinese/Japanese pages where a
        //   Latin font is specified first), and Pango's 64-entry pattern
        //   cache is not large enough, then a fontset cache here could be
        //   helpful.  Ideally we'd only cache the fonts that are actually
        //   accessed rather than all the fonts from the FcFontSort.
        //
        // * Mozilla's langGroup font prefs could be used to specify preferred
        //   fallback fonts for the script of the characters (as indicated by
        //   Pango in mLanguage), by doing the conversion from gfxFontGroup
        //   "families" to PangoFcFontMap "family" here.
        self->mFallbackFontset =
            gfx_pango_font_map_load_fallback_fontset(self->mFontMap,
                                                     self->mContext,
                                                     self->mFontDesc,
                                                     self->mLanguage);
    }
    return self->mFallbackFontset;
}

static void
gfx_pango_fontset_foreach(PangoFontset *fontset, PangoFontsetForeachFunc func,
                          gpointer data)
{
    gfxPangoFontset *self = GFX_PANGO_FONTSET(fontset);

    if (self->mBaseFont && (*func)(fontset, self->mBaseFont, data))
        return;

    // Falling back to secondary fonts
    PangoFontset *childFontset = EnsureFallbackFontset(self);
    ForeachExceptBaseData baseData = { self->mBaseFont, fontset, func, data };
    pango_fontset_foreach(childFontset, foreach_except_base_cb, &baseData);
}

static PangoFont *
gfx_pango_fontset_get_font(PangoFontset *fontset, guint wc)
{
    gfxPangoFontset *self = GFX_PANGO_FONTSET(fontset);

    PangoCoverageLevel baseLevel = PANGO_COVERAGE_NONE;
    if (self->mBaseFont) {
        // PangoFcFontMap caches this:
        PangoCoverage *coverage =
            pango_font_get_coverage(self->mBaseFont, self->mLanguage);
        if (coverage) {
            baseLevel = pango_coverage_get(coverage, wc);
            pango_coverage_unref(coverage);
        }
    }

    if (baseLevel != PANGO_COVERAGE_EXACT) {
        PangoFontset *childFontset = EnsureFallbackFontset(self);
        PangoFont *childFont = pango_fontset_get_font(childFontset, wc);
        if (!self->mBaseFont || childFont == self->mBaseFont)
            return childFont;

        if (childFont) {
            PangoCoverage *coverage =
                pango_font_get_coverage(childFont, self->mLanguage);
            if (coverage) {
                PangoCoverageLevel childLevel =
                    pango_coverage_get(coverage, wc);
                pango_coverage_unref(coverage);

                // Only use the child font if better than the base font.
                if (childLevel > baseLevel)
                    return childFont;
            }
            g_object_unref(childFont);
        }
    }

    g_object_ref(self->mBaseFont);
    return self->mBaseFont;
}

static void
gfx_pango_fontset_class_init (gfxPangoFontsetClass *klass)
{
    GObjectClass *object_class = G_OBJECT_CLASS (klass);
    PangoFontsetClass *fontset_class = PANGO_FONTSET_CLASS (klass);

    object_class->finalize = gfx_pango_fontset_finalize;
    fontset_class->get_font = gfx_pango_fontset_get_font;
    // inherit fontset_class->get_metrics (which won't be used anyway)
    fontset_class->get_language = gfx_pango_fontset_get_language;
    fontset_class->foreach = gfx_pango_fontset_foreach;
}

/**
 * gfxPangoFontMap: An implementation of a PangoFontMap.
 *
 * This allows the primary (base) font to be specified.  There are two
 * advantages to this:
 *
 * 1. Always using the same base font irrespective of the language that Pango
 *    chooses for the script means that PANGO_SCRIPT_COMMON characters are
 *    consistently rendered with the same font.  (Bug 339513 and bug 416725)
 *
 * 2. We normally have the base font from the gfxFont cache so this saves a
 *    FcFontSort when the entry has expired from Pango's much smaller pattern
 *    cache.
 */

#define GFX_TYPE_PANGO_FONT_MAP              (gfx_pango_font_map_get_type())
#define GFX_PANGO_FONT_MAP(object)           (G_TYPE_CHECK_INSTANCE_CAST ((object), GFX_TYPE_PANGO_FONT_MAP, gfxPangoFontMap))
#define GFX_IS_PANGO_FONT_MAP(object)        (G_TYPE_CHECK_INSTANCE_TYPE ((object), GFX_TYPE_PANGO_FONT_MAP))

GType gfx_pango_font_map_get_type (void);

#define GFX_PANGO_FONT_MAP_CLASS(klass)      (G_TYPE_CHECK_CLASS_CAST ((klass), GFX_TYPE_PANGO_FONT_MAP, gfxPangoFontMapClass))
#define GFX_IS_PANGO_FONT_MAP_CLASS(klass)   (G_TYPE_CHECK_CLASS_TYPE ((klass), GFX_TYPE_PANGO_FONT_MAP))
#define GFX_PANGO_FONT_MAP_GET_CLASS(obj)    (G_TYPE_INSTANCE_GET_CLASS ((obj), GFX_TYPE_PANGO_FONT_MAP, gfxPangoFontMapClass))

// Do not instantiate this class directly, but use NewFontMap.
// This struct is POD so that it can be used as a GObject.
struct gfxPangoFontMap {
    PangoFcFontMap parent_instance;

    static PangoFontMap *
    NewFontMap()
    {
        gfxPangoFontMap *fontmap = static_cast<gfxPangoFontMap *>
            (g_object_new(GFX_TYPE_PANGO_FONT_MAP, NULL));

        return PANGO_FONT_MAP(fontmap);
    }
};

struct gfxPangoFontMapClass {
    PangoFcFontMapClass parent_class;
};

G_DEFINE_TYPE (gfxPangoFontMap, gfx_pango_font_map, PANGO_TYPE_FC_FONT_MAP)

static void
gfx_pango_font_map_init(gfxPangoFontMap *fontset)
{
}

static PangoFont *
gfx_pango_font_map_load_font(PangoFontMap *fontmap, PangoContext *context,
                             const PangoFontDescription *description)
{
    PangoFont *baseFont = GetBaseFont(context);
    if (baseFont) {
        g_object_ref(baseFont);
        return baseFont;
    }

    return PANGO_FONT_MAP_CLASS(gfx_pango_font_map_parent_class)->
        load_font(fontmap, context, description);
}

static PangoFontset *
gfx_pango_font_map_load_fontset(PangoFontMap *fontmap, PangoContext *context,
                               const PangoFontDescription *desc,
                               PangoLanguage *language)
{
    return gfxPangoFontset::NewFontset(fontmap, context, desc, language);
}

static PangoFontset *
gfx_pango_font_map_load_fallback_fontset(PangoFontMap *fontmap,
                                         PangoContext *context,
                                         const PangoFontDescription *desc,
                                         PangoLanguage *language)
{
    return PANGO_FONT_MAP_CLASS(gfx_pango_font_map_parent_class)->
        load_fontset(fontmap, context, desc, language);
}

static void
gfx_pango_font_map_list_families(PangoFontMap *fontmap,
                                 PangoFontFamily ***families, int *n_families)
{
    return PANGO_FONT_MAP_CLASS(gfx_pango_font_map_parent_class)->
        list_families(fontmap, families, n_families);
}

static double
gfx_pango_font_map_get_resolution(PangoFcFontMap *fcfontmap,
                                  PangoContext *context)
{
    // This merely enables the FC_SIZE field of the pattern to be accurate.
    // We use gfxPlatformGtk::DPI() much of the time...
    return gfxPlatformGtk::DPI();
}

static void
gfx_pango_font_map_context_substitute(PangoFcFontMap *fontmap,
                                      PangoContext *context,
                                      FcPattern *pattern)
{
    FcConfigSubstitute(NULL, pattern, FcMatchPattern);

    // XXXkt This gets cairo_font_options_t for the Screen.  We should have
    // different font options for printing (no hinting) but we are not told
    // what we are measuring for.
    const cairo_font_options_t *options =
        gdk_screen_get_font_options(gdk_screen_get_default());

    cairo_ft_font_options_substitute(options, pattern);

    FcDefaultSubstitute(pattern);
}

static PangoFcFont *
gfx_pango_font_map_create_font(PangoFcFontMap *fontmap,
                               PangoContext *context,
                               const PangoFontDescription *desc,
                               FcPattern *pattern)
{
    // A pattern is needed for pango_fc_font_finalize.
    //
    // Adding a ref to one of fontconfig's patterns would use much less memory
    // than using the fully resolved pattern here.  This could be done by
    // setting the PangoFcFont field is_hinted directly.  (is_hinted is used
    // by pango_fc_font_kern_glyphs, which is sometimes used by
    // pango_ot_buffer_output.)  is_transformed is not used but maybe it
    // should be set too.  describe_absolute would need to be overridden if
    // required, and description would need to be set if describe is required
    // but not overridden.
    //
    // An alternative memory-saving effort might remove elements from the
    // resolved pattern that are unnecessary.

    // Protect against any fontconfig settings that may have incorrectly
    // modified the pixelsize.
    PRBool newPattern = PR_FALSE;
    double size;
    if (FcPatternGetDouble(pattern, FC_PIXEL_SIZE, 0, &size) != FcResultMatch) {
        size = pango_font_description_get_size(desc) / FLOAT_PANGO_SCALE;
        pattern = FcPatternDuplicate(pattern);
        newPattern = PR_TRUE;
        FcPatternDel(pattern, FC_PIXEL_SIZE);
        FcPatternAddDouble(pattern, FC_PIXEL_SIZE, size);
    }

    PangoFcFont *font = PANGO_FC_FONT(g_object_new(GFX_TYPE_PANGO_FC_FONT,
                                                   "pattern", pattern, NULL));

    if (newPattern) {
        FcPatternDestroy(pattern);
    }
    return font;
}

static void
gfx_pango_font_map_class_init(gfxPangoFontMapClass *klass)
{
    // inherit GObjectClass::finalize from the parent as there is nothing to
    // finalize in this object.

    PangoFontMapClass *fontmap_class = PANGO_FONT_MAP_CLASS (klass);
    fontmap_class->load_font = gfx_pango_font_map_load_font;
    fontmap_class->load_fontset = gfx_pango_font_map_load_fontset;
    fontmap_class->list_families = gfx_pango_font_map_list_families;
    // inherit fontmap_class->shape_engine_type from PangoFcFontMap

    PangoFcFontMapClass *fcfontmap_class = PANGO_FC_FONT_MAP_CLASS (klass);
    fcfontmap_class->get_resolution = gfx_pango_font_map_get_resolution;
    // context_key_* virtual functions are only necessary if we want to
    // dynamically respond to changes in the screen cairo_font_options_t.
    fcfontmap_class->context_substitute = gfx_pango_font_map_context_substitute;
    fcfontmap_class->create_font = gfx_pango_font_map_create_font;
}

/**
 ** gfxPangoFontGroup
 **/

static int
FFRECountHyphens (const nsAString &aFFREName)
{
    int h = 0;
    PRInt32 hyphen = 0;
    while ((hyphen = aFFREName.FindChar('-', hyphen)) >= 0) {
        ++h;
        ++hyphen;
    }
    return h;
}

static PRBool
FontCallback (const nsAString& fontName, const nsACString& genericName,
              void *closure)
{
    nsStringArray *sa = static_cast<nsStringArray*>(closure);

    // We ignore prefs that have three hypens since they are X style prefs.
    if (genericName.Length() && FFRECountHyphens(fontName) >= 3)
        return PR_TRUE;

    if (sa->IndexOf(fontName) < 0) {
        sa->AppendString(fontName);
    }

    return PR_TRUE;
}

gfxPangoFontGroup::gfxPangoFontGroup (const nsAString& families,
                                      const gfxFontStyle *aStyle)
    : gfxFontGroup(families, aStyle),
      mBasePangoFont(nsnull), mAdjustedSize(0)
{
    mFonts.AppendElements(1);
}

gfxPangoFontGroup::~gfxPangoFontGroup()
{
    if (mBasePangoFont)
        g_object_unref(mBasePangoFont);
}

gfxFontGroup *
gfxPangoFontGroup::Copy(const gfxFontStyle *aStyle)
{
    return new gfxPangoFontGroup(mFamilies, aStyle);
}

// A string of family names suitable for fontconfig
void
gfxPangoFontGroup::GetFcFamilies(nsAString& aFcFamilies)
{
    nsStringArray familyArray;

    // Leave non-existing fonts in the list so that fontconfig can get the
    // best match.
    ForEachFontInternal(mFamilies, mStyle.langGroup, PR_TRUE, PR_FALSE,
                        FontCallback, &familyArray);

    if (familyArray.Count()) {
        int i = 0;
        while (1) {
            aFcFamilies.Append(*familyArray[i]);
            ++i;
            if (i >= familyArray.Count())
                break;
            aFcFamilies.Append(NS_LITERAL_STRING(","));
        }
    }
    else {
        // XXX If there are no fonts, we should use dummy family.
        // Pango will resolve from this.
        // behdad: yep, looks good.
        // printf("%s(%s)\n", NS_ConvertUTF16toUTF8(families).get(),
        //                    aStyle->langGroup.get());
        aFcFamilies.Append(NS_LITERAL_STRING("sans-serif"));
    }
}

gfxFont *
gfxPangoFontGroup::GetFontAt(PRInt32 i) {
    NS_PRECONDITION(i == 0, "Only have one font");

    if (!mFonts[0]) {
        PangoFont *pangoFont = GetBasePangoFont();
        mFonts[0] = gfxPangoFcFont::GfxFont(GFX_PANGO_FC_FONT(pangoFont));
    }

    return mFonts[0];
}

/**
 ** gfxFcFont
 **/

cairo_user_data_key_t gfxFcFont::sGfxFontKey;

gfxFcFont::gfxFcFont(cairo_scaled_font_t *aCairoFont,
                     gfxPangoFontEntry *aFontEntry,
                     const gfxFontStyle *aFontStyle)
    : gfxFont(aFontEntry, aFontStyle),
      mCairoFont(aCairoFont),
      mHasMetrics(PR_FALSE)
{
    cairo_scaled_font_reference(mCairoFont);
    cairo_scaled_font_set_user_data(mCairoFont, &sGfxFontKey, this, NULL);
}

gfxFcFont::~gfxFcFont()
{
    cairo_scaled_font_set_user_data(mCairoFont, &sGfxFontKey, NULL, NULL);
    cairo_scaled_font_destroy(mCairoFont);
}

/* static */ void
gfxPangoFontGroup::Shutdown()
{
    gfxPangoFontCache::Shutdown();

    if (gPangoFontMap) {
        if (PANGO_IS_FC_FONT_MAP (gPangoFontMap)) {
            // This clears circular references from the fontmap to itself
            // through its fonts.
            pango_fc_font_map_shutdown(PANGO_FC_FONT_MAP(gPangoFontMap));
        }
        g_object_unref(gPangoFontMap);
        gPangoFontMap = NULL;
    }
}

static PangoStyle
ThebesStyleToPangoStyle (const gfxFontStyle *fs)
{
    if (fs->style == FONT_STYLE_ITALIC)
        return PANGO_STYLE_ITALIC;
    if (fs->style == FONT_STYLE_OBLIQUE)
        return PANGO_STYLE_OBLIQUE;

    return PANGO_STYLE_NORMAL;
}

static PangoWeight
ThebesStyleToPangoWeight (const gfxFontStyle *fs)
{
    PRInt32 w = fs->weight;

    /*
     * weights come in two parts crammed into one
     * integer -- the "base" weight is weight / 100,
     * the rest of the value is the "offset" from that
     * weight -- the number of steps to move to adjust
     * the weight in the list of supported font weights,
     * this value can be negative or positive.
     */
    PRInt32 baseWeight = (w + 50) / 100;
    PRInt32 offset = w - baseWeight * 100;

    /* clip weights to range 0 to 9 */
    if (baseWeight < 0)
        baseWeight = 0;
    if (baseWeight > 9)
        baseWeight = 9;

    /* Map from weight value to fcWeights index */
    static const int fcWeightLookup[10] = {
        0, 0, 0, 0, 1, 1, 2, 3, 3, 4,
    };

    PRInt32 fcWeight = fcWeightLookup[baseWeight];

    /*
     * adjust by the offset value, make sure we stay inside the 
     * fcWeights table
     */
    fcWeight += offset;

    if (fcWeight < 0)
        fcWeight = 0;
    if (fcWeight > 4)
        fcWeight = 4;

    /* Map to final PANGO_WEIGHT value */
    static const int fcWeights[5] = {
        349,
        449,
        649,
        749,
        900
    };

    return (PangoWeight)fcWeights[fcWeight];
}

/* Note this doesn't check sizeAdjust */
static PangoFontDescription *
NewPangoFontDescription(const nsAString &aName, const gfxFontStyle *aFontStyle)
{
    PangoFontDescription *fontDesc = pango_font_description_new();

    pango_font_description_set_family(fontDesc,
                                      NS_ConvertUTF16toUTF8(aName).get());
    pango_font_description_set_absolute_size
        (fontDesc, moz_pango_units_from_double(aFontStyle->size));
    pango_font_description_set_style(fontDesc,
                                     ThebesStyleToPangoStyle(aFontStyle));
    pango_font_description_set_weight(fontDesc,
                                      ThebesStyleToPangoWeight(aFontStyle));
    return fontDesc;
}

/**
 * The following gfxPangoFonts are accessed from the PangoFont, not from the
 * gfxFontCache hash table.  The gfxFontCache hash table is keyed by desired
 * family and style, whereas here we only know actual family and style.  There
 * may be more than one of these fonts with the same family and style, but
 * different PangoFont and actual font face.
 * 
 * The point of this is to record the exact font face for gfxTextRun glyph
 * indices.  The style of this font does not necessarily represent the exact
 * gfxFontStyle used to build the text run.  Notably, the language is not
 * recorded.
 */

/* static */
already_AddRefed<gfxFcFont>
gfxFcFont::GetOrMakeFont(FcPattern *aPattern)
{
    cairo_scaled_font_t *cairoFont = CreateScaledFont(aPattern);

    nsRefPtr<gfxFcFont> font = static_cast<gfxFcFont*>
        (cairo_scaled_font_get_user_data(cairoFont, &sGfxFontKey));

    if (!font) {
        double size;
        if (FcPatternGetDouble(aPattern,
                               FC_PIXEL_SIZE, 0, &size) != FcResultMatch) {
            NS_NOTREACHED("No size on pattern");
            size = 0.0;
        }

        // Shouldn't actually need to take too much care about the correct
        // name or style, as size is the only thing expected to be important.
        PRUint8 style = gfxFontconfigUtils::GetThebesStyle(aPattern);
        PRUint16 weight = gfxFontconfigUtils::GetThebesWeight(aPattern);

        // The LangSet in the FcPattern does not have an order so there is no
        // one particular language to choose and converting the set to a
        // string through FcNameUnparse() is more trouble than it's worth.
        NS_NAMED_LITERAL_CSTRING(langGroup, "x-unicode");
        gfxFontStyle fontStyle(style, weight, size, langGroup, 0.0,
                               PR_TRUE, PR_FALSE);

        FcChar8 *fc_file; // unsigned char
        const char *file; // signed for Mozilla string APIs
        if (FcPatternGetString(aPattern,
                               FC_FILE, 0, &fc_file) == FcResultMatch) {
            file = reinterpret_cast<char*>(fc_file);
        } else {
            // cairo won't know which font to open without a file.
            // (We don't create fonts from an FT_Face.)
            NS_NOTREACHED("Fonts without a file are not supported");
            static const char *noFile = "NO FILE";
            file = noFile;
        }
        int index;
        if (FcPatternGetInteger(aPattern, FC_INDEX, 0, &index)
            != FcResultMatch) {
            // cairo won't know what to do here either.
            NS_NOTREACHED("No index in pattern");
            index = 0;
        }
        // Get a unique face name from the file and id.
        nsAutoString name;
        AppendUTF8toUTF16(file, name);
        if (index != 0) {
            name.AppendLiteral("/");
            name.AppendInt(index);
        }

        nsRefPtr<gfxPangoFontEntry> fe = new gfxPangoFontEntry(name);

        // Note that the unique face in the name/fe and the gfxFontStyle are
        // not necessarily enough to provide a key that will describe a unique
        // font.  cairoFont contains information from aPattern, which is a
        // fully resolved pattern from FcFontRenderPrepare.
        // FcFontRenderPrepare takes the requested pattern and the face
        // pattern as input and can modify elements of the resulting pattern
        // that affect rendering but are not included in the gfxFontStyle.
        font = new gfxFcFont(cairoFont, fe, &fontStyle);
    }

    cairo_scaled_font_destroy(cairoFont);
    return font.forget();
}

static PangoContext *
GetPangoContext()
{
    PangoContext *context = pango_context_new();

    // Change the font map to recognize a base font on the context
    if (!gPangoFontMap) {
        gPangoFontMap = gfxPangoFontMap::NewFontMap();
    }
    pango_context_set_font_map(context, gPangoFontMap);

    return context;
}

static PangoFont*
LoadPangoFont(PangoContext *aPangoCtx, const PangoFontDescription *aPangoFontDesc)
{
    gfxPangoFontCache *cache = gfxPangoFontCache::GetPangoFontCache();
    if (!cache)
        return nsnull; // Error
    PangoFont* pangoFont = cache->Get(aPangoFontDesc);
    if (!pangoFont) {
        pangoFont = pango_context_load_font(aPangoCtx, aPangoFontDesc);
        if (pangoFont) {
            cache->Put(aPangoFontDesc, pangoFont);
        }
    }
    return pangoFont;
}

// The font group holds the reference to the PangoFont
PangoFont *
gfxPangoFontGroup::GetBasePangoFont()
{
    if (mBasePangoFont)
        return mBasePangoFont;

    nsAutoString fcFamilies;
    GetFcFamilies(fcFamilies);
    PangoFontDescription *pangoFontDesc = 
        NewPangoFontDescription(fcFamilies, GetStyle());

    PangoContext *pangoCtx = GetPangoContext();

    if (!GetStyle()->langGroup.IsEmpty()) {
        PangoLanguage *lang = GetPangoLanguage(GetStyle()->langGroup);
        if (lang)
            pango_context_set_language(pangoCtx, lang);
    }

    PangoFont *pangoFont = LoadPangoFont(pangoCtx, pangoFontDesc);

    gfxFloat size = GetStyle()->size;
    if (size != 0.0 && GetStyle()->sizeAdjust != 0.0) {
        LockedFTFace
            face(gfxPangoFcFont::GfxFont(GFX_PANGO_FC_FONT(pangoFont)));
        // Could try xHeight from TrueType/OpenType fonts.
        cairo_text_extents_t extents;
        if (face.GetCharExtents('x', &extents) &&
            extents.y_bearing < 0.0) {
            gfxFloat aspect = -extents.y_bearing / size;
            size = GetStyle()->GetAdjustedSize(aspect);

            pango_font_description_set_absolute_size
                (pangoFontDesc, moz_pango_units_from_double(size));
            g_object_unref(pangoFont);
            pangoFont = LoadPangoFont(pangoCtx, pangoFontDesc);
        }
    }

    if (pangoFontDesc)
        pango_font_description_free(pangoFontDesc);
    if (pangoCtx)
        g_object_unref(pangoCtx);

    mBasePangoFont = pangoFont;
    mAdjustedSize = size;

    return pangoFont;
}

void
gfxFcFont::GetGlyphExtents(PRUint32 aGlyph, cairo_text_extents_t* aExtents)
{
    NS_PRECONDITION(aExtents != NULL, "aExtents must not be NULL");

    cairo_glyph_t glyphs[1];
    glyphs[0].index = aGlyph;
    glyphs[0].x = 0.0;
    glyphs[0].y = 0.0;
    // cairo does some caching for us here but perhaps a small gain could be
    // made by caching more.  It is usually only the advance that is needed,
    // so caching only the advance could allow many requests to be cached with
    // little memory use.  Ideally this cache would be merged with
    // gfxGlyphExtents.
    cairo_scaled_font_glyph_extents(CairoScaledFont(), glyphs, 1, aExtents);
}

PRUint32
LockedFTFace::GetCharExtents(char aChar,
                             cairo_text_extents_t* aExtents)
{
    NS_PRECONDITION(aExtents != NULL, "aExtents must not be NULL");

    if (!mFace)
        return 0;

    // pango_fc_font_real_get_glyph uses FcFreeTypeCharIndex which may change
    // the charmap currently selected on the FT_Face, so, while
    // pango_fc_font_real_get_glyph might be used, we should use the same
    // function so as to search the charmaps.
    //
    // Unfortunately this considers the mac/roman cmap even when there is a
    // unicode cmap, which will be bad for symbol fonts, so we should do this
    // ourselves, perhaps with a lightweight cache like
    // pango_fc_font_real_get_glyph uses.
    FT_UInt gid = FcFreeTypeCharIndex(mFace, aChar); // glyph id
    if (gid) {
        mGfxFont->GetGlyphExtents(gid, aExtents);
    }

    return gid;
}

// rounding and truncation functions for a Freetype fixed point number 
// (FT26Dot6) stored in a 32bit integer with high 26 bits for the integer
// part and low 6 bits for the fractional part. 
#define FLOAT_FROM_26_6(x) ((x) / 64.0)
#define FLOAT_FROM_16_16(x) ((x) / 65536.0)
#define ROUND_26_6_TO_INT(x) ((x) >= 0 ?  ((32 + (x)) >> 6) \
                                       : -((32 - (x)) >> 6))
// aScale is intended for a 16.16 x/y_scale of an FT_Size_Metrics
static inline FT_Long
ScaleRoundDesignUnits(FT_Short aDesignMetric, FT_Fixed aScale)
{
    FT_Long fixed26dot6 = FT_MulFix(aDesignMetric, aScale);
    return ROUND_26_6_TO_INT(fixed26dot6);
}

// Snap a line to pixels while keeping the center and size of the line as
// close to the original position as possible.
//
// Pango does similar snapping for underline and strikethrough when fonts are
// hinted, but nsCSSRendering::GetTextDecorationRectInternal always snaps the
// top and size of lines.  Optimizing the distance between the line and
// baseline is probably good for the gap between text and underline, but
// optimizing the center of the line is better for positioning strikethough.
static void
SnapLineToPixels(gfxFloat& aOffset, gfxFloat& aSize)
{
    gfxFloat snappedSize = PR_MAX(NS_floor(aSize + 0.5), 1.0);
    // Correct offset for change in size
    gfxFloat offset = aOffset - 0.5 * (aSize - snappedSize);
    // Snap offset
    aOffset = NS_floor(offset + 0.5);
    aSize = snappedSize;
}

void
LockedFTFace::GetMetrics(gfxFont::Metrics* aMetrics, PRUint32* aSpaceGlyph)
{
    NS_PRECONDITION(aMetrics != NULL, "aMetrics must not be NULL");
    NS_PRECONDITION(aSpaceGlyph != NULL, "aSpaceGlyph must not be NULL");

    if (NS_UNLIKELY(!mFace)) {
        // No face.  This unfortunate situation might happen if the font
        // file is (re)moved at the wrong time.
        aMetrics->emHeight = mGfxFont->GetStyle()->size;
        aMetrics->emAscent = 0.8 * aMetrics->emHeight;
        aMetrics->emDescent = 0.2 * aMetrics->emHeight;
        aMetrics->maxAscent = aMetrics->emAscent;
        aMetrics->maxDescent = aMetrics->maxDescent;
        aMetrics->maxHeight = aMetrics->emHeight;
        aMetrics->internalLeading = 0.0;
        aMetrics->externalLeading = 0.2 * aMetrics->emHeight;
        aSpaceGlyph = 0;
        aMetrics->spaceWidth = 0.5 * aMetrics->emHeight;
        aMetrics->maxAdvance = aMetrics->spaceWidth;
        aMetrics->aveCharWidth = aMetrics->spaceWidth;
        aMetrics->zeroOrAveCharWidth = aMetrics->spaceWidth;
        aMetrics->xHeight = 0.5 * aMetrics->emHeight;
        aMetrics->underlineSize = aMetrics->emHeight / 14.0;
        aMetrics->underlineOffset = -aMetrics->underlineSize;
        aMetrics->strikeoutOffset = 0.25 * aMetrics->emHeight;
        aMetrics->strikeoutSize = aMetrics->underlineSize;
        aMetrics->superscriptOffset = aMetrics->xHeight;
        aMetrics->subscriptOffset = aMetrics->xHeight;

        return;
    }

    const FT_Size_Metrics& ftMetrics = mFace->size->metrics;

    // Scale for vertical design metric conversion: pixels per design unit.
    gfxFloat yScale;
    if (FT_IS_SCALABLE(mFace)) {
        // Prefer FT_Size_Metrics::x_scale to x_ppem as x_ppem does not
        // have subpixel accuracy.
        //
        // FT_Size_Metrics::y_scale is in 16.16 fixed point format.  Its
        // (fractional) value is a factor that converts vertical metrics from
        // design units to units of 1/64 pixels, so that the result may be
        // interpreted as pixels in 26.6 fixed point format.
        yScale = FLOAT_FROM_26_6(FLOAT_FROM_16_16(ftMetrics.y_scale));
        aMetrics->emHeight = mFace->units_per_EM * yScale;
    } else { // Not scalable.
        // FT_Size_Metrics doc says x_scale is "only relevant for scalable
        // font formats".
        gfxFloat emUnit = mFace->units_per_EM;
        aMetrics->emHeight = ftMetrics.y_ppem;
        yScale = aMetrics->emHeight / emUnit;
    }

    TT_OS2 *os2 =
        static_cast<TT_OS2*>(FT_Get_Sfnt_Table(mFace, ft_sfnt_os2));

    aMetrics->maxAscent = FLOAT_FROM_26_6(ftMetrics.ascender);
    aMetrics->maxDescent = -FLOAT_FROM_26_6(ftMetrics.descender);
    aMetrics->maxAdvance = FLOAT_FROM_26_6(ftMetrics.max_advance);

    gfxFloat lineHeight;
    if (os2 && os2->sTypoAscender) {
        aMetrics->emAscent = os2->sTypoAscender * yScale;
        aMetrics->emDescent = -os2->sTypoDescender * yScale;
        FT_Short typoHeight =
            os2->sTypoAscender - os2->sTypoDescender + os2->sTypoLineGap;
        lineHeight = typoHeight * yScale;

        // maxAscent/maxDescent get used for frame heights, and some fonts
        // don't have the HHEA table ascent/descent set (bug 279032).
        if (aMetrics->emAscent > aMetrics->maxAscent)
            aMetrics->maxAscent = aMetrics->emAscent;
        if (aMetrics->emDescent > aMetrics->maxDescent)
            aMetrics->maxDescent = aMetrics->emDescent;
    } else {
        aMetrics->emAscent = aMetrics->maxAscent;
        aMetrics->emDescent = aMetrics->maxDescent;
        lineHeight = FLOAT_FROM_26_6(ftMetrics.height);
    }

    cairo_text_extents_t extents;
    *aSpaceGlyph = GetCharExtents(' ', &extents);
    if (*aSpaceGlyph) {
        aMetrics->spaceWidth = extents.x_advance;
    } else {
        aMetrics->spaceWidth = aMetrics->maxAdvance; // guess
    }

    aMetrics->zeroOrAveCharWidth = 0.0;
    if (GetCharExtents('0', &extents)) {
        aMetrics->zeroOrAveCharWidth = extents.x_advance;
    }

    // Prefering a measured x over sxHeight because sxHeight doesn't consider
    // hinting, but maybe the x extents are not quite right in some fancy
    // script fonts.  CSS 2.1 suggests possibly using the height of an "o",
    // which would have a more consistent glyph across fonts.
    if (GetCharExtents('x', &extents) && extents.y_bearing < 0.0) {
        aMetrics->xHeight = -extents.y_bearing;
        aMetrics->aveCharWidth = extents.x_advance;
    } else {
        if (os2 && os2->sxHeight) {
            aMetrics->xHeight = os2->sxHeight * yScale;
        } else {
            // CSS 2.1, section 4.3.2 Lengths: "In the cases where it is
            // impossible or impractical to determine the x-height, a value of
            // 0.5em should be used."
            aMetrics->xHeight = 0.5 * aMetrics->emHeight;
        }
        aMetrics->aveCharWidth = 0.0; // updated below
    }
    // aveCharWidth is used for the width of text input elements so be
    // liberal rather than conservative in the estimate.
    if (os2 && os2->xAvgCharWidth) {
        // Round to pixels as this is compared with maxAdvance to guess
        // whether this is a fixed width font.
        gfxFloat avgCharWidth =
            ScaleRoundDesignUnits(os2->xAvgCharWidth, ftMetrics.x_scale);
        aMetrics->aveCharWidth =
            PR_MAX(aMetrics->aveCharWidth, avgCharWidth);
    }
    aMetrics->aveCharWidth =
        PR_MAX(aMetrics->aveCharWidth, aMetrics->zeroOrAveCharWidth);
    if (aMetrics->aveCharWidth == 0.0) {
        aMetrics->aveCharWidth = aMetrics->spaceWidth;
    }
    if (aMetrics->zeroOrAveCharWidth == 0.0) {
        aMetrics->zeroOrAveCharWidth = aMetrics->aveCharWidth;
    }
    // Apparently hinting can mean that max_advance is not always accurate.
    aMetrics->maxAdvance =
        PR_MAX(aMetrics->maxAdvance, aMetrics->aveCharWidth);

    // gfxFont::Metrics::underlineOffset is the position of the top of the
    // underline.
    //
    // FT_FaceRec documentation describes underline_position as "the
    // center of the underlining stem".  This was the original definition
    // of the PostScript metric, but in the PostScript table of OpenType
    // fonts the metric is "the top of the underline"
    // (http://www.microsoft.com/typography/otspec/post.htm), and FreeType
    // (up to version 2.3.7) doesn't make any adjustment.
    //
    // Therefore get the underline position directly from the table
    // ourselves when this table exists.  Use FreeType's metrics for
    // other (including older PostScript) fonts.
    if (mFace->underline_position && mFace->underline_thickness) {
        aMetrics->underlineSize = mFace->underline_thickness * yScale;
        TT_Postscript *post = static_cast<TT_Postscript*>
            (FT_Get_Sfnt_Table(mFace, ft_sfnt_post));
        if (post && post->underlinePosition) {
            aMetrics->underlineOffset = post->underlinePosition * yScale;
        } else {
            aMetrics->underlineOffset = mFace->underline_position * yScale
                + 0.5 * aMetrics->underlineSize;
        }
    } else { // No underline info.
        // Imitate Pango.
        aMetrics->underlineSize = aMetrics->emHeight / 14.0;
        aMetrics->underlineOffset = -aMetrics->underlineSize;
    }

    if (os2 && os2->yStrikeoutSize && os2->yStrikeoutPosition) {
        aMetrics->strikeoutSize = os2->yStrikeoutSize * yScale;
        aMetrics->strikeoutOffset = os2->yStrikeoutPosition * yScale;
    } else { // No strikeout info.
        aMetrics->strikeoutSize = aMetrics->underlineSize;
        // Use OpenType spec's suggested position for Roman font.
        aMetrics->strikeoutOffset = aMetrics->emHeight * 409.0 / 2048.0
            + 0.5 * aMetrics->strikeoutSize;
    }
    SnapLineToPixels(aMetrics->strikeoutOffset, aMetrics->strikeoutSize);

    if (os2 && os2->ySuperscriptYOffset) {
        gfxFloat val = ScaleRoundDesignUnits(os2->ySuperscriptYOffset,
                                             ftMetrics.y_scale);
        aMetrics->superscriptOffset = PR_MAX(1.0, val);
    } else {
        aMetrics->superscriptOffset = aMetrics->xHeight;
    }
    
    if (os2 && os2->ySubscriptYOffset) {
        gfxFloat val = ScaleRoundDesignUnits(os2->ySubscriptYOffset,
                                             ftMetrics.y_scale);
        // some fonts have the incorrect sign. 
        val = fabs(val);
        aMetrics->subscriptOffset = PR_MAX(1.0, val);
    } else {
        aMetrics->subscriptOffset = aMetrics->xHeight;
    }

    aMetrics->maxHeight = aMetrics->maxAscent + aMetrics->maxDescent;

    // Ensure emAscent + emDescent == emHeight
    gfxFloat sum = aMetrics->emAscent + aMetrics->emDescent;
    aMetrics->emAscent = sum > 0.0 ?
        aMetrics->emAscent * aMetrics->emHeight / sum : 0.0;
    aMetrics->emDescent = aMetrics->emHeight - aMetrics->emAscent;

    aMetrics->internalLeading = aMetrics->maxHeight - aMetrics->emHeight;
    // Text input boxes currently don't work well with lineHeight < maxHeight
    // (with Verdana, for example).
    aMetrics->externalLeading = PR_MAX(lineHeight - aMetrics->maxHeight, 0);
}

const gfxFont::Metrics&
gfxFcFont::GetMetrics()
{
    if (mHasMetrics)
        return mMetrics;

    if (NS_UNLIKELY(GetStyle()->size <= 0.0)) {
        new(&mMetrics) gfxFont::Metrics(); // zero initialize
        mSpaceGlyph = 0;
    } else {
        LockedFTFace(this).GetMetrics(&mMetrics, &mSpaceGlyph);
    }

    SanitizeMetrics(&mMetrics, PR_FALSE);

#if 0
    //    printf("font name: %s %f\n", NS_ConvertUTF16toUTF8(GetName()).get(), GetStyle()->size);
    //    printf ("pango font %s\n", pango_font_description_to_string (pango_font_describe (font)));

    fprintf (stderr, "Font: %s\n", NS_ConvertUTF16toUTF8(GetName()).get());
    fprintf (stderr, "    emHeight: %f emAscent: %f emDescent: %f\n", mMetrics.emHeight, mMetrics.emAscent, mMetrics.emDescent);
    fprintf (stderr, "    maxAscent: %f maxDescent: %f\n", mMetrics.maxAscent, mMetrics.maxDescent);
    fprintf (stderr, "    internalLeading: %f externalLeading: %f\n", mMetrics.externalLeading, mMetrics.internalLeading);
    fprintf (stderr, "    spaceWidth: %f aveCharWidth: %f xHeight: %f\n", mMetrics.spaceWidth, mMetrics.aveCharWidth, mMetrics.xHeight);
    fprintf (stderr, "    uOff: %f uSize: %f stOff: %f stSize: %f suOff: %f suSize: %f\n", mMetrics.underlineOffset, mMetrics.underlineSize, mMetrics.strikeoutOffset, mMetrics.strikeoutSize, mMetrics.superscriptOffset, mMetrics.subscriptOffset);
#endif

    mHasMetrics = PR_TRUE;
    return mMetrics;
}

nsString
gfxFcFont::GetUniqueName()
{
    return GetName();
}

/**
 ** gfxTextRun
 * 
 * A serious problem:
 *
 * -- We draw with a font that's hinted for the CTM, but we measure with a font
 * hinted to the identity matrix, so our "bounding metrics" may not be accurate.
 * 
 **/

/**
 * We use this to append an LTR or RTL Override character to the start of the
 * string. This forces Pango to honour our direction even if there are neutral characters
 * in the string.
 */
static PRInt32 AppendDirectionalIndicatorUTF8(PRBool aIsRTL, nsACString& aString)
{
    static const PRUnichar overrides[2][2] =
      { { 0x202d, 0 }, { 0x202e, 0 }}; // LRO, RLO
    AppendUTF16toUTF8(overrides[aIsRTL], aString);
    return 3; // both overrides map to 3 bytes in UTF8
}

gfxTextRun *
gfxPangoFontGroup::MakeTextRun(const PRUint8 *aString, PRUint32 aLength,
                               const Parameters *aParams, PRUint32 aFlags)
{
    NS_ASSERTION(aFlags & TEXT_IS_8BIT, "8bit should have been set");
    gfxTextRun *run = gfxTextRun::Create(aParams, aString, aLength, this, aFlags);
    if (!run)
        return nsnull;

    PRBool isRTL = run->IsRightToLeft();
    if ((aFlags & TEXT_IS_ASCII) && !isRTL) {
        // We don't need to send an override character here, the characters must be all LTR
        const gchar *utf8Chars = reinterpret_cast<const gchar*>(aString);
        InitTextRun(run, utf8Chars, aLength, 0, PR_TRUE);
    } else {
        // this is really gross...
        const char *chars = reinterpret_cast<const char*>(aString);
        NS_ConvertASCIItoUTF16 unicodeString(chars, aLength);
        nsCAutoString utf8;
        PRInt32 headerLen = AppendDirectionalIndicatorUTF8(isRTL, utf8);
        AppendUTF16toUTF8(unicodeString, utf8);
        InitTextRun(run, utf8.get(), utf8.Length(), headerLen, PR_TRUE);
    }
    run->FetchGlyphExtents(aParams->mContext);
    return run;
}

#if defined(ENABLE_FAST_PATH_8BIT)
PRBool
gfxPangoFontGroup::CanTakeFastPath(PRUint32 aFlags)
{
    // Can take fast path only if OPTIMIZE_SPEED is set and IS_RTL isn't.
    // We need to always use Pango for RTL text, in case glyph mirroring is
    // required.
    PRBool speed = aFlags & gfxTextRunFactory::TEXT_OPTIMIZE_SPEED;
    PRBool isRTL = aFlags & gfxTextRunFactory::TEXT_IS_RTL;
    return speed && !isRTL && PANGO_IS_FC_FONT(GetBasePangoFont());
}
#endif

gfxTextRun *
gfxPangoFontGroup::MakeTextRun(const PRUnichar *aString, PRUint32 aLength,
                               const Parameters *aParams, PRUint32 aFlags)
{
    gfxTextRun *run = gfxTextRun::Create(aParams, aString, aLength, this, aFlags);
    if (!run)
        return nsnull;

    run->RecordSurrogates(aString);

    nsCAutoString utf8;
    PRInt32 headerLen = AppendDirectionalIndicatorUTF8(run->IsRightToLeft(), utf8);
    AppendUTF16toUTF8(Substring(aString, aString + aLength), utf8);
    PRBool is8Bit = PR_FALSE;

#if defined(ENABLE_FAST_PATH_8BIT)
    if (CanTakeFastPath(aFlags)) {
        PRUint32 allBits = 0;
        PRUint32 i;
        for (i = 0; i < aLength; ++i) {
            allBits |= aString[i];
        }
        is8Bit = (allBits & 0xFF00) == 0;
    }
#endif
    InitTextRun(run, utf8.get(), utf8.Length(), headerLen, is8Bit);
    run->FetchGlyphExtents(aParams->mContext);
    return run;
}

void
gfxPangoFontGroup::InitTextRun(gfxTextRun *aTextRun, const gchar *aUTF8Text,
                               PRUint32 aUTF8Length, PRUint32 aUTF8HeaderLength,
                               PRBool aTake8BitPath)
{
#if defined(ENABLE_FAST_PATH_ALWAYS)
    CreateGlyphRunsFast(aTextRun, aUTF8Text + aUTF8HeaderLength, aUTF8Length - aUTF8HeaderLength);
#else
#if defined(ENABLE_FAST_PATH_8BIT)
    if (aTake8BitPath && CanTakeFastPath(aTextRun->GetFlags())) {
        nsresult rv = CreateGlyphRunsFast(aTextRun, aUTF8Text + aUTF8HeaderLength, aUTF8Length - aUTF8HeaderLength);
        if (NS_SUCCEEDED(rv))
            return;
    }
#endif

    CreateGlyphRunsItemizing(aTextRun, aUTF8Text, aUTF8Length, aUTF8HeaderLength);
#endif
}

// This will fetch an existing scaled_font if one exists.
static cairo_scaled_font_t *
CreateScaledFont(FcPattern *aPattern)
{
    cairo_font_face_t *face = cairo_ft_font_face_create_for_pattern(aPattern);
    double size;
    if (FcPatternGetDouble(aPattern,
                           FC_PIXEL_SIZE, 0, &size) != FcResultMatch) {
        NS_NOTREACHED("No size on pattern");
        size = 0.0;
    }
        
    cairo_matrix_t fontMatrix;
    FcMatrix *fcMatrix;
    if (FcPatternGetMatrix(aPattern, FC_MATRIX, 0, &fcMatrix) == FcResultMatch)
        cairo_matrix_init(&fontMatrix, fcMatrix->xx, -fcMatrix->yx, -fcMatrix->xy, fcMatrix->yy, 0, 0);
    else
        cairo_matrix_init_identity(&fontMatrix);
    cairo_matrix_scale(&fontMatrix, size, size);

    // The cairo_scaled_font is created with a unit ctm so that metrics and
    // positions are in user space, but this means that hinting effects will
    // not be estimated accurately for non-unit transformations.
    cairo_matrix_t identityMatrix;
    cairo_matrix_init_identity(&identityMatrix);

    // Font options are set explicitly here to improve cairo's caching
    // behavior and to record the relevant parts of the pattern for
    // SetupCairoFont (so that the pattern can be released).
    //
    // Most font_options have already been set as defaults on the FcPattern
    // with cairo_ft_font_options_substitute(), then user and system
    // fontconfig configurations were applied.  The resulting font_options
    // have been recorded on the face during
    // cairo_ft_font_face_create_for_pattern().
    //
    // None of the settings here cause this scaled_font to behave any
    // differently from how it would behave if it were created from the same
    // face with default font_options.
    //
    // We set options explicitly so that the same scaled_font will be found in
    // the cairo_scaled_font_map when cairo loads glyphs from a context with
    // the same font_face, font_matrix, ctm, and surface font_options.
    //
    // Unfortunately, _cairo_scaled_font_keys_equal doesn't know about the
    // font_options on the cairo_ft_font_face, and doesn't consider default
    // option values to not match any explicit values.
    //
    // Even after cairo_set_scaled_font is used to set font_options for the
    // cairo context, when cairo looks for a scaled_font for the context, it
    // will look for a font with some option values from the target surface if
    // any values are left default on the context font_options.  If this
    // scaled_font is created with default font_options, cairo will not find
    // it.
    cairo_font_options_t *fontOptions = cairo_font_options_create();

    // The one option not recorded in the pattern is hint_metrics, which will
    // affect glyph metrics.  The default behaves as CAIRO_HINT_METRICS_ON.
    // We should be considering the font_options of the surface on which this
    // font will be used, but currently we don't have different gfxFonts for
    // different surface font_options, so we'll create a font suitable for the
    // Screen. Image and xlib surfaces default to CAIRO_HINT_METRICS_ON.
    cairo_font_options_set_hint_metrics(fontOptions, CAIRO_HINT_METRICS_ON);

    // The remaining options have been recorded on the pattern and the face.
    // _cairo_ft_options_merge has some logic to decide which options from the
    // scaled_font or from the cairo_ft_font_face take priority in the way the
    // font behaves.
    //
    // In the majority of cases, _cairo_ft_options_merge uses the options from
    // the cairo_ft_font_face, so sometimes it is not so important which
    // values are set here so long as they are not defaults, but we'll set
    // them to the exact values that we expect from the font, to be consistent
    // and to protect against changes in cairo.
    //
    // In some cases, _cairo_ft_options_merge uses some options from the
    // scaled_font's font_options rather than options on the
    // cairo_ft_font_face (from fontconfig).
    // https://bugs.freedesktop.org/show_bug.cgi?id=11838
    //
    // Surface font options were set on the pattern in
    // cairo_ft_font_options_substitute.  If fontconfig has changed the
    // hint_style then that is what the user (or distribution) wants, so we
    // use the setting from the FcPattern.
    //
    // Fallback values here mirror treatment of defaults in cairo-ft-font.c.
    FcBool hinting;
    if (FcPatternGetBool(aPattern, FC_HINTING, 0, &hinting) != FcResultMatch) {
        hinting = FcTrue;
    }
    cairo_hint_style_t hint_style;
    if (!hinting) {
        hint_style = CAIRO_HINT_STYLE_NONE;
    } else {
#ifdef FC_HINT_STYLE  // FC_HINT_STYLE is available from fontconfig 2.2.91.
        int fc_hintstyle;
        if (FcPatternGetInteger(aPattern, FC_HINT_STYLE,
                                0, &fc_hintstyle        ) != FcResultMatch) {
            fc_hintstyle = FC_HINT_FULL;
        }
        switch (fc_hintstyle) {
            case FC_HINT_NONE:
                hint_style = CAIRO_HINT_STYLE_NONE;
                break;
            case FC_HINT_SLIGHT:
                hint_style = CAIRO_HINT_STYLE_SLIGHT;
                break;
            case FC_HINT_MEDIUM:
            default: // This fallback mirrors _get_pattern_ft_options in cairo.
                hint_style = CAIRO_HINT_STYLE_MEDIUM;
                break;
            case FC_HINT_FULL:
                hint_style = CAIRO_HINT_STYLE_FULL;
                break;
        }
#else // no FC_HINT_STYLE
        hint_style = CAIRO_HINT_STYLE_FULL;
#endif
    }
    cairo_font_options_set_hint_style(fontOptions, hint_style);

    int rgba;
    if (FcPatternGetInteger(aPattern,
                            FC_RGBA, 0, &rgba) != FcResultMatch) {
        rgba = FC_RGBA_UNKNOWN;
    }
    cairo_subpixel_order_t subpixel_order = CAIRO_SUBPIXEL_ORDER_DEFAULT;
    switch (rgba) {
        case FC_RGBA_UNKNOWN:
        case FC_RGBA_NONE:
        default:
            // There is no CAIRO_SUBPIXEL_ORDER_NONE.  Subpixel antialiasing
            // is disabled through cairo_antialias_t.
            rgba = FC_RGBA_NONE;
            // subpixel_order won't be used by the font as we won't use
            // CAIRO_ANTIALIAS_SUBPIXEL, but don't leave it at default for
            // caching reasons described above.  Fall through:
        case FC_RGBA_RGB:
            subpixel_order = CAIRO_SUBPIXEL_ORDER_RGB;
            break;
        case FC_RGBA_BGR:
            subpixel_order = CAIRO_SUBPIXEL_ORDER_BGR;
            break;
        case FC_RGBA_VRGB:
            subpixel_order = CAIRO_SUBPIXEL_ORDER_VRGB;
            break;
        case FC_RGBA_VBGR:
            subpixel_order = CAIRO_SUBPIXEL_ORDER_VBGR;
            break;
    }
    cairo_font_options_set_subpixel_order(fontOptions, subpixel_order);

    FcBool fc_antialias;
    if (FcPatternGetBool(aPattern,
                         FC_ANTIALIAS, 0, &fc_antialias) != FcResultMatch) {
        fc_antialias = FcTrue;
    }
    cairo_antialias_t antialias;
    if (!fc_antialias) {
        antialias = CAIRO_ANTIALIAS_NONE;
    } else if (rgba == FC_RGBA_NONE) {
        antialias = CAIRO_ANTIALIAS_GRAY;
    } else {
        antialias = CAIRO_ANTIALIAS_SUBPIXEL;
    }
    cairo_font_options_set_antialias(fontOptions, antialias);

    cairo_scaled_font_t *scaledFont =
        cairo_scaled_font_create(face, &fontMatrix, &identityMatrix,
                                 fontOptions);

    cairo_font_options_destroy(fontOptions);
    cairo_font_face_destroy(face);

    NS_ASSERTION(cairo_scaled_font_status(scaledFont) == CAIRO_STATUS_SUCCESS,
                 "Failed to create scaled font");
    return scaledFont;
}

PRBool
gfxFcFont::SetupCairoFont(gfxContext *aContext)
{
    cairo_t *cr = aContext->GetCairo();

    // The scaled font ctm is not relevant right here because
    // cairo_set_scaled_font does not record the scaled font itself, but
    // merely the font_face, font_matrix, font_options.  The scaled_font used
    // for the target can be different from the scaled_font passed to
    // cairo_set_scaled_font.  (Unfortunately we have measured only for an
    // identity ctm.)
    cairo_scaled_font_t *cairoFont = CairoScaledFont();

    if (cairo_scaled_font_status(cairoFont) != CAIRO_STATUS_SUCCESS) {
        // Don't cairo_set_scaled_font as that would propagate the error to
        // the cairo_t, precluding any further drawing.
        return PR_FALSE;
    }
    // Thoughts on which font_options to set on the context:
    //
    // cairoFont has been created for screen rendering.
    //
    // When the context is being used for screen rendering, we should set
    // font_options such that the same scaled_font gets used (when the ctm is
    // the same).  The use of explicit font_options recorded in
    // CreateScaledFont ensures that this will happen.
    //
    // XXXkt: For pdf and ps surfaces, I don't know whether it's better to
    // remove surface-specific options, or try to draw with the same
    // scaled_font that was used to measure.  As the same font_face is being
    // used, its font_options will often override some values anyway (unless
    // perhaps we remove those from the FcPattern at face creation).
    //
    // I can't see any significant difference in printing, irrespective of
    // what is set here.  It's too late to change things here as measuring has
    // already taken place.  We should really be measuring with a different
    // font for pdf and ps surfaces (bug 403513).
    cairo_set_scaled_font(cr, cairoFont);
    return PR_TRUE;
}

static void
SetupClusterBoundaries(gfxTextRun* aTextRun, const gchar *aUTF8, PRUint32 aUTF8Length,
                       PRUint32 aUTF16Offset, PangoAnalysis *aAnalysis)
{
    if (aTextRun->GetFlags() & gfxTextRunFactory::TEXT_IS_8BIT) {
        // 8-bit text doesn't have clusters.
        // XXX is this true in all languages???
        // behdad: don't think so.  Czech for example IIRC has a
        // 'ch' grapheme.
        return;
    }

    // Pango says "the array of PangoLogAttr passed in must have at least N+1
    // elements, if there are N characters in the text being broken".
    // Could use g_utf8_strlen(aUTF8, aUTF8Length) + 1 but the memory savings
    // may not be worth the call.
    nsAutoTArray<PangoLogAttr,2000> buffer;
    if (!buffer.AppendElements(aUTF8Length + 1))
        return;

    pango_break(aUTF8, aUTF8Length, aAnalysis,
                buffer.Elements(), buffer.Length());

    const gchar *p = aUTF8;
    const gchar *end = aUTF8 + aUTF8Length;
    const PangoLogAttr *attr = buffer.Elements();
    gfxTextRun::CompressedGlyph g;
    while (p < end) {
        if (!attr->is_cursor_position) {
            aTextRun->SetGlyphs(aUTF16Offset, g.SetComplex(PR_FALSE, PR_TRUE, 0), nsnull);
        }
        ++aUTF16Offset;
        
        gunichar ch = g_utf8_get_char(p);
        NS_ASSERTION(ch != 0, "Shouldn't have NUL in pango_break");
        NS_ASSERTION(!IS_SURROGATE(ch), "Shouldn't have surrogates in UTF8");
        if (ch >= 0x10000) {
            // set glyph info for the UTF-16 low surrogate
            aTextRun->SetGlyphs(aUTF16Offset, g.SetComplex(PR_FALSE, PR_FALSE, 0), nsnull);
            ++aUTF16Offset;
        }
        // We produced this utf8 so we don't need to worry about malformed stuff
        p = g_utf8_next_char(p);
        ++attr;
    }
}

static PRInt32
ConvertPangoToAppUnits(PRInt32 aCoordinate, PRUint32 aAppUnitsPerDevUnit)
{
    PRInt64 v = (PRInt64(aCoordinate)*aAppUnitsPerDevUnit + PANGO_SCALE/2)/PANGO_SCALE;
    return PRInt32(v);
}

/**
 * Given a run of Pango glyphs that should be treated as a single
 * cluster/ligature, store them in the textrun at the appropriate character
 * and set the other characters involved to be ligature/cluster continuations
 * as appropriate.
 */ 
static nsresult
SetGlyphsForCharacterGroup(const PangoGlyphInfo *aGlyphs, PRUint32 aGlyphCount,
                           gfxTextRun *aTextRun,
                           const gchar *aUTF8, PRUint32 aUTF8Length,
                           PRUint32 *aUTF16Offset,
                           PangoGlyphUnit aOverrideSpaceWidth)
{
    PRUint32 utf16Offset = *aUTF16Offset;
    PRUint32 textRunLength = aTextRun->GetLength();
    const PRUint32 appUnitsPerDevUnit = aTextRun->GetAppUnitsPerDevUnit();
    const gfxTextRun::CompressedGlyph *charGlyphs = aTextRun->GetCharacterGlyphs();

    // Override the width of a space, but only for spaces that aren't
    // clustered with something else (like a freestanding diacritical mark)
    PangoGlyphUnit width = aGlyphs[0].geometry.width;
    if (aOverrideSpaceWidth && aUTF8[0] == ' ' &&
        (utf16Offset + 1 == textRunLength ||
         charGlyphs[utf16Offset].IsClusterStart())) {
        width = aOverrideSpaceWidth;
    }
    PRInt32 advance = ConvertPangoToAppUnits(width, appUnitsPerDevUnit);

    gfxTextRun::CompressedGlyph g;
    PRBool atClusterStart = aTextRun->IsClusterStart(utf16Offset);
    // See if we fit in the compressed area.
    if (aGlyphCount == 1 && advance >= 0 && atClusterStart &&
        aGlyphs[0].geometry.x_offset == 0 &&
        aGlyphs[0].geometry.y_offset == 0 &&
        !IS_EMPTY_GLYPH(aGlyphs[0].glyph) &&
        gfxTextRun::CompressedGlyph::IsSimpleAdvance(advance) &&
        gfxTextRun::CompressedGlyph::IsSimpleGlyphID(aGlyphs[0].glyph)) {
        aTextRun->SetSimpleGlyph(utf16Offset,
                                 g.SetSimpleGlyph(advance, aGlyphs[0].glyph));
    } else {
        nsAutoTArray<gfxTextRun::DetailedGlyph,10> detailedGlyphs;
        if (!detailedGlyphs.AppendElements(aGlyphCount))
            return NS_ERROR_OUT_OF_MEMORY;

        PRInt32 direction = aTextRun->IsRightToLeft() ? -1 : 1;
        PRUint32 pangoIndex = direction > 0 ? 0 : aGlyphCount - 1;
        PRUint32 detailedIndex = 0;
        for (PRUint32 i = 0; i < aGlyphCount; ++i) {
            const PangoGlyphInfo &glyph = aGlyphs[pangoIndex];
            pangoIndex += direction;
            // The zero width characters return empty glyph ID at
            // shaping; we should skip these.
            if (IS_EMPTY_GLYPH(glyph.glyph))
                continue;

            gfxTextRun::DetailedGlyph *details = &detailedGlyphs[detailedIndex];
            ++detailedIndex;

            details->mGlyphID = glyph.glyph;
            NS_ASSERTION(details->mGlyphID == glyph.glyph,
                         "Seriously weird glyph ID detected!");
            details->mAdvance =
                ConvertPangoToAppUnits(glyph.geometry.width,
                                       appUnitsPerDevUnit);
            details->mXOffset =
                float(glyph.geometry.x_offset)*appUnitsPerDevUnit/PANGO_SCALE;
            details->mYOffset =
                float(glyph.geometry.y_offset)*appUnitsPerDevUnit/PANGO_SCALE;
        }
        g.SetComplex(atClusterStart, PR_TRUE, detailedIndex);
        aTextRun->SetGlyphs(utf16Offset, g, detailedGlyphs.Elements());
    }

    // Check for ligatures and set *aUTF16Offset.
    const gchar *p = aUTF8;
    const gchar *end = aUTF8 + aUTF8Length;
    while (1) {
        // Skip the CompressedGlyph that we have added, but check if the
        // character was supposed to be ignored. If it's supposed to be ignored,
        // overwrite the textrun entry with an invisible missing-glyph.
        gunichar ch = g_utf8_get_char(p);
        NS_ASSERTION(!IS_SURROGATE(ch), "surrogates should not appear in UTF8");
        if (ch >= 0x10000) {
            // Skip surrogate
            ++utf16Offset;
        }
        NS_ASSERTION(!gfxFontGroup::IsInvalidChar(PRUnichar(ch)),
                     "Invalid character detected");
        ++utf16Offset;

        // We produced this UTF8 so we don't need to worry about malformed stuff
        p = g_utf8_next_char(p);
        if (p >= end)
            break;

        if (utf16Offset >= textRunLength) {
            NS_ERROR("Someone has added too many glyphs!");
            return NS_ERROR_FAILURE;
        }

        g.SetComplex(aTextRun->IsClusterStart(utf16Offset), PR_FALSE, 0);
        aTextRun->SetGlyphs(utf16Offset, g, nsnull);
    }
    *aUTF16Offset = utf16Offset;
    return NS_OK;
}

nsresult
gfxPangoFontGroup::SetGlyphs(gfxTextRun *aTextRun,
                             const gchar *aUTF8, PRUint32 aUTF8Length,
                             PRUint32 *aUTF16Offset, PangoGlyphString *aGlyphs,
                             PangoGlyphUnit aOverrideSpaceWidth,
                             PRBool aAbortOnMissingGlyph)
{
    gint numGlyphs = aGlyphs->num_glyphs;
    PangoGlyphInfo *glyphs = aGlyphs->glyphs;
    const gint *logClusters = aGlyphs->log_clusters;
    // We cannot make any assumptions about the order of glyph clusters
    // provided by pango_shape (see 375864), so we work through the UTF8 text
    // and process the glyph clusters in logical order.

    // logGlyphs is like an inverse of logClusters.  For each UTF8 byte:
    //   >= 0 indicates that the byte is first in a cluster and
    //        gives the position of the starting glyph for the cluster.
    //     -1 indicates that the byte does not start a cluster.
    nsAutoTArray<gint,2000> logGlyphs;
    if (!logGlyphs.AppendElements(aUTF8Length + 1))
        return NS_ERROR_OUT_OF_MEMORY;
    PRUint32 utf8Index = 0;
    for(; utf8Index < aUTF8Length; ++utf8Index)
        logGlyphs[utf8Index] = -1;
    logGlyphs[aUTF8Length] = numGlyphs;

    gint lastCluster = -1; // != utf8Index
    for (gint glyphIndex = 0; glyphIndex < numGlyphs; ++glyphIndex) {
        gint thisCluster = logClusters[glyphIndex];
        if (thisCluster != lastCluster) {
            lastCluster = thisCluster;
            NS_ASSERTION(0 <= thisCluster && thisCluster < gint(aUTF8Length),
                         "garbage from pango_shape - this is bad");
            logGlyphs[thisCluster] = glyphIndex;
        }
    }

    PRUint32 utf16Offset = *aUTF16Offset;
    PRUint32 textRunLength = aTextRun->GetLength();
    utf8Index = 0;
    // The next glyph cluster in logical order. 
    gint nextGlyphClusterStart = logGlyphs[utf8Index];
    NS_ASSERTION(nextGlyphClusterStart >= 0, "No glyphs! - NUL in string?");
    while (utf8Index < aUTF8Length) {
        if (utf16Offset >= textRunLength) {
          NS_ERROR("Someone has added too many glyphs!");
          return NS_ERROR_FAILURE;
        }
        gint glyphClusterStart = nextGlyphClusterStart;
        // Find the utf8 text associated with this glyph cluster.
        PRUint32 clusterUTF8Start = utf8Index;
        // Check we are consistent with pango_break data.
        NS_ASSERTION(aTextRun->GetCharacterGlyphs()->IsClusterStart(),
                     "Glyph cluster not aligned on character cluster.");
        do {
            ++utf8Index;
            nextGlyphClusterStart = logGlyphs[utf8Index];
        } while (nextGlyphClusterStart < 0);
        const gchar *clusterUTF8 = &aUTF8[clusterUTF8Start];
        PRUint32 clusterUTF8Length = utf8Index - clusterUTF8Start;

        PRBool haveMissingGlyph = PR_FALSE;
        gint glyphIndex = glyphClusterStart;

        // It's now unncecessary to do NUL handling here.
        do {
            if (IS_MISSING_GLYPH(glyphs[glyphIndex].glyph)) {
                // Does pango ever provide more than one glyph in the
                // cluster if there is a missing glyph?
                // behdad: yes
                haveMissingGlyph = PR_TRUE;
            }
            glyphIndex++;
        } while (glyphIndex < numGlyphs && 
                 logClusters[glyphIndex] == gint(clusterUTF8Start));

        if (haveMissingGlyph && aAbortOnMissingGlyph)
            return NS_ERROR_FAILURE;

        nsresult rv;
        if (haveMissingGlyph) {
            rv = SetMissingGlyphs(aTextRun, clusterUTF8, clusterUTF8Length,
                             &utf16Offset);
        } else {
            rv = SetGlyphsForCharacterGroup(&glyphs[glyphClusterStart],
                                            glyphIndex - glyphClusterStart,
                                            aTextRun,
                                            clusterUTF8, clusterUTF8Length,
                                            &utf16Offset, aOverrideSpaceWidth);
        }
        NS_ENSURE_SUCCESS(rv,rv);
    }
    *aUTF16Offset = utf16Offset;
    return NS_OK;
}

nsresult
gfxPangoFontGroup::SetMissingGlyphs(gfxTextRun *aTextRun,
                                    const gchar *aUTF8, PRUint32 aUTF8Length,
                                    PRUint32 *aUTF16Offset)
{
    PRUint32 utf16Offset = *aUTF16Offset;
    PRUint32 textRunLength = aTextRun->GetLength();
    for (PRUint32 index = 0; index < aUTF8Length;) {
        if (utf16Offset >= textRunLength) {
            NS_ERROR("Someone has added too many glyphs!");
            break;
        }
        gunichar ch = g_utf8_get_char(aUTF8 + index);
        aTextRun->SetMissingGlyph(utf16Offset, ch);

        ++utf16Offset;
        NS_ASSERTION(!IS_SURROGATE(ch), "surrogates should not appear in UTF8");
        if (ch >= 0x10000)
            ++utf16Offset;
        // We produced this UTF8 so we don't need to worry about malformed stuff
        index = g_utf8_next_char(aUTF8 + index) - aUTF8;
    }

    *aUTF16Offset = utf16Offset;
    return NS_OK;
}

#if defined(ENABLE_FAST_PATH_8BIT) || defined(ENABLE_FAST_PATH_ALWAYS)
nsresult
gfxPangoFontGroup::CreateGlyphRunsFast(gfxTextRun *aTextRun,
                                       const gchar *aUTF8, PRUint32 aUTF8Length)
{
    const gchar *p = aUTF8;
    PangoFont *pangofont = GetBasePangoFont();
    PangoFcFont *fcfont = PANGO_FC_FONT (pangofont);
    gfxFcFont *gfxFont = gfxPangoFcFont::GfxFont(GFX_PANGO_FC_FONT(pangofont));
    PRUint32 utf16Offset = 0;
    gfxTextRun::CompressedGlyph g;
    const PRUint32 appUnitsPerDevUnit = aTextRun->GetAppUnitsPerDevUnit();

    aTextRun->AddGlyphRun(gfxFont, 0);

    while (p < aUTF8 + aUTF8Length) {
        // glib-2.12.9: "If p does not point to a valid UTF-8 encoded
        // character, results are undefined." so it is not easy to assert that
        // aUTF8 in fact points to UTF8 data but asserting
        // g_unichar_validate(ch) may be mildly useful.
        gunichar ch = g_utf8_get_char(p);
        p = g_utf8_next_char(p);
        
        if (ch == 0) {
            // treat this null byte as a missing glyph. Pango
            // doesn't create glyphs for these, not even missing-glyphs.
            aTextRun->SetMissingGlyph(utf16Offset, 0);
        } else {
            NS_ASSERTION(!IsInvalidChar(ch), "Invalid char detected");
            FT_UInt glyph = pango_fc_font_get_glyph (fcfont, ch);
            if (!glyph)                  // character not in font,
                return NS_ERROR_FAILURE; // fallback to CreateGlyphRunsItemizing

            cairo_text_extents_t extents;
            gfxFont->GetGlyphExtents(glyph, &extents);

            PRInt32 advance = NS_lround(extents.x_advance * appUnitsPerDevUnit);
            if (advance >= 0 &&
                gfxTextRun::CompressedGlyph::IsSimpleAdvance(advance) &&
                gfxTextRun::CompressedGlyph::IsSimpleGlyphID(glyph)) {
                aTextRun->SetSimpleGlyph(utf16Offset,
                                         g.SetSimpleGlyph(advance, glyph));
            } else {
                gfxTextRun::DetailedGlyph details;
                details.mGlyphID = glyph;
                NS_ASSERTION(details.mGlyphID == glyph,
                             "Seriously weird glyph ID detected!");
                details.mAdvance = advance;
                details.mXOffset = 0;
                details.mYOffset = 0;
                g.SetComplex(aTextRun->IsClusterStart(utf16Offset), PR_TRUE, 1);
                aTextRun->SetGlyphs(utf16Offset, g, &details);
            }

            NS_ASSERTION(!IS_SURROGATE(ch), "Surrogates shouldn't appear in UTF8");
            if (ch >= 0x10000) {
                // This character is a surrogate pair in UTF16
                ++utf16Offset;
            }
        }

        ++utf16Offset;
    }
    return NS_OK;
}
#endif

void 
gfxPangoFontGroup::CreateGlyphRunsItemizing(gfxTextRun *aTextRun,
                                            const gchar *aUTF8, PRUint32 aUTF8Length,
                                            PRUint32 aUTF8HeaderLen)
{

    PangoContext *context = GetPangoContext();

    // The font description could be cached on the gfxPangoFontGroup...
    nsAutoString fcFamilies;
    GetFcFamilies(fcFamilies);
    PangoFontDescription *fontDesc =
        NewPangoFontDescription(fcFamilies, GetStyle());
    if (GetStyle()->sizeAdjust != 0.0) {
        gfxFloat size = GetAdjustedSize();
        pango_font_description_set_absolute_size
            (fontDesc, moz_pango_units_from_double(size));
    }

    pango_context_set_font_description(context, fontDesc);
    pango_font_description_free(fontDesc);

    PangoLanguage *lang = GetPangoLanguage(GetStyle()->langGroup);

    // we should set this to null if we don't have a text language from the page...
    // except that we almost always have something...
    pango_context_set_language(context, lang);

    // Set the primary font for consistent font selection for common
    // characters, but use the default Pango behavior
    // (selecting generic fonts from the script of the characters)
    // in two situations:
    //   1. When we don't have a language to make a good choice for the
    //      primary font.
    //   2. For system fonts, use the default Pango behavior
    //      to give consistency with other apps.
    if (lang && !GetStyle()->systemFont) {
        SetBaseFont(context, GetBasePangoFont());
    }

    PangoDirection dir = aTextRun->IsRightToLeft() ? PANGO_DIRECTION_RTL : PANGO_DIRECTION_LTR;
    GList *items = pango_itemize_with_base_dir(context, dir, aUTF8, 0, aUTF8Length, nsnull, nsnull);

    PRUint32 utf16Offset = 0;
#ifdef DEBUG
    PRBool isRTL = aTextRun->IsRightToLeft();
#endif
    GList *pos = items;
    PangoGlyphString *glyphString = pango_glyph_string_new();
    if (!glyphString)
        goto out; // OOM

    for (; pos && pos->data; pos = pos->next) {
        PangoItem *item = (PangoItem *)pos->data;
        NS_ASSERTION(isRTL == item->analysis.level % 2, "RTL assumption mismatch");

        PRUint32 offset = item->offset;
        PRUint32 length = item->length;
        if (offset < aUTF8HeaderLen) {
            if (offset + length <= aUTF8HeaderLen)
                continue;

            length -= aUTF8HeaderLen - offset;
            offset = aUTF8HeaderLen;
        }

        gfxFcFont *font =
            gfxPangoFcFont::GfxFont(GFX_PANGO_FC_FONT(item->analysis.font));

        nsresult rv = aTextRun->AddGlyphRun(font, utf16Offset, PR_TRUE);
        if (NS_FAILED(rv)) {
            NS_ERROR("AddGlyphRun Failed");
            goto out;
        }

        PRUint32 spaceWidth =
            moz_pango_units_from_double(font->GetMetrics().spaceWidth);

        const gchar *p = aUTF8 + offset;
        const gchar *end = p + length;
        while (p < end) {
            if (*p == 0) {
                aTextRun->SetMissingGlyph(utf16Offset, 0);
                ++p;
                ++utf16Offset;
                continue;
            }

            // It's necessary to loop over pango_shape as it treats
            // NULs as string terminators
            const gchar *text = p;
            do {
                ++p;
            } while(p < end && *p != 0);
            gint len = p - text;

            pango_shape(text, len, &item->analysis, glyphString);
            SetupClusterBoundaries(aTextRun, text, len, utf16Offset, &item->analysis);
            SetGlyphs(aTextRun, text, len, &utf16Offset, glyphString, spaceWidth, PR_FALSE);
        }
    }

    aTextRun->SortGlyphRuns();

out:
    if (glyphString)
        pango_glyph_string_free(glyphString);

    for (pos = items; pos; pos = pos->next)
        pango_item_free((PangoItem *)pos->data);

    if (items)
        g_list_free(items);

    g_object_unref(context);
}

/* static */
PangoLanguage *
GetPangoLanguage(const nsACString& aLangGroup)
{
    // see if the lang group needs to be translated from mozilla's
    // internal mapping into fontconfig's
    nsCAutoString lang;
    gfxFontconfigUtils::GetSampleLangForGroup(aLangGroup, &lang);

    if (lang.IsEmpty())
        return NULL;

    return pango_language_from_string(lang.get());
}

gfxPangoFontCache::gfxPangoFontCache()
{
    mPangoFonts.Init(500);
}

gfxPangoFontCache::~gfxPangoFontCache()
{
}

void
gfxPangoFontCache::Put(const PangoFontDescription *aFontDesc, PangoFont *aPangoFont)
{
    if (mPangoFonts.Count() > 5000)
        mPangoFonts.Clear();
    PRUint32 key = pango_font_description_hash(aFontDesc);
    gfxPangoFontWrapper *value = new gfxPangoFontWrapper(aPangoFont);
    if (!value)
        return;
    mPangoFonts.Put(key, value);
}

PangoFont*
gfxPangoFontCache::Get(const PangoFontDescription *aFontDesc)
{
    PRUint32 key = pango_font_description_hash(aFontDesc);
    gfxPangoFontWrapper *value;
    if (!mPangoFonts.Get(key, &value))
        return nsnull;
    PangoFont *font = value->Get();
    g_object_ref(font);
    return font;
}