fontcache.cpp

linux下开源浏览器WebKit的源码,市面上的很多商用浏览器都是移植自WebKit

    static const bool safeToCompareToEmptyOrDeleted = true;
};

struct FontDataCacheKeyTraits : WTF::GenericHashTraits<FontPlatformData> {
    static const bool emptyValueIsZero = true;
    static const bool needsDestruction = true;
    static const FontPlatformData& emptyValue()
    {
        DEFINE_STATIC_LOCAL(FontPlatformData, key, (0.f, false, false));
        return key;
    }
    static void constructDeletedValue(FontPlatformData& slot)
    {
        new (&slot) FontPlatformData(HashTableDeletedValue);
    }
    static bool isDeletedValue(const FontPlatformData& value)
    {
        return value.isHashTableDeletedValue();
    }
};

typedef HashMap<FontPlatformData, pair<SimpleFontData*, unsigned>, FontDataCacheKeyHash, FontDataCacheKeyTraits> FontDataCache;

static FontDataCache* gFontDataCache = 0;

const int cMaxInactiveFontData = 120;  // Pretty Low Threshold
const float cTargetInactiveFontData = 100;
static ListHashSet<const SimpleFontData*>* gInactiveFontData = 0;

SimpleFontData* FontCache::getCachedFontData(const FontPlatformData* platformData)
{
    if (!platformData)
        return 0;

    if (!gFontDataCache) {
        gFontDataCache = new FontDataCache;
        gInactiveFontData = new ListHashSet<const SimpleFontData*>;
    }
    
    FontDataCache::iterator result = gFontDataCache->find(*platformData);
    if (result == gFontDataCache->end()) {
        pair<SimpleFontData*, unsigned> newValue(new SimpleFontData(*platformData), 1);
        gFontDataCache->set(*platformData, newValue);
        return newValue.first;
    }
    if (!result.get()->second.second++) {
        ASSERT(gInactiveFontData->contains(result.get()->second.first));
        gInactiveFontData->remove(result.get()->second.first);
    }

    return result.get()->second.first;
}

void FontCache::releaseFontData(const SimpleFontData* fontData)
{
    ASSERT(gFontDataCache);
    ASSERT(!fontData->isCustomFont());

    FontDataCache::iterator it = gFontDataCache->find(fontData->platformData());
    ASSERT(it != gFontDataCache->end());

    if (!--it->second.second) {
        gInactiveFontData->add(fontData);
        if (gInactiveFontData->size() > cMaxInactiveFontData)
            purgeInactiveFontData(gInactiveFontData->size() - cTargetInactiveFontData);
    }
}

void FontCache::purgeInactiveFontData(int count)
{
    if (!gInactiveFontData)
        return;

    static bool isPurging;  // Guard against reentry when e.g. a deleted FontData releases its small caps FontData.
    if (isPurging)
        return;

    isPurging = true;

    ListHashSet<const SimpleFontData*>::iterator end = gInactiveFontData->end();
    ListHashSet<const SimpleFontData*>::iterator it = gInactiveFontData->begin();
    for (int i = 0; i < count && it != end; ++it, ++i) {
        const SimpleFontData* fontData = *it.get();
        gFontDataCache->remove(fontData->platformData());
        delete fontData;
    }

    if (it == end) {
        // Removed everything
        gInactiveFontData->clear();
    } else {
        for (int i = 0; i < count; ++i)
            gInactiveFontData->remove(gInactiveFontData->begin());
    }

    Vector<FontPlatformDataCacheKey> keysToRemove;
    keysToRemove.reserveInitialCapacity(gFontPlatformDataCache->size());
    FontPlatformDataCache::iterator platformDataEnd = gFontPlatformDataCache->end();
    for (FontPlatformDataCache::iterator platformData = gFontPlatformDataCache->begin(); platformData != platformDataEnd; ++platformData) {
        if (platformData->second && !gFontDataCache->contains(*platformData->second))
            keysToRemove.append(platformData->first);
    }

    size_t keysToRemoveCount = keysToRemove.size();
    for (size_t i = 0; i < keysToRemoveCount; ++i)
        delete gFontPlatformDataCache->take(keysToRemove[i]);

    isPurging = false;
}

size_t FontCache::fontDataCount()
{
    if (gFontDataCache)
        return gFontDataCache->size();
    return 0;
}

size_t FontCache::inactiveFontDataCount()
{
    if (gInactiveFontData)
        return gInactiveFontData->size();
    return 0;
}

const FontData* FontCache::getFontData(const Font& font, int& familyIndex, FontSelector* fontSelector)
{
    FontPlatformData* result = 0;

    int startIndex = familyIndex;
    const FontFamily* startFamily = &font.fontDescription().family();
    for (int i = 0; startFamily && i < startIndex; i++)
        startFamily = startFamily->next();
    const FontFamily* currFamily = startFamily;
    while (currFamily && !result) {
        familyIndex++;
        if (currFamily->family().length()) {
            if (fontSelector) {
                FontData* data = fontSelector->getFontData(font.fontDescription(), currFamily->family());
                if (data)
                    return data;
            }
            result = getCachedFontPlatformData(font.fontDescription(), currFamily->family());
        }
        currFamily = currFamily->next();
    }

    if (!currFamily)
        familyIndex = cAllFamiliesScanned;

    if (!result)
        // We didn't find a font. Try to find a similar font using our own specific knowledge about our platform.
        // For example on OS X, we know to map any families containing the words Arabic, Pashto, or Urdu to the
        // Geeza Pro font.
        result = getSimilarFontPlatformData(font);

    if (!result && startIndex == 0) {
        // If it's the primary font that we couldn't find, we try the following. In all other cases, we will
        // just use per-character system fallback.

        if (fontSelector) {
            // Try the user's preferred standard font.
            if (FontData* data = fontSelector->getFontData(font.fontDescription(), "-webkit-standard"))
                return data;
        }

        // Still no result.  Hand back our last resort fallback font.
        result = getLastResortFallbackFont(font.fontDescription());
    }

    // Now that we have a result, we need to go from FontPlatformData -> FontData.
    return getCachedFontData(result);
}

static HashSet<FontSelector*>* gClients;

void FontCache::addClient(FontSelector* client)
{
    if (!gClients)
        gClients = new HashSet<FontSelector*>;

    ASSERT(!gClients->contains(client));
    gClients->add(client);
}

void FontCache::removeClient(FontSelector* client)
{
    ASSERT(gClients);
    ASSERT(gClients->contains(client));

    gClients->remove(client);
}

static unsigned gGeneration = 0;

unsigned FontCache::generation()
{
    return gGeneration;
}

void FontCache::invalidate()
{
    if (!gClients) {
        ASSERT(!gFontPlatformDataCache);
        return;
    }

    if (gFontPlatformDataCache) {
        deleteAllValues(*gFontPlatformDataCache);
        delete gFontPlatformDataCache;
        gFontPlatformDataCache = new FontPlatformDataCache;
    }

    gGeneration++;

    Vector<RefPtr<FontSelector> > clients;
    size_t numClients = gClients->size();
    clients.reserveInitialCapacity(numClients);
    HashSet<FontSelector*>::iterator end = gClients->end();
    for (HashSet<FontSelector*>::iterator it = gClients->begin(); it != end; ++it)
        clients.append(*it);

    ASSERT(numClients == clients.size());
    for (size_t i = 0; i < numClients; ++i)
        clients[i]->fontCacheInvalidated();

    purgeInactiveFontData();
}

} // namespace WebCore