root/Source/platform/fonts/win/FontCacheSkiaWin.cpp

DEFINITIONS

1. fontContainsCharacter
2. minSizeForAntiAlias
3. fontRequiresFullHinting
4. platformFallbackForCharacter
5. equalIgnoringCase
6. typefacesMatchesFamily
7. createFontPlatformData

/*
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#include "config.h"
#include "platform/fonts/FontCache.h"

#include "RuntimeEnabledFeatures.h"
#include "SkFontMgr.h"
#include "SkTypeface_win.h"
#include "platform/fonts/FontDescription.h"
#include "platform/fonts/SimpleFontData.h"
#include "platform/fonts/harfbuzz/FontPlatformDataHarfbuzz.h"
#include "platform/fonts/win/FontFallbackWin.h"

namespace WebCore {

FontCache::FontCache()
    : m_purgePreventCount(0)
{
    SkFontMgr* fontManager;

    if (s_useDirectWrite) {
        fontManager = SkFontMgr_New_DirectWrite(s_directWriteFactory);
    } else {
        fontManager = SkFontMgr_New_GDI();
        // Subpixel text positioning is not supported by the GDI backend.
        s_useSubpixelPositioning = false;
    }

    ASSERT(fontManager);
    m_fontManager = adoptPtr(fontManager);
}

static bool fontContainsCharacter(const FontPlatformData* fontData, const wchar_t* family, UChar32 character)
{
    SkPaint paint;
    fontData->setupPaint(&paint);
    paint.setTextEncoding(SkPaint::kUTF32_TextEncoding);

    uint16_t glyph;
    paint.textToGlyphs(&character, sizeof(character), &glyph);
    return glyph;
}

// Minimum size, in pixels, at which anti alias is enabled for certain
// scripts. Only applies to the Direct Write backend for now.
static unsigned minSizeForAntiAlias(UScriptCode script)
{
    switch (script) {
    case USCRIPT_TRADITIONAL_HAN:
        return 24;
    case USCRIPT_SIMPLIFIED_HAN:
    case USCRIPT_HIRAGANA:
    case USCRIPT_KATAKANA:
    case USCRIPT_KATAKANA_OR_HIRAGANA:
    case USCRIPT_HANGUL:
    case USCRIPT_BENGALI:
        return 16;
    case USCRIPT_THAI:
    case USCRIPT_HEBREW:
    case USCRIPT_ARABIC:
    case USCRIPT_DEVANAGARI:
    case USCRIPT_GURMUKHI:
    case USCRIPT_GUJARATI:
    case USCRIPT_TAMIL:
    case USCRIPT_TELUGU:
    case USCRIPT_KANNADA:
    case USCRIPT_GEORGIAN:
    case USCRIPT_ARMENIAN:
    case USCRIPT_THAANA:
    case USCRIPT_CANADIAN_ABORIGINAL:
    case USCRIPT_CHEROKEE:
    case USCRIPT_MONGOLIAN:
    default:
        return 0;
    }
}

static bool fontRequiresFullHinting(const AtomicString& familyName)
{
    DEFINE_STATIC_LOCAL(AtomicString, courierNew, ("Courier New", AtomicString::ConstructFromLiteral));
    if (equalIgnoringCase(familyName, courierNew))
        return true;

    return false;
}

// Given the desired base font, this will create a SimpleFontData for a specific
// font that can be used to render the given range of characters.
PassRefPtr<SimpleFontData> FontCache::platformFallbackForCharacter(const FontDescription& fontDescription, UChar32 character, const SimpleFontData*)
{
    // FIXME: Consider passing fontDescription.dominantScript()
    // to GetFallbackFamily here.
    UScriptCode script;
    const wchar_t* family = getFallbackFamily(character,
        fontDescription.genericFamily(),
        &script);
    FontPlatformData* data = 0;
    if (family)
        data = getFontPlatformData(fontDescription,  AtomicString(family, wcslen(family)));

    // Last resort font list : PanUnicode. CJK fonts have a pretty
    // large repertoire. Eventually, we need to scan all the fonts
    // on the system to have a Firefox-like coverage.
    // Make sure that all of them are lowercased.
    const static wchar_t* const cjkFonts[] = {
        L"arial unicode ms",
        L"ms pgothic",
        L"simsun",
        L"gulim",
        L"pmingliu",
        L"wenquanyi zen hei", // Partial CJK Ext. A coverage but more widely known to Chinese users.
        L"ar pl shanheisun uni",
        L"ar pl zenkai uni",
        L"han nom a", // Complete CJK Ext. A coverage.
        L"code2000" // Complete CJK Ext. A coverage.
        // CJK Ext. B fonts are not listed here because it's of no use
        // with our current non-BMP character handling because we use
        // Uniscribe for it and that code path does not go through here.
    };

    const static wchar_t* const commonFonts[] = {
        L"tahoma",
        L"arial unicode ms",
        L"lucida sans unicode",
        L"microsoft sans serif",
        L"palatino linotype",
        // Six fonts below (and code2000 at the end) are not from MS, but
        // once installed, cover a very wide range of characters.
        L"dejavu serif",
        L"dejavu sasns",
        L"freeserif",
        L"freesans",
        L"gentium",
        L"gentiumalt",
        L"ms pgothic",
        L"simsun",
        L"gulim",
        L"pmingliu",
        L"code2000"
    };

    const wchar_t* const* panUniFonts = 0;
    int numFonts = 0;
    if (script == USCRIPT_HAN) {
        panUniFonts = cjkFonts;
        numFonts = WTF_ARRAY_LENGTH(cjkFonts);
    } else {
        panUniFonts = commonFonts;
        numFonts = WTF_ARRAY_LENGTH(commonFonts);
    }
    // Font returned from getFallbackFamily may not cover |character|
    // because it's based on script to font mapping. This problem is
    // critical enough for non-Latin scripts (especially Han) to
    // warrant an additional (real coverage) check with fontCotainsCharacter.
    int i;
    for (i = 0; (!data || !fontContainsCharacter(data, family, character)) && i < numFonts; ++i) {
        family = panUniFonts[i];
        data = getFontPlatformData(fontDescription, AtomicString(family, wcslen(family)));
    }

    // When i-th font (0-base) in |panUniFonts| contains a character and
    // we get out of the loop, |i| will be |i + 1|. That is, if only the
    // last font in the array covers the character, |i| will be numFonts.
    // So, we have to use '<=" rather than '<' to see if we found a font
    // covering the character.
    if (i <= numFonts) {
        if (s_useDirectWrite)
            data->setMinSizeForAntiAlias(minSizeForAntiAlias(script));
        return fontDataFromFontPlatformData(data, DoNotRetain);
    }

    return nullptr;
}

static inline bool equalIgnoringCase(const AtomicString& a, const SkString& b)
{
    return equalIgnoringCase(a, AtomicString::fromUTF8(b.c_str()));
}

static bool typefacesMatchesFamily(const SkTypeface* tf, const AtomicString& family)
{
    SkTypeface::LocalizedStrings* actualFamilies = tf->createFamilyNameIterator();
    bool matchesRequestedFamily = false;
    SkTypeface::LocalizedString actualFamily;

    while (actualFamilies->next(&actualFamily)) {
        if (equalIgnoringCase(family, actualFamily.fString)) {
            matchesRequestedFamily = true;
            break;
        }
    }
    actualFamilies->unref();

    // getFamilyName may return a name not returned by the createFamilyNameIterator.
    // Specifically in cases where Windows substitutes the font based on the
    // HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontSubstitutes registry entries.
    if (!matchesRequestedFamily) {
        SkString familyName;
        tf->getFamilyName(&familyName);
        if (equalIgnoringCase(family, familyName))
            matchesRequestedFamily = true;
    }

    return matchesRequestedFamily;
}

FontPlatformData* FontCache::createFontPlatformData(const FontDescription& fontDescription, const AtomicString& family, float fontSize)
{
    CString name;
    RefPtr<SkTypeface> tf = createTypeface(fontDescription, family, name);
    if (!tf)
        return 0;

    // Windows will always give us a valid pointer here, even if the face name
    // is non-existent. We have to double-check and see if the family name was
    // really used.
    // FIXME: Do we need to use predefined fonts "guaranteed" to exist
    // when we're running in layout-test mode?
    if (!typefacesMatchesFamily(tf.get(), family)) {
        return 0;
    }

    FontPlatformData* result = new FontPlatformData(tf,
        name.data(),
        fontSize,
        fontDescription.weight() >= FontWeightBold && !tf->isBold() || fontDescription.isSyntheticBold(),
        fontDescription.style() == FontStyleItalic && !tf->isItalic() || fontDescription.isSyntheticItalic(),
        fontDescription.orientation(),
        s_useSubpixelPositioning);

    // FIXME: It might be sufficient to set the "full hinting" flag for
    // CJK instead of forcing aliased rendering.
    if (s_useDirectWrite) {
        result->setMinSizeForAntiAlias(
            minSizeForAntiAlias(fontDescription.script()));
        if (fontRequiresFullHinting(family))
            result->setHinting(SkPaint::kFull_Hinting);
    }

    return result;
}

}