uniscribehelper.cpp

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            // Generate a last fallback font based on the script of
            // a character to draw while inheriting size and styles
            // from the primary font
            if (!m_logfont.lfFaceName[0])
                setLogFontAndStyle(m_hfont, &m_logfont, &m_style);

            // TODO(jungshik): generic type should come from webkit for
            // UniscribeHelperTextRun (a derived class used in webkit).
            const UChar *family = getFallbackFamily(input, itemLength,
                FontDescription::StandardFamily, 0, 0);
            bool fontOk = getDerivedFontData(family, m_style, &m_logfont,
                                              &ascent, &hfont, &scriptCache);

            if (!fontOk) {
                // If this GetDerivedFontData is called from the renderer it
                // might fail because the sandbox is preventing it from opening
                // the font files.  If we are running in the renderer,
                // TryToPreloadFont is overridden to ask the browser to preload
                // the font for us so we can access it.
                tryToPreloadFont(hfont);

                // Try again.
                fontOk = getDerivedFontData(family, m_style, &m_logfont,
                                             &ascent, &hfont, &scriptCache);
                ASSERT(fontOk);
            }

            // TODO(jungshik) : Currently GetDerivedHFont always returns a
            // a valid HFONT, but in the future, I may change it to return 0.
            ASSERT(hfont);

            // We don't need a font_properties for the last resort fallback font
            // because we don't have anything more to try and are forced to
            // accept empty glyph boxes. If we tried a series of fonts as
            // 'last-resort fallback', we'd need it, but currently, we don't.
            continue;
        } else if (hr == USP_E_SCRIPT_NOT_IN_FONT) {
            run.a.eScript = SCRIPT_UNDEFINED;
            continue;
        } else if (FAILED(hr)) {
            // Error shaping.
            generatedGlyphs = 0;
            result = false;
            goto cleanup;
        }
    }

    // Sets Windows font data for this run to those corresponding to
    // a font supporting this run. we don't need to store font_properties
    // because it's not used elsewhere.
    shaping.m_hfont = hfont;
    shaping.m_scriptCache = scriptCache;

    // The ascent of a font for this run can be different from
    // that of the primary font so that we need to keep track of
    // the difference per run and take that into account when calling
    // ScriptTextOut in |draw|. Otherwise, different runs rendered by
    // different fonts would not be aligned vertically.
    shaping.m_ascentOffset = m_ascent ? ascent - m_ascent : 0;
    result = true;

  cleanup:
    shaping.m_glyphs.resize(generatedGlyphs);
    shaping.m_visualAttributes.resize(generatedGlyphs);
    shaping.m_advance.resize(generatedGlyphs);
    shaping.m_offsets.resize(generatedGlyphs);
    if (tempDC) {
        SelectObject(tempDC, oldFont);
        ReleaseDC(0, tempDC);
    }
    // On failure, our logs don't mean anything, so zero those out.
    if (!result)
        shaping.m_logs.clear();

    return result;
}

void UniscribeHelper::fillShapes()
{
    m_shapes.resize(m_runs.size());
    for (size_t i = 0; i < m_runs.size(); i++) {
        int startItem = m_runs[i].iCharPos;
        int itemLength = m_inputLength - startItem;
        if (i < m_runs.size() - 1)
            itemLength = m_runs[i + 1].iCharPos - startItem;

        int numGlyphs;
        if (itemLength < UNISCRIBE_HELPER_STACK_CHARS) {
            // We'll start our buffer sizes with the current stack space
            // available in our buffers if the current input fits. As long as
            // it doesn't expand past that we'll save a lot of time mallocing.
            numGlyphs = UNISCRIBE_HELPER_STACK_CHARS;
        } else {
            // When the input doesn't fit, give up with the stack since it will
            // almost surely not be enough room (unless the input actually
            // shrinks, which is unlikely) and just start with the length
            // recommended by the Uniscribe documentation as a "usually fits"
            // size.
            numGlyphs = itemLength * 3 / 2 + 16;
        }

        // Convert a string to a glyph string trying the primary font, fonts in
        // the fallback list and then script-specific last resort font.
        Shaping& shaping = m_shapes[i];
        if (!shape(&m_input[startItem], itemLength, numGlyphs, m_runs[i], shaping))
            continue;

        // At the moment, the only time m_disableFontFallback is set is
        // when we look up glyph indices for non-BMP code ranges. So,
        // we can skip the glyph placement. When that becomes not the case
        // any more, we have to add a new flag to control glyph placement.
        if (m_disableFontFallback)
          continue;

        // Compute placements. Note that offsets is documented incorrectly
        // and is actually an array.

        // DC that we lazily create if Uniscribe commands us to.
        // (this does not happen often because scriptCache is already
        //  updated when calling ScriptShape).
        HDC tempDC = 0;
        HGDIOBJ oldFont = 0;
        HRESULT hr;
        while (true) {
            shaping.m_prePadding = 0;
            hr = ScriptPlace(tempDC, shaping.m_scriptCache,
                             &shaping.m_glyphs[0],
                             static_cast<int>(shaping.m_glyphs.size()),
                             &shaping.m_visualAttributes[0], &m_runs[i].a,
                             &shaping.m_advance[0], &shaping.m_offsets[0],
                             &shaping.m_abc);
            if (hr != E_PENDING)
                break;

            // Allocate the DC and run the loop again.
            tempDC = GetDC(0);
            oldFont = SelectObject(tempDC, shaping.m_hfont);
        }

        if (FAILED(hr)) {
            // Some error we don't know how to handle. Nuke all of our data
            // since we can't deal with partially valid data later.
            m_runs.clear();
            m_shapes.clear();
            m_screenOrder.clear();
        }

        if (tempDC) {
            SelectObject(tempDC, oldFont);
            ReleaseDC(0, tempDC);
        }
    }

    adjustSpaceAdvances();

    if (m_letterSpacing != 0 || m_wordSpacing != 0)
        applySpacing();
}

void UniscribeHelper::fillScreenOrder()
{
    m_screenOrder.resize(m_runs.size());

    // We assume that the input has only one text direction in it.
    // TODO(brettw) are we sure we want to keep this restriction?
    if (m_isRtl) {
        for (int i = 0; i < static_cast<int>(m_screenOrder.size()); i++)
            m_screenOrder[static_cast<int>(m_screenOrder.size()) - i - 1] = i;
    } else {
        for (int i = 0; i < static_cast<int>(m_screenOrder.size()); i++)
            m_screenOrder[i] = i;
    }
}

void UniscribeHelper::adjustSpaceAdvances()
{
    if (m_spaceWidth == 0)
        return;

    int spaceWidthWithoutLetterSpacing = m_spaceWidth - m_letterSpacing;

    // This mostly matches what WebKit's UniscribeController::shapeAndPlaceItem.
    for (size_t run = 0; run < m_runs.size(); run++) {
        Shaping& shaping = m_shapes[run];

        for (int i = 0; i < shaping.charLength(); i++) {
            if (!treatAsSpace(m_input[m_runs[run].iCharPos + i]))
                continue;

            int glyphIndex = shaping.m_logs[i];
            int currentAdvance = shaping.m_advance[glyphIndex];

            // currentAdvance does not include additional letter-spacing, but
            // space_width does. Here we find out how off we are from the
            // correct width for the space not including letter-spacing, then
            // just subtract that diff.
            int diff = currentAdvance - spaceWidthWithoutLetterSpacing;
            // The shaping can consist of a run of text, so only subtract the
            // difference in the width of the glyph.
            shaping.m_advance[glyphIndex] -= diff;
            shaping.m_abc.abcB -= diff;
        }
    }
}

void UniscribeHelper::applySpacing()
{
    for (size_t run = 0; run < m_runs.size(); run++) {
        Shaping& shaping = m_shapes[run];
        bool isRtl = m_runs[run].a.fRTL;

        if (m_letterSpacing != 0) {
            // RTL text gets padded to the left of each character. We increment
            // the run's advance to make this happen. This will be balanced out
            // by NOT adding additional advance to the last glyph in the run.
            if (isRtl)
                shaping.m_prePadding += m_letterSpacing;

            // Go through all the glyphs in this run and increase the "advance"
            // to account for letter spacing. We adjust letter spacing only on
            // cluster boundaries.
            //
            // This works for most scripts, but may have problems with some
            // indic scripts. This behavior is better than Firefox or IE for
            // Hebrew.
            for (int i = 0; i < shaping.glyphLength(); i++) {
                if (shaping.m_visualAttributes[i].fClusterStart) {
                    // Ick, we need to assign the extra space so that the glyph
                    // comes first, then is followed by the space. This is
                    // opposite for RTL.
                    if (isRtl) {
                        if (i != shaping.glyphLength() - 1) {
                            // All but the last character just get the spacing
                            // applied to their advance. The last character
                            // doesn't get anything,
                            shaping.m_advance[i] += m_letterSpacing;
                            shaping.m_abc.abcB += m_letterSpacing;
                        }
                    } else {
                        // LTR case is easier, we just add to the advance.
                        shaping.m_advance[i] += m_letterSpacing;
                        shaping.m_abc.abcB += m_letterSpacing;
                    }
                }
            }
        }

        // Go through all the characters to find whitespace and insert the
        // extra wordspacing amount for the glyphs they correspond to.
        if (m_wordSpacing != 0) {
            for (int i = 0; i < shaping.charLength(); i++) {
                if (!treatAsSpace(m_input[m_runs[run].iCharPos + i]))
                    continue;

                // The char in question is a word separator...
                int glyphIndex = shaping.m_logs[i];

                // Spaces will not have a glyph in Uniscribe, it will just add
                // additional advance to the character to the left of the
                // space. The space's corresponding glyph will be the character
                // following it in reading order.
                if (isRtl) {
                    // In RTL, the glyph to the left of the space is the same
                    // as the first glyph of the following character, so we can
                    // just increment it.
                    shaping.m_advance[glyphIndex] += m_wordSpacing;
                    shaping.m_abc.abcB += m_wordSpacing;
                } else {
                    // LTR is actually more complex here, we apply it to the
                    // previous character if there is one, otherwise we have to
                    // apply it to the leading space of the run.
                    if (glyphIndex == 0)
                        shaping.m_prePadding += m_wordSpacing;
                    else {
                        shaping.m_advance[glyphIndex - 1] += m_wordSpacing;
                        shaping.m_abc.abcB += m_wordSpacing;
                    }
                }
            }
        }  // m_wordSpacing != 0

        // Loop for next run...
    }
}

// The advance is the ABC width of the run
int UniscribeHelper::advanceForItem(int itemIndex) const
{
    int accum = 0;
    const Shaping& shaping = m_shapes[itemIndex];

    if (shaping.m_justify.size() == 0) {
        // Easy case with no justification, the width is just the ABC width of
        // the run. (The ABC width is the sum of the advances).
        return shaping.m_abc.abcA + shaping.m_abc.abcB +
               shaping.m_abc.abcC + shaping.m_prePadding;
    }

    // With justification, we use the justified amounts instead. The
    // justification array contains both the advance and the extra space
    // added for justification, so is the width we want.
    int justification = 0;
    for (size_t i = 0; i < shaping.m_justify.size(); i++)
        justification += shaping.m_justify[i];

    return shaping.m_prePadding + justification;
}

}  // namespace WebCore