Bug 261651

Manage to sort out other as well:

void SVGTextQuery::modifyStartEndPositionsRespectingLigatures(Data* queryData, const SVGTextFragment& fragment, unsigned& startPosition, unsigned& endPosition) const
{
    SVGTextLayoutAttributes* layoutAttributes = queryData->textRenderer->layoutAttributes();
    Vector<SVGTextMetrics>& textMetricsValues = layoutAttributes->textMetricsValues();

    unsigned textMetricsOffset = fragment.metricsListOffset;

    // Compute the offset of the fragment within the box, since that's the
    // space <startPosition, endPosition> is in (and that's what we need).
    int fragmentOffsetInBox = fragment.characterOffset - queryData->textBox->start();
    int fragmentEndInBox = fragmentOffsetInBox + fragment.length;
    // Find the text metrics cell that start at or contain the character startPosition.
    while (fragmentOffsetInBox < fragmentEndInBox) {
        SVGTextMetrics& metrics = textMetricsValues[textMetricsOffset];
        int glyphEnd = fragmentOffsetInBox + metrics.length();
        if (static_cast<int>(startPosition) < glyphEnd)
            break;
        fragmentOffsetInBox = glyphEnd;
        textMetricsOffset++;
    }
    startPosition = fragmentOffsetInBox;

    // Find the text metrics cell that contain or ends at the character endPosition.
    while (fragmentOffsetInBox < fragmentEndInBox) {
        SVGTextMetrics& metrics = textMetricsValues[textMetricsOffset];
        fragmentOffsetInBox += metrics.length();
        if (fragmentOffsetInBox >= static_cast<int>(endPosition))
            break;
        textMetricsOffset++;
    }

    endPosition = fragmentOffsetInBox;

This is another simplification on top of one from here: https://src.chromium.org/viewvc/blink?view=revision&revision=193017

Created attachment 467724 [details]
SVGTextQuery.cpp local file with changes from Blink Commits

Change in `SVGInlineTextBox.cpp`:

bool SVGInlineTextBox::mapStartEndPositionsIntoFragmentCoordinates(const SVGTextFragment& fragment, unsigned& startPosition, unsigned& endPosition) const
{
    int fragmentOffsetInBox = static_cast<int>(fragment.characterOffset) - start();

    // Compute positions relative to the fragment.
    startPosition -= fragmentOffsetInBox;
    endPosition -= fragmentOffsetInBox;

    // Intersect with the fragment range.
    startPosition = std::max<unsigned>(startPosition, 0);
    endPosition = std::min<unsigned>(endPosition, static_cast<int>(fragment.length));

    return startPosition < endPosition;
}

and attaching 'SVGTextQuery.cpp' file with all my changes from this.

<rdar://problem/115953998>

Pretty much everything is done here - only pending work is in 'See Also' and also has its own conclusion (issue) in 1-1 merge.

Marking this as 'RESOLVED CONFIGURATION CHANGED'. Thanks!