Function parseLookupTable

libraries/p5.js:4829–4859

(data, start)

// Parse a LookupTable (present in of GPOS, GSUB, GDEF, BASE, JSTF tables).
function parseLookupTable(data, start) {
    var p = new parse.Parser(data, start);
    var lookupType = p.parseUShort();
    var lookupFlag = p.parseUShort();
    var useMarkFilteringSet = lookupFlag & 0x10;
    var subTableCount = p.parseUShort();
    var subTableOffsets = p.parseOffset16List(subTableCount);
    var table = {
        lookupType: lookupType,
        lookupFlag: lookupFlag,
        markFilteringSet: useMarkFilteringSet ? p.parseUShort() : -1
    };
    // LookupType 2, Pair adjustment
    if (lookupType === 2) {
        var subtables = [];
        for (var i = 0; i < subTableCount; i++) {
            subtables.push(parsePairPosSubTable(data, start + subTableOffsets[i]));
        }
        // Return a function which finds the kerning values in the subtables.
        table.getKerningValue = function(leftGlyph, rightGlyph) {
            for (var i = subtables.length; i--;) {
                var value = subtables[i](leftGlyph, rightGlyph);
                if (value !== undefined) return value;
            }

            return 0;
        };
    }

    return table;
}

// Parse the `GPOS` table which contains, among other things, kerning pairs.
// https://www.microsoft.com/typography/OTSPEC/gpos.htm