function createHeadTable(font) {
var buf = new ByteBuffer(54); // fixed table length
buf.writeInt32(0x10000); // version
buf.writeInt32(font.revision * 0x10000); // fontRevision
buf.writeUint32(0); // checkSumAdjustment
buf.writeUint32(0x5F0F3CF5); // magicNumber
// FLag meanings:
// Bit 0: Baseline for font at y=0;
// Bit 1: Left sidebearing point at x=0;
// Bit 3: Force ppem to integer values for all internal scaler math; may use fractional ppem sizes if this bit is clear;
buf.writeUint16(0x000B); // flags
buf.writeUint16(font.unitsPerEm); // unitsPerEm
buf.writeUint64(dateToUInt64(font.createdDate)); // created
buf.writeUint64(dateToUInt64(font.modifiedDate)); // modified
buf.writeInt16(font.xMin); // xMin
buf.writeInt16(font.yMin); // yMin
buf.writeInt16(font.xMax); // xMax
buf.writeInt16(font.yMax); // yMax
buf.writeUint16(font.macStyle); //macStyle
buf.writeUint16(font.lowestRecPPEM); // lowestRecPPEM
buf.writeInt16(2); // fontDirectionHint
buf.writeInt16(font.ttf_glyph_size < 0x20000 ? 0 : 1); // indexToLocFormat, 0 for short offsets, 1 for long offsets
buf.writeInt16(0); // glyphDataFormat
return buf;
}
// Write one feature containing all ligatures
function createFeatureList() {
var header = (0
+ 2 // FeatureCount
+ 4 // FeatureTag[0]
+ 2 // Feature Offset[0]
);
var length = (0
+ header
+ 2 // FeatureParams[0]
+ 2 // LookupCount[0]
+ 2 // Lookup[0] LookupListIndex[0]
);
var buffer = new ByteBuffer(length);
// FeatureCount
buffer.writeUint16(1);
// FeatureTag[0]
buffer.writeUint32(identifier('liga'));
// Feature Offset[0]
buffer.writeUint16(header);
// FeatureParams[0]
buffer.writeUint16(0);
// LookupCount[0]
buffer.writeUint16(1);
// Index into lookup table. Since we only have ligatures, the index is always 0
buffer.writeUint16(0);
return buffer;
}
function createScriptList() {
var header = (0
+ 2 // Script count
+ 4 // Tag[0]
+ 2 // Offset[0]
);
var scriptRecord = (0
+ 2 // Script[0] DefaultLangSys Offset
+ 2 // Script[0] LangSysCount (0)
);
var langSys = (0
+ 2 // Script[0] DefaultLangSys LookupOrder
+ 2 // Script[0] DefaultLangSys ReqFeatureIndex
+ 2 // Script[0] DefaultLangSys FeatureCount (0?)
+ 2 // Script[0] Optional Feature Index[0]
);
var length = (0
+ header
+ scriptRecord
+ langSys
);
var buffer = new ByteBuffer(length);
// Script count
buffer.writeUint16(1);
// Script identifier DFLT
buffer.writeUint32(identifier('DFLT'));
// Offset to the ScriptRecord
buffer.writeUint16(header);
// Script Record
// Offset to the start of langSys from the start of scriptRecord
buffer.writeUint16(scriptRecord); // DefaultLangSys
// Number of LangSys entries other than the default
buffer.writeUint16(0);
// LangSys record
// LookupOrder
buffer.writeUint16(0);
// ReqFeatureIndex -> only one required feature: all ligatures
buffer.writeUint16(0);
// Number of FeatureIndex values for this language system (excludes the required feature)
buffer.writeUint16(1);
// FeatureIndex for the first optional feature
// Note: Adding the same feature to both the optional
// and the required features is a clear violation of the spec
// but it fixes IE not displaying the ligatures.
// See http://partners.adobe.com/public/developer/opentype/index_table_formats.html, Section “Language System Table”
// “FeatureCount: Number of FeatureIndex values for this language system-*excludes the required feature*” (emphasis added)
buffer.writeUint16(0);
return buffer;
}
function createGSUB(font) {
var scriptList = createScriptList();
var featureList = createFeatureList();
var lookupList = createLookupList(font);
var lists = [scriptList, featureList, lookupList];
var offset = (0
+ 4 // Version
+ 2 * lists.length // List offsets
);
// Calculate offsets
_.forEach(lists, function(list) {
list._listOffset = offset;
offset += list.length;
});
var length = offset;
var buffer = new ByteBuffer(length);
// Version
buffer.writeUint32(0x00010000);
// Offsets
_.forEach(lists, function(list) {
buffer.writeUint16(list._listOffset);
});
// List contents
_.forEach(lists, function(list) {
buffer.writeBytes(list.buffer);
});
return buffer;
}