private static Metadata LoadMetadata(Stream stream)
{
using var reader = new DataReader(stream);
var tables = SfntTables.ReadFaceHeader(reader);
var names = SfntTables.ReadNames(reader, tables);
var os2Data = SfntTables.ReadOS2(reader, tables);
return(new Metadata
{
Family = names.TypographicFamilyName ?? names.FamilyName,
Weight = os2Data.Weight,
Stretch = os2Data.Stretch,
Style = os2Data.Style
});
}
/// <summary>
/// Initializes a new instance of the <see cref="FontFace"/> class.
/// </summary>
/// <param name="stream">A stream pointing to the font file.</param>
/// <remarks>
/// All relevant font data is loaded into memory and retained by the FontFace object.
/// Once the constructor finishes you are free to close the stream.
/// </remarks>
public FontFace(Stream stream)
{
// read the face header and table records
using (var reader = new DataReader(stream))
{
var tables = SfntTables.ReadFaceHeader(reader);
// read head and maxp tables for font metadata and limits
SfntTables.ReadHead(reader, tables, out var head);
SfntTables.ReadMaxp(reader, tables, ref head);
unitsPerEm = head.UnitsPerEm;
integerPpems = (head.Flags & HeadFlags.IntegerPpem) != 0;
// horizontal metrics header and data
SfntTables.SeekToTable(reader, tables, FourCC.Hhea, required: true);
var hMetricsHeader = SfntTables.ReadMetricsHeader(reader);
SfntTables.SeekToTable(reader, tables, FourCC.Hmtx, required: true);
hmetrics = SfntTables.ReadMetricsTable(reader, head.GlyphCount, hMetricsHeader.MetricCount);
// font might optionally have vertical metrics
if (SfntTables.SeekToTable(reader, tables, FourCC.Vhea))
{
var vMetricsHeader = SfntTables.ReadMetricsHeader(reader);
SfntTables.SeekToTable(reader, tables, FourCC.Vmtx, required: true);
vmetrics = SfntTables.ReadMetricsTable(reader, head.GlyphCount, vMetricsHeader.MetricCount);
}
// OS/2 table has even more metrics
var os2Data = SfntTables.ReadOS2(reader, tables);
xHeight = os2Data.XHeight;
capHeight = os2Data.CapHeight;
Weight = os2Data.Weight;
Stretch = os2Data.Stretch;
Style = os2Data.Style;
// optional PostScript table has random junk in it
SfntTables.ReadPost(reader, tables, ref head);
IsFixedWidth = head.IsFixedPitch;
// read character-to-glyph mapping tables and kerning table
charMap = CharacterMap.ReadCmap(reader, tables);
kernTable = KerningTable.ReadKern(reader, tables);
// name data
var names = SfntTables.ReadNames(reader, tables);
Family = names.TypographicFamilyName ?? names.FamilyName;
Subfamily = names.TypographicSubfamilyName ?? names.SubfamilyName;
FullName = names.FullName;
UniqueID = names.UniqueID;
Version = names.Version;
Description = names.Description;
// load glyphs if we have them
if (SfntTables.SeekToTable(reader, tables, FourCC.Glyf))
{
unsafe
{
// read in the local table, which tells us the byte offset of each glyph
var loca = stackalloc uint[head.GlyphCount];
SfntTables.ReadLoca(reader, tables, head.IndexFormat, loca, head.GlyphCount);
// we need to know the length of the glyf table because of some weirdness in the loca table:
// if a glyph is "missing" (like a space character), then its loca[n] entry is equal to loca[n+1]
// if the last glyph in the set is missing, then loca[n] == glyf table length
SfntTables.SeekToTable(reader, tables, FourCC.Glyf);
var glyfOffset = reader.Position;
var glyfLength = tables[SfntTables.FindTable(tables, FourCC.Glyf)].Length;
// read in all glyphs
glyphs = new BaseGlyph[head.GlyphCount];
for (var i = 0; i < glyphs.Length; i++)
{
SfntTables.ReadGlyph(reader, i, 0, glyphs, glyfOffset, glyfLength, loca);
}
}
}
// embedded bitmaps
SbitTable.Read(reader, tables);
// metrics calculations: if the UseTypographicMetrics flag is set, then
// we should use the sTypo*** data for line height calculation
if (os2Data.UseTypographicMetrics)
{
// include the line gap in the ascent so that
// white space is distributed above the line
cellAscent = os2Data.TypographicAscender + os2Data.TypographicLineGap;
cellDescent = -os2Data.TypographicDescender;
lineHeight = os2Data.TypographicAscender + os2Data.TypographicLineGap - os2Data.TypographicDescender;
}
else
{
// otherwise, we need to guess at whether hhea data or os/2 data has better line spacing
// this is the recommended procedure based on the OS/2 spec extra notes
cellAscent = os2Data.WinAscent;
cellDescent = Math.Abs(os2Data.WinDescent);
lineHeight = Math.Max(
Math.Max(0, hMetricsHeader.LineGap) + hMetricsHeader.Ascender + Math.Abs(hMetricsHeader.Descender),
cellAscent + cellDescent
);
}
// give sane defaults for underline and strikeout data if missing
underlineSize = head.UnderlineThickness != 0 ?
head.UnderlineThickness : (head.UnitsPerEm + 7) / 14;
underlinePosition = head.UnderlinePosition != 0 ?
head.UnderlinePosition : -((head.UnitsPerEm + 5) / 10);
strikeoutSize = os2Data.StrikeoutSize != 0 ?
os2Data.StrikeoutSize : underlineSize;
strikeoutPosition = os2Data.StrikeoutPosition != 0 ?
os2Data.StrikeoutPosition : head.UnitsPerEm / 3;
// create some vertical metrics in case we haven't loaded any
verticalSynthesized = new MetricsEntry
{
FrontSideBearing = os2Data.TypographicAscender,
Advance = os2Data.TypographicAscender - os2Data.TypographicDescender
};
// read in global font program data
controlValueTable = SfntTables.ReadCvt(reader, tables);
prepProgram = SfntTables.ReadProgram(reader, tables, FourCC.Prep);
interpreter = new Interpreter(
head.MaxStackSize,
head.MaxStorageLocations,
head.MaxFunctionDefs,
head.MaxInstructionDefs,
head.MaxTwilightPoints
);
// the fpgm table optionally contains a program to run at initialization time
var fpgm = SfntTables.ReadProgram(reader, tables, FourCC.Fpgm);
if (fpgm != null)
{
interpreter.InitializeFunctionDefs(fpgm);
}
}
Id = Interlocked.Increment(ref currentId);
}