Module: Fontisan::Ufo::Compile::GlyfLoca

Defined in:
lib/fontisan/ufo/compile/glyf_loca.rb

Overview

Builds the TrueType glyf + loca tables. Each glyph's outline is delta-encoded into the glyf table; loca is the offset index.

For OTF output this module is NOT used — CFF takes its place.

See Also:

Constant Summary collapse

FLAG_ON_CURVE =

Flag bits (simple glyph)

0x01
FLAG_X_SHORT = 
0x02
FLAG_Y_SHORT = 
0x04
FLAG_REPEAT = 
0x08
FLAG_X_IS_POSITIVE =

only meaningful if FLAG_X_SHORT

0x10
FLAG_Y_IS_POSITIVE =

only meaningful if FLAG_Y_SHORT

0x20
FLAG_OVERLAP_SIMPLE = 
0x40

Class Method Summary collapse

Class Method Details

.build(_font, glyphs:) ⇒ Hash<String, String>

Returns => bytes, "loca" => bytes.

Parameters:

Returns:

  • (Hash<String, String>) —

    => bytes, "loca" => bytes



25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
 
# File 'lib/fontisan/ufo/compile/glyf_loca.rb', line 25

def self.build(_font, glyphs:)
  glyf_bytes = +""
  offsets = [0]

  glyphs.each do |glyph|
    glyf_bytes << encode_glyph(glyph)
    glyf_bytes << "\x00" while glyf_bytes.bytesize.odd? # 2-byte align
    offsets << glyf_bytes.bytesize
  end

  # Choose loca format based on the largest offset.
  use_long = offsets.max > 0x1FFFE # 2 × uint16 max
  loca_bytes =
    if use_long
      offsets.pack("N*")
    else
      offsets.map { |o| o / 2 }.pack("n*")
    end

  { "glyf" => glyf_bytes, "loca" => loca_bytes, :loca_format => use_long ? 1 : 0 }
end