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# frozen_string_literal: true
require_relative '../table'
module TTFunk
class Table
# Font Header (`head`) Table.
class Head < TTFunk::Table
# Table version.
# @return [Integer]
attr_reader :version
# Font revision.
# @return [Integer]
attr_reader :font_revision
# Checksum adjustment.
# @return [Integer]
attr_reader :checksum_adjustment
# Magic number.
# @return [Integer] must be `0x5F0F3CF5`
attr_reader :magic_number
# Flags.
# @return [Integer]
attr_reader :flags
# Units per Em.
# @return [Integer]
attr_reader :units_per_em
# Font creation time.
# @return [Integer] Long Date Time timestamp.
attr_reader :created
# Font modification time.
# @return [Integer] Long Date Time timestamp.
attr_reader :modified
# Minimum x coordinate across all glyph bounding boxes.
# @return [Integer]
attr_reader :x_min
# Minimum y coordinate across all glyph bounding boxes.
# @return [Integer]
attr_reader :y_min
# Maximum x coordinate across all glyph bounding boxes.
# @return [Integer]
attr_reader :x_max
# Maximum y coordinate across all glyph bounding boxes.
# @return [Integer]
attr_reader :y_max
# Mac font style.
# @return [Integer]
attr_reader :mac_style
# Smallest readable size in pixels.
# @return [Integer]
attr_reader :lowest_rec_ppem
# Font direction hint. Deprecated, set to 2.
# @return [Integer]
attr_reader :font_direction_hint
# Index to Location format.
# @return [Integer]
attr_reader :index_to_loc_format
# Glyph data format.
# @return [Integer]
attr_reader :glyph_data_format
class << self
# Long date time (used in TTF headers).
# January 1, 1904 00:00:00 UTC basis used by Long date time.
# @see https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6.html
# TrueType Font Tables
LONG_DATE_TIME_BASIS = Time.new(1904, 1, 1, 0, 0, 0, 0).to_i
private_constant :LONG_DATE_TIME_BASIS
# Encode table.
#
# @param head [TTFunk::Table::Head]
# @param loca [Hash] result of encoding Index to Location (`loca`) table
# @param mapping [Hash{Integer => Integer}] keys are new glyph IDs, values
# are old glyph IDs
# @return [EncodedString]
def encode(head, loca, mapping)
EncodedString.new do |table|
table <<
[head.version, head.font_revision].pack('N2') <<
Placeholder.new(:checksum, length: 4) <<
[
head.magic_number,
head.flags, head.units_per_em,
head.created, head.modified,
*min_max_values_for(head, mapping),
head.mac_style, head.lowest_rec_ppem, head.font_direction_hint,
loca[:type] || 0, head.glyph_data_format,
].pack('Nn2q>2n*')
end
end
# Convert Long Date Time timestamp to Time.
# @param ldt [Float, Integer]
# @return [Time]
def from_long_date_time(ldt)
Time.at(ldt + LONG_DATE_TIME_BASIS, in: 'UTC')
end
# Convert Time to Long Date Time timestamp
# @param time [Time]
# @return [Integer]
def to_long_date_time(time)
Integer(time) - LONG_DATE_TIME_BASIS
end
private
def min_max_values_for(head, mapping)
x_min = Min.new
x_max = Max.new
y_min = Min.new
y_max = Max.new
mapping.each_value do |old_glyph_id|
glyph = head.file.find_glyph(old_glyph_id)
next unless glyph
x_min << glyph.x_min
x_max << glyph.x_max
y_min << glyph.y_min
y_max << glyph.y_max
end
[
x_min.value_or(0), y_min.value_or(0),
x_max.value_or(0), y_max.value_or(0),
]
end
end
private
def parse!
@version, @font_revision, @check_sum_adjustment, @magic_number,
@flags, @units_per_em, @created, @modified = read(36, 'N4n2q>2')
@x_min, @y_min, @x_max, @y_max = read_signed(4)
@mac_style, @lowest_rec_ppem, @font_direction_hint,
@index_to_loc_format, @glyph_data_format = read(10, 'n*')
end
end
end
end
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