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# frozen_string_literal: true
require_relative '../table'
module TTFunk
class Table
# Horizontal Metrics (`hmtx`) table.
class Hmtx < Table
# Glyph horizontal metrics.
# @return [Array<HorizontalMetric>]
attr_reader :metrics
# Left side bearings.
# @return [Array<Ingteger>]
attr_reader :left_side_bearings
# Glyph widths.
# @return [Array<Integer>]
attr_reader :widths
# Encode table.
#
# @param hmtx [TTFunk::Table::Hmtx]
# @param mapping [Hash{Integer => Integer}] keys are new glyph IDs, values
# are old glyph IDs
# @return [Hash{:number_of_metrics => Integer, :table => String}]
# * `:number_of_metrics` - number of mertrics is the table.
# * `:table` - encoded table.
def self.encode(hmtx, mapping)
metrics =
mapping.keys.sort.map { |new_id|
metric = hmtx.for(mapping[new_id])
[metric.advance_width, metric.left_side_bearing]
}
{
number_of_metrics: metrics.length,
table: metrics.flatten.pack('n*'),
}
end
# Horyzontal glyph metric.
#
# @!attribute [rw] advance_width
# @return [Integer] Advance width.
# @!attribute [rw] left_side_bearing
# @return [Integer] Left side bearing.
HorizontalMetric = Struct.new(:advance_width, :left_side_bearing)
# Get horizontal metric for glyph.
#
# @param glyph_id [Integer]
# @return [HorizontalMetric]
def for(glyph_id)
@metrics[glyph_id] ||
metrics_cache[glyph_id] ||=
HorizontalMetric.new(
@metrics.last.advance_width,
@left_side_bearings[glyph_id - @metrics.length],
)
end
private
def metrics_cache
@metrics_cache ||= {}
end
def parse!
@metrics = []
file.horizontal_header.number_of_metrics.times do
advance = read(2, 'n').first
lsb = read_signed(1).first
@metrics.push(HorizontalMetric.new(advance, lsb))
end
lsb_count = file.maximum_profile.num_glyphs -
file.horizontal_header.number_of_metrics
@left_side_bearings = read_signed(lsb_count)
@widths = @metrics.map(&:advance_width)
@widths += [@widths.last] * @left_side_bearings.length
end
end
end
end
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