Class: TTFunk::Table::Kern::Format0

Inherits:
Object
  • Object
show all
Includes:
Reader
Defined in:
lib/ttfunk/table/kern/format0.rb

Overview

Format 0 kerning subtable.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(attributes = {}) ⇒ Format0

Returns a new instance of Format0.

Parameters:

  • attributes (Hash{Symbol => any}) (defaults to: {})
Source Code
lib/ttfunk/table/kern/format0.rb, line 21
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def initialize(attributes = {})
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  @attributes = attributes
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  num_pairs, *pairs = attributes.delete(:data).unpack('nx6n*')
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  @pairs = {}
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  num_pairs.times do |i|
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    # sanity check, in case there's a bad length somewhere
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    break if (i * 3) + 2 > pairs.length
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    left = pairs[i * 3]
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    right = pairs[(i * 3) + 1]
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    value = to_signed(pairs[(i * 3) + 2])
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    @pairs[[left, right]] = value
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  end
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end

Instance Attribute Details

#attributesHash{Symbol => any} (readonly)

Subtable attributes.

Returns:

  • (Hash{Symbol => any})
Source Code
lib/ttfunk/table/kern/format0.rb, line 14
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def attributes
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  @attributes
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end

#pairsHash{Array(Integer, Integer) => Integer} (readonly)

Kerning pairs.

Returns:

  • (Hash{Array(Integer, Integer) => Integer})
Source Code
lib/ttfunk/table/kern/format0.rb, line 18
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def pairs
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  @pairs
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end

Instance Method Details

#cross_stream?Boolean

Is this cross-stream kerning?

Returns:

  • (Boolean)
Source Code
lib/ttfunk/table/kern/format0.rb, line 52
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def cross_stream?
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  @attributes[:cross]
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end

#horizontal?Boolean

Is this horizontal kerning?

Returns:

  • (Boolean)
Source Code
lib/ttfunk/table/kern/format0.rb, line 46
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def horizontal?
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  !vertical?
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end

#recode(mapping) ⇒ String

Recode this subtable using the specified mapping.

Parameters:

  • mapping (Hash{Integer => Integer})

    keys are new glyph IDs, values are old glyph IDs

Returns:

  • (String)
Source Code
lib/ttfunk/table/kern/format0.rb, line 61
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def recode(mapping)
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  subset = []
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  pairs.each do |(left, right), value|
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    if mapping[left] && mapping[right]
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      subset << [mapping[left], mapping[right], value]
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    end
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  end
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  return if subset.empty?
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  num_pairs = subset.length
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  search_range = 2 * (2**Integer(Math.log(num_pairs) / Math.log(2)))
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  entry_selector = Integer(Math.log(search_range / 2) / Math.log(2))
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  range_shift = (2 * num_pairs) - search_range
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  [
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    attributes[:version],
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    (num_pairs * 6) + 14,
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    attributes[:coverage],
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    num_pairs,
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    search_range,
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    entry_selector,
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    range_shift,
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    subset,
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  ].flatten.pack('n*')
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end

#vertical?Boolean

Is this vertical kerning?

Returns:

  • (Boolean)
Source Code
lib/ttfunk/table/kern/format0.rb, line 40
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def vertical?
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  @attributes[:vertical]
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end