Class: Prawn::Fonts::AFM

Inherits:
Prawn::Font show all
Defined in:
lib/prawn/fonts/afm.rb

Overview

Note:

You shouldn’t use this class directly.

AFM font. AFM stands for Adobe Font Metrics. It’s not a complete font, it doesn’t provide actual glyph outlines. It only contains glyph metrics to make text layout possible. AFM is used for PDF built-in fonts. Those fonts are supposed to be present on the target system making it possible to save a little bit of space by not embedding the fonts. A file that uses these fonts can not be read on a system that doesn’t have these fonts installed.

Constant Summary collapse

BUILT_INS =

List of PDF built-in fonts.

%w[
  Courier Helvetica Times-Roman Symbol ZapfDingbats
  Courier-Bold Courier-Oblique Courier-BoldOblique
  Times-Bold Times-Italic Times-BoldItalic
  Helvetica-Bold Helvetica-Oblique Helvetica-BoldOblique
].freeze

Class Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(document, name, options = {}) ⇒ AFM

Returns a new instance of AFM.

Parameters:

  • document (Prawn::Document)
  • name (String)
  • options (Hash) (defaults to: {})

Options Hash (options):

  • :family (String)
  • :style (Symbol) 


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# File 'lib/prawn/fonts/afm.rb', line 75

def initialize(document, name, options = {})
  name ||= options[:family]
  unless BUILT_INS.include?(name)
    raise Prawn::Errors::UnknownFont,
      "#{name} (#{options[:style] || 'normal'}) is not a known font."
  end

  super

  file_name = @name.dup
  file_name << '.afm' unless /\.afm$/.match?(file_name)
  file_name = find_font(file_name) unless file_name[0] == '/'

  font_data = self.class.font_data[file_name] ||= parse_afm(file_name)
  @glyph_widths = font_data[:glyph_widths]
  @glyph_table = font_data[:glyph_table]
  @bounding_boxes = font_data[:bounding_boxes]
  @kern_pairs = font_data[:kern_pairs]
  @kern_pair_table = font_data[:kern_pair_table]
  @attributes = font_data[:attributes]

  @ascender = Integer(@attributes.fetch('ascender', '0'), 10)
  @descender = Integer(@attributes.fetch('descender', '0'), 10)
  @line_gap = Float(bbox[3] - bbox[1]) - (@ascender - @descender)
end

Class Attribute Details

.hide_m17n_warning ⇒ Boolean

Prawn would warn you if you’re using non-ASCII glyphs with AFM fonts as not all implementations provide those glyphs. This attribute suppresses that warning.

Returns:

  • (Boolean) —

    (false)



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# File 'lib/prawn/fonts/afm.rb', line 23

def hide_m17n_warning
  @hide_m17n_warning
end

Class Method Details

.font_data ⇒ SynchronizedCache

Parsed AFM data cache.

Returns:

  • (SynchronizedCache) 


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# File 'lib/prawn/fonts/afm.rb', line 66

def self.font_data
  @font_data ||= SynchronizedCache.new
end

.metrics_path ⇒ Array<String>

Paths to look for AFM files at.

Returns:

  • (Array<String>) 


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# File 'lib/prawn/fonts/afm.rb', line 46

def self.metrics_path
  @metrics_path ||=
    if ENV['METRICS']
      ENV['METRICS'].split(':')
    else
      [
        '.', '/usr/lib/afm',
        '/usr/local/lib/afm',
        '/usr/openwin/lib/fonts/afm',
        "#{Prawn::DATADIR}/fonts",
      ]
    end
end

Instance Method Details

#bbox ⇒ Array(Number, Number, Number, Number)

The font bbox.

Returns:

  • (Array(Number, Number, Number, Number)) 


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# File 'lib/prawn/fonts/afm.rb', line 104

def bbox
  @bbox ||= @attributes['fontbbox'].split(/\s+/).map { |e| Integer(e) }
end

#character_count(str) ⇒ Integer

Returns the number of characters in ‘str` (a WinAnsi-encoded string).

Parameters:

  • str (String)

Returns:

  • (Integer) 


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# File 'lib/prawn/fonts/afm.rb', line 165

def character_count(str)
  str.length
end

#compute_width_of(string, options = {}) ⇒ Number

Compute width of a string at the specified size, optionally with kerning applied.

Parameters:

  • string (String) —

    must be encoded as WinAnsi

  • options (Hash{Symbol => any}) (defaults to: {})

Options Hash (options):

  • :size (Number)
  • :kerning (Boolean) — default: false

Returns:

  • (Number) 


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# File 'lib/prawn/fonts/afm.rb', line 116

def compute_width_of(string, options = {})
  scale = (options[:size] || size) / 1000.0

  if options[:kerning]
    strings, numbers = kern(string).partition { |e| e.is_a?(String) }
    total_kerning_offset = numbers.sum
    (unscaled_width_of(strings.join) - total_kerning_offset) * scale
  else
    unscaled_width_of(string) * scale
  end
end

#encode_text(text, options = {}) ⇒ Array<Array(0, (String, Array)>]

Perform any changes to the string that need to happen before it is rendered to the canvas. Returns an array of subset “chunks”, where each chunk is an array of two elements. The first element is the font subset number, and the second is either a string or an array (for kerned text).

For Adobe fonts, there is only ever a single subset, so the first element of the array is ‘0`, and the second is the string itself (or an array, if kerning is performed).

The ‘text` argument must be in WinAnsi encoding (cp1252).

Parameters:

  • text (String)
  • options (Hash{Symbol => any}) (defaults to: {})

Options Hash (options):

  • :kerning (Boolean)

Returns:

  • (Array<Array(0, (String, Array)>]) —

    Array<Array(0, (String, Array)>]



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# File 'lib/prawn/fonts/afm.rb', line 185

def encode_text(text, options = {})
  [[0, options[:kerning] ? kern(text) : text]]
end

#glyph_present?(char) ⇒ Boolean

Does this font has a glyph for the character?

Parameters:

  • char (String)

Returns:

  • (Boolean) 


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# File 'lib/prawn/fonts/afm.rb', line 193

def glyph_present?(char)
  !normalize_encoding(char).nil?
rescue Prawn::Errors::IncompatibleStringEncoding
  false
end

#has_kerning_data? ⇒ Boolean

Does this font contain kerning data.

Returns:

  • (Boolean) 


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# File 'lib/prawn/fonts/afm.rb', line 131

def has_kerning_data? # rubocop: disable Naming/PredicateName
  @kern_pairs.any?
end

#normalize_encoding(text) ⇒ String

Built-in fonts only work with WinAnsi encoding, so translate the string. Changes the encoding in-place, so the argument itself is replaced with a string in WinAnsi encoding.

Parameters:

  • text (String)

Returns:

  • (String) 


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# File 'lib/prawn/fonts/afm.rb', line 141

def normalize_encoding(text)
  text.encode('windows-1252')
rescue ::Encoding::InvalidByteSequenceError,
       ::Encoding::UndefinedConversionError

  raise Prawn::Errors::IncompatibleStringEncoding,
    "Your document includes text that's not compatible with the " \
      "Windows-1252 character set.\n" \
      'If you need full UTF-8 support, use external fonts instead of ' \
      "PDF's built-in fonts.\n"
end

#to_utf8(text) ⇒ String

Encode text to UTF-8.

Parameters:

  • text (String)

Returns:

  • (String) 


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# File 'lib/prawn/fonts/afm.rb', line 157

def to_utf8(text)
  text.encode('UTF-8')
end

#unicode? ⇒ false

Does this font support Unicode?

Returns:

  • (false) 


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# File 'lib/prawn/fonts/afm.rb', line 39

def unicode?
  false
end