Module: Cooltrainer::DistorteD::Molecule::Font

Includes:
Technology::Pango, Technology::TTFunk, Technology::Vips::Save
Defined in:
lib/distorted/media_molecule/font.rb

Constant Summary collapse

LOWER_WORLD =

TODO: Test OTF, OTB, and others. NOTE: Traditional bitmap fonts won’t be supported due to Pango 1.44 and later switching to Harfbuzz from Freetype: gitlab.gnome.org/GNOME/pango/-/issues/386 blogs.gnome.org/mclasen/2019/05/25/pango-future-directions/

CHECKING::YOU::IN(/^font\/ttf/).to_hash
OUTER_LIMITS = 
CHECKING::YOU::IN(/^font\/ttf/).to_hash
ATTRIBUTES = 
Set[
  :alt,
]
ATTRIBUTES_VALUES = 
{
}
ATTRIBUTES_DEFAULT = 
{
}

Constants included from Technology::Vips::Save

Technology::Vips::Save::VIPS_SAVERS

Instance Method Summary collapse

Methods included from Technology::Pango

#cr, #crlf, #g_markup_escape_char, #g_markup_escape_text, #lf, #overlong_null

Methods included from Technology::TTFunk

#font_copyright, #font_description, #font_name, #font_spacing, #font_version, #to_ttfunk

Instance Method Details

#font_path ⇒ Object

Return the ‘src` as the font_path since we aren’t using any of the built-in fonts.



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# File 'lib/distorted/media_molecule/font.rb', line 147

def font_path
  path
end

#to_pango ⇒ Object

irb(main):089:0> chars.take(5)

> [[1, 255], [2, 1], [3, 2], [4, 3], [5, 4]]

irb(main):090:0> chars.values.take(5)

> [255, 1, 2, 3, 4]

irb(main):091:0> chars.values.map(&:chr).take(5)

> [“xFF”, “x01”, “x02”, “x03”, “x04”]



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# File 'lib/distorted/media_molecule/font.rb', line 54

def to_pango
  output = '' << cr << '<span>' << cr

  output << "<span size='35387'> #{font_name}</span>" << cr << cr

  output << "<span size='24576'> #{font_description}</span>" << cr
  output << "<span size='24576'> #{font_copyright}</span>" << cr
  output << "<span size='24576'> #{font_version}</span>" << cr << cr

  # Print a preview String in using the loaded font. Or don't.
  if abstract(:title)
    output << cr << cr << "<span size='24576' foreground='grey'> #{g_markup_escape_text(abstract(:title))}</span>" << cr << cr << cr
  end

  #                        /!\ MANDATORY READING /!\
  # https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6cmap.html
  #
  # "The 'cmap' table maps character codes to glyph indices.
  # The choice of encoding for a particular font is dependent upon the conventions
  # used by the intended platform. A font intended to run on multiple platforms
  # with different encoding conventions will require multiple encoding tables.
  # As a result, the 'cmap' table may contain multiple subtables,
  # one for each supported encoding scheme."
  #
  # Cmap#unicode is a convenient shortcut to sorting the subtables
  # and removing any unusable ones:
  # https://github.com/prawnpdf/ttfunk/blob/master/lib/ttfunk/table/cmap.rb
  #
  # irb(main):174:0> font_meta.cmap.tables.count
  # => 3
  # irb(main):175:0> font_meta.cmap.unicode.count
  # => 2
  to_ttfunk.cmap.tables.each do |table|
    next if !table.unicode?
    # Each subtable's `code_map` is a Hash map of character codes (the Hash keys)
    # to the glyph IDs from the original font (the Hash's values).
    #
    # Subtable::encode takes:
    #  - a Hash mapping character codes to original font glyph IDs.
    #  - the desired output encoding — Set[:mac_roman, :unicode, :unicode_ucs4]
    #    https://github.com/prawnpdf/ttfunk/blob/master/lib/ttfunk/table/cmap/subtable.rb
    # …and returns a Hash with keys:
    #  - :charmap  — Hash mapping the characters in the input charmap
    #                to a another hash containing both the `:old`
    #                and `:new` glyph ids for each character code.
    #  - :subtable — String encoded subtable for the given encoding.
    encoded = TTFunk::Table::Cmap::Subtable::encode(table&.code_map, :unicode).dig(:charmap)

    output << "<span size='49152'>"

    i = 0
    encoded.each_pair { |c, (old, new)|

      begin
        if glyph = to_ttfunk.glyph_outlines.for(c)
          # Add a space on either side of the character so they aren't
          # all smooshed up against each other and unreadable.
          output << ' ' << g_markup_escape_char(c) << ' '
          if i >= 15
            output << cr
            i = 0
          else
            i = i + 1
          end
        else
        end
      rescue NoMethodError => nme
        # TTFunk's `glyph_outlines.for()` will raise this if we call it
        # for a codepoint that does not exist in the font, which we will
        # not do because we are enumerating the codepoints in the font,
        # but we should still handle the possibility.
        # irb(main):060:0> font.glyph_outlines.for(555555)
        #
        # Traceback (most recent call last):
        #   6: from /usr/bin/irb:23:in `<main>'
        #   5: from /usr/bin/irb:23:in `load'
        #   4: from /home/okeeblow/.gems/gems/irb-1.2.4/exe/irb:11:in `<top (required)>'
        #   3: from (irb):60
        #   2: from /home/okeeblow/.gems/gems/ttfunk-1.6.2.1/lib/ttfunk/table/glyf.rb:35:in `for'
        #   1: from /home/okeeblow/.gems/gems/ttfunk-1.6.2.1/lib/ttfunk/table/loca.rb:35:in `size_of'
        # NoMethodError (undefined method `-' for nil:NilClass)
      end
    }

    output << '</span>' << cr
  end

  output << '</span>'
  output
end

#to_vips_image ⇒ Object 



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# File 'lib/distorted/media_molecule/font.rb', line 151

def to_vips_image
  # https://libvips.github.io/libvips/API/current/libvips-create.html#vips-text
  Vips::Image.text(
    # This string must be well-escaped Pango Markup:
    # https://developer.gnome.org/pango/stable/pango-Markup.html
    # However the official function for escaping text is
    # not implemented in Ruby GLib, so we have to do it ourselves.
    to_pango,
    **{
      # String absolute path to TTF
      :fontfile => font_path,
      # It's not enough to just specify the TTF path;
      # we must also specify a font family, subfamily, and size.
      :font => "#{font_name}",
      # Space between lines (in Points).
      :spacing => to_ttfunk.line_gap,
      # Requires libvips 8.8
      :justify => false,
      :dpi => 144,
    },
  )
end