Module: Cooltrainer::DistorteD::Technology::Pango

Included in:
Molecule::Font, Molecule::Text
Defined in:
lib/distorted/modular_technology/pango.rb

Instance Method Summary collapse

Instance Method Details

#cr ⇒ Object

Returns a Pango-escaped Carriage Return. Use this for linebreaking Pango Markup output.



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# File 'lib/distorted/modular_technology/pango.rb', line 24

def cr
  g_markup_escape_char(0x0D)
end

#crlf ⇒ Object

Returns a Pango’escaped CRLF pair. Also not needed for anything.



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# File 'lib/distorted/modular_technology/pango.rb', line 37

def crlf
  cr << lf
end

#g_markup_escape_char(c) ⇒ Object

The char-by-char actual function used by g_markup_escape_text



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# File 'lib/distorted/modular_technology/pango.rb', line 49

def g_markup_escape_char(c)
  # I think a fully-working version of this function would
  # be as simple as `sprintf('&#x%x;', c.ord)` ALL THE THINGS,
  # but I want to copy the structure of the C implementation
  # as closely as possible, which means using the named escape
  # sequences for common characters and separating the
  # Latin-1 Supplement range from the other
  # the Unicode control characters (> 0x7f) even though three's no
  # need to in Ruby.
  case c.ord
  when '&'.ord
    '&amp;'
  when '<'.ord
    '&lt;'
  when '>'.ord
    '&gt;'
  when '\''.ord
    '&apos;'
  when '"'.ord
    '&quot;'
  when 0x1..0x8, 0xb..0xc, 0xe..0x1f, 0x7f
    sprintf('&#x%x;', c.ord)
  when 0x80..0x84, 0x86..0x9f
    # The original C implementation separates this range
    # from the above range due to its need to handle the
    # UTF control character bytes with gunichar:
    # https://wiki.tcl-lang.org/page/UTF%2D8+bit+by+bit
    # https://www.fileformat.info/info/unicode/utf8.htm
    # Ruby has already done this for us here :)
    sprintf('&#x%x;', c.ord)
  when 0x0 # what's this…?
    # Avoid a `ArgumentError: string contains null byte`
    # by not printing one :)
  else
    c
  end
end

#g_markup_escape_text(text) ⇒ Object

Escape text as necessary for Pango Markup, which is what Vips::Image.text() expects for its argv. This code should be in GLib but is unimplemented in Ruby’s:

ruby-gnome2.osdn.jp/hiki.cgi?Gtk%3A%3ALabel#Markup+%28styled+text%29 “The markup passed to Gtk::Label#set_markup() must be valid; for example, literal </>/& characters must be escaped as &lt;, &gt;, and &amp;. If you pass text obtained from the user, file, or a network to Gtk::Label#set_markup(), you’ll want to escape it with GLib::Markup.escape_text?(not implemented yet).”

Base my own implementation on the original C version found in gmarkup: gitlab.gnome.org/GNOME/glib/-/blob/master/glib/gmarkup.c



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# File 'lib/distorted/modular_technology/pango.rb', line 18

def g_markup_escape_text(text)
  text.map{ |c| g_markup_escape_char(c) }
end

#lf ⇒ Object

Returns a Pango-escapped Line Feed. This isn’t used/needed for anything with Pango but it felt weird to include CR and not LF lmao



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# File 'lib/distorted/modular_technology/pango.rb', line 31

def lf
  g_markup_escape_char(0x0A)
end

#overlong_null ⇒ Object

“Modified UTF-8” uses a normally-illegal byte sequence to encode the NULL character so 0x00 can exclusively be a string terminator.



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# File 'lib/distorted/modular_technology/pango.rb', line 44

def overlong_null
  [0xC0, 0x80].pack('C*').force_encoding('UTF-8')
end