Class: HexaPDF::Layout::TextShaper

Inherits:
Object
  • Object
show all
Defined in:
lib/hexapdf/layout/text_shaper.rb

Overview

This class is used to perform text shaping, i.e. changing the position of glyphs (e.g. for kerning) or substituting one or more glyphs for other glyphs (e.g. for ligatures).

Status of the implementation:

  • All text shaping functionality possible for Type1 fonts is implemented, i.e. kerning and ligature substitution.

  • For TrueType fonts only kerning via the ‘kern’ table is implemented.

Instance Method Summary collapse

Instance Method Details

#shape_text(text_fragment) ⇒ Object

Shapes the given text fragment in-place.

The following shaping options, retrieved from the text fragment’s Style#font_features, are supported:

:kern

Pair-wise kerning.

:liga

Ligature substitution.



62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
 
# File 'lib/hexapdf/layout/text_shaper.rb', line 62

def shape_text(text_fragment)
  font = text_fragment.style.font
  if text_fragment.style.font_features[:liga] && font.wrapped_font.features.include?(:liga)
    if font.font_type == :Type1
      process_type1_ligatures(text_fragment)
    end
    text_fragment.clear_cache
  end
  if text_fragment.style.font_features[:kern] && font.wrapped_font.features.include?(:kern)
    case font.font_type
    when :TrueType
      process_true_type_kerning(text_fragment)
    when :Type1
      process_type1_kerning(text_fragment)
    end
    text_fragment.clear_cache
  end
  text_fragment
end