Fix performance regression when encoding char codes for TrueType fonts

The recent change for supporting multiple codepoint referencing the same
glyph lead to a performance regression because the char codes 13, 40, 41
and 92 were used again.

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Checksum calculation for TrueType tables
 * Automatic wrapping of dictionary entry /CIDToGIDMap for CID fonts
+* Performance regression when encoding char codes for TrueType fonts
 
 
 ## 1.0.1 - 2024-11-04

lib/hexapdf/font/true_type_wrapper.rb

@@ -239,6 +239,11 @@ def encode(glyph)
             raise HexaPDF::MissingGlyphError.new(glyph) if glyph.kind_of?(InvalidGlyph)
             @subsetter.use_glyph(glyph.id) if @subsetter
             @last_char_code += 1
+            # Handle codes for ASCII characters \r (13), (, ) (40, 41) and \ (92) specially so that
+            # they never appear in the output (PDF serialization would need to escape them)
+            if @last_char_code == 13 || @last_char_code == 40 || @last_char_code == 92
+              @last_char_code += (@last_char_code == 40 ? 2 : 1)
+            end
             [[@last_char_code].pack('n'), @last_char_code]
           end)[0]
       end

test/hexapdf/font/test_true_type_wrapper.rb

@@ -119,6 +119,11 @@
       assert_equal([3].pack('n'), code)
     end
 
+    it "doesn't use char codes 13, 40, 41 and 92 because they would need to be escaped" do
+      codes = 1.upto(93).map {|i| @font_wrapper.encode(@font_wrapper.glyph(i)) }.join
+      assert_equal([1..12, 14..39, 42..91, 93..97].flat_map(&:to_a).pack('n*'), codes)
+    end
+
     it "raises an error if an InvalidGlyph is encoded" do
       exp = assert_raises(HexaPDF::MissingGlyphError) do
         @font_wrapper.encode(@font_wrapper.decode_utf8("ö").first)