lib/ttfunk/table/head.rb in ttfunk-1.7.0 vs lib/ttfunk/table/head.rb in ttfunk-1.8.0

@@ -2,31 +2,95 @@
 
 require_relative '../table'
 
 module TTFunk
   class Table
+    # Font Header (`head`) Table.
     class Head < TTFunk::Table
+      # Table version.
+      # @return [Integer]
       attr_reader :version
+
+      # Font revision.
+      # @return [Integer]
       attr_reader :font_revision
+
+      # Checksum adjustment.
+      # @return [Integer]
       attr_reader :checksum_adjustment
+
+      # Magic number.
+      # @return [Integer] must be `0x5F0F3CF5`
       attr_reader :magic_number
+
+      # Flags.
+      # @return [Integer]
       attr_reader :flags
+
+      # Units per Em.
+      # @return [Integer]
       attr_reader :units_per_em
+
+      # Font creation time.
+      # @return [Integer] Long Date Time timestamp.
       attr_reader :created
+
+      # Font modification time.
+      # @return [Integer] Long Date Time timestamp.
       attr_reader :modified
+
+      # Minimum x coordinate across all glyph bounding boxes.
+      # @return [Integer]
       attr_reader :x_min
+
+      # Minimum y coordinate across all glyph bounding boxes.
+      # @return [Integer]
       attr_reader :y_min
+
+      # Maximum x coordinate across all glyph bounding boxes.
+      # @return [Integer]
       attr_reader :x_max
+
+      # Maximum y coordinate across all glyph bounding boxes.
+      # @return [Integer]
       attr_reader :y_max
+
+      # Mac font style.
+      # @return [Integer]
       attr_reader :mac_style
+
+      # Smallest readable size in pixels.
+      # @return [Integer]
       attr_reader :lowest_rec_ppem
+
+      # Font direction hint. Deprecated, set to 2.
+      # @return [Integer]
       attr_reader :font_direction_hint
+
+      # Index to Location format.
+      # @return [Integer]
       attr_reader :index_to_loc_format
+
+      # Glyph data format.
+      # @return [Integer]
       attr_reader :glyph_data_format
 
       class << self
-        # mapping is new -> old glyph ids
+        # Long date time (used in TTF headers).
+        # January 1, 1904 00:00:00 UTC basis used by Long date time.
+        # @see https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6.html
+        #   TrueType Font Tables
+        LONG_DATE_TIME_BASIS = Time.new(1904, 1, 1, 0, 0, 0, 0).to_i
+        private_constant :LONG_DATE_TIME_BASIS
+
+        # Encode table.
+        #
+        # @param head [TTFunk::Table::Head]
+        # @param loca [Hash] result of encoding Index to Location (`loca`) table
+        # @param mapping [Hash{Integer => Integer}] keys are new glyph IDs, values
+        #   are old glyph IDs
+        # @return [EncodedString]
         def encode(head, loca, mapping)
           EncodedString.new do |table|
             table <<
               [head.version, head.font_revision].pack('N2') <<
               Placeholder.new(:checksum, length: 4) <<
@@ -34,24 +98,38 @@
                 head.magic_number,
                 head.flags, head.units_per_em,
                 head.created, head.modified,
                 *min_max_values_for(head, mapping),
                 head.mac_style, head.lowest_rec_ppem, head.font_direction_hint,
-                loca[:type] || 0, head.glyph_data_format
-              ].pack('Nn2q2n*')
+                loca[:type] || 0, head.glyph_data_format,
+              ].pack('Nn2q>2n*')
           end
         end
 
+        # Convert Long Date Time timestamp to Time.
+        # @param ldt [Float, Integer]
+        # @return [Time]
+        def from_long_date_time(ldt)
+          Time.at(ldt + LONG_DATE_TIME_BASIS, in: 'UTC')
+        end
+
+        # Convert Time to Long Date Time timestamp
+        # @param time [Time]
+        # @return [Integer]
+        def to_long_date_time(time)
+          Integer(time) - LONG_DATE_TIME_BASIS
+        end
+
         private
 
         def min_max_values_for(head, mapping)
           x_min = Min.new
           x_max = Max.new
           y_min = Min.new
           y_max = Max.new
 
-          mapping.each do |_, old_glyph_id|
+          mapping.each_value do |old_glyph_id|
             glyph = head.file.find_glyph(old_glyph_id)
             next unless glyph
 
             x_min << glyph.x_min
             x_max << glyph.x_max
@@ -59,19 +137,19 @@
             y_max << glyph.y_max
           end
 
           [
             x_min.value_or(0), y_min.value_or(0),
-            x_max.value_or(0), y_max.value_or(0)
+            x_max.value_or(0), y_max.value_or(0),
           ]
         end
       end
 
       private
 
       def parse!
         @version, @font_revision, @check_sum_adjustment, @magic_number,
-          @flags, @units_per_em, @created, @modified = read(36, 'N4n2q2')
+          @flags, @units_per_em, @created, @modified = read(36, 'N4n2q>2')
 
         @x_min, @y_min, @x_max, @y_max = read_signed(4)
 
         @mac_style, @lowest_rec_ppem, @font_direction_hint,
           @index_to_loc_format, @glyph_data_format = read(10, 'n*')