From e619567f35bb74ab4d697bec25656eb8e9c06d6b Mon Sep 17 00:00:00 2001
From: Thomas Leitner <t_leitner@gmx.at>
Date: Wed, 23 Aug 2023 22:49:47 +0200
Subject: [PATCH] Experimental horizontal filling support

---
 lib/hexapdf/layout/style.rb         |  1 +
 lib/hexapdf/layout/text_fragment.rb | 16 ++++++++++++++++
 lib/hexapdf/layout/text_layouter.rb | 13 +++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/lib/hexapdf/layout/style.rb b/lib/hexapdf/layout/style.rb
index cdcdfc8c..031b0d60 100644
--- a/lib/hexapdf/layout/style.rb
+++ b/lib/hexapdf/layout/style.rb
@@ -1293,6 +1293,7 @@ def update(**properties)
            "{type: value, value: extra_arg} : value))",
           extra_args: ", extra_arg = nil"}],
         [:last_line_gap, false, {valid_values: [true, false]}],
+        [:fill_horizontal, nil],
         [:background_color, nil],
         [:background_alpha, 1],
         [:padding, "Quad.new(0)", {setter: "Quad.new(value)"}],
diff --git a/lib/hexapdf/layout/text_fragment.rb b/lib/hexapdf/layout/text_fragment.rb
index 79583422..a6506e07 100644
--- a/lib/hexapdf/layout/text_fragment.rb
+++ b/lib/hexapdf/layout/text_fragment.rb
@@ -283,6 +283,22 @@ def valign
         :text
       end
 
+      def fill_horizontal(new_width)
+        factor, rest = new_width.divmod(width)
+        items = @items * factor
+        rest = @items.inject(rest) do |available_width, item|
+          new_width = available_width - style.scaled_item_width(item)
+          break available_width if new_width < 0
+          items << item
+          new_width
+        end
+        # spacing needs to be correctly scaled
+        spacing = - (rest / (items.size - 1) / style.scaled_font_size)
+        items = items.each_with_object([]) {|i, result| result << i << spacing }
+        items.pop
+        dup_attributes(items)
+      end
+
       # Clears all cached values.
       #
       # This method needs to be called if the fragment's items or attributes are changed!
diff --git a/lib/hexapdf/layout/text_layouter.rb b/lib/hexapdf/layout/text_layouter.rb
index 76dd6165..453362c8 100644
--- a/lib/hexapdf/layout/text_layouter.rb
+++ b/lib/hexapdf/layout/text_layouter.rb
@@ -363,6 +363,7 @@ def initialize(items, width_block)
           @last_breakpoint_index = 0
           @last_breakpoint_line_items_index = 0
           @break_prohibited_state = false
+          @fill_horizontal = false
 
           @height_calc = Line::HeightCalculator.new
           @line = DummyLine.new(0, 0)
@@ -508,6 +509,7 @@ def add_box_item(item)
           return false unless @width + item.width <= @available_width
           @line_items.concat(@glue_items).push(item)
           @width += item.width
+          @fill_horizontal ||= item.style.fill_horizontal
           @glue_items.clear
           true
         end
@@ -547,6 +549,17 @@ def item_fits_on_line?(item)
 
         # Creates a Line object from the current line items.
         def create_line
+          if @fill_horizontal
+            rest_width = @available_width - @width
+            indices = []
+            @line_items.each_with_index do |item, index|
+              next unless item.style.fill_horizontal
+              indices << [index, item.style.fill_horizontal]
+              rest_width += item.width
+            end
+            unit_width = rest_width / indices.sum(&:last)
+            indices.each {|i, count| @line_items[i] = @line_items[i].fill_horizontal(unit_width * count) }
+          end
           Line.new(@line_items)
         end