Update AcroForm appearance generator to support fallback glyphs

lib/hexapdf/type/acro_form/appearance_generator.rb

@@ -361,12 +361,16 @@ def draw_single_line_text(canvas, width, height, style, padding)
           value, text_color = apply_javascript_formatting(@field.field_value)
           style.fill_color = text_color if text_color
           calculate_and_apply_font_size(value, style, width, height, padding)
-          fragment = HexaPDF::Layout::TextFragment.create(value, style)
+          line = HexaPDF::Layout::Line.new(@document.layout.text_fragments(value, style: style))
 
-          if @field.concrete_field_type == :comb_text_field
+          if @field.concrete_field_type == :comb_text_field && !value.empty?
             unless @field.key?(:MaxLen)
               raise HexaPDF::Error, "Missing or invalid dictionary field /MaxLen for comb text field"
             end
+            unless line.items.size == 1
+              raise HexaPDF::Error, "Fallback glyphs are not yet supported with comb text fields"
+            end
+            fragment = line.items[0]
             new_items = []
             cell_width = width.to_f / @field[:MaxLen]
             scaled_cell_width = cell_width / style.scaled_font_size.to_f
@@ -376,6 +380,7 @@ def draw_single_line_text(canvas, width, height, style, padding)
             new_items << fragment.items.last
             fragment.items.replace(new_items)
             fragment.clear_cache
+            line.clear_cache
             # Adobe always seems to add 1 to the first offset...
             x_offset = 1 + (cell_width - style.scaled_item_width(fragment.items[0])) / 2.0
             x = case @field.text_alignment
@@ -387,8 +392,8 @@ def draw_single_line_text(canvas, width, height, style, padding)
             # Adobe seems to be left/right-aligning based on twice the border width
             x = case @field.text_alignment
                 when :left then 2 * padding
-                when :right then [width - 2 * padding - fragment.width, 2 * padding].max
-                when :center then [(width - fragment.width) / 2.0, 2 * padding].max
+                when :right then [width - 2 * padding - line.width, 2 * padding].max
+                when :center then [(width - line.width) / 2.0, 2 * padding].max
                 end
           end
 
@@ -400,12 +405,12 @@ def draw_single_line_text(canvas, width, height, style, padding)
             style.font_size
           y = padding + (height - 2 * padding - cap_height) / 2.0
           y = padding - style.scaled_font_descender if y < 0
-          fragment.draw(canvas, x, y)
+          line.each {|fragment, fx, _| fragment.draw(canvas, x + fx, y) }
         end
 
         # Draws multiple lines  of text inside the widget's rectangle.
         def draw_multiline_text(canvas, width, height, style, padding)
-          items = [Layout::TextFragment.create(@field.field_value, style)]
+          items = @document.layout.text_fragments(@field.field_value, style: style)
           layouter = Layout::TextLayouter.new(style)
           layouter.style.text_align(@field.text_alignment).line_spacing(:proportional, 1.25)
 
@@ -437,7 +442,7 @@ def draw_list_box(canvas, width, height, style, padding)
 
           option_items = @field.option_items
           top_index = @field.list_box_top_index
-          items = [Layout::TextFragment.create(option_items[top_index..-1].join("\n"), style)]
+          items = @document.layout.text_fragments(option_items[top_index..-1].join("\n"), style: style)
           # Should use /I but if it differs from /V, we need to use /V; so just use /V...
           indices = [@field.field_value].flatten.compact.map {|val| option_items.index(val) }
 
@@ -490,8 +495,8 @@ def calculate_and_apply_font_size(value, style, width, height, padding)
             font.scaling_factor / 1000.0
           # The constant factor was found empirically by checking what Adobe Reader etc. do
           style.font_size = (height - 2 * padding) / unit_font_size * 0.85
-          fragment = HexaPDF::Layout::TextFragment.create(value, style)
-          style.font_size = [style.font_size, style.font_size * (width - 4 * padding) / fragment.width].min
+          calc_width = @document.layout.text_fragments(value, style: style).sum(&:width)
+          style.font_size = [style.font_size, style.font_size * (width - 4 * padding) / calc_width].min
           style.clear_cache
         end
 

test/hexapdf/type/acro_form/test_appearance_generator.rb

@@ -598,20 +598,29 @@ def assert_format(arg_string, result, range)
       end
 
       it "creates the /N appearance stream according to the set string" do
-        @field.field_value = 'Text'
+        @doc.config['font.on_invalid_glyph'] = lambda do |codepoint, _|
+          [@doc.fonts.add('ZapfDingbats').decode_codepoint(codepoint)]
+        end
         @field.set_default_appearance_string(font_color: "red")
+        @field[:V] = 'Te ✂ xt'
         @generator.create_appearances
         assert_operators(@widget[:AP][:N].stream,
                          [[:begin_marked_content, [:Tx]],
                           [:save_graphics_state],
                           [:append_rectangle, [1, 1, 98, 9.25]],
                           [:clip_path_non_zero],
                           [:end_path],
-                          [:set_font_and_size, [:F1, 6.801471]],
+                          [:set_font_and_size, [:F1, 10]],
                           [:set_device_rgb_non_stroking_color, [1.0, 0.0, 0.0]],
                           [:begin_text],
-                          [:set_text_matrix, [1, 0, 0, 1, 2, 3.183272]],
-                          [:show_text, ["Text"]],
+                          [:set_text_matrix, [1, 0, 0, 1, 2, 2.035]],
+                          [:show_text, ["Te "]],
+                          [:set_font_and_size, [:F2, 10]],
+                          [:move_text, [14.45, 0]],
+                          [:show_text, ["\""]],
+                          [:set_font_and_size, [:F1, 10]],
+                          [:move_text, [9.61, 0]],
+                          [:show_text, [" xt"]],
                           [:end_text],
                           [:restore_graphics_state],
                           [:end_marked_content]])
@@ -774,11 +783,29 @@ def assert_format(arg_string, result, range)
                           [:end_marked_content]])
       end
 
+      it "works for empty strings" do
+        @field[:V] = ''
+        @generator.create_appearances
+        assert_operators(@widget[:AP][:N].stream,
+                         [[:begin_text],
+                          [:set_text_matrix, [1, 0, 0, 1, 2, 6.41]],
+                          [:end_text]], range: 6..8)
+      end
+
       it "fails if the /MaxLen key is not set" do
         @field.delete(:MaxLen)
         @field[:V] = 't'
         assert_raises(HexaPDF::Error) { @generator.create_appearances }
       end
+
+      it "fails if fallback glyphs are needed for rendering" do
+        @doc.config['font.on_invalid_glyph'] = lambda do |codepoint, _|
+          [@doc.fonts.add('ZapfDingbats').decode_codepoint(codepoint)]
+        end
+        @field[:V] = 'Test ✂'
+        ex = assert_raises(HexaPDF::Error) { @generator.create_appearances }
+        assert_match(/Fallback glyphs/, ex.message)
+      end
     end
 
     describe "choice fields" do