resolves asciidoctor#110 fix xrefs to non-section content

- introduce add_dest_for_block for adding xref targets (i.e, destinations)
- call add_dest_for_block in each block handler
- add support in parser for <a name> to set inline destinations
- handle render_behind callback to add inline destinations
- enable inline ref and bibref targets

lib/asciidoctor-pdf/converter.rb

@@ -37,6 +37,7 @@ def self.unicode_char number
   TabSpaces = ' ' * 4
   NoBreakSpace = unicode_char 0x00a0
   NarrowNoBreakSpace = unicode_char 0x202f
+  ZeroWidthSpace = unicode_char 0x200b
   HairSpace = unicode_char 0x200a
   DotLeader = %(#{HairSpace}.)
   EmDash = unicode_char 0x2014
@@ -259,9 +260,7 @@ def convert_section sect, opts = {}
       end
       # QUESTION should we store page_start & destination in internal map?
       sect.set_attr 'page_start', page_number
-      dest_y = at_page_top? ? page_height : y
-      sect.set_attr 'destination', (sect_destination = (dest_xyz 0, dest_y))
-      add_dest sect.id, sect_destination
+      add_dest_for_block sect
       sect.chapter? ? (layout_chapter_title sect, title) : (layout_heading title)
     end
 
@@ -270,12 +269,14 @@ def convert_section sect, opts = {}
   end
 
   def convert_floating_title node
+    add_dest_for_block node if node.id
     theme_font :heading, level: (node.level + 1) do
       layout_heading node.title
     end
   end
 
   def convert_abstract node
+    add_dest_for_block node if node.id
     pad_box @theme.abstract_padding do
       theme_font :abstract do
         # FIXME control first_line_options using theme
@@ -313,6 +314,7 @@ def convert_preamble node
 
   # TODO add prose around image logic (use role to add special logic for headshot)
   def convert_paragraph node
+    add_dest_for_block node if node.id
     is_lead = false
     prose_opts = {}
     node.roles.each do |role|
@@ -345,6 +347,7 @@ def convert_paragraph node
 
   # FIXME alignment of content is off
   def convert_admonition node
+    add_dest_for_block node if node.id
     #move_down @theme.block_margin_top unless at_page_top?
     theme_margin :block, :top
     icons = node.document.attr? 'icons', 'font'
@@ -391,6 +394,7 @@ def convert_admonition node
   end
 
   def convert_example node
+    add_dest_for_block node if node.id
     #move_down @theme.block_margin_top unless at_page_top?
     theme_margin :block, :top
     keep_together do |box_height = nil|
@@ -421,14 +425,17 @@ def convert_open node
       if node.blocks.size == 1 && node.blocks.first.style == 'abstract'
         convert_abstract node.blocks.first
       else
+        add_dest_for_block node if node.id
         convert_content_for_block node
       end
     else
+      add_dest_for_block node if node.id
       convert_content_for_block node
     end
   end
 
   def convert_quote_or_verse node
+    add_dest_for_block node if node.id
     border_width = @theme.blockquote_border_width
     #move_down @theme.block_margin_top unless at_page_top?
     theme_margin :block, :top
@@ -466,6 +473,7 @@ def convert_quote_or_verse node
   alias :convert_verse :convert_quote_or_verse
 
   def convert_sidebar node
+    add_dest_for_block node if node.id
     #move_down @theme.block_margin_top unless at_page_top?
     theme_margin :block, :top
     keep_together do |box_height = nil|
@@ -495,6 +503,7 @@ def convert_sidebar node
   end
 
   def convert_colist node
+    add_dest_for_block node if node.id
     # HACK undo the margin below the listing
     move_up ((@theme.block_margin_bottom || @theme.vertical_rhythm) * 0.5)
     @list_numbers ||= []
@@ -508,6 +517,7 @@ def convert_colist node
   end
 
   def convert_dlist node
+    add_dest_for_block node if node.id
     node.items.each do |terms, desc|
       terms = [*terms]
       # NOTE don't orphan the terms, allow for at least one line of content
@@ -525,6 +535,7 @@ def convert_dlist node
   end
 
   def convert_olist node
+    add_dest_for_block node if node.id
     @list_numbers ||= []
     list_number = case node.style
     when 'arabic'
@@ -554,6 +565,7 @@ def convert_olist node
 
   # TODO implement checklist
   def convert_ulist node
+    add_dest_for_block node if node.id
     bullet_type = if (style = node.style)
       case style
       when 'bibliography'
@@ -629,6 +641,7 @@ def convert_content_for_list_item node
   end
 
   def convert_image node
+    add_dest_for_block node if node.id
     #move_down @theme.block_margin_top unless at_page_top?
     theme_margin :block, :top
     target = node.attr 'target'
@@ -699,6 +712,7 @@ def convert_image node
   end
 
   def convert_listing_or_literal node
+    add_dest_for_block node if node.id
     # HACK disable built-in syntax highlighter; must be done before calling node.content!
     if (node.style == 'source')
       node.subs.delete :highlight
@@ -771,6 +785,7 @@ def convert_listing_or_literal node
   alias :convert_literal :convert_listing_or_literal
 
   def convert_table node
+    add_dest_for_block node if node.id
     num_rows = 0
     num_cols = node.columns.size
     table_header = false
@@ -971,15 +986,11 @@ def convert_inline_anchor node
         end
       end
     when :ref
-      # FIXME add destination to PDF document
-      #target = node.target
-      #%(<a id="#{target}"></a>)
-      ''
+      # NOTE destination is created inside callback registered by FormattedTextTransform#build_fragment
+      %(<a name="#{node.target}">#{ZeroWidthSpace}</a>)
     when :bibref
-      # FIXME add destination to PDF document
-      #target = node.target
-      #%(<a id="#{target}"></a>[#{target}])
-      %([#{node.target}])
+      # NOTE destination is created inside callback registered by FormattedTextTransform#build_fragment
+      %(<a name="#{target = node.target}">#{ZeroWidthSpace}</a>[#{target}])
     else
       warn %(asciidoctor: WARNING: unknown anchor type: #{node.type.inspect})
     end
@@ -1052,7 +1063,7 @@ def convert_inline_quoted node
       quoted_text = %(#{open}#{node.text}#{close})
     end
 
-    node.id ? %(<a id="#{node.id}"></a>#{quoted_text}) : quoted_text
+    node.id ? %(<a name="#{node.id}">#{ZeroWidthSpace}</a>#{quoted_text}) : quoted_text
   end
 
   def layout_title_page doc
@@ -1469,6 +1480,28 @@ def sanitize string
         .strip
   end
 
+  # If the node passed as the first argument has an id, add a named destination
+  # to the document equivalent to the node id at the current y position. If the
+  # node does not have an id, do nothing.
+  #
+  # If the node is a section, and the current y position is the top of the
+  # page, set the position equal to the page height to improve the navigation
+  # experience.
+  def add_dest_for_block node
+    if !scratch? && (id = node.id)
+      dest_y = if node.context == :section && at_page_top?
+        page_height
+      else
+        y
+      end
+      # QUESTION should this attribute be named pdf-destination instead?
+      # FIXME destination is not always the left margin; use x value of current bounding box
+      node.set_attr 'destination', (node_dest = (dest_xyz 0, dest_y))
+      add_dest id, node_dest
+    end
+    nil
+  end
+
   def resolve_imagesdir doc
     @imagesdir ||= begin
       imagesdir = (doc.attr 'imagesdir', '.').chomp '/'

lib/asciidoctor-pdf/prawn_ext/formatted_text/transform.rb

@@ -133,6 +133,10 @@ def build_fragment(fragment, tag_name = nil, attrs = {})
       if !fragment[:local] && (value = attrs[:local])
         fragment[:local] = value
       end
+      if !fragment[:name] && (value = attrs[:name])
+        fragment[:name] = value
+        fragment[:callback] = InlineDestinationMarker.instance
+      end
       fragment[:color] ||= @link_font_color
     when :sub
       styles << :subscript
@@ -174,5 +178,23 @@ def build_fragment(fragment, tag_name = nil, attrs = {})
     fragment
   end
 end
+
+class InlineDestinationMarker
+  @__instance__ = new
+
+  def self.instance
+    @__instance__
+  end
+
+  def render_behind fragment
+    unless (doc = fragment.instance_variable_get :@document).scratch?
+      if (name = (fragment.instance_variable_get :@format_state)[:name])
+        # get precise position of the reference
+        dest_rect = fragment.absolute_bounding_box
+        doc.add_dest name, (doc.dest_xyz dest_rect.first, dest_rect.last)
+      end
+    end
+  end
+end
 end
 end