resolves #185 autofit font size in listing & literal blocks

- autofit (reduce font size) to prevent wrapping in listing & literal blocks
- prevent font size from being reduced more than *_font_size_min
- activate autofit if autofit option is specified on block
- activate autofit if autofit-option attribute is specified on document
- add autofit example to chronicles.adoc
- add additional helper methods to core_ext and sanitizer

data/themes/default-theme.yml

@@ -52,6 +52,7 @@ base:
   line_height: $base_line_height_length / $base_font_size
   font_size_large: round($base_font_size * 1.25)
   font_size_small: round($base_font_size * 0.85)
+  font_size_min: $base_font_size * 0.75
   font_style: normal
   align: justify
   border_radius: 4

examples/chronicles.adoc

@@ -268,31 +268,35 @@ code {
 ```
 
 Where could we go without some Java?
+Naturally, some autosizing is necessary.
 
-```java
+[source%autofit,java]
+----
 package org.javaee7.cdi.events;
 
 import javax.enterprise.context.SessionScoped;
 import javax.enterprise.event.Observes;
-import java.io.Serializable;
+import java.util.*;
+import javax.ws.rs.*;
 
 /**
  * @author The Duke
  */
 @SessionScoped
-public class GreetingReceiver implements EventReceiver, Serializable {
-    private String greet = "Willkommen";
+public class GreetingReceiver implements EventReceiver, java.io.Serializable {
+    private List<String> greetings = new ArrayList<String>();
 
     void receive(@Observes String greet) {
-        this.greet = greet;
+        this.greetings.add(greet);
     }
 
-    @Override
-    public String getGreet() {
-        return greet;
+    @GET @Produces("application/json")
+    public List<String> listAll(@QueryParam("start") Integer start, @QueryParam("max") Integer max) {
+        // TODO implement filtering by start and max
+        this.greetings;
     }
 }
-```
+----
 
 We already showed you an XML example in <<ravages>>.
 

lib/asciidoctor-pdf/converter.rb

@@ -1,6 +1,6 @@
 # encoding: UTF-8
 # TODO cleanup imports...decide what belongs in asciidoctor-pdf.rb
-require_relative 'core_ext/array'
+require_relative 'core_ext'
 require 'prawn'
 require 'prawn-svg'
 require 'prawn/table'
@@ -67,6 +67,7 @@ def self.unicode_char number
   # CalloutExtractRx synced from /lib/asciidoctor.rb of Asciidoctor core
   CalloutExtractRx = /(?:(?:\/\/|#|--|;;) ?)?(\\)?<!?(--|)(\d+)\2>(?=(?: ?\\?<!?\2\d+\2>)*$)/
   ImageAttributeValueRx = /^image:{1,2}(.*?)\[(.*?)\]$/
+  LineScanRx = /\n|.+/
 
   def initialize backend, opts
     super
@@ -864,7 +865,7 @@ def convert_image node
     unlink_tmp_file image_path
   end
 
-  # TODO shrink text if it's too wide to fit in the bounding box
+  # QUESTION can we avoid arranging fragments multiple times (conums & autofit) by eagerly preparing arranger?
   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!
@@ -873,13 +874,11 @@ def convert_listing_or_literal node
       highlighter = node.document.attr 'source-highlighter'
       # NOTE the source highlighter logic below handles the callouts and highlight subs
       prev_subs = subs.dup
-      subs.delete :callouts
-      subs.delete :highlight
+      subs.delete_all :highlight, :callouts
     else
       highlighter = nil
       prev_subs = nil
     end
-    # FIXME source highlighter freaks out about the non-breaking space characters; does it?
     source_string = preserve_indentation node.content
     source_chunks = case highlighter
     when 'coderay'
@@ -897,14 +896,24 @@ def convert_listing_or_literal node
       conum_mapping ? (restore_conums fragments, conum_mapping) : fragments
     else
       # NOTE only format if we detect a need
-      (source_string =~ BuiltInEntityCharOrTagRx) ? (text_formatter.format source_string) : [{ text: source_string }]
+      if source_string =~ BuiltInEntityCharOrTagRx
+        text_formatter.format source_string
+      else
+        [{ text: source_string }]
+      end
     end
 
     node.subs.replace prev_subs if prev_subs
 
     #move_down @theme.block_margin_top unless at_page_top?
     theme_margin :block, :top
 
+    if (node.option? 'autofit') || (node.document.attr? 'autofit-option')
+      adjusted_font_size = theme_font_size_autofit source_chunks, :code
+    else
+      adjusted_font_size = nil
+    end
+
     keep_together do |box_height = nil|
       caption_height = node.title? ? (layout_caption node) : 0
       theme_font :code do
@@ -927,7 +936,9 @@ def convert_listing_or_literal node
         end
 
         pad_box @theme.code_padding do
-          typeset_formatted_text source_chunks, (calc_line_metrics @theme.code_line_height), color: (@theme.code_font_color || @font_color)
+          typeset_formatted_text source_chunks, (calc_line_metrics @theme.code_line_height),
+              color: (@theme.code_font_color || @font_color),
+              size: adjusted_font_size
         end
       end
     end
@@ -962,6 +973,9 @@ def extract_conums string
   end
 
   # Restore the conums into the Array of formatted text fragments
+  #--
+  # QUESTION can this be done more efficiently?
+  # QUESTION can we reuse arrange_fragments_by_line?
   def restore_conums fragments, conum_mapping
     lines = []
     line_num = 0
@@ -2004,6 +2018,75 @@ def theme_font category, opts = {}
     @text_transform = prev_transform if transform
   end
 
+  # Calculate the font size (down to the minimum font size) that would allow
+  # all the specified fragments to fit in the available width without wrapping lines.
+  #
+  # Return the calculated font size if an adjustment is necessary or nil if no
+  # font size adjustment is necessary.
+  def theme_font_size_autofit fragments, category
+    arranger = arrange_fragments_by_line fragments
+    adjusted_font_size = nil
+    theme_font category do
+      # NOTE finalizing the line here generates fragments using current font settings
+      arranger.finalize_line
+      actual_width = width_of_fragments arranger.fragments
+      unless ::Array === (padding = @theme[%(#{category}_padding)])
+        padding = [padding] * 4
+      end
+      bounds.add_left_padding(p_left = padding[3] || 0)
+      bounds.add_right_padding(p_right = padding[1] || 0)
+      if actual_width > bounds.width
+        adjusted_font_size = ((bounds.width * font_size).to_f / actual_width).with_precision 4
+        if (min = @theme[%(#{category}_font_size_min)] || @theme.base_font_size_min) && adjusted_font_size < min
+          adjusted_font_size = min
+        end
+      else
+        adjusted_font_size = nil
+      end
+      bounds.subtract_left_padding p_left
+      bounds.subtract_right_padding p_right
+    end
+    adjusted_font_size
+  end
+
+  # Arrange fragments by line in an arranger and return an unfinalized arranger.
+  #
+  # Finalizing the arranger is deferred since it must be done in the context of
+  # the global font settings you want applied to each fragment.
+  def arrange_fragments_by_line fragments, opts = {}
+    arranger = ::Prawn::Text::Formatted::Arranger.new self
+    by_line = arranger.consumed = []
+    fragments.each do |fragment|
+      if (txt = fragment[:text]) == EOL
+        by_line << fragment
+      elsif txt.include? EOL
+        txt.scan(LineScanRx) do |line|
+          by_line << fragment.merge(text: line)
+        end
+      else
+        by_line << fragment
+      end
+    end
+    arranger
+  end
+
+  # Calculate the width that is needed to print all the
+  # fragments without wrapping any lines.
+  #
+  # This method assumes endlines are represented as discrete entries in the
+  # fragments array.
+  def width_of_fragments fragments
+    line_widths = [0]
+    fragments.each do |fragment|
+      if fragment.text == EOL
+        line_widths << 0
+      else
+        line_widths[-1] += fragment.width
+      end
+    end
+    line_widths.max
+  end
+
   # TODO document me, esp the first line formatting functionality
   def typeset_text string, line_metrics, opts = {}
     move_down line_metrics.padding_top

lib/asciidoctor-pdf/core_ext.rb

@@ -0,0 +1,3 @@
+require_relative 'core_ext/array'
+require_relative 'core_ext/numeric'
+#require_relative 'core_ext/ostruct'

lib/asciidoctor-pdf/core_ext/array.rb

@@ -1,5 +1,11 @@
 class Array
-  def to_h
-    Hash[to_a]
-  end unless respond_to? :to_h
-end if RUBY_VERSION < '2.1.0'
+  if RUBY_VERSION < '2.1.0'
+    def to_h
+      Hash[to_a]
+    end unless respond_to? :to_h
+  end
+
+  def delete_all *entries
+    entries.map {|entry| delete entry }.compact
+  end unless respond_to? :delete_all
+end

lib/asciidoctor-pdf/core_ext/numeric.rb

@@ -0,0 +1,11 @@
+class Numeric
+  def with_precision precision
+    precision = precision.to_i
+    if precision > 0
+      factor = 10 ** precision
+      (self * factor).truncate / factor.to_f
+    else
+      self.truncate
+    end
+  end unless respond_to? :with_precision
+end

lib/asciidoctor-pdf/sanitizer.rb

@@ -25,6 +25,16 @@ def sanitize string
         .gsub(BuiltInEntityCharRx, BuiltInEntityChars)
   end
 
+  def unescape_all string
+    string
+      .gsub(NumericCharRefRx) { [$1.to_i].pack('U*') }
+      .gsub(BuiltInEntityCharRx, BuiltInEntityChars)
+  end
+
+  def unescape_builtin string
+    string.gsub(BuiltInEntityCharRx, BuiltInEntityChars)
+  end
+
   def upcase_pcdata string
     if BuiltInEntityCharOrTagRx =~ string
       string.gsub(SegmentPcdataRx) { $2 ? $2.upcase : $1 }