Adding the simplest possible extension system to prawn.

lib/prawn/core.rb

@@ -65,6 +65,7 @@ def configuration(*args)
 
 require "prawn/compatibility"
 require "prawn/errors"
+require "prawn/extendable"
 require "prawn/pdf_object"
 require "prawn/object_store"
 require "prawn/snapshot"

lib/prawn/document.rb

@@ -50,7 +50,8 @@ module Prawn
   # 
   # See the new and generate methods for further details on the above.
   class Document
-
+
+    extend  Extendable
     include Text
     include PageGeometry
     include Internals

lib/prawn/extendable.rb

@@ -0,0 +1,13 @@
+# coding: utf-8
+
+module Extendable
+  def extensions
+    @extensions ||= [ ]
+  end
+
+  def new(*args, &block)
+    o = super
+    o.extend(*extensions.reverse) unless extensions.empty?
+    o
+  end
+end

spec/document_spec.rb

@@ -3,6 +3,12 @@
 
 require File.join(File.expand_path(File.dirname(__FILE__)), "spec_helper") 
 
+describe "Prawn Document" do
+  it "should be Extendable" do
+    assert_kind_of(Extendable, Prawn::Document)
+  end
+end 
+
 describe "The cursor" do
   it "should equal pdf.y - bounds.absolute_bottom" do
     pdf = Prawn::Document.new

spec/extendable_spec.rb

@@ -0,0 +1,38 @@
+# encoding: utf-8
+
+require File.join(File.expand_path(File.dirname(__FILE__)), "spec_helper") 
+
+class ExampleClass
+  extend Extendable
+
+  def example
+    :example
+  end
+end
+
+module ExampleExtension
+  def example
+    "extended #{super}"
+  end
+end
+
+ExampleClass.extensions << ExampleExtension
+
+describe "Extenable" do
+  it "should add extension management to a class" do
+    assert_kind_of(Extendable, ExampleClass)
+    assert_instance_of(Array, ExampleClass.extensions)
+  end
+
+  it "should mix all extensions into new instances" do
+    assert(!ExampleClass.extensions.empty?, "There were no extensions added")
+    instance = ExampleClass.new
+    ExampleClass.extensions.each do |extension|
+      assert_kind_of(extension, instance)
+    end
+  end
+
+  it "should allow for the normal use of super" do
+    ExampleClass.new.example.should == "extended example"
+  end
+end