After importing template content streams, create a new empty content …

…stream for each page

* prawn will add it's content to the new stream
* means we can leave the old streams in the pristene state they were
  imported in, even if they use filters we don't recognise, etc

lib/prawn/core/page.rb

@@ -65,6 +65,20 @@ def content
         @stamp_stream || document.state.store[@content]
       end
 
+      # As per the PDF spec, each page can have multiple content streams. This will
+      # add a fresh, empty content stream this the page, mainly for use in loading
+      # template files.
+      #
+      def new_content_stream
+        return if in_stamp_stream?
+
+        unless dictionary.data[:Contents].is_a?(Array)
+          dictionary.data[:Contents] = [content]
+        end
+        @content    = document.ref(:Length => 0)
+        dictionary.data[:Contents] << document.state.store[@content]
+      end
+
       def dictionary
         @stamp_dictionary || document.state.store[@dictionary]
       end
@@ -102,8 +116,15 @@ def ext_gstates
       end
 
       def finalize
-        content.compress_stream if document.compression_enabled?
-        content.data[:Length] = content.stream.size
+        if dictionary.data[:Contents].is_a?(Array)
+          dictionary.data[:Contents].each do |stream|
+            stream.compress_stream if document.compression_enabled?
+            stream.data[:Length] = stream.stream.size
+          end
+        else
+          content.compress_stream if document.compression_enabled?
+          content.data[:Length] = content.stream.size
+        end
       end
 
       private

lib/prawn/document.rb

@@ -198,7 +198,10 @@ def initialize(options={},&block)
        options[:size] = options.delete(:page_size)
        options[:layout] = options.delete(:page_layout)
 
-       if !options[:template]
+       if options[:template]
+         fresh_content_streams
+         go_to_page(1)
+       else
          if options[:skip_page_creation] || options[:template]
            start_new_page(options.merge(:orphan => true))
          else
@@ -207,7 +210,6 @@ def initialize(options={},&block)
        end
 
        @bounding_box = @margin_box
-       go_to_page(1) if options[:template]
 
        if block
          block.arity < 1 ? instance_eval(&block) : block[self]
@@ -291,8 +293,7 @@ def page_count
     end
 
     # Re-opens the page with the given (1-based) page number so that you can
-    # draw on it. Does not restore page state such as margins, page orientation,
-    # or paper size, so you'll have to handle that yourself.
+    # draw on it. 
     #
     # See Prawn::Document#number_pages for a sample usage of this capability.
     #
@@ -315,7 +316,6 @@ def cursor
       y - bounds.absolute_bottom
     end
 
-
     # Moves to the specified y position in relative terms to the bottom margin.
     # 
     def move_cursor_to(new_y)

lib/prawn/document/internals.rb

@@ -89,6 +89,17 @@ def on_page_create(&block)
 
       private      
 
+      # adds a new, empty content stream to each page. Used in templating so
+      # that imported content streams can be left pristine
+      #
+      def fresh_content_streams
+        (1..page_count).each do |i|
+          go_to_page i
+          state.page.new_content_stream
+          use_graphic_settings
+        end
+      end
+
       def finalize_all_page_contents
         (1..page_count).each do |i|
           go_to_page i

spec/document_spec.rb

@@ -433,3 +433,29 @@
     text.strings.include?("Healy").should == true
   end
 end
+
+describe "content stream characteristics" do
+ it "should have 1 single content stream for a single page PDF with no templates" do
+    @pdf = Prawn::Document.new
+    @pdf.text "James"
+    output = StringIO.new(@pdf.render)
+    hash = PDF::Hash.new(output)
+
+    streams = hash.values.select { |obj| obj.kind_of?(PDF::Reader::Stream) }
+
+    streams.size.should == 1
+  end
+
+ it "should have 1 single content stream for a single page PDF with no templates, even if go_to_page is used" do
+    @pdf = Prawn::Document.new
+    @pdf.text "James"
+    @pdf.go_to_page(1)
+    @pdf.text "Healy"
+    output = StringIO.new(@pdf.render)
+    hash = PDF::Hash.new(output)
+
+    streams = hash.values.select { |obj| obj.kind_of?(PDF::Reader::Stream) }
+
+    streams.size.should == 1
+  end
+end

spec/template_spec.rb

@@ -44,6 +44,18 @@
     pages.size.should == 1
   end
 
+  it "should have two content streams if importing a single page template" do
+    filename = "#{Prawn::BASEDIR}/data/pdfs/hexagon.pdf"
+
+    @pdf = Prawn::Document.new(:template => filename)
+    output = StringIO.new(@pdf.render)
+    hash = PDF::Hash.new(output)
+
+    streams = hash.values.select { |obj| obj.kind_of?(PDF::Reader::Stream) }
+
+    streams.size.should == 2
+  end
+
   it "should allow text to be added to a single page template" do
     filename = "#{Prawn::BASEDIR}/data/pdfs/hexagon.pdf"