Add document ID to trailer for PDF-X spec compat

lib/pdf/core/document_state.rb

@@ -14,7 +14,7 @@ def initialize(options)
         @version                 = 1.3
         @pages                   = []
         @page                    = nil
-        @trailer                 = {}
+        @trailer                 = options.fetch(:trailer, default_trailer)
         @compress                = options.fetch(:compress, false)
         @encrypt                 = options.fetch(:encrypt, false)
         @encryption_key          = options[:encryption_key]
@@ -71,6 +71,14 @@ def render_body(output)
                                 ref.object)
         end
       end
+
+      private
+
+      # Document ID is required by PDF-X spec, presence ok for standard PDF
+      def default_trailer
+        { :ID => 2.times.map { SecureRandom.hex(8) }}
+      end
+
     end
   end
 end

spec/document_state_spec.rb

@@ -0,0 +1,23 @@
+require_relative "spec_helper"
+
+describe "PDF Document State" do
+  before { @state = PDF::Core::DocumentState.new({}) }
+
+  describe "initialization" do
+    it { expect(@state.compress).to eq(false) }
+    it { expect(@state.encrypt).to eq(false) }
+    it { expect(@state.skip_encoding).to eq(false) }
+  end
+
+  describe "normalize_metadata" do
+    it { expect(@state.store.info.data[:Creator]).to eq("Prawn") }
+    it { expect(@state.store.info.data[:Producer]).to eq("Prawn") }
+  end
+
+  describe "default trailer" do
+    it "should contain an ID entry with two values in trailer" do
+      expect(@state.trailer[:ID].count).to eq(2)
+    end
+  end
+
+end