SVG backend: PDF implemented, tests passing

Wrapping up the svg backend work

Still some bugs to stamp out, but this is getting close to release ready.

spec/graphics/graphics_save_doc_spec.rb

@@ -2,29 +2,30 @@ require 'spec_helper'
 require 'squib'
 
 describe Squib::Deck, '#save_pdf' do
-  def expect_card_place(x, y)
-    expect(cxt).to receive(:set_source)
-                    .with(instance_of(Cairo::ImageSurface), -37, -37)
-                    .once  # trim the card
-    expect(cxt).to receive(:paint).once  # paint trimmed card
-    expect(cxt).to receive(:set_source)  # place the card
-                    .with(instance_of(Cairo::ImageSurface), x, y).at_least(1).times
-    expect(cxt).to receive(:paint).once  # paint placed card
-  end
 
   context 'typical inputs' do
     let(:cxt) { double(Cairo::Context) }
 
+    def expect_card_place(x, y)
+      expect(cxt).to receive(:translate).with(x, y).once
+      expect(cxt).to receive(:rectangle).once
+      expect(cxt).to receive(:clip).once
+      expect(cxt).to receive(:set_source)  # place the card
+                      .with(instance_of(Cairo::ImageSurface), 0, 0).once
+      expect(cxt).to receive(:paint).once  # paint placed card
+      expect(cxt).to receive(:translate).with(-x,-y).once
+      expect(cxt).to receive(:reset_clip).once
+    end
+
     before(:each) do
       allow(Cairo::PDFSurface).to receive(:new).and_return(nil) #don't create the file
+      allow(Cairo::Context).to    receive(:new).and_return(cxt)
     end
 
     it 'make all the expected calls on a smoke test' do
       num_cards = 9
-      args = { file: 'foo.pdf', dir: '_out', margin: 75, gap: 5, trim: 37 }
-      deck = Squib::Deck.new(cards: num_cards, width: 825, height: 1125)
+      deck = Squib::Deck.new(cards: 9, width: 825, height: 1125)
       expect(Squib.logger).to receive(:debug).at_least(:once)
-      expect(Cairo::Context).to receive(:new).and_return(cxt).at_least(num_cards + 1).times
       expect(deck).to receive(:dirify) { |arg| arg } #don't create the dir
 
       expect_card_place(75, 75)
@@ -38,6 +39,7 @@ describe Squib::Deck, '#save_pdf' do
       expect(cxt).to receive(:show_page).once
       expect_card_place(75, 75)
 
+      args = { file: 'foo.pdf', dir: '_out', margin: 75, gap: 5, trim: 37 }
       deck.save_pdf(args)
     end
 
@@ -46,7 +48,6 @@ describe Squib::Deck, '#save_pdf' do
       args = { range: 2..4, file: 'foo.pdf', dir: '_out', margin: 75, gap: 5, trim: 37 }
       deck = Squib::Deck.new(cards: num_cards, width: 825, height: 1125)
       expect(Squib.logger).to receive(:debug).at_least(:once)
-      expect(Cairo::Context).to receive(:new).and_return(cxt).exactly(4).times
       expect(deck).to receive(:dirify) { |arg| arg }  #don't create the dir
 
       expect_card_place(75, 75)

spec/graphics/graphics_shapes_spec.rb

@@ -37,7 +37,7 @@ describe Squib::Card do
   context 'circle' do
     it 'make all the expected calls on a smoke test' do
       expect(@context).to receive(:save).once
-      expect(@context).to receive(:move_to).with(37, 38)
+      expect(@context).to receive(:move_to).with(137, 38)
       expect(@context).to receive(:circle).with(37, 38, 100).twice
       expect_stroke('#fff', '#f00', 2.0)
       expect(@context).to receive(:restore).once