add position_chaning to event interface

by reacting to the change _before it happens, we can move any BinaryCode out of the way

So when Instruction are inserted and code gets inserted, we don't need to set up the correct listener explicitly (which is tricky across mathods and changing chains), but instead just move anything that is in the way along

test/risc/position/test_code_listener.rb

@@ -30,9 +30,5 @@ module Risc
       pos = Position.get(@binary)
       assert_equal CodeListener , pos.event_table[:position_changed].first.class
     end
-    def test_extends_creates_jump
-      @binary.extend_one
-      CodeListener.init(@binary)
-    end
   end
 end

test/risc/position/test_code_listener1.rb

@@ -4,25 +4,29 @@ module Risc
   # tests that require a boot and test propagation
   class TestCodeListenerFull < MiniTest::Test
     def setup
-      #@machine = DummyPlatform.boot
       @machine = Risc.machine.boot
       @binary = Parfait::BinaryCode.new(1)
       @method = Parfait.object_space.types.values.first.methods
       @label = Risc.label("hi","ho")
-      #@machine.set_translated
       @machine.translate(:interpreter)
       @machine.position_all
     end
     def test_listener_after_extend
-      CodeListener.init(@binary).set(0)
+      CodeListener.init(@binary).set(10)
       @binary.extend_one
       pos = Position.get(@binary.next)
       assert_equal CodeListener , pos.event_table[:position_changed].first.class
     end
     def test_extend_sets_next_pos
-      CodeListener.init(@binary).set(0)
+      CodeListener.init(@binary).set(10)
       @binary.extend_one
       assert Position.get(@binary.next)
     end
+    def test_extends_creates_jump
+      CodeListener.init(@binary).set(10)
+      assert_equal 0 , @binary.get_last
+      @binary.extend_one
+      assert 0 != @binary.get_last
+    end
   end
 end

test/risc/position/test_position1.rb

@@ -36,11 +36,23 @@ module Risc
       @position.trigger_inserted
       assert_equal @position , @trigger
     end
+    def test_position_set_triggers
+      @object = @instruction
+      Position.new(self, 0)
+      @position.register_event(:position_changed , self)#can't use helper
+      @position.set(10)
+      assert_equal @position , @trigger
+      assert_equal @to , 10
+    end
     def position_changed(pos)
       @trigger = pos
     end
     def position_inserted(pos)
       @trigger = pos
     end
+    def position_changing(pos , to)
+      @trigger = pos
+      @to = to
+    end
   end
 end