[pitivi] Add checkpoint() and dirty() to UndoableActionLog.

[Edward Hervey <edwardrv src gnome org>]

commit 3f4186726709107ad6d1976e3fe00d00bd4fe312
Author: Alessandro Decina <alessandro d gmail com>
Date:   Fri Jun 12 13:41:26 2009 +0200

    Add checkpoint() and dirty() to UndoableActionLog.
    
    The methods can be used to save the current state of the log and check if it's
    been modified.

 pitivi/undo.py     |   14 ++++++++++++++
 tests/test_undo.py |   21 +++++++++++++++++++++
 2 files changed, 35 insertions(+), 0 deletions(-)
---
diff --git a/pitivi/undo.py b/pitivi/undo.py
index dfa3cfc..c2efc60 100644
--- a/pitivi/undo.py
+++ b/pitivi/undo.py
@@ -104,6 +104,7 @@ class UndoableActionLog(Signallable):
         self.redo_stacks = []
         self.stacks = []
         self.running = False
+        self._checkpoint = self._takeSnapshot()
 
     def begin(self, action_group_name):
         if self.running:
@@ -185,6 +186,19 @@ class UndoableActionLog(Signallable):
             self._runStack(stack, stack.clean)
         self.emit("cleaned")
 
+    def _takeSnapshot(self):
+        return list(self.undo_stacks)
+
+    def checkpoint(self):
+        if self.stacks:
+            raise UndoWrongStateError()
+
+        self._checkpoint = self._takeSnapshot()
+
+    def dirty(self):
+        current_snapshot = self._takeSnapshot()
+        return current_snapshot != self._checkpoint
+
     def _runStack(self, stack, run):
         self.running = True
         try:
diff --git a/tests/test_undo.py b/tests/test_undo.py
index 8db84f8..dbcad1a 100644
--- a/tests/test_undo.py
+++ b/tests/test_undo.py
@@ -178,6 +178,27 @@ class TestUndoableActionLog(TestCase):
     def testRedoWrongState(self):
         self.failUnlessRaises(UndoWrongStateError, self.log.redo)
 
+    def testCheckpoint(self):
+        self.log.begin("meh")
+        self.log.push(DummyUndoableAction())
+        self.failUnlessRaises(UndoWrongStateError, self.log.checkpoint)
+        self.log.rollback()
+        self.log.checkpoint()
+        self.failIfEqual(self.log._checkpoint, None)
+
+    def testDirty(self):
+        self.failIf(self.log.dirty())
+        self.log.begin("meh")
+        self.log.push(DummyUndoableAction())
+        self.log.commit()
+        self.failUnless(self.log.dirty())
+        self.log.checkpoint()
+        self.failIf(self.log.dirty())
+        self.log.undo()
+        self.failUnless(self.log.dirty())
+        self.log.redo()
+        self.failIf(self.log.dirty())
+
     def testCommit(self):
         """
         Commit a stack.