Hi, I think we need a PersistentPosition that auto-corrects itself and survives DOM mutations without being orphaned; similar to how Range is automatically updated.
Why? 1. ReplaceSelectionCommand and DeleteSelectionCommand have wrapper for removeNode, deleteTextFromNode, etc... to update Positions they maintain. 2. InsertListCommand and IndentOutdentCommand crash all the time because Position get lost in moveParagraph, etc... 3. FrameSelection has a special function that gets called whenever Node is removed to update its end points but VisibleSelection doesn't so endingSelection() becomes stale very easily compared to FrameSelection. On the other hand, adding this new class and instantiating them as member variables of subclasses of CompositeEditCommand may impact performance because CompositeEditCommand stays on the memory even after it's pushed into undo stack. Also, maintaining a pointer (probably from Document) to stack object (although member variables of CompositeEditCommand will end up living in heap) seems like a dangerous design although we could make it ref-counted as well. To address the performance impact, we can modify CompositeEditCommand so that it won't be added to the undo stack. Instead, CompositeEditCommand will create an EditCommandComposition that stores a tree of SimpleEditCommands that inherits from EditCommand and will be added to the undo stack. Any thoughts? Best, Ryosuke Niwa Software Engineer Google Inc.
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