onElementModified does not get triggered before onTransactionRedo

### SketchUp Ruby API Issue **Redo** command does not send on modified/on cha…nge events, after an **Undo**. **Repeated undoing and redoing shows inconsistent observer behavior.** Each time the **undo** command is used, **both** the [`ModelObserver#onTransactionUndo`](http://ruby.sketchup.com/Sketchup/ModelObserver.html#onTransactionUndo-instance_method) and the [`EntityObserver#onChangeEntity`](http://ruby.sketchup.com/Sketchup/EntityObserver.html#onChangeEntity-instance_method) callbacks fire, ... ... but only the [`ModelObserver#onTransactionRedo`](http://ruby.sketchup.com/Sketchup/ModelObserver.html#onTransactionRedo-instance_method) callback fires on an **redo** command. If you again **undo**, ... **both** the [`ModelObserver#onTransactionUndo`](http://ruby.sketchup.com/Sketchup/ModelObserver.html#onTransactionUndo-instance_method) and the [`EntityObserver#onChangeEntity`](http://ruby.sketchup.com/Sketchup/EntityObserver.html#onChangeEntity-instance_method) callbacks fire even though there was no intervening change event firing off an observer callback (of any kind.) **This is inconsistent and unexpected.** #### Suggestion: Either an intervening [`EntityObserver#onChangeEntity`](http://ruby.sketchup.com/Sketchup/EntityObserver.html#onChangeEntity-instance_method) callback should fire **for Redo,** (This would be consistent with Undo behavior,) ... ... and posssibly, a new **[`EntityObserver`](http://ruby.sketchup.com/Sketchup/EntityObserver.html)`#onRevertEntity`** callback should be implemented for **undo** that fires **before** the [`ModelObserver#onTransactionUndo`](http://ruby.sketchup.com/Sketchup/ModelObserver.html#onTransactionUndo-instance_method) event., to signal the reverting and reversal of the original [`EntityObserver#onChangeEntity`](http://ruby.sketchup.com/Sketchup/EntityObserver.html#onChangeEntity-instance_method) call after the pre-undo (the original) change. (But then this latter `#onRevertEntity` implementation would possibly break existing plugins unless it also still fired the `#onChangeEntity` event in the absence of a `#onRevertEntity` callback.) #### Test code: ```ruby class MyEntityObserver < Sketchup::EntityObserver def onChangeEntity(entity) puts "onChangeEntity: #{entity}" end end class MyModelObserver < Sketchup::ModelObserver def onTransactionCommit(model) puts "Transaction committed." end def onTransactionUndo(model) puts "Transaction undone." end def onTransactionRedo(model) puts "Transaction redone." end end # Draw an entity or insert a component, then select it ... model = Sketchup.active_model entity = model.selection[0] entity.add_observer(MyEntityObserver.new) Sketchup.active_model.add_observer(MyModelObserver.new) ``` ---- _Ref public forum thread:_ https://forums.sketchup.com/t/redo-observer-does-not-send-on-modified-on-change-events/68621

esekkin · November 16, 2021, 8:10pm

this looks exactly like my experience