# Undo process not work correctly

**URL:** <https://discourse.slicer.org/t/undo-process-not-work-correctly/33899>\
**Category:** Support\
**Created:** [January 22, 2024, 7:37am UTC](https://discourse.slicer.org/t/undo-process-not-work-correctly/33899 "2024-01-22T07:37:27Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![park](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/park/32/5717_2.png) [@park](https://discourse.slicer.org/u/park)\
**Post date:** [January 22, 2024, 7:37am UTC](https://discourse.slicer.org/t/undo-process-not-work-correctly/33899/1 "2024-01-22T07:37:27Z")

</div>

Hi all

I am currently testing undo/redo process using “SetUndoEnabled”

I checked that the function works well when there is only one markups ground, but it malfunctions when there are two or more groups, as shown in the video below.

Also, the undo function does not work in “vtkMRMLModelNode”. Do I need to add “SaveStateForUndo” to the Slicer Model source code and rebuild to address this issue?

My codes in “.slicerry.py” looks like below.

```auto
 slicer.mrmlScene.SetUndoOn()

undoEnabledNodeClassNames = [
  "vtkMRMLMarkupsFiducialNode",
  "vtkMRMLMarkupsLineNode",
  "vtkMRMLMarkupsAngleNode",
  "vtkMRMLMarkupsCurveNode",
  "vtkMRMLMarkupsClosedCurveNode",
  "vtkMRMLMarkupsPlaneNode",
  "vtkMRMLMarkupsROINode",
  "vtkMRMLModelNode",
  "vtkMRMLScalarVolumeNode",
  "vtkMRMLLinearTransformNode",
  ]
for className in undoEnabledNodeClassNames:
  node = slicer.mrmlScene.CreateNodeByClass(className)
  node.SetUndoEnabled(True)
  slicer.mrmlScene.AddDefaultNode(node)

def onRedo():
  slicer.mrmlScene.Redo()

def onUndo():
  slicer.mrmlScene.Undo()

redoShortcuts = []
redoKeyBindings = qt.QKeySequence.keyBindings(qt.QKeySequence.Redo)
for redoBinding in redoKeyBindings:
  redoShortcut = qt.QShortcut(slicer.util.mainWindow())
  redoShortcut.setKey(redoBinding)
  redoShortcut.connect("activated()", onRedo)
  redoShortcuts.append(redoShortcut)

undoShortcuts = []
undoKeyBindings = qt.QKeySequence.keyBindings(qt.QKeySequence.Undo)
for undoBinding in undoKeyBindings:
  undoShortcut = qt.QShortcut(slicer.util.mainWindow())
  undoShortcut.setKey(undoBinding)
  undoShortcut.connect("activated()", onUndo)
  undoShortcuts.append(undoShortcut)

toolBar = qt.QToolBar("Undo/Redo")
toolBar.addAction(qt.QIcon(":/Icons/Medium/SlicerUndo.png"), "Undo", onUndo)
toolBar.addAction(qt.QIcon(":/Icons/Medium/SlicerRedo.png"), "Redo", onRedo)
slicer.util.mainWindow().addToolBar(toolBar)

```

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<div class="post-metadata">

**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [January 22, 2024, 8:59pm UTC](https://discourse.slicer.org/t/undo-process-not-work-correctly/33899/2 "2024-01-22T20:59:49Z")

</div>

Yes, that looks like the kind of situation that led us to disable it by default. Probably there is a sequence of events triggered by other events that doesn’t unroll correctly, Some of the GUI/Logic code tracks changes in order to avoid completely re-syncing with the scene at every change and those efficiency heuristics can get disrupted by undo/redo.

What would help would be to try replicating the issue using a SelfTest, or better a set of SelfTests that are representative of how undo/redo should be working and seeing how things hold up. That would form a basis for investigating the underlying issues (e.g. running the same tests with and without the GUI connected).