Diagram not up-to-date when "FinishedUndo" ChangeEvent is fired

GoJS
1

I want to perform a certain action on the diagram after the user has performed an Undo/Redo.

In order to do so, I currently listen to a Model ChangedEvent:

e.change === go.ChangedEvent.Transaction &&
            (e.propertyName === "FinishedUndo" || e.propertyName === "FinishedRedo")

However, when adding a new node and then undoing this action, in the event listener:

  • the diagram still contains the added node in diagram.nodes (even though the node should be removed by undo)
  • the node.data is null

I assume this is by design? The diagram is not expected to be in sync with the model in the UndoFinished Model ChangedEvent?
If so, how can I listen to an undo/redo event and access a diagram which already contains all undo/redo changes?

2

I’m sorry, but I’m not getting that behavior.

I just took a random sample that I had lying around and added this listener:

  $(go.Diagram, . . .,
      "ModelChanged": e => {
        if (e.isTransactionFinished) {
          console.log(e.propertyName, e.model.nodeDataArray.length, myDiagram.nodes.count);
          myDiagram.nodes.each(node => console.log(node.data));
        }
      },
      "undoManager.isEnabled": true
    })

I first selected all two nodes and copy-and-pasted them, resulting in four nodes. Then I did an undo and then a redo. The results were as expected:

CommittedTransaction 4 4
Object { key: 1, text: "hello", color: "green", location: "0 0", __gohashid: 725, loc: "19.5 13" }
Object { key: 2, text: "world", color: "red", location: "70 0", __gohashid: 726, loc: "91 13" }
Object { key: -3, text: "hello", color: "green", location: "0 0", __gohashid: 840, loc: "19.5 13" }
Object { key: -4, text: "world", color: "red", location: "70 0", __gohashid: 848, loc: "91 13" }
FinishedUndo 2 2
Object { key: 1, text: "hello", color: "green", location: "0 0", __gohashid: 725, loc: "19.5 13" }
Object { key: 2, text: "world", color: "red", location: "70 0", __gohashid: 726, loc: "91 13" }
FinishedRedo 4 4
Object { key: 1, text: "hello", color: "green", location: "0 0", __gohashid: 725, loc: "19.5 13" }
Object { key: 2, text: "world", color: "red", location: "70 0", __gohashid: 726, loc: "91 13" }
Object { key: -3, text: "hello", color: "green", location: "0 0", __gohashid: 840, loc: "19.5 13" }
Object { key: -4, text: "world", color: "red", location: "70 0", __gohashid: 848, loc: "91 13" }
3

Hi @walter, sorry for the late reply.
I was able to narrow down the issue. The origin of the issue is not in the ChangeEvent listener.
The issue is that I am accessing the part.data in a node.selectionChanged handler, and the part.data is null during an undo operation. This causes the undo oepration to fail.

I did not expect the part.data to be null in the node.selectionChanged handler, so I am wondering if this is by design or if there is some other issue?

I have attached an example project, and here is a short gif:
undo

Example project: https://file.io/9FFHsloFTIJ3

4

When undoing the adding of a Part to the Diagram, the Part.selectionChanged event happens when the at-that-time-new Part had not yet gotten its data binding.

5

What do you mean by ‘at-that-time-new Part’? The undo operation removes the newly added node (Delta2 in the above example), and node “Delta2” seems to have a data binding?

Whatever the reason, if this is not something which should be changed in the goJS library, maybe its worth to add a note to the docs that the data might not be set? At least I didn’t know or find any information that the node.data might not be available in the selectionChanged handler.

6

The Part.data property might be null for other reasons. For example, unmodeled Parts never get any data because there is no data in the model for the Part.

7

okay, thank you!