[Solved] RadDiagram MVVM + UndoRedo

[Kamil]

Hi,

Consider my scenario 

- I added items to graph from my custom toolbox (not telerik), i implemented ICommnad, and execute under UndoRedoService
- Moving newly added item on graph surface - OK
- Pressing Ctrl-Z until element disappear(Undo on my custom Command) - position of element changed properly -  OK
- Pressing Ctrl-Y - element appear - OK
- Pressing Ctrl-Y - element should move, but it stays in same position.. - BUG

To clarify,  further pressing Ctrl-Z/Y has no impact on element position

public void Undo(object a_state)
{
   if (m_createdNode == null)
   {
      return;
   }

   GraphSource.RemoveItem(m_createdNode);
}

public void Redo()
{
   if (m_createdNode == null)
   {
      return;
   }

   GraphSource.AddNode(m_createdNode);
}

Any help appreciated.

[Pavel R. Pavlov]

Hello Kamil,

I am not sure that I fully understand your custom scenario. I am not sure where the provided code is implemented and what exactly you expect to happen when Ctrl+Z/Y combination is pressed. Also could you please elaborate on the actions that you need to Undo/Redo. You talk about changing the position, but the provided code handles the Removing/Adding items, only. It will be great if you can reproduce the reported behavior in a small test project and send it over. By doing so we will be able to fully understand your scenario and investigate the reasons behind the issue.

For your convenience and demonstration purposes I created a sample solution showing how the UndoRedo service can be used. Please take a look at it and let us know if you have any other questions.

Regards,
Pavel R. Pavlov
Telerik

[Barış]

Hello Pavel,

There seems I also suffer from save behavior. I implemented my graph source. I call AddLink and link appears. Then I click "Undo" and link disappears. And finally if I click "Redo", I expect to link reappears but it doesn't. Because in AddLink function, I check if the target and source property is not null. But in that case, after "Redo", AddLink is triggered, but Target is null. Actually target is set to null even in the RemoveLink function. Can you please help me to solve this.

 

/// <summary>
/// Adds the link.
/// </summary>
/// <param name="link">
/// The link.
/// </param>
public override void AddLink(Link<T> link)
{
    if (link == null)
    {
        throw new ArgumentNullException("link");
    }

    if (link.Source != null)
    {
        link.Source = this.GetNode(link.Source.Entity.GetIdentifier());
    }

    if (link.Target != null)
    {
        link.Target = this.GetNode(link.Target.Entity.GetIdentifier());
    }

    base.AddLink(link);

    if (link.Source != null && link.Target != null)
    {
        link.Source.ChildrenCount++;
        link.Target.ParentCount++;

        var foundLink =
            this.InternalLinks.FirstOrDefault(
                x =>
                (IsSameNode(x.Source, link.Source) && IsSameNode(x.Target, link.Target))
                || (IsSameNode(x.Target, link.Source) && IsSameNode(x.Source, link.Target)));
        if (foundLink == null)
        {
            this.RemoveLink(link);
        }
    }
    else
    {
        this.RemoveLink(link);
    }
}
/// <summary>
/// Removes the link.
/// </summary>
/// <param name="link">
/// The link.
/// </param>
/// <returns>
/// The operation result.
/// </returns>
public override bool RemoveLink(Link<T> link)
{
    if (link == null)
    {
        throw new ArgumentNullException("link");
    }

    bool result = base.RemoveLink(link);
    if (result)
    {
        if (link.Source != null)
        {
            link.Source.ChildrenCount--;
        }

        if (link.Target != null)
        {
            link.Target.ParentCount--;
        }
    }

    return result;
}

     

[Milena]

Hello Barış, 

Thank you for the code-snippet. 

When you add connection (Link) the diagram executes 2 undoable actions  - create a connection and then change its target. In this case when you redo this user action (connect shape1 to shape2), in the overrided AddLink method the target is not yet set. If you need to get the Target, you can subscribe to PropertyChanged event of the link: 

public override bool AddLink(Link link)

{

if (link.Target == null)

{

  link.PropertyChanged += link_PropertyChanged;

}

....

}



void link_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
    if (e.PropertyName == "Target")
    {
       // GetIdentifier
    };
}

The same applies to RemoveLink. 

I hope this information helps.

Regards,
Milena
Telerik