Detecting deletion of component.

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Permalink Reply by David Rutten on August 16, 2011 at 6:50am

Hi Randall,

 

it's odd that the destructor isn't called until Rhino exists. Makes me thing something somewhere is holding on to a pointer. But anyway, you shouldn't do things in the destructor in .NET unless you have absolutely no other choice, so let's try and find a better solution.

 

GH_Document raises events when objects are added slash deleted, so this would be the obvious place to start.

 

Since you're doing this inside something derived from GH_Param, I recommend doing something the following:

 




private bool m_documentEventRegistered = false;

protected override void OnvolatileDataCollected()

{

  if (!m_documentEventRegisted)

  {

    GH_Document doc = OnPingDocument();

    if (doc != null)

    {

      m_documentEventRegistered = true;

      doc.ObjectsDeleted += DocumentObjectsDeleted;

    }

  }

}

 

private void DocumentObjectsDeleted(object sender, GH_DocObjectEventArgs e)

{

  if (e.Objects.Contains(this))

  {

    e.Document.ObjectsDeleted -= DocumentObjectsDeleted;

    m_documentEventRegistered = false;

    // Dispose of expensive resource.

  }

}

 

This is pretty involved and you'll need to jump through additional hoops if your parameter is part of a component instead of standalone.

 

I'll see if I can add some useful places to add specific calls informing objects they are added to or removed from documents.

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia

• ▶ Reply

Permalink Reply by David Rutten on August 16, 2011 at 7:25am

I just added three methods to the IGH_DocumentObject interface (the grand-daddy of all things on the Grasshopper canvas):

 




''' <summary>
''' This method will be called when an object is added to a document.
''' </summary>
''' <param name="document">Document that now owns this object.</param>
Sub AddedToDocument(ByVal document As GH_Document)


''' <summary>
''' This method will be called when an object is removed from a document.
''' </summary>
''' <param name="document">Document that now no longer owns this object.</param>
Sub RemovedFromDocument(ByVal document As GH_Document)


''' <summary>
''' This method will be called when an object is moved from one document to another.
''' </summary>
''' <param name="oldDocument">Document that used to own this object.</param>
''' <param name="newDocument">Document that now owns ths object.</param>
Sub MovedBetweenDocuments(ByVal oldDocument As GH_Document, ByVal newDocument As GH_Document)

 

Starting with 0.8.0051 you'll have access to this. 

Document object management is a pretty damn complicated business in Grasshopper (I didn't properly bottleneck this stuff in the beginning) so it's possible I missed cases.

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia

• ▶ Reply

Permalink Reply by Randall Boland on August 16, 2011 at 8:55am

Thanks a lot for the replies David, they're both very helpful.

The solution you provided appears to be working fine.
I'll await the next version eagerly.

 

Cheers,

Randall 

• ▶ Reply

Permalink Reply by Randall Boland on August 16, 2011 at 11:43pm

Hi again David.

I just thought I should point out for those who might need it that the ObjectsDeleted event doesn't appear to fire when the document is deleted by the user.

I was able to get around this by also registering with the DocumentRemoved event on the DocumentServer like so (changes to your code are bolded):


private bool m_documentEventRegistered = false;
protected override void OnvolatileDataCollected()
{
  if (!m_documentEventRegisted)
  {
    GH_Document doc = OnPingDocument();
    if (doc != null)
    {
      m_documentEventRegistered = true;
      doc.ObjectsDeleted += DocumentObjectsDeleted;
      Grasshopper.GH_InstanceServer.DocumentServer.DocumentRemoved += this.DocumentRemoved;
    }
  }
}

private void DocumentObjectsDeleted(object sender, GH_DocObjectEventArgs e)
{
  if (e.Objects.Contains(this))
  {
    e.Document.ObjectsDeleted -= DocumentObjectsDeleted;
    Grasshopper.GH_InstanceServer.DocumentServer.DocumentRemoved -= this.DocumentRemoved;
    m_documentEventRegistered = false;
    // Dispose of expensive resource.
  }
}

private void DocumentRemoved(GH_DocumentServer sender, GH_Document doc)
{
  if (doc.Objects.Contains(this))
  {
    doc.ObjectsDeleted -= this.DocumentObjectsDeleted;
    Grasshopper.GH_InstanceServer.DocumentServer.DocumentRemoved -= this.DocumentRemoved;
    m_documentEventRegistered = false;
    // Dispose of expensive resource.
  }
} 

Cheers once again,
Randall

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Permalink Reply by David Rutten on August 17, 2011 at 4:54am

Hmm, you're right. When a document is removed, the objects in it are not deleted from the document, they just disappear along with the document. Perhaps there should be additional methods that inform objects when their document becomes (in)active.

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia

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Permalink Reply by David Rutten on August 17, 2011 at 5:44am

I added: 

 

DocumentContextChanged(GH_Document, GH_DocumentContext)

 

method that is called when important things happen to a document. Predefined 'things' include:

 

Open (create new document from file)

Close (remove document from memory entirely)

Focus (document is loaded into Canvas)

Defocus (document is removed from Canvas)

Lock (document is clustered and cluster gets locked)

Unlock (document is clustered ans cluster gets unlocked)

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia

 

• ▶ Reply

Permalink Reply by Randall Boland on August 17, 2011 at 5:50am

Awesome, this should help a lot.

Thanks once again David!

Cheers,

Randall 

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