Rotation with gumball give me also a translation

I’m using the event RhinoDocOnBeforeTransformObjects(object sender, RhinoTransformObjectsEventArgs ea) and then I want to know if the user do a rotation, a translation or a rotation+translation (the last one happen when th user use the rotate command). I use ea.Transform.DecomposeAffine(out translation, out transform); to get translation and rotation but when I rotate with the gumball (so from the center of the bbox) it gives me also a translation and I can’t understand why.
Can someone help me please?

@mikko, is this something you can help with?

– Dale