What is "PartRenderingEngine's limbo"?

[xpomul]

Hi,

can someone explain to me what the "PartRenderingEngine's limbo" shell does?
(What I assume from my research/intuition: it is an off-screen shell that "stores" a Composite hierarchy for hidden ViewParts and other things (ToolItems, ToolBars?) as a performance optimization so the UI resources do not have to be instantiated/disposed of all the time - is that about right?)

In my concrete problem, I am analyzing an RCPTT issue (bug?) in which RCPTT tries to find the correct Shell for a given ViewReference.
(for details about the RCPTT problem, see my post here

The code in RCPTT that locates this shell effectively boils down to:

var control = ((org.eclipse.ui.internal.WorkbenchPartReference)reference).getPane().getControl();
var shell = control.getShell();

So, my concrete question is: when/how can the widget/control of the WorkbenchPartReference end up in PartRenderingEngine's limbo? Is there a way to patch RCPTT so that, when it detects that shell is PartRenderingEngine's limbo, I can somhow get the control out of there?

(The strange thing is that this only happens sometimes, and the affected view part (Eclipse's own Project Explorer in our case), seems to be actually visible on screen when this happens, so the view is not hidden or otherwise invisible... at least that is what the screenshots of the failed tests tell. It is odd, however, that in some screenshots, the View's control seems to be ininitialized (grey background instead of white)).

Thanks in advance for any enlightenment...

Best
Stefan