Initial auto-selection does not work in QmitkSingleNodeSelectionWidget
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Authored By

	kislinsk
	Apr 6 2023, 1:27 PM

Description

Scenario

Data storage contains an auto-selectable node but a view with a QmitkSingleNodeSelectionWidget with auto-select mode is not yet open
Open a view with a QmitkSingleNodeSelectionWidget with auto-select mode

Expected behavior

The auto-selectable node is selected

Actual behavior

Nothing is selected, the invalid selection error text is shown

Reason

A view typically calls QmitkAbstractNodeSelectionWidget::SetDataStorage() on its initialization
This method calls OnDataStorageChanged() which is correctly delegated to the QmitkSingleNodeSelectionWidget subclass and the node actually is selected for now
However, also HandleChangeOfInternalSelection({}) is called:
- The method correctly notices that the current selection is different as the new selection is empty
- It calls ReviseSelectionChanged() with both the old and new selection so the QmitkSingleNodeSelectionWidget can decide to intervene which it should and actually does in this scenario
- Here's the catch:

QmitkSingleNodeSelectionWidget::ReviseSelectionChanged(const NodeList& oldInternalSelection, NodeList& newInternalSelection)

if (newInternalSelection.empty())
{
  if (m_AutoSelectNodes)
  {
    auto autoSelectedNode = this->DetermineAutoSelectNode(oldInternalSelection);

    if (autoSelectedNode.IsNotNull())
    {
      newInternalSelection.append(autoSelectedNode);
    }
  }
}

NOTE: The oldInternalSelection passed to DetermineAutoSelectNode() tells the method to ignore it in any checks so it cannot be determined to be selected anymore even so it definitely should.

Question

Is it an easy fix or is there a good reason to ignore the selection in that case for other scenarios?

Event Timeline

kislinsk claimed this task.Apr 6 2023, 1:27 PM

kislinsk triaged this task as High priority.

kislinsk created this task.

kislinsk moved this task from Backlog to Cycle on the MITK (v2023.04) board.

It is indeed two conflicting mechanisms.

Your proposed fix would break another behavior. It would not possible to have the widget optional and autoselecting at the same time.

One real fix that I see would be

to introduce a state (e.g. m_UnrevisedDataStorageReset) in QmitkSingleNodeSelectionWidget.
default is False.
QmitkSingleNodeSelectionWidget:::OnDataStorageChanged sets it to true.
QmitkSingleNodeSelectionWidget::ReviseSelectionChanged checks the state and if true calls DetermineAutoSelectNode with no argument. If false it is called like it is currently.
At the end RevisedSelectionChanged sets m_UnrevisedDataStorageReset to false again.

But I would not say that this issue is release relevant as we have an easy mitigation strategy at hand. Move the widget->->SetAutoSelectNewNodes(true) to the end of your CreateQtPartControl (when everything else for the widget is configred and connected) (see SegmentationView for example).
Then it works already like expected.

Because we have more pressing issues (and my solution might miss something), I would propose to

use the workarround for now
move that issue out of the cycle and lower priority
document that problem in the SingelNodeSelection class including the work arround and the reference to the open issue.

kislinsk lowered the priority of this task from High to Normal.Apr 13 2023, 9:36 AM

kislinsk moved this task from Cycle to Backlog on the MITK (v2023.04) board.

kislinsk removed kislinsk as the assignee of this task.Apr 14 2023, 5:22 AM

kislinsk edited projects, added MITK (v2023.12); removed MITK (v2023.04).May 17 2023, 2:55 PM

kislinsk edited projects, added MITK (v2024.06); removed MITK (v2023.12).Dec 5 2023, 10:38 AM

Initial auto-selection does not work in QmitkSingleNodeSelectionWidgetOpen, NormalPublicActions