Method OnToolDeactivated

Modules/PythonSegmentationUI/src/QmitknnInteractiveToolGUI.cpp:1043–1118

}

void QmitknnInteractiveToolGUI::OnToolDeactivated()
{
  if (!m_AutoCreatedLabelValue.has_value())
    return;

  // Capture state locally and clear our tracking. Lock() returns a
  // SmartPointer that keeps the segmentation alive for the deferred call.
  auto segmentationPtr = m_AutoCreatedLabelSegmentation.Lock();
  const auto value = *m_AutoCreatedLabelValue;
  const auto previousActive = m_PreviousActiveLabelValue;
  auto* inspector = this->GetMultiLabelInspector();
  this->InvalidateAutoCreatedLabel();

  if (segmentationPtr.IsNull())
    return;

  // Defer the destructive part to the next event-loop tick.
  //
  // - Normal user-initiated tool switch: the Qt event loop is alive, so the
  //   lambda fires a tick later, after any synchronous BlueBerry chatter
  //   from the tool-switch path has settled.
  //
  // - Workbench close: BlueBerry's Workbench::Close() runs synchronously and
  //   tears down views/widgets in a sequence that leaves some segmentation
  //   observers (renderer mappers, etc.) dangling. When it eventually quits
  //   the Qt event loop, pending single-shot timers are discarded, so our
  //   lambda never fires and RemoveLabel is never called. Harmless: the
  //   unused label vanishes with the application anyway.
  QTimer::singleShot(0, qApp, [segmentationPtr, value, previousActive, inspector]() {
    if (QCoreApplication::closingDown())
      return;

    auto* segmentation = segmentationPtr.GetPointer();

    if (segmentation == nullptr || !segmentation->ExistLabel(value))
      return;

    if (!segmentation->IsEmpty(value, 0))
      return;

    const auto* activeLabel = segmentation->GetActiveLabel();
    if (activeLabel != nullptr && activeLabel->GetValue() == value)
    {
      mitk::MultiLabelSegmentation::LabelValueType fallback = 0;
      bool haveFallback = false;

      if (previousActive.has_value() && *previousActive != value && segmentation->ExistLabel(*previousActive))
      {
        fallback = *previousActive;
        haveFallback = true;
      }
      else
      {
        for (const auto& label : segmentation->GetLabels())
        {
          if (label.IsNotNull() && label->GetValue() != value)
          {
            fallback = label->GetValue();