Guard against empty port values

This fixes a segfault.

Also fixes a re-entrant `processEvents()` call.

Signed-off-by: Patrick Avery <patrick.avery@kitware.com>

Author: psavery

tomviz/ProgressDialogManager.cxx

@@ -160,7 +160,14 @@ void ProgressDialogManager::onNodeExecutionStarted(pipeline::Node* node)
   dialog->adjustSize();
   dialog->resize(500, dialog->height());
   dialog->show();
-  QCoreApplication::processEvents();
+  dialog->raise();
+  // NOTE: deliberately no QCoreApplication::processEvents() here. This slot
+  // runs while handling a nodeExecutionStarted event, and pumping the event
+  // loop would re-entrantly deliver other already-queued executor signals
+  // (e.g. executionComplete -> Pipeline::executionFinished), firing finish
+  // handlers mid-execution while upstream ports are still empty -- a crash.
+  // The pipeline runs on a worker thread (ThreadedExecutor), so the main loop
+  // is not blocked and the dialog paints on the next event-loop iteration.
 }
 
 void ProgressDialogManager::onNodeExecutionFinished(pipeline::Node* node,

tomviz/pipeline/GatedEditorWidget.cxx

@@ -95,19 +95,28 @@ void GatedEditorWidget::onExecutionFinished()
     return;
   }
 
+  // Build the inner editor first. The factory can legitimately return null if
+  // the upstream data isn't actually usable yet (e.g. this finished signal was
+  // delivered re-entrantly mid-execution); in that case stay in the not-ready
+  // state rather than tearing down the widget and showing a blank editor.
+  if (!buildInner()) {
+    m_notReadyWidget->setRunEnabled(true);
+    return;
+  }
+
   m_layout->removeWidget(m_notReadyWidget);
   m_notReadyWidget->deleteLater();
   m_notReadyWidget = nullptr;
-  buildInner();
 }
 
-void GatedEditorWidget::buildInner()
+bool GatedEditorWidget::buildInner()
 {
   m_inner = m_factory(this);
   if (m_inner) {
     m_layout->addWidget(m_inner, 1);
   }
   emit canApplyChanged();
+  return m_inner != nullptr;
 }
 
 } // namespace pipeline

tomviz/pipeline/GatedEditorWidget.h

@@ -48,7 +48,7 @@ class GatedEditorWidget : public EditNodeWidget
   void onRunRequested();
   void onExecutionFinished();
   bool inputsReady() const;
-  void buildInner();
+  bool buildInner();
 
   Node* m_node;
   Pipeline* m_pipeline;

tomviz/pipeline/transforms/ArrayWranglerTransform.cxx

@@ -166,6 +166,9 @@ EditNodeWidget* ArrayWranglerTransform::createPropertiesWidget(
     this, pipeline,
     [this](QWidget* p) -> EditNodeWidget* {
       auto vol = inputPorts()[0]->data().value<VolumeDataPtr>();
+      if (!vol || !vol->imageData()) {
+        return nullptr;
+      }
       return new ArrayWranglerWidget(this, vol, p);
     },
     parent);

tomviz/pipeline/transforms/CropTransform.cxx

@@ -126,6 +126,9 @@ EditNodeWidget* CropTransform::createPropertiesWidget(Pipeline* pipeline,
     this, pipeline,
     [this](QWidget* p) -> EditNodeWidget* {
       auto vol = inputPorts()[0]->data().value<VolumeDataPtr>();
+      if (!vol || !vol->imageData()) {
+        return nullptr;
+      }
       return new CropWidget(this, vol, p);
     },
     parent);

tomviz/pipeline/transforms/SetTiltAnglesTransform.cxx

@@ -467,6 +467,14 @@ EditNodeWidget* SetTiltAnglesTransform::createPropertiesWidget(
     this, pipeline,
     [this](QWidget* p) -> EditNodeWidget* {
       auto vol = inputPorts()[0]->data().value<VolumeDataPtr>();
+      // Guard against an empty/mismatched port value. value<T>() is
+      // non-throwing and yields a null pointer when the upstream data is not
+      // (yet) a usable volume; constructing the widget would then dereference
+      // it. Returning nullptr lets GatedEditorWidget stay in its not-ready
+      // state instead of crashing.
+      if (!vol || !vol->imageData()) {
+        return nullptr;
+      }
       return new SetTiltAnglesWidget(this, vol, p);
     },
     parent);

tomviz/pipeline/transforms/TranslateAlignTransform.cxx

@@ -95,6 +95,9 @@ EditNodeWidget* TranslateAlignTransform::createPropertiesWidget(
     this, pipeline,
     [this](QWidget* p) -> EditNodeWidget* {
       auto vol = inputPorts()[0]->data().value<VolumeDataPtr>();
+      if (!vol || !vol->imageData()) {
+        return nullptr;
+      }
       vtkSmartPointer<vtkImageData> imageData(vol->imageData());
       return new AlignWidget(this, imageData, p);
     },