BUG: Fix OpenGL errors/segfault when entering volume rendering module

Libs/MRML/Widgets/qMRMLSliceView.cxx

@@ -50,6 +50,7 @@
 #include <vtkCollection.h>
 #include <vtkNew.h>
 #include <vtkObjectFactory.h>
+#include <vtkRenderWindow.h>
 #include <vtkSmartPointer.h>
 
 //--------------------------------------------------------------------------
@@ -148,6 +149,14 @@ void qMRMLSliceViewPrivate::init()
  this->LightBoxRendererManagerProxy->SetLightBoxRendererManager(
  q->lightBoxRendererManager());
  this->initDisplayableManagers();
+
+ // Force an initial render to ensure that the render window creates an OpenGL
+ // context. If operations that require a context--such as hardware
+ // picking--are performed when no context exists, OpenGL errors will occur.
+ // When using the VTK OpenGL2 backend the errors may be followed by a
+ // segfault. Such a scenario can occur when the app is started using a layout
+ // that hides one or more of the slice views.
+ q->renderWindow()->Render();
 }
 
 //---------------------------------------------------------------------------

Modules/Loadable/VolumeRendering/Testing/Python/CMakeLists.txt

@@ -1,7 +1,12 @@
 if(Slicer_USE_QtTesting AND Slicer_USE_PYTHONQT)
 
- # add a self test
+ # add tests
  slicer_add_python_unittest(SCRIPT VolumeRenderingSceneClose.py)
+ slicer_add_python_unittest(SCRIPT VolumeRenderingThreeDOnlyLayout.py)
+ set_tests_properties(
+ py_VolumeRenderingThreeDOnlyLayout
+ PROPERTIES FAIL_REGULAR_EXPRESSION "OpenGL errors detected"
+ )
  set(KIT_PYTHON_SCRIPTS
  VolumeRenderingSceneClose.py
  )

Modules/Loadable/VolumeRendering/Testing/Python/VolumeRenderingThreeDOnlyLayout.py

@@ -0,0 +1,33 @@
+import unittest
+import slicer
+
+
+class VolumeRenderingThreeDOnlyLayout(unittest.TestCase):
+ def setUp(self):
+ pass
+
+ def tearDown(self):
+ slicer.mrmlScene.Clear(0)
+
+ def test_VolumeRenderThreeDOnlyLayout(self):
+ """
+ Test that the following workflow does not segfault:
+ - Set 3D-only layout, reinitialize slice widgets
+ - Load volume
+ - Enter the volume rendering module
+ """
+ # Set 3D-only layout
+ layoutManager = slicer.app.layoutManager()
+ layoutManager.setLayout(slicer.vtkMRMLLayoutNode.SlicerLayoutOneUp3DView)
+
+ # Reinitialize MRML scene to force re-creating slice widgets
+ mrmlScene = layoutManager.mrmlScene()
+ layoutManager.setMRMLScene(None)
+ layoutManager.setMRMLScene(mrmlScene)
+
+ # Load MRHead volume
+ from SampleData import SampleDataLogic
+ SampleDataLogic().downloadMRHead()
+
+ # Enter the volume rendering module
+ slicer.util.mainWindow().moduleSelector().selectModule('VolumeRendering')