BUG: Fixed widget texture update in VR view

A workaround was implemented, a better solution will be needed in the long run.

Re KitwareMedical#43

GUIWidgets/VTKWidgets/vtkSlicerQWidgetRepresentation.cxx

@@ -28,6 +28,9 @@
 #include "vtkMRMLGUIWidgetNode.h"
 #include "vtkMRMLGUIWidgetDisplayNode.h"
 
+// MRML includes
+#include <vtkMRMLScene.h>
+
 // VTK includes
 #include <vtkActor.h>
 #include <vtkCallbackCommand.h>
@@ -270,8 +273,30 @@ void vtkSlicerQWidgetRepresentation::OnTextureModified(
   self->PlaceWidget(bounds);
 
   // Trigger rendering in view
-  if (self->GetViewNode()->GetSelectable())
+  vtkMRMLNode* vrViewNode = self->GetViewNode()->GetScene()->GetSingletonNode("Active", "vtkMRMLVirtualRealityViewNode");
+  if (vrViewNode)
   {
-    self->GetViewNode()->Modified();
+    if (self->GetViewNode()->GetSelectable()) //TODO: Workaround for stack overflow, see vtkSlicerQWidgetWidget::CreateDefaultRepresentation
+    {
+      self->GetViewNode()->Modified();
+
+      //TODO: Workaround for fixing the texture update in the VR view.
+      // Apparently the QGraphicsScene::changed signal is not emitted for the widget representation in the VR view.
+      // However, a connection was added for testing to the QObject::objectNameChanged signal, which does work.
+      // Need to fix the graphics scene changed signal connection.
+      if (self->GetViewNode() != vrViewNode)
+      {
+        if (!vrViewNode->GetAttribute("WaitingForTextureUpdate") || strcmp(vrViewNode->GetAttribute("WaitingForTextureUpdate"), "1"))
+        {
+          vrViewNode->SetAttribute("WaitingForTextureUpdate", "1");
+
+          widget->setObjectName(widget->objectName().compare("AlternateObjectName1") ? "AlternateObjectName1" : "AlternateObjectName2");
+        }
+      }
+      else
+      {
+        vrViewNode->SetAttribute("WaitingForTextureUpdate", "0");  // Indicate that VR view has updated the texture
+      }
+    }
   }
 }

GUIWidgets/VTKWidgets/vtkSlicerQWidgetTexture.cxx

@@ -109,7 +109,7 @@ void vtkSlicerQWidgetTexture::SetupWidget()
   this->Scene->addWidget(this->Widget);
 
   QObject::connect(this->Scene, &QGraphicsScene::changed, this->UpdateTextureMethod);
-  QObject::connect(this->Widget, &QObject::objectNameChanged, this->UpdateTextureMethod); //TODO: For debugging
+  QObject::connect(this->Widget, &QObject::objectNameChanged, this->UpdateTextureMethod); //TODO: Workaround, see vtkSlicerQWidgetRepresentation::OnTextureModified
 
   if (this->TextureImageData.GetPointer() == nullptr)
   {

GUIWidgets/VTKWidgets/vtkSlicerQWidgetWidget.cxx

@@ -95,7 +95,7 @@ void vtkSlicerQWidgetWidget::CreateDefaultRepresentation(
   }
 
   bool wasSelectable = viewNode->GetSelectable();
-  viewNode->SetSelectable(false);  // Workaround to disable texture updates until setup is completed
+  viewNode->SetSelectable(false);  //TODO: Workaround to disable texture updates until setup is completed
 
   vtkNew<vtkSlicerQWidgetRepresentation> rep;
   this->SetRenderer(renderer);