ENH: Generalize handling of complex gesture events in VR

Considering that the handling of complex gesture may be customized to be
independent of the grip button, this commit implements the following changes:
* rename HandleGripEvents to HandleComplexGestureEvents
* remove input check based of "vtkEventDataDeviceInput::Grip" in HandleComplexGestureEvents

Rendering/OpenVR/vtkOpenVRRenderWindowInteractor.cxx

@@ -56,9 +56,9 @@ void vtkOpenVRRenderWindowInteractor::Initialize()
     "/user/head", &this->Trackers[vtkOpenVRRenderWindowInteractor::HEAD].Source);
 
   this->AddAction("/actions/vtk/in/LeftGripAction", false,
-    [this](vtkEventData* ed) { this->HandleGripEvents(ed); });
+    [this](vtkEventData* ed) { this->HandleComplexGestureEvents(ed); });
   this->AddAction("/actions/vtk/in/RightGripAction", false,
-    [this](vtkEventData* ed) { this->HandleGripEvents(ed); });
+    [this](vtkEventData* ed) { this->HandleComplexGestureEvents(ed); });
 
   // add extra event actions
   for (auto& it : this->ActionMap)

Rendering/OpenXR/vtkOpenXRRenderWindowInteractor.cxx

@@ -518,10 +518,12 @@ void vtkOpenXRRenderWindowInteractor::Initialize()
     return;
   }
 
-  // Grip actions are handled by the interactor directly (why?)
-  this->AddAction("leftgripaction", [this](vtkEventData* ed) { this->HandleGripEvents(ed); });
+  // Complex gesture actions are handled by the interactor directly (why?)
+  this->AddAction(
+    "leftgripaction", [this](vtkEventData* ed) { this->HandleComplexGestureEvents(ed); });
 
-  this->AddAction("rightgripaction", [this](vtkEventData* ed) { this->HandleGripEvents(ed); });
+  this->AddAction(
+    "rightgripaction", [this](vtkEventData* ed) { this->HandleComplexGestureEvents(ed); });
 
   // Create an entry for pose actions that are used to retrieve
   // Orientation and locations of trackers

Rendering/VR/vtkVRRenderWindowInteractor.cxx

@@ -328,7 +328,7 @@ void vtkVRRenderWindowInteractor::StartEventLoop()
 }
 
 //------------------------------------------------------------------------------
-void vtkVRRenderWindowInteractor::HandleGripEvents(vtkEventData* ed)
+void vtkVRRenderWindowInteractor::HandleComplexGestureEvents(vtkEventData* ed)
 {
   vtkEventDataDevice3D* edata = ed->GetAsEventDataDevice3D();
   if (!edata)
@@ -351,7 +351,7 @@ void vtkVRRenderWindowInteractor::HandleGripEvents(vtkEventData* ed)
     vtkVRRenderWindow* renWin = vtkVRRenderWindow::SafeDownCast(this->RenderWindow);
     renWin->GetPhysicalToWorldMatrix(this->StartingPhysicalToWorldMatrix);
 
-    // Both controllers have the grip down, start multitouch
+    // Both controllers have a button down, start complex gesture handling (aka multitouch)
     if (this->DeviceInputDownCount[static_cast<int>(vtkEventDataDevice::LeftController)] &&
       this->DeviceInputDownCount[static_cast<int>(vtkEventDataDevice::RightController)])
     {
@@ -365,24 +365,21 @@ void vtkVRRenderWindowInteractor::HandleGripEvents(vtkEventData* ed)
   {
     this->DeviceInputDownCount[this->PointerIndex] = 0;
 
-    if (edata->GetInput() == vtkEventDataDeviceInput::Grip)
+    if (this->CurrentGesture == vtkCommand::PinchEvent)
     {
-      if (this->CurrentGesture == vtkCommand::PinchEvent)
-      {
-        this->EndPinchEvent();
-      }
-      if (this->CurrentGesture == vtkCommand::PanEvent)
-      {
-        this->EndPanEvent();
-      }
-      if (this->CurrentGesture == vtkCommand::RotateEvent)
-      {
-        this->EndRotateEvent();
-      }
-      this->CurrentGesture = vtkCommand::NoEvent;
-
-      return;
+      this->EndPinchEvent();
     }
+    if (this->CurrentGesture == vtkCommand::PanEvent)
+    {
+      this->EndPanEvent();
+    }
+    if (this->CurrentGesture == vtkCommand::RotateEvent)
+    {
+      this->EndRotateEvent();
+    }
+    this->CurrentGesture = vtkCommand::NoEvent;
+
+    return;
   }
 }
 

Rendering/VR/vtkVRRenderWindowInteractor.h

@@ -181,10 +181,10 @@ protected:
    * After computing the distance along each of these axes in meters, the first
    * to break the hard-coded threshold wins.
    *
-   * Overriding both HandleGripEvents()  and RecognizeComplexGesture() allows to define
-   * a different heuristic
+   * Overriding both HandleComplexGestureEvents() and RecognizeComplexGesture() allows to define
+   * a different heuristic.
    */
-  virtual void HandleGripEvents(vtkEventData* ed);
+  virtual void HandleComplexGestureEvents(vtkEventData* ed);
   virtual void RecognizeComplexGesture(vtkEventDataDevice3D* edata);
   ///@}