Added View copy constructor that shares viewID and common state.

include/vsg/app/View.h

@@ -26,6 +26,9 @@ namespace vsg
     public:
         View();
 
+        View(const View& view);
+
+        // share the viewID, mask and camera's ViewportState
         explicit View(ref_ptr<Camera> in_camera, ref_ptr<Node> in_scenegraph = {});
 
         template<class N, class V>

src/vsg/app/View.cpp

@@ -18,7 +18,7 @@ using namespace vsg;
 
 // thread safe container for managing the deviceID for each vsg::View
 static std::mutex s_ViewCountMutex;
-static std::vector<bool> s_ActiveViews;
+static std::vector<uint32_t> s_ActiveViews;
 
 static uint32_t getUniqueViewID()
 {
@@ -27,22 +27,38 @@ static uint32_t getUniqueViewID()
     uint32_t viewID = 0;
     for (viewID = 0; viewID < static_cast<uint32_t>(s_ActiveViews.size()); ++viewID)
     {
-        if (!s_ActiveViews[viewID])
+        if (s_ActiveViews[viewID]==0)
         {
-            s_ActiveViews[viewID] = true;
+            ++s_ActiveViews[viewID];
             return viewID;
         }
     }
 
-    s_ActiveViews.push_back(true);
+    s_ActiveViews.push_back(1);
+
+    return viewID;
+}
+
+static uint32_t sharedViewID(uint32_t viewID)
+{
+    std::scoped_lock<std::mutex> guard(s_ViewCountMutex);
+
+    if (viewID < static_cast<uint32_t>(s_ActiveViews.size()))
+    {
+        ++s_ActiveViews[viewID];
+        return viewID;
+    }
+
+    viewID = static_cast<uint32_t>(s_ActiveViews.size());
+    s_ActiveViews.push_back(1);
 
     return viewID;
 }
 
 static void releaseViewID(uint32_t viewID)
 {
     std::scoped_lock<std::mutex> guard(s_ViewCountMutex);
-    s_ActiveViews[viewID] = false;
+    --s_ActiveViews[viewID];
 }
 
 //////////////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -55,6 +71,18 @@ View::View() :
 {
 }
 
+View::View(const View& view):
+    Inherit(view),
+    viewID(sharedViewID(view.viewID)),
+    mask(view.mask)
+{
+    if (view.camera)
+    {
+        camera = vsg::Camera::create();
+        camera->viewportState = view.camera->viewportState;
+    }
+}
+
 View::View(ref_ptr<Camera> in_camera, ref_ptr<Node> in_scenegraph) :
     camera(in_camera),
     viewID(getUniqueViewID()),