Added support for sorting the graphics contexts so that the first context/window

returned from Viewer::getContexts/getWindows will be the left most window on the lowest screen number.

Added ability for StatsHandler and HelpHandler to support end users setting their
Camera's graphics context.

src/osgViewer/HelpHandler.cpp

@@ -22,8 +22,10 @@ using namespace osgViewer;
 HelpHandler::HelpHandler(osg::ApplicationUsage* au):
     _applicationUsage(au),
     _keyEventTogglesOnScreenHelp('h'),
-    _helpEnabled(false)
+    _helpEnabled(false),
+    _initialized(false)
 {
+    _camera = new osg::Camera;
 }
 
 bool HelpHandler::handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa)
@@ -37,7 +39,7 @@ bool HelpHandler::handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapt
         {
             if (ea.getKey()==_keyEventTogglesOnScreenHelp)
             {
-                if (!_camera.valid())
+                if (!_initialized)
                 {
                     setUpHUDCamera(viewer);
                     setUpScene(viewer);
@@ -84,6 +86,8 @@ void HelpHandler::setUpHUDCamera(osgViewer::Viewer* viewer)
     _camera->setClearMask(0);
 
     viewer->setUpRenderingSupport();
+    
+    _initialized = true;
 }
 
 void HelpHandler::setUpScene(osgViewer::Viewer* viewer)

src/osgViewer/StatsHandler.cpp

@@ -22,6 +22,7 @@ StatsHandler::StatsHandler():
     _keyEventTogglesOnScreenStats('s'),
     _keyEventPrintsOutStats('S'),
     _statsType(NO_STATS),
+    _initialized(false),
     _threadingModel(osgViewer::Viewer::SingleThreaded),
     _frameRateChildNum(0),
     _viewerChildNum(0),
@@ -29,6 +30,7 @@ StatsHandler::StatsHandler():
     _numBlocks(8),
     _blockMultiplier(10000.0)
 {
+    _camera = new osg::Camera;
 }
 
 bool StatsHandler::handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa)
@@ -50,7 +52,7 @@ bool StatsHandler::handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdap
             {
                 if (viewer->getStats())
                 {
-                    if (!_camera.valid())
+                    if (!_initialized)
                     {
                         setUpHUDCamera(viewer);
                         setUpScene(viewer);
@@ -184,17 +186,28 @@ void StatsHandler::updateThreadingModelText()
     }
 }
 
+void StatsHandler::reset()
+{
+    _initialized = false;
+    _camera->setGraphicsContext(0);
+}
+
 void StatsHandler::setUpHUDCamera(osgViewer::Viewer* viewer)
 {
-    osgViewer::Viewer::Windows windows;
-    viewer->getWindows(windows);
+    osgViewer::GraphicsWindow* window = dynamic_cast<osgViewer::GraphicsWindow*>(_camera->getGraphicsContext());
 
-    if (windows.empty()) return;
+    if (!window)
+    {    
+        osgViewer::Viewer::Windows windows;
+        viewer->getWindows(windows);
 
-    osgViewer::GraphicsWindow* window = windows.front();
+        if (windows.empty()) return;
+
+        window = windows.front();
+
+        _camera->setGraphicsContext(window);
+    }
 
-    _camera = new osg::Camera;
-    _camera->setGraphicsContext(window);
     _camera->setViewport(0, 0, window->getTraits()->width, window->getTraits()->height);
 
     _camera->setProjectionMatrix(osg::Matrix::ortho2D(0,1280,0,1024));
@@ -205,6 +218,8 @@ void StatsHandler::setUpHUDCamera(osgViewer::Viewer* viewer)
     _camera->setClearMask(0);
 
     viewer->setUpRenderingSupport();
+    
+    _initialized = true;
 }
 
 struct TextDrawCallback : public virtual osg::Drawable::DrawCallback

src/osgViewer/Viewer.cpp

@@ -1299,6 +1299,29 @@ void Viewer::checkWindowStatus()
 }
 
 
+struct LessGraphicsContext
+{
+    bool operator () (const osg::GraphicsContext* lhs, const osg::GraphicsContext* rhs) const
+    {
+        int screenLeft = lhs->getTraits()? lhs->getTraits()->screenNum : 0;
+        int screenRight = rhs->getTraits()? rhs->getTraits()->screenNum : 0;
+        if (screenLeft < screenRight) return true;
+        if (screenLeft > screenRight) return false;
+
+        screenLeft = lhs->getTraits()? lhs->getTraits()->x : 0;
+        screenRight = rhs->getTraits()? rhs->getTraits()->x : 0;
+        if (screenLeft < screenRight) return true;
+        if (screenLeft > screenRight) return false;
+
+        screenLeft = lhs->getTraits()? lhs->getTraits()->y : 0;
+        screenRight = rhs->getTraits()? rhs->getTraits()->y : 0;
+        if (screenLeft < screenRight) return true;
+        if (screenLeft > screenRight) return false;
+        
+        return lhs < rhs;
+    } 
+};
+
 void Viewer::getContexts(Contexts& contexts, bool onlyValid)
 {
     typedef std::set<osg::GraphicsContext*> ContextSet;
@@ -1331,6 +1354,11 @@ void Viewer::getContexts(Contexts& contexts, bool onlyValid)
     {
         contexts.push_back(const_cast<osg::GraphicsContext*>(*itr));
     }
+
+    if (contexts.size()>=2)
+    {
+        std::sort(contexts.begin(), contexts.end(), LessGraphicsContext()); 
+    }
 }
 
 void Viewer::getWindows(Windows& windows, bool onlyValid)