Added realize() and isRealized() methods to osg::GraphicsContext.

Added osgcamera example that uses osg::GraphicsContext to create the required
window for rendering too, will eventually use osg::CameraNode to replace usage
of osgUtil::SceneView.

examples/osgcamera/GNUmakefile

@@ -0,0 +1,27 @@
+TOPDIR = ../..
+include $(TOPDIR)/Make/makedefs 
+
+CXXFILES =\
+	osgcamera.cpp\
+
+LIBS     += -losgProducer -lProducer -losgDB -losgUtil -losg $(GL_LIBS) $(X_LIBS) $(OTHER_LIBS) -lOpenThreads
+
+INSTFILES = \
+	$(CXXFILES)\
+	GNUmakefile.inst=GNUmakefile
+
+EXEC = osgcamera
+
+INC      += $(X_INC) 
+LDFLAGS  += -L/usr/X11R6/lib
+
+
+ifeq ($(USE_OPEN_THREAD),1)
+    DEF         += -D_USE_OPEN_THREAD
+    INC         += $(INC_OPEN_THREAD)
+    LDFLAGS     += $(LIB_OPEN_THREAD)
+    LIBS        +=  -lOpenThread
+endif
+
+include $(TOPDIR)/Make/makerules 
+

examples/osgcamera/GNUmakefile.inst

@@ -0,0 +1,14 @@
+TOPDIR = ../..
+include $(TOPDIR)/Make/makedefs
+
+CXXFILES =\
+	osgcamera.cpp\
+
+LIBS     += -lProducer -losgDB --losgUtil -losg $(GL_LIBS) $(X_LIBS) $(OTHER_LIBS) 
+
+EXEC = osgcamera
+
+INC += $(PRODUCER_INCLUDE_DIR) $(X_INC)
+LDFLAGS  += $(PRODUCER_LIB_DIR)
+
+include $(TOPDIR)/Make/makerules

examples/osgcamera/osgcamera.cpp

@@ -0,0 +1,97 @@
+// C++ source file - (C) 2003 Robert Osfield, released under the OSGPL.
+//
+// Simple example of use of Producer::RenderSurface to create an OpenGL
+// graphics window, and OSG for rendering.
+
+#include <osg/Timer>
+#include <osg/GraphicsContext>
+#include <osgUtil/SceneView>
+#include <osgDB/ReadFile>
+#include <iostream>
+
+int main( int argc, char **argv )
+{
+    if (argc<2) 
+    {
+        std::cout << argv[0] <<": requires filename argument." << std::endl;
+        return 1;
+    }
+
+    // load the scene.
+    osg::ref_ptr<osg::Node> loadedModel = osgDB::readNodeFile(argv[1]);
+    if (!loadedModel) 
+    {
+        std::cout << argv[0] <<": No data loaded." << std::endl;
+        return 1;
+    }
+    
+    osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;
+    traits->_windowName = "osgcamera";
+    traits->_x = 100;
+    traits->_y = 100;
+    traits->_width = 800;
+    traits->_height = 800;
+    traits->_windowDecoration = true;
+    traits->_doubleBuffer = true;
+    
+    osg::ref_ptr<osg::GraphicsContext> gfxc = osg::GraphicsContext::createGraphicsContext(traits.get());
+    
+    if (!gfxc)
+    {
+        std::cout<<"Unable to create window."<<std::endl;
+        return 1;
+    }
+    
+    // realise the window
+    gfxc->realize();
+
+    // create the view of the scene.
+    osg::ref_ptr<osgUtil::SceneView> sceneView = new osgUtil::SceneView;
+    sceneView->setDefaults();
+    sceneView->setSceneData(loadedModel.get());
+
+    // initialize the view to look at the center of the scene graph
+    const osg::BoundingSphere& bs = loadedModel->getBound();
+    osg::Matrix viewMatrix;
+    viewMatrix.makeLookAt(bs.center()-osg::Vec3(0.0,2.0f*bs.radius(),0.0),bs.center(),osg::Vec3(0.0f,0.0f,1.0f));
+
+    // record the timer tick at the start of rendering.    
+    osg::Timer_t start_tick = osg::Timer::instance()->tick();
+    
+    unsigned int frameNum = 0;
+    
+    // make the graphics context current
+    gfxc->makeCurrent();
+
+    // main loop (note, window toolkits which take control over the main loop will require a window redraw callback containing the code below.)
+    while( gfxc->isRealized() )
+    {
+        // set up the frame stamp for current frame to record the current time and frame number so that animtion code can advance correctly
+        osg::ref_ptr<osg::FrameStamp> frameStamp = new osg::FrameStamp;
+        frameStamp->setReferenceTime(osg::Timer::instance()->delta_s(start_tick,osg::Timer::instance()->tick()));
+        frameStamp->setFrameNumber(frameNum++);
+        
+        // pass frame stamp to the SceneView so that the update, cull and draw traversals all use the same FrameStamp
+        sceneView->setFrameStamp(frameStamp.get());
+        
+        // update the viewport dimensions, incase the window has been resized.
+        sceneView->setViewport(0,0,traits->_width,traits->_height);
+        
+        // set the view
+        sceneView->setViewMatrix(viewMatrix);
+
+        // do the update traversal the scene graph - such as updating animations
+        sceneView->update();
+        
+        // do the cull traversal, collect all objects in the view frustum into a sorted set of rendering bins
+        sceneView->cull();
+        
+        // draw the rendering bins.
+        sceneView->draw();
+
+    	// Swap Buffers
+    	gfxc->swapBuffers();
+    }
+
+    return 0;
+}