additional initialization for osgEarth

Earth plugin needs to be enabled, so that it is loaded early enough, before any GL contexts have been established/windows created

Author: aumuell

src/OpenCOVER/plugins/general/Earth/EarthPlugin.cpp

@@ -162,7 +162,13 @@ struct KMLUIBuilder : public osg::NodeVisitor
 EarthPlugin::EarthPlugin()
 : coVRPlugin(COVER_PLUGIN_NAME)
 {
+    assert(!plugin);
     plugin = this;
+
+    osgEarth::initialize(); // has to be called before creating windows: load plugin from config
+    realizeOp = new osgEarth::GL3RealizeOperation();
+    VRViewer::instance()->addRealizeOperation(realizeOp);
+
     mapNode = NULL;
     oldDump = NULL;
 
@@ -445,6 +451,7 @@ int EarthPlugin::unloadKmlFile(const char *fn)
 // this is called if the plugin is removed at runtime
 EarthPlugin::~EarthPlugin()
 {
+    VRViewer::instance()->removeRealizeOperation(realizeOp);
     plugin = NULL;
 }
 

src/OpenCOVER/plugins/general/Earth/EarthPlugin.h

@@ -78,6 +78,7 @@ class EarthPlugin : public coVRPlugin, public coTUIListener
     static EarthPlugin *plugin;
 
 private:
+    osg::Operation *realizeOp = nullptr;
     osg::Node *loadedModel;
     osgEarth::MapNode *mapNode;
     bool useSky;