Canvas placement on dynamic models

1. A canvas can be placed on dynamically created models. 
Implemented by adding a new placement factory.

2. Added a "loaded" property in every "models/model[...]" 
path to track when a model is finally loaded by OSG.

See https://forum.flightgear.org/viewtopic.php?f=30&t=38318

src/Canvas/canvas_mgr.cxx

@@ -22,8 +22,10 @@
 #include <Main/fg_props.hxx>
 #include <Scripting/NasalModelData.hxx>
 #include <Viewer/CameraGroup.hxx>
+#include <Model/modelmgr.hxx>
 
 #include <simgear/canvas/Canvas.hxx>
+#include <simgear/scene/model/placement.hxx>
 
 namespace sc = simgear::canvas;
 
@@ -54,6 +56,31 @@ static sc::Placements addSceneObjectPlacement( SGPropertyNode* placement,
   );
 }
 
+
+//------------------------------------------------------------------------------
+static sc::Placements addDynamicModelPlacement(SGPropertyNode* placement,
+                                              sc::CanvasPtr canvas)
+{
+    const string dyn_model_path = placement->getStringValue("model-path");
+    if (dyn_model_path.empty())
+        return {};
+
+    auto  modelmgr = globals->get_subsystem<FGModelMgr>();
+    if (!modelmgr)
+        return {};
+
+    FGModelMgr::Instance* model_instance = modelmgr->findInstanceByNodePath(dyn_model_path);
+    if (!model_instance || !model_instance->model || !model_instance->model->getSceneGraph())
+        return {};
+
+    return FGODGauge::set_texture(
+        model_instance->model->getSceneGraph(),
+        placement,
+        canvas->getTexture(),
+        canvas->getCullCallback(),
+        canvas);
+}
+
 //------------------------------------------------------------------------------
 CanvasMgr::CanvasMgr():
   simgear::canvas::CanvasMgr( fgGetNode("/canvas/by-index", true) ),
@@ -85,6 +112,7 @@ void CanvasMgr::init()
           });
           
           sc::Canvas::addPlacementFactory("scenery-object", &addSceneObjectPlacement);
+          sc::Canvas::addPlacementFactory("dynamic-model", &addDynamicModelPlacement);
       }
   }
   simgear::canvas::CanvasMgr::init();
@@ -97,6 +125,7 @@ void CanvasMgr::shutdown()
 
   sc::Canvas::removePlacementFactory("object");
   sc::Canvas::removePlacementFactory("scenery-object");
+  sc::Canvas::removePlacementFactory("dynamic-model");
 
     _gui_camera = 0;
 }

src/Model/modelmgr.cxx

@@ -25,13 +25,59 @@
 #include <Main/fg_props.hxx>
 #include <Scenery/scenery.hxx>
 
+#include <osg/ProxyNode>
 
 #include "modelmgr.hxx"
 
 using namespace simgear;
 
-// OSGFIXME
+namespace {
-// extern SGShadowVolume *shadows;
+
+class CheckInstanceModelLoadedVisitor : public osg::NodeVisitor
+{
+public:
+    CheckInstanceModelLoadedVisitor() :
+        osg::NodeVisitor(osg::NodeVisitor::NODE_VISITOR, osg::NodeVisitor::TRAVERSE_ALL_CHILDREN)
+    {}
+    
+    ~CheckInstanceModelLoadedVisitor() = default;
+
+    void apply(osg::Node& node) override
+    {
+        if (!_loaded)
+            return;
+        traverse(node);
+    }
+    
+    void apply(osg::ProxyNode& node) override
+    {
+        if (!_loaded)
+            return;
+
+        for (unsigned i = 0; i < node.getNumFileNames(); ++i) {
+            if (node.getFileName(i).empty())
+                continue;
+            
+            // Check if this is already loaded.
+            if (i < node.getNumChildren() && node.getChild(i))
+                continue;
+
+            _loaded=false;
+            return;
+        }
+        traverse(node);
+    }
+
+    bool isLoaded() const
+    {
+        return _loaded;
+    }
+
+private:
+    bool _loaded = true;
+};
+
+} // of anonymous namespace
 
 FGModelMgr::FGModelMgr ()
 {
@@ -76,6 +122,10 @@ FGModelMgr::add_model (SGPropertyNode * node)
   const char *model_path = node->getStringValue("path", "Models/Geometry/glider.ac");
   osg::Node *object;
 
+  Instance * instance = new Instance;
+  instance->loaded_node = node->addChild("loaded");
+  instance->loaded_node->setBoolValue(false);
+    
   try {
       std::string fullPath = simgear::SGModelLib::findDataFile(model_path);
       object = SGModelLib::loadDeferredModel(fullPath, globals->get_props());
@@ -85,7 +135,6 @@ FGModelMgr::add_model (SGPropertyNode * node)
     return;
   }
 
-  Instance * instance = new Instance;
   SGModelPlacement *model = new SGModelPlacement;
   instance->model = model;
   instance->node = node;
@@ -217,6 +266,7 @@ void FGModelMgr::update(double dt)
             model->setHeadingDeg(heading);
 
         instance->model->update();
+        instance->checkLoaded();
     });
 }
 
@@ -239,31 +289,55 @@ FGModelMgr::remove_instance (Instance * instance)
     }
 }
 
-
+FGModelMgr::Instance*
+FGModelMgr::findInstanceByNodePath(const std::string& node_path) const
+{
+    if (node_path.empty())
+        return nullptr;
+
+    SGPropertyNode* node = fgGetNode(node_path, false);
+    if (!node)
+        return nullptr;
+    
+    auto it = std::find_if(_instances.begin(), _instances.end(),
+                           [node](const Instance* instance)
+    { return instance->node == node; });
+    
+    if (it == _instances.end()) {
+        return nullptr;
+    }
+    
+    return *it;
+}
+
 ////////////////////////////////////////////////////////////////////////
 // Implementation of FGModelMgr::Instance
 ////////////////////////////////////////////////////////////////////////
 
-FGModelMgr::Instance::Instance ()
-  : model(0),
-    node(0),
-    lon_deg_node(0),
-    lat_deg_node(0),
-    elev_ft_node(0),
-    roll_deg_node(0),
-    pitch_deg_node(0),
-    heading_deg_node(0),
-    shadow(false)
-{
-}
-
 FGModelMgr::Instance::~Instance ()
 {
     delete model;
 }
 
+bool FGModelMgr::Instance::checkLoaded() const
+{
+    if (!model)
+        return false;
+    
+    if (loaded_node->getBoolValue()) {
+        return true;
+    }
+    
+    CheckInstanceModelLoadedVisitor cilv;
+    model->getSceneGraph()->accept(cilv);
+    const bool loadedNow = cilv.isLoaded();
+    
+    if (loadedNow) {
+        loaded_node->setBoolValue(true);
+    }
+    return loadedNow;
+}
 
-
 ////////////////////////////////////////////////////////////////////////
 // Implementation of FGModelMgr::Listener
 ////////////////////////////////////////////////////////////////////////

src/Model/modelmgr.hxx

@@ -12,6 +12,8 @@
 #include <simgear/compiler.h>    // for SG_USING_STD
 #include <simgear/structure/subsystem_mgr.hxx>
 
+#include <Scripting/NasalModelData.hxx>
+
 // Don't pull in headers, since we don't need them here.
 class SGPropertyNode;
 class SGModelPlacement;
@@ -23,6 +25,7 @@ class SGModelPlacement;
 class FGModelMgr : public SGSubsystem
 {
 public:
+
     /**
      * A dynamically-placed model using properties.
      *
@@ -38,9 +41,8 @@ public:
      */
     struct Instance
     {
-        Instance ();
         virtual ~Instance ();
-        SGModelPlacement * model;
+        SGModelPlacement * model = nullptr;
         SGPropertyNode_ptr node;
         SGPropertyNode_ptr lon_deg_node;
         SGPropertyNode_ptr lat_deg_node;
@@ -48,7 +50,10 @@ public:
         SGPropertyNode_ptr roll_deg_node;
         SGPropertyNode_ptr pitch_deg_node;
         SGPropertyNode_ptr heading_deg_node;
-        bool shadow;
+        SGPropertyNode_ptr loaded_node;
+        bool shadow = false;
+
+        bool checkLoaded() const;
     };
 
     FGModelMgr ();
@@ -86,6 +91,15 @@ public:
      */
     virtual void remove_instance (Instance * instance);
 
+
+     /**
+     * Finds an instance in the model manager from a given node path in the property tree.
+     * A possible path could be "models/model[0]"
+     *
+     * NOTE: the manager will delete the instance as well.
+     */
+    Instance* findInstanceByNodePath(const std::string& nodePath) const;
+
 private:
     /**
      * Listener class that adds models at runtime.