Support reloading Compositor instances at runtime via a fgcommand

src/Main/fg_scene_commands.cxx

@@ -34,6 +34,7 @@
 #include <Sound/sample_queue.hxx>
 #include <Airports/xmlloader.hxx>
 #include <Network/HTTPClient.hxx>
+#include <Viewer/CameraGroup.hxx>
 #include <Viewer/viewmgr.hxx>
 #include <Viewer/view.hxx>
 #include <Environment/presets.hxx>
@@ -215,6 +216,15 @@ do_hires_screen_capture (const SGPropertyNode * arg, SGPropertyNode * root)
   return true;
 }
 
+/**
+ * Reload all Compositor instances in the default CameraGroup.
+ */
+static bool
+do_reload_compositor(const SGPropertyNode*, SGPropertyNode*)
+{
+    flightgear::reloadCompositors(flightgear::CameraGroup::getDefault());
+    return true;
+}
 
 /**
  * Reload the tile cache.
@@ -544,6 +554,7 @@ static struct {
     { "print-visible-scene", do_print_visible_scene_info },
     { "reload-shaders", do_reload_shaders },
     { "reload-materials", do_materials_reload },
+    { "reload-compositor", do_reload_compositor },
     { "open-launcher", do_open_launcher },
     { 0, 0 }			// zero-terminated
 };

src/Viewer/CameraGroup.cxx

@@ -689,10 +689,16 @@ void CameraGroup::buildCamera(SGPropertyNode* cameraNode)
         // If no width or height has been specified, fill the entire window
         viewportNode->getDoubleValue("width", window->gc->getTraits()->width),
         viewportNode->getDoubleValue("height",window->gc->getTraits()->height));
-    std::string default_compositor =
-        fgGetString("/sim/rendering/default-compositor", "Compositor/default");
-    std::string compositor_path =
-        cameraNode->getStringValue("compositor", default_compositor.c_str());
+
+    std::string compositor_path = cameraNode->getStringValue("compositor", "");
+    if (compositor_path.empty()) {
+        compositor_path = fgGetString("/sim/rendering/default-compositor",
+                                      "Compositor/default");
+    } else {
+        // Store the custom path in case we need to reload later
+        info->compositor_path = compositor_path;
+    }
+
     osg::ref_ptr<SGReaderWriterOptions> options =
         SGReaderWriterOptions::fromPath(globals->get_fg_root());
     options->setPropertyNode(globals->get_props());
@@ -705,7 +711,7 @@ void CameraGroup::buildCamera(SGPropertyNode* cameraNode)
                                                 compositor_path,
                                                 options);
     if (compositor) {
-        info->compositor = compositor;
+        info->compositor.reset(compositor);
     } else {
         throw sg_exception(std::string("Failed to create Compositor in path '") +
                            compositor_path + "'");
@@ -787,7 +793,7 @@ void CameraGroup::buildGUICamera(SGPropertyNode* cameraNode,
     info->name = "GUI camera";
     info->viewOffset = osg::Matrix::identity();
     info->projOffset = osg::Matrix::identity();
-    info->compositor = compositor;
+    info->compositor.reset(compositor);
     _cameras.push_back(info);
 
     // Disable statistics for the GUI camera.
@@ -944,6 +950,36 @@ void warpGUIPointer(CameraGroup* cgroup, int x, int y)
     cgroup->getView()->getEventQueue()->mouseWarped(viewerX, viewerY);
 }
 
+void reloadCompositors(CameraGroup *cgroup)
+{
+    for (auto &info : cgroup->_cameras) {
+        // Ignore the GUI camera
+        if (info->flags & CameraInfo::GUI)
+            continue;
+        // Get the viewport and the graphics context from the old Compositor
+        osg::ref_ptr<osg::Viewport> viewport = info->compositor->getViewport();
+        osg::ref_ptr<osg::GraphicsContext> gc =
+            info->compositor->getGraphicsContext();
+        osg::ref_ptr<SGReaderWriterOptions> options =
+            SGReaderWriterOptions::fromPath(globals->get_fg_root());
+        options->setPropertyNode(globals->get_props());
+
+        cgroup->_viewer->getViewerBase()->stopThreading();
+        // Force deletion
+        info->compositor.reset(nullptr);
+        // Then replace it with a new instance
+        std::string compositor_path = info->compositor_path.empty() ?
+            fgGetString("/sim/rendering/default-compositor", "Compositor/default") :
+            info->compositor_path;
+        info->compositor.reset(Compositor::create(cgroup->_viewer,
+                                                  gc,
+                                                  viewport,
+                                                  compositor_path,
+                                                  options));
+        cgroup->_viewer->getViewerBase()->startThreading();
+    }
+}
+
 void CameraGroup::buildDefaultGroup(osgViewer::View* viewer)
 {
     // Look for windows, camera groups, and the old syntax of

src/Viewer/CameraGroup.hxx

@@ -114,7 +114,12 @@ struct CameraInfo : public osg::Referenced
     osg::Matrix viewMatrix, projMatrix;
     /** The Compositor used to manage the pipeline of this camera.
      */
-    osg::ref_ptr<simgear::compositor::Compositor> compositor;
+    std::unique_ptr<simgear::compositor::Compositor> compositor;
+    /** Compositor path. Used to recreate the pipeline when reloading.
+     * If the path is empty, it means that this camera isn't using a custom
+     * Compositor path and should use the default one.
+     */
+    std::string compositor_path;
 };
 
 class CameraGroup : public osg::Referenced
@@ -190,6 +195,7 @@ protected:
                                      const osg::Vec2d& windowPos,
                                      osgUtil::LineSegmentIntersector::Intersections&
                                      intersections);
+    friend void reloadCompositors(CameraGroup *cgroup);
 
     typedef std::vector<osg::ref_ptr<CameraInfo>> CameraList;
     CameraList _cameras;
@@ -237,6 +243,11 @@ bool computeIntersections(const CameraGroup* cgroup,
  */
 void warpGUIPointer(CameraGroup* cgroup, int x, int y);
 
+/** Force a reload of all Compositor instances in the CameraGroup,
+ * except the one used by the GUI camera.
+ */
+void reloadCompositors(CameraGroup *cgroup);
+
 }
 
 #endif