Expose rendering teardown event (#1539)

Signed-off-by: Michel Hidalgo <[email protected]>

include/gz/sim/rendering/Events.hh

@@ -77,6 +77,18 @@ namespace gz
       using PostRender = gz::common::EventT<void(void),
           struct PostRenderTag>;
 
+      /// \brief The render teardown event is emitted right before the
+      /// rendering thread is torn down. The event is emitted in the
+      /// rendering thread so last minute, cleanup rendering calls can
+      /// be made in this event callback.
+      ///
+      /// For example:
+      /// \code
+      /// eventManager.Emit<gz::sim::events::RenderTeardown>();
+      /// \endcode
+      using RenderTeardown = gz::common::EventT<void(void),
+          struct RenderTeardownTag>;
+
       /// \brief The force render event may be emitted outside the
       /// rendering thread to force rendering calls ie. to ensure
       /// rendering occurs even if it wasn't seemingly necessary.

src/systems/sensors/Sensors.cc

@@ -396,6 +396,8 @@ void SensorsPrivate::RenderThread()
     this->RunOnce();
   }
 
+  this->eventManager->Emit<events::RenderTeardown>();
+
   // clean up before exiting
   for (const auto id : this->sensorIds)
     this->sensorManager.Remove(id);