Repeatedly calling rendering::sceneFromFirstRenderEngine loads the engine plugin every time

[azeey]

Environment

• OS Version: Ubuntu 22.04
• Source or binary build? gz-rendering8, dad0364

Description

• Expected behavior: rendering::sceneFromFirstRenderEngine should load the engine plugin only the first time it's called.
• Actual behavior: It loads the plugin every time. I suspect that the cache for which engines have been loaded uses the filename of the library as the key to a map, but RenderEngineManager::Engine tries to look up the engine by its name.
  

  gz-rendering/src/RenderEngineManager.cc

  Line 553 in dad0364

  this->engines[_filename] = renderPlugin->Engine();

and

gz-rendering/src/RenderEngineManager.cc

Lines 211 to 215 in dad0364

	EngineInfo info{_name, nullptr};
	std::lock_guard<std::recursive_mutex> lock(this->dataPtr->enginesMutex);
	// check in the list of available engines
	auto iter = this->dataPtr->engines.find(_name);
	if (iter != this->dataPtr->engines.end())

Steps to reproduce

The easiest way to see this to run a gz-sim plugin that calls rendering::sceneFromFirstRenderEngine on every OnRender callback.

1. gz sim -s -r -v3 --iterations 50 model_photo_shoot.sdf

This will repeatedly print

[Msg] Loading plugin [gz-rendering-ogre2]