[Metal] fix issues with OpenGL context thread affinity

- The OpenGL context must be moved from the QSGRenderThread to the main thread for initialisation
- After initialisation the OpenGL context is then moved to the Ignition render thread

Signed-off-by: Rhys Mainwaring <[email protected]>

src/plugins/minimal_scene/MinimalScene.cc

@@ -896,34 +896,29 @@ void RenderWindowItem::Ready()
     this->dataPtr->renderThread->Surface()->create();
   }
 
-  // Carry out any initialization before moving to Render thread
+  // Carry out initialization on main thread before moving to render thread
   this->dataPtr->renderThread->Initialize();
 
-  this->dataPtr->renderThread->ignRenderer.textureSize =
-      QSize(std::max({this->width(), 1.0}), std::max({this->height(), 1.0}));
-
-  // Move to Render thread
   if (this->dataPtr->graphicsAPI == rendering::GraphicsAPI::OPENGL)
   {
+    // Move context to the render thread
     this->dataPtr->renderThread->Context()->moveToThread(
         this->dataPtr->renderThread);
   }
 
   this->dataPtr->renderThread->moveToThread(this->dataPtr->renderThread);
 
+  this->dataPtr->renderThread->ignRenderer.textureSize =
+      QSize(std::max({this->width(), 1.0}), std::max({this->height(), 1.0}));
+
   this->connect(this, &QQuickItem::widthChanged,
       this->dataPtr->renderThread, &RenderThread::SizeChanged);
   this->connect(this, &QQuickItem::heightChanged,
       this->dataPtr->renderThread, &RenderThread::SizeChanged);
 
-  // Running on Render thread
   this->dataPtr->renderThread->start();
-
-  // Completed initialising
   this->dataPtr->initializing = false;
   this->dataPtr->initialized = true;
-
-  // Trigger update
   this->update();
 }
 
@@ -959,10 +954,14 @@ QSGNode *RenderWindowItem::updatePaintNode(QSGNode *_node,
       this->dataPtr->renderThread->Context()->setShareContext(current);
       this->dataPtr->renderThread->Context()->create();
 
-      // Initialize on main thread
-      QMetaObject::invokeMethod(this, "Ready", Qt::QueuedConnection);
+      // The slot "Ready" runs on the main thread, move the context to match
+      this->dataPtr->renderThread->Context()->moveToThread(
+          QApplication::instance()->thread());
 
       current->makeCurrent(this->window());
+
+      // Initialize on main thread
+      QMetaObject::invokeMethod(this, "Ready", Qt::QueuedConnection);
     }
     else if (this->dataPtr->graphicsAPI == rendering::GraphicsAPI::METAL)
     {