core: switch to custom incubation controller

This change requires more QtPrivate usage but eliminates generation or
cleanup related window incubation controller bugs. Additionally it
enables async loads prior to rendering windows.

src/core/generation.cpp

@@ -49,7 +49,8 @@ EngineGeneration::EngineGeneration(const QDir& rootPath, QmlScanner scanner)
 	this->engine->addImportPath("qs:@/");
 
 	this->engine->setNetworkAccessManagerFactory(&this->interceptNetFactory);
-	this->engine->setIncubationController(&this->delayedIncubationController);
+	this->incubationController.initLoop();
+	this->engine->setIncubationController(&this->incubationController);
 
 	this->engine->addImageProvider("icon", new IconImageProvider());
 	this->engine->addImageProvider("qsimage", new QsImageProvider());
@@ -134,7 +135,7 @@ void EngineGeneration::onReload(EngineGeneration* old) {
 		// new generation acquires it then incubators will hang intermittently
 		qCDebug(logIncubator) << "Locking incubation controllers of old generation" << old;
 		old->incubationControllersLocked = true;
-		old->assignIncubationController();
+		old->updateIncubationMode();
 	}
 
 	QObject::connect(this->engine, &QQmlEngine::quit, this, &EngineGeneration::quit);
@@ -288,29 +289,18 @@ void EngineGeneration::trackWindowIncubationController(QQuickWindow* window) {
 
 	QObject::connect(window, &QObject::destroyed, this, &EngineGeneration::onTrackedWindowDestroyed);
 	this->trackedWindows.append(window);
-	this->assignIncubationController();
+	this->updateIncubationMode();
 }
 
 void EngineGeneration::onTrackedWindowDestroyed(QObject* object) {
 	this->trackedWindows.removeAll(static_cast<QQuickWindow*>(object)); // NOLINT
-	this->assignIncubationController();
+	this->updateIncubationMode();
 }
 
-void EngineGeneration::assignIncubationController() {
-	QQmlIncubationController* controller = &this->delayedIncubationController;
-
-	for (auto* window: this->trackedWindows) {
-		if (auto* wctl = window->incubationController()) {
-			controller = wctl;
-			break;
-		}
-	}
-
-	qCDebug(logIncubator) << "Assigning incubation controller" << controller << "to generation"
-	                      << this
-	                      << "fallback:" << (controller == &this->delayedIncubationController);
-
-	this->engine->setIncubationController(controller);
+void EngineGeneration::updateIncubationMode() {
+	// If we're in a situation with only hidden but tracked windows this might be wrong,
+	// but it seems to at least work.
+	this->incubationController.setIncubationMode(!this->trackedWindows.empty());
 }
 
 EngineGeneration* EngineGeneration::currentGeneration() {