core/reloader: simplify generation teardown

The extra complexity previously masked the use after free in 6c95267.

src/core/generation.cpp

@@ -14,7 +14,6 @@
 #include <qqmlcontext.h>
 #include <qqmlengine.h>
 #include <qqmlincubator.h>
-#include <qtimer.h>
 #include <qtmetamacros.h>
 
 #include "iconimageprovider.hpp"
@@ -47,32 +46,30 @@ EngineGeneration::EngineGeneration(const QDir& rootPath, QmlScanner scanner)
 }
 
 EngineGeneration::~EngineGeneration() {
-	g_generations.remove(this->engine);
-	delete this->engine;
+	if (this->engine != nullptr) {
+		qFatal() << this << "destroyed without calling destroy()";
+	}
 }
 
 void EngineGeneration::destroy() {
 	// Multiple generations can detect a reload at the same time.
-	delete this->watcher;
+	QObject::disconnect(this->watcher, nullptr, this, nullptr);
+	this->watcher->deleteLater();
 	this->watcher = nullptr;
 
-	// Yes all of this is actually necessary.
 	if (this->engine != nullptr && this->root != nullptr) {
 		QObject::connect(this->root, &QObject::destroyed, this, [this]() {
-			// The timer seems to fix *one* of the possible qml item destructor crashes.
-			QTimer::singleShot(0, [this]() {
-				// Garbage is not collected during engine destruction.
-				this->engine->collectGarbage();
+			// prevent further js execution between garbage collection and engine destruction.
+			this->engine->setInterrupted(true);
 
-				QObject::connect(this->engine, &QObject::destroyed, this, [this]() { delete this; });
+			g_generations.remove(this->engine);
 
-				// Even after all of that there's still multiple failing assertions and segfaults.
-				// Pray you don't hit one.
-				// Note: it appeats *some* of the crashes are related to values owned by the generation.
-				// Test by commenting the connect() above.
-				this->engine->deleteLater();
-				this->engine = nullptr;
-			});
+			// Garbage is not collected during engine destruction.
+			this->engine->collectGarbage();
+
+			delete this->engine;
+			this->engine = nullptr;
+			delete this;
 		});
 
 		this->root->deleteLater();

src/core/rootwrapper.cpp

@@ -65,7 +65,7 @@ void RootWrapper::reloadGraph(bool hard) {
 	auto* obj = component.beginCreate(generation->engine->rootContext());
 
 	if (obj == nullptr) {
-		QString error = "failed to create root component\n" + component.errorString();
+		const QString error = "failed to create root component\n" + component.errorString();
 		qWarning().noquote() << error;
 		delete generation;
 
@@ -78,7 +78,7 @@ void RootWrapper::reloadGraph(bool hard) {
 
 	auto* newRoot = qobject_cast<ShellRoot*>(obj);
 	if (newRoot == nullptr) {
-		QString error = "root component was not a Quickshell.ShellRoot";
+		const QString error = "root component was not a Quickshell.ShellRoot";
 		qWarning().noquote() << error;
 		delete obj;
 		delete generation;
@@ -96,7 +96,11 @@ void RootWrapper::reloadGraph(bool hard) {
 
 	auto isReload = this->generation != nullptr;
 	generation->onReload(hard ? nullptr : this->generation);
-	if (hard) delete this->generation;
+
+	if (hard && this->generation != nullptr) {
+		this->generation->destroy();
+	}
+
 	this->generation = generation;
 
 	qInfo() << "Configuration Loaded";

src/wayland/wlr_layershell/surface.cpp

@@ -7,7 +7,6 @@
 #include <private/qwaylandsurface_p.h>
 #include <private/qwaylandwindow_p.h>
 #include <qlogging.h>
-#include <qpoint.h>
 #include <qrect.h>
 #include <qsize.h>
 #include <qtversionchecks.h>
@@ -18,6 +17,10 @@
 #include "shell_integration.hpp"
 #include "window.hpp"
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 7, 0)
+#include <qpoint.h>
+#endif
+
 // clang-format off
 [[nodiscard]] QtWayland::zwlr_layer_shell_v1::layer toWaylandLayer(const WlrLayer::Enum& layer) noexcept;
 [[nodiscard]] QtWayland::zwlr_layer_surface_v1::anchor toWaylandAnchors(const Anchors& anchors) noexcept;
@@ -72,7 +75,10 @@ QSWaylandLayerSurface::QSWaylandLayerSurface(
 }
 
 QSWaylandLayerSurface::~QSWaylandLayerSurface() {
-	this->ext->surface = nullptr;
+	if (this->ext != nullptr) {
+		this->ext->surface = nullptr;
+	}
+
 	this->destroy();
 }
 
@@ -106,6 +112,7 @@ void QSWaylandLayerSurface::applyConfigure() {
 }
 
 void QSWaylandLayerSurface::setWindowGeometry(const QRect& geometry) {
+	if (this->ext == nullptr) return;
 	auto size = constrainedSize(this->ext->mAnchors, geometry.size());
 	this->set_size(size.width(), size.height());
 }

src/wayland/wlr_layershell/window.cpp

@@ -13,6 +13,12 @@
 #include "shell_integration.hpp"
 #include "surface.hpp"
 
+LayershellWindowExtension::~LayershellWindowExtension() {
+	if (this->surface != nullptr) {
+		this->surface->ext = nullptr;
+	}
+}
+
 LayershellWindowExtension* LayershellWindowExtension::get(QWindow* window) {
 	auto v = window->property("layershell_ext");
 

src/wayland/wlr_layershell/window.hpp

@@ -2,6 +2,7 @@
 
 #include <qobject.h>
 #include <qscreen.h>
+#include <qtclasshelpermacros.h>
 #include <qtmetamacros.h>
 #include <qtypes.h>
 #include <qwindow.h>
@@ -56,6 +57,8 @@ class LayershellWindowExtension: public QObject {
 
 public:
 	LayershellWindowExtension(QObject* parent = nullptr): QObject(parent) {}
+	~LayershellWindowExtension() override;
+	Q_DISABLE_COPY_MOVE(LayershellWindowExtension);
 
 	// returns the layershell extension if attached, otherwise nullptr
 	static LayershellWindowExtension* get(QWindow* window);