wayland: resolve session lock crashes on unlock, sleep, and output changes

- Destroys Wayland lock surface roles synchronously prior to sending unlock_and_destroy.
- Avoids creating lock surfaces on invalid/placeholder/removed outputs to prevent early initialization failures.
- Fixes Qt 6.6.3 compilation compatibility when QPointer uses incomplete forward-declared types.
- Reverts memory cleanup to asynchronous deleteLater() for QML safety.

Author: Luke458

changelog/next.md

@@ -4,3 +4,4 @@
 - Fixed WlSessionLockSurface.visible crashing if accessed before backing surface creation.
 - Fixed mpris players returning `rate` for `minRate` and `maxRate`.
 - Fixed missing/wrong change signals on various properties.
+- Fixed multiple session lock client crashes on sleep, wake, DPMS, and unlocking.

src/wayland/session_lock.cpp

@@ -56,9 +56,12 @@ void WlSessionLock::updateSurfaces(bool show, WlSessionLock* old) {
 	auto screens = QGuiApplication::screens();
 
 	screens.removeIf([](QScreen* screen) {
-		if (dynamic_cast<QtWaylandClient::QWaylandScreen*>(screen->handle()) == nullptr) {
+		auto* waylandScreen = dynamic_cast<QtWaylandClient::QWaylandScreen*>(screen->handle());
+		if (waylandScreen == nullptr || waylandScreen->isPlaceholder()
+		    || waylandScreen->output() == nullptr)
+		{
 			qDebug() << "Not creating lock surface for screen" << screen
-			         << "as it is not backed by a wayland screen.";
+			         << "as it is not backed by a valid wayland output.";
 
 			return true;
 		}
@@ -144,7 +147,6 @@ void WlSessionLock::unlock() {
 		for (auto* surface: this->surfaces) {
 			surface->deleteLater();
 		}
-
 		this->surfaces.clear();
 
 		emit this->lockStateChanged();
@@ -207,6 +209,7 @@ WlSessionLockSurface::WlSessionLockSurface(QObject* parent)
 
 WlSessionLockSurface::~WlSessionLockSurface() {
 	if (this->window != nullptr) {
+		this->window->destroy();
 		this->window->deleteLater();
 	}
 }

src/wayland/session_lock.hpp

@@ -185,4 +185,6 @@ private slots:
 	QScreen* mScreen = nullptr;
 	QColor mColor = Qt::white;
 	LockWindowExtension* ext;
+
+	friend class WlSessionLock;
 };

src/wayland/session_lock/session_lock.cpp

@@ -4,6 +4,7 @@
 #include <qlogging.h>
 #include <qobject.h>
 #include <qwindow.h>
+#include <wayland-client.h> // NOLINT(misc-include-cleaner)
 
 #include "lock.hpp"
 #include "manager.hpp"
@@ -49,6 +50,8 @@ bool SessionLockManager::isLocked() const { return this->mLock != nullptr; }
 bool SessionLockManager::sessionLocked() { return manager()->isLocked(); }
 bool SessionLockManager::isSecure() { return manager()->isSecure(); }
 
+LockWindowExtension::LockWindowExtension(QObject* parent): QObject(parent) {}
+
 LockWindowExtension::~LockWindowExtension() {
 	if (this->surface != nullptr) {
 		this->surface->setExtension(nullptr);

src/wayland/session_lock/session_lock.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <qobject.h>
+#include <qpointer.h>
 #include <qtclasshelpermacros.h>
 #include <qtmetamacros.h>
 #include <qwindow.h>
@@ -59,7 +60,7 @@ class LockWindowExtension: public QObject {
 	Q_OBJECT;
 
 public:
-	explicit LockWindowExtension(QObject* parent = nullptr): QObject(parent) {}
+	explicit LockWindowExtension(QObject* parent = nullptr);
 	~LockWindowExtension() override;
 	Q_DISABLE_COPY_MOVE(LockWindowExtension);
 

src/wayland/session_lock/surface.cpp

@@ -21,7 +21,8 @@ QSWaylandSessionLockSurface::QSWaylandSessionLockSurface(QtWaylandClient::QWayla
 		qFatal() << "QSWaylandSessionLockSurface created with null LockWindowExtension";
 	}
 
-	if (this->ext->lock == nullptr) {
+	auto* lock = this->ext->lock;
+	if (lock == nullptr) {
 		qFatal() << "QSWaylandSessionLock for QSWaylandSessionLockSurface died";
 	}
 
@@ -34,11 +35,18 @@ QSWaylandSessionLockSurface::QSWaylandSessionLockSurface(QtWaylandClient::QWayla
 		qFatal() << "Session lock screen does not correspond to a real screen. Force closing window";
 	}
 
-	this->init(this->ext->lock->get_lock_surface(window->waylandSurface()->object(), output));
+	this->init(lock->get_lock_surface(window->waylandSurface()->object(), output));
 }
 
 QSWaylandSessionLockSurface::~QSWaylandSessionLockSurface() {
-	if (this->ext != nullptr) this->ext->surface = nullptr;
+	if (this->object() == nullptr) {
+		return;
+	}
+
+	if (this->ext != nullptr) {
+		this->ext->surface = nullptr;
+	}
+
 	this->destroy();
 }