launch: initialize QuickshellTracked before almost anything else

This fixes consumers like WlSessionLock getting connections to
QGuiApplication::screenAdded before QuickshellTracked::updateScreens
can run if the user never references the Quickshell singleton from QML
first.

changelog/next.md

@@ -4,3 +4,4 @@
 - Fixed crashes when attempting to create or modify session locks reentrantly.
 - Fixed networking state breaking after restarting NetworkManager.
 - Fixed accessibility information not being provided for Quickshell windows.
+- Fixed `WlSessionLockSurface.screen` being null and never updating with a real screen on monitor plug.

src/core/qmlglobal.cpp

@@ -88,6 +88,8 @@ QuickshellTracked::QuickshellTracked() {
 	}
 }
 
+// FIXME: Some callers can potentially pass a freed QScreen here which is why we don't init a new one.
+// The QuickshellTracked::init() in launch.cpp makes sure our screenAdded handler runs first for now.
 QuickshellScreenInfo* QuickshellTracked::screenInfo(QScreen* screen) const {
 	for (auto* info: this->screens) {
 		if (info->screen == screen) return info;
@@ -96,13 +98,19 @@ QuickshellScreenInfo* QuickshellTracked::screenInfo(QScreen* screen) const {
 	return nullptr;
 }
 
+namespace {
+static QuickshellTracked* qsTrackedInstance = nullptr; // NOLINT
+}
+
+void QuickshellTracked::init() {
+	if (qsTrackedInstance) qFatal() << "Tried to reinitialize QuickshellTracked";
+	qsTrackedInstance = new QuickshellTracked();
+	QJSEngine::setObjectOwnership(qsTrackedInstance, QJSEngine::CppOwnership);
+}
+
 QuickshellTracked* QuickshellTracked::instance() {
-	static QuickshellTracked* instance = nullptr; // NOLINT
-	if (instance == nullptr) {
-		QJSEngine::setObjectOwnership(instance, QJSEngine::CppOwnership);
-		instance = new QuickshellTracked();
-	}
-	return instance;
+	if (!qsTrackedInstance) qFatal() << "Tried to get QuickshellTracked instance before init";
+	return qsTrackedInstance;
 }
 
 void QuickshellTracked::updateScreens() {

src/core/qmlglobal.hpp

@@ -70,6 +70,7 @@ public:
 	QVector<QuickshellScreenInfo*> screens;
 	QuickshellScreenInfo* screenInfo(QScreen* screen) const;
 
+	static void init();
 	static QuickshellTracked* instance();
 
 private slots:

src/launch/launch.cpp

@@ -22,6 +22,7 @@
 #include "../core/logging.hpp"
 #include "../core/paths.hpp"
 #include "../core/plugin.hpp"
+#include "../core/qmlglobal.hpp"
 #include "../core/rootwrapper.hpp"
 #include "../ipc/ipc.hpp"
 #include "build.hpp"
@@ -299,6 +300,10 @@ int launch(const LaunchArgs& args, char** argv) {
 		QQmlDebuggingEnabler::startTcpDebugServer(args.debugPort, wait);
 	}
 
+	// This needs to run early to get the first connection to QGuiApplication::screenAdded() in Qs.
+	// If we don't do that, attempts to get a QuickshellScreenInfo from a QScreen will fail in screenAdded bindings.
+	QuickshellTracked::init();
+
 	QsEnginePlugin::initPlugins();
 
 	// Base window transparency appears to be additive.