wayland/background-effect: attach effect surface when manager global appears late

changelog/next.md

@@ -12,3 +12,4 @@
 - Fixed unhandled notifications sending `NotificationClosed` out of order.
 - Fixed `qs kill` not waiting for the process to exit.
 - Fixed IPC calls from children of a crashed and relaunched process crashing.
+- Fixed BackgroundEffect never applying if the compositor announces ext-background-effect-v1 after surface creation.

src/wayland/background_effect/manager.cpp

@@ -32,7 +32,7 @@ void BackgroundEffectManager::ext_background_effect_manager_v1_capabilities(uint
 
 BackgroundEffectManager* BackgroundEffectManager::instance() {
 	static auto* instance = new BackgroundEffectManager(); // NOLINT
-	return instance->isInitialized() ? instance : nullptr;
+	return instance;
 }
 
 } // namespace qs::wayland::background_effect::impl

src/wayland/background_effect/qml.cpp

@@ -192,12 +192,40 @@ void BackgroundEffect::onWaylandWindowDestroyed() { this->mWaylandWindow = nullp
 void BackgroundEffect::onWaylandSurfaceCreated() {
 	auto* manager = impl::BackgroundEffectManager::instance();
 
-	if (!manager) {
-		qWarning() << "Cannot enable background effect as ext-background-effect-v1 is not supported "
-		              "by the current compositor.";
+	if (!manager->isActive()) {
+		qWarning() << "Cannot enable background effect as ext-background-effect-v1 is not currently "
+		              "supported by the compositor. The effect will be enabled if the protocol "
+		              "becomes available.";
+
+		// The manager global may be announced at any point, including after surfaces
+		// that want an effect are created.
+		QObject::connect(
+		    manager,
+		    &impl::BackgroundEffectManager::activeChanged,
+		    this,
+		    &BackgroundEffect::onManagerActiveChanged
+		);
+
 		return;
 	}
 
+	this->attachEffectSurface();
+}
+
+void BackgroundEffect::onManagerActiveChanged() {
+	auto* manager = impl::BackgroundEffectManager::instance();
+	if (!manager->isActive()) return;
+
+	QObject::disconnect(manager, nullptr, this, nullptr);
+
+	if (this->proxyWindow && this->mWaylandWindow && this->mWaylandWindow->surface()) {
+		this->attachEffectSurface();
+	}
+}
+
+void BackgroundEffect::attachEffectSurface() {
+	auto* manager = impl::BackgroundEffectManager::instance();
+
 	// Steal protocol surface from previous BackgroundEffect to avoid duplicate-attachment on reload.
 	auto v = this->mWaylandWindow->property("qs_background_effect");
 	if (v.canConvert<BackgroundEffect*>()) {
@@ -222,6 +250,8 @@ void BackgroundEffect::onWaylandSurfaceCreated() {
 }
 
 void BackgroundEffect::onWaylandSurfaceDestroyed() {
+	QObject::disconnect(impl::BackgroundEffectManager::instance(), nullptr, this, nullptr);
+
 	this->surface = nullptr;
 	this->pendingBlurRegion = false;
 

src/wayland/background_effect/qml.hpp

@@ -62,12 +62,15 @@ private slots:
 	void onWaylandWindowDestroyed();
 	void onWaylandSurfaceCreated();
 	void onWaylandSurfaceDestroyed();
+	void onManagerActiveChanged();
 	void onProxyWindowDestroyed();
 	void onBlurRegionDestroyed();
 	void onWindowPolished();
 	void updateBlurRegion();
 
 private:
+	void attachEffectSurface();
+
 	ProxyWindowBase* proxyWindow = nullptr;
 	QWindow* mWindow = nullptr;
 	QtWaylandClient::QWaylandWindow* mWaylandWindow = nullptr;