Fix handling of the case where specified surface can't imported

An xdg_imported resource must be created no matter whether there is an
exported surface with the specified handle.

This change fixes handling of that case in kwaylandserver by introducing
a dummy imported object.

If there is no exported surface with the given handle, the compositor
should create an xdg_imported resource and immediately send the
destroyed event.

A dummy imported object is needed because generated code sets resource
implementation; otherwise we would set an implementation without any
user data to mark the resource as inert.

src/wayland/autotests/client/test_xdg_foreign.cpp

@@ -37,6 +37,7 @@ private Q_SLOTS:
     void testDeleteExported();
     void testExportTwoTimes();
     void testImportTwoTimes();
+    void testImportInvalidToplevel();
 
 private:
     void doExport();
@@ -353,5 +354,17 @@ void TestForeign::testImportTwoTimes()
     QCOMPARE(m_foreignInterface->transientFor(childSurface2Interface), m_exportedSurfaceInterface.data());
 }
 
+void TestForeign::testImportInvalidToplevel()
+{
+    // This test verifies that the compositor properly handles the case where a client
+    // attempts to import a toplevel with an invalid handle.
+
+    KWayland::Client::XdgImported *imported = m_importer->importTopLevel(QStringLiteral("foobar"));
+    QVERIFY(imported->isValid());
+
+    QSignalSpy importedDestroySpy(imported, &KWayland::Client::XdgImported::importedDestroyed);
+    QVERIFY(importedDestroySpy.wait());
+}
+
 QTEST_GUILESS_MAIN(TestForeign)
 #include "test_xdg_foreign.moc"

src/wayland/xdgforeign_v2_interface.cpp

@@ -111,12 +111,6 @@ void XdgImporterV2Interface::zxdg_importer_v2_destroy(Resource *resource)
 
 void XdgImporterV2Interface::zxdg_importer_v2_import_toplevel(Resource *resource, uint32_t id, const QString &handle)
 {
-    XdgExportedV2Interface *exported = m_foreign->d->exporter->exportedSurface(handle);
-    if (!exported) {
-        zxdg_imported_v2_send_destroyed(resource->handle);
-        return;
-    }
-
     wl_resource *importedResource = wl_resource_create(resource->client(),
                                                        &zxdg_imported_v2_interface,
                                                        resource->version(), id);
@@ -125,6 +119,15 @@ void XdgImporterV2Interface::zxdg_importer_v2_import_toplevel(Resource *resource
         return;
     }
 
+    // If there is no exported surface with the specified handle, we must still create an
+    // inert xdg_imported object and send the destroyed event right afterwards.
+    XdgExportedV2Interface *exported = m_foreign->d->exporter->exportedSurface(handle);
+    if (!exported) {
+        auto imported = new XdgDummyImportedV2Interface(importedResource);
+        imported->send_destroyed();
+        return;
+    }
+
     XdgImportedV2Interface *imported = new XdgImportedV2Interface(exported, importedResource);
 
     connect(imported, &XdgImportedV2Interface::childChanged, this, [this, imported](SurfaceInterface *child) {
@@ -196,6 +199,22 @@ void XdgExportedV2Interface::handleSurfaceDestroyed()
     delete this;
 }
 
+XdgDummyImportedV2Interface::XdgDummyImportedV2Interface(wl_resource *resource)
+    : QtWaylandServer::zxdg_imported_v2(resource)
+{
+}
+
+void XdgDummyImportedV2Interface::zxdg_imported_v2_destroy(Resource *resource)
+{
+    wl_resource_destroy(resource->handle);
+}
+
+void XdgDummyImportedV2Interface::zxdg_imported_v2_destroy_resource(Resource *resource)
+{
+    Q_UNUSED(resource)
+    delete this;
+}
+
 XdgImportedV2Interface::XdgImportedV2Interface(XdgExportedV2Interface *exported, wl_resource *resource)
     : QtWaylandServer::zxdg_imported_v2(resource)
     , m_exported(exported)

src/wayland/xdgforeign_v2_interface_p.h

@@ -87,6 +87,16 @@ private:
     SurfaceInterface *m_surface;
 };
 
+class XdgDummyImportedV2Interface : public QtWaylandServer::zxdg_imported_v2
+{
+public:
+    explicit XdgDummyImportedV2Interface(wl_resource *resource);
+
+protected:
+    void zxdg_imported_v2_destroy(Resource *resource) override;
+    void zxdg_imported_v2_destroy_resource(Resource *resource) override;
+};
+
 class XdgImportedV2Interface : public QObject, QtWaylandServer::zxdg_imported_v2
 {
     Q_OBJECT