Fix check whether there is already a ShellSurface for a given Surface

Incorrect logic prevented that more than one ShellSurface could be
created.

src/wayland/autotests/client/test_wayland_shell.cpp

@@ -43,6 +43,7 @@ private Q_SLOTS:
     void init();
     void cleanup();
 
+    void testCreateMultiple();
     void testFullscreen();
     void testPing();
     void testTitle();
@@ -169,6 +170,43 @@ void TestWaylandShell::cleanup()
     m_display = nullptr;
 }
 
+void TestWaylandShell::testCreateMultiple()
+{
+    using namespace KWayland::Server;
+    using namespace KWayland::Client;
+
+    QScopedPointer<Surface> s1(m_compositor->createSurface());
+    QScopedPointer<Surface> s2(m_compositor->createSurface());
+    QVERIFY(!s1.isNull());
+    QVERIFY(s1->isValid());
+    QVERIFY(!s2.isNull());
+    QVERIFY(s2->isValid());
+
+    QSignalSpy serverSurfaceSpy(m_shellInterface, SIGNAL(surfaceCreated(KWayland::Server::ShellSurfaceInterface*)));
+    QVERIFY(serverSurfaceSpy.isValid());
+    QScopedPointer<ShellSurface> surface1(m_shell->createSurface(s1.data()));
+    QVERIFY(!surface1.isNull());
+    QVERIFY(surface1->isValid());
+
+    QVERIFY(serverSurfaceSpy.wait());
+    QCOMPARE(serverSurfaceSpy.count(), 1);
+
+    QScopedPointer<ShellSurface> surface2(m_shell->createSurface(s2.data()));
+    QVERIFY(!surface2.isNull());
+    QVERIFY(surface2->isValid());
+
+    QVERIFY(serverSurfaceSpy.wait());
+    QCOMPARE(serverSurfaceSpy.count(), 2);
+
+    // try creating for one which already exist should not be possible
+    QScopedPointer<ShellSurface> surface3(m_shell->createSurface(s2.data()));
+    QVERIFY(!surface3.isNull());
+    QVERIFY(surface3->isValid());
+
+    QVERIFY(!serverSurfaceSpy.wait(100));
+    QCOMPARE(serverSurfaceSpy.count(), 2);
+}
+
 void TestWaylandShell::testFullscreen()
 {
     using namespace KWayland::Server;

src/wayland/server/shell_interface.cpp

@@ -176,7 +176,7 @@ void ShellInterface::Private::createSurface(wl_client *client, uint32_t version,
             return surface == s->surface();
         }
     );
-    if (it != surfaces.constBegin()) {
+    if (it != surfaces.constEnd()) {
         wl_resource_post_error(surface->surface(), WL_DISPLAY_ERROR_INVALID_OBJECT, "ShellSurface already created");
         return;
     }