Quick: Fortify QQuickApplication ctor

If the qApp we have is in fact not a QGuiApplication we cannot
connect those signals. The "if (qApp)" was probably supposed to check
for this but actually doesn't because qApp is a static_cast.

Change-Id: Iaa30e3d56768e97601d51d30500fc3b12d0626a3
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 8a555cc22afb93dbe0e0da83f211c6e4f032bd09)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 13 insertions, 12 deletions

diff --git a/src/quick/util/qquickapplication.cpp b/src/quick/util/qquickapplication.cpp
index 1c0522451a..fa67823824 100644
--- a/src/quick/util/qquickapplication.cpp
+++ b/src/quick/util/qquickapplication.cpp
@@ -58,18 +58,19 @@ QT_BEGIN_NAMESPACE
 QQuickApplication::QQuickApplication(QObject *parent)
     : QQmlApplication(parent)
 {
-    if (qApp) {
-        connect(qApp, SIGNAL(layoutDirectionChanged(Qt::LayoutDirection)),
-                this, SIGNAL(layoutDirectionChanged()));
-        connect(qApp, SIGNAL(applicationStateChanged(Qt::ApplicationState)),
-                this, SIGNAL(stateChanged(Qt::ApplicationState)));
-        connect(qApp, SIGNAL(applicationStateChanged(Qt::ApplicationState)),
-                this, SIGNAL(activeChanged()));
-        connect(qApp, SIGNAL(applicationDisplayNameChanged()),
-                this, SIGNAL(displayNameChanged()));
-
-        connect(qApp, &QGuiApplication::screenAdded, this, &QQuickApplication::updateScreens);
-        connect(qApp, &QGuiApplication::screenRemoved, this, &QQuickApplication::updateScreens);
+    QCoreApplication *app = QCoreApplication::instance();
+    if (QGuiApplication *guiApp = qobject_cast<QGuiApplication *>(app)) {
+        connect(guiApp, &QGuiApplication::layoutDirectionChanged,
+                this, &QQuickApplication::layoutDirectionChanged);
+        connect(guiApp, &QGuiApplication::applicationStateChanged,
+                this, &QQuickApplication::stateChanged);
+        connect(guiApp, &QGuiApplication::applicationStateChanged,
+                this, &QQuickApplication::activeChanged);
+        connect(guiApp, &QGuiApplication::applicationDisplayNameChanged,
+                this, &QQuickApplication::displayNameChanged);
+
+        connect(guiApp, &QGuiApplication::screenAdded, this, &QQuickApplication::updateScreens);
+        connect(guiApp, &QGuiApplication::screenRemoved, this, &QQuickApplication::updateScreens);
         updateScreens();
     }
 }