QApplication: use desktopStyleKey if styleOverride was invalid

When the application is passed an invalid style option, we should fall
back to the style provided by the platform theme, not to the first
available style.

Change-Id: I59e25b00d4a32221dea7c960d0f4e0068247b2dd
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 8 insertions, 6 deletions

diff --git a/src/widgets/kernel/qapplication.cpp b/src/widgets/kernel/qapplication.cpp
index 9b8677e6a8..7fa3b26e45 100644
--- a/src/widgets/kernel/qapplication.cpp
+++ b/src/widgets/kernel/qapplication.cpp
@@ -1068,15 +1068,17 @@ QStyle *QApplication::style()
     if (!QApplicationPrivate::app_style) {
         // Compile-time search for default style
         //
-        QString style;
+        QStyle *&app_style = QApplicationPrivate::app_style;
+
         if (!QApplicationPrivate::styleOverride.isEmpty()) {
-            style = QApplicationPrivate::styleOverride.toLower();
-        } else {
-            style = QApplicationPrivate::desktopStyleKey();
+            const QString style = QApplicationPrivate::styleOverride.toLower();
+            app_style = QStyleFactory::create(style);
+            if (!app_style)
+                qWarning("QApplication: invalid style override passed, ignoring it.");
         }
+        if (!app_style)
+            app_style = QStyleFactory::create(QApplicationPrivate::desktopStyleKey());
 
-        QStyle *&app_style = QApplicationPrivate::app_style;
-        app_style = QStyleFactory::create(style);
         if (!app_style) {
             const QStringList styles = QStyleFactory::keys();
             for (const auto &style : styles) {