QScreen manual test: don't crash when a QScreen is null

Need to survive having screens detached/reattached on X11.

Task-number: QTBUG-42985
Change-Id: I81cf9721f0cb61a29180c60d44d588063266e651
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>

1 files changed, 13 insertions, 4 deletions

diff --git a/tests/manual/qscreen/main.cpp b/tests/manual/qscreen/main.cpp
index 8ed9cebfb4..298996a59b 100644
--- a/tests/manual/qscreen/main.cpp
+++ b/tests/manual/qscreen/main.cpp
@@ -131,10 +131,19 @@ static inline QString msgScreenChange(const QWidget *w, const QScreen *oldScreen
     QString result;
     const QRect geometry = w->geometry();
     const QPoint pos = QCursor::pos();
-    QTextStream(&result) << "Screen changed \"" << oldScreen->name() << "\" --> \""
-        << newScreen->name() << "\" at " << pos.x() << ',' << pos.y() << " geometry: "
-        << geometry.width() << 'x' << geometry.height() << forcesign << geometry.x()
-        << geometry.y() << '.';
+    if (!newScreen) {
+        result = QLatin1String("Screen changed --> null");
+    } else if (!oldScreen) {
+        QTextStream(&result) << "Screen changed null --> \""
+            << newScreen->name() << "\" at " << pos.x() << ',' << pos.y() << " geometry: "
+            << geometry.width() << 'x' << geometry.height() << forcesign << geometry.x()
+            << geometry.y() << '.';
+    } else {
+        QTextStream(&result) << "Screen changed \"" << oldScreen->name() << "\" --> \""
+            << newScreen->name() << "\" at " << pos.x() << ',' << pos.y() << " geometry: "
+            << geometry.width() << 'x' << geometry.height() << forcesign << geometry.x()
+            << geometry.y() << '.';
+    }
     return result;
 }