Add nullptr guard to QHighDScaling::scaleAndOrigin(QPlatformScreen *)

Commit b6ded193 added an unconditional dereference
of the platformScreen pointer, for calls where nativePostion
is non-nullptr.

Change-Id: I4a6fbbd0337f91d4fcb76c17b4dc60e1b9ad10ed
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 18 insertions, 0 deletions

diff --git a/tests/auto/gui/kernel/qhighdpiscaling/tst_qhighdpiscaling.cpp b/tests/auto/gui/kernel/qhighdpiscaling/tst_qhighdpiscaling.cpp
index 969b2351ec..ec80c2d02c 100644
--- a/tests/auto/gui/kernel/qhighdpiscaling/tst_qhighdpiscaling.cpp
+++ b/tests/auto/gui/kernel/qhighdpiscaling/tst_qhighdpiscaling.cpp
@@ -36,6 +36,7 @@ class tst_QHighDpiScaling: public QObject
     Q_OBJECT
 
 private slots:
+    void factor();
     void scale();
 };
 
@@ -50,6 +51,23 @@ public:
     QImage::Format format() const override { return QImage::Format_ARGB32_Premultiplied; }
 };
 
+void tst_QHighDpiScaling::factor()
+{
+    QHighDpiScaling::setGlobalFactor(2);
+
+    // Verfy that QHighDpiScaling::factor() does not crash on nullptr contexts.
+    QPoint fakeNativePosition = QPoint(5, 5);
+    QPlatformScreen *screenContext = nullptr;
+    QVERIFY(QHighDpiScaling::factor(screenContext) >= 0);
+    QVERIFY(QHighDpiScaling::factor(screenContext, &fakeNativePosition) >= 0);
+    QPlatformScreen *platformScreenContext = nullptr;
+    QVERIFY(QHighDpiScaling::factor(platformScreenContext) >= 0);
+    QVERIFY(QHighDpiScaling::factor(platformScreenContext, &fakeNativePosition) >= 0);
+    QWindow *windowContext = nullptr;
+    QVERIFY(QHighDpiScaling::factor(windowContext) >= 0);
+    QVERIFY(QHighDpiScaling::factor(windowContext, &fakeNativePosition) >= 0);
+}
+
 // QTBUG-77255: Test some scaling overloads
 void tst_QHighDpiScaling::scale()
 {