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diff --git a/tests/auto/gui/kernel/qhighdpiscaling/tst_qhighdpiscaling.cpp b/tests/auto/gui/kernel/qhighdpiscaling/tst_qhighdpiscaling.cpp
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+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <private/qhighdpiscaling_p.h>
+#include <qpa/qplatformscreen.h>
+
+#include <QtTest/QtTest>
+
+class tst_QHighDpiScaling: public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void factor();
+    void scale();
+};
+
+// Emulate the case of a High DPI secondary screen
+class MyPlatformScreen : public QPlatformScreen
+{
+public:
+    QRect geometry() const override { return QRect(3840, 0, 3840, 1920); }
+    QRect availableGeometry() const override { return geometry(); }
+
+    int depth() const override { return 32; }
+    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()
+{
+    QHighDpiScaling::setGlobalFactor(2);
+    QScopedPointer<QPlatformScreen> screen(new MyPlatformScreen);
+
+    qreal nativeValue = 10;
+    const qreal value = QHighDpi::fromNativePixels(nativeValue, screen.data());
+    QCOMPARE(value, qreal(5));
+    QCOMPARE(QHighDpi::toNativePixels(value, screen.data()), nativeValue);
+
+    // 10, 10 within screen should translate to 5,5 with origin preserved
+    const QPoint nativePoint = screen->geometry().topLeft() + QPoint(10, 10);
+    const QPoint point = QHighDpi::fromNativePixels(nativePoint, screen.data());
+    QCOMPARE(point, QPoint(3845, 5));
+    QCOMPARE(QHighDpi::toNativePixels(point, screen.data()), nativePoint);
+
+    const QPointF nativePointF(nativePoint);
+    const QPointF pointF = QHighDpi::fromNativePixels(nativePointF, screen.data());
+    QCOMPARE(pointF, QPointF(3845, 5));
+    QCOMPARE(QHighDpi::toNativePixels(pointF, screen.data()), nativePointF);
+}
+
+#include "tst_qhighdpiscaling.moc"
+QTEST_MAIN(tst_QHighDpiScaling);