Add auto-test for QT_USE_PHYSICAL_DPI

Test that setting QT_USE_PHYSICAL_DPI uses physical
DPI instead of logical DPI.

Change-Id: I7f89cf1af5e013454cc3d8ec3559f2719514fea3
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp b/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp
index 339ff0ed20..31a41eeff6 100644
--- a/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp
+++ b/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp
@@ -56,6 +56,7 @@ private slots:
     void screenDpiAndDpr();
     void environment_QT_SCALE_FACTOR();
     void environment_QT_SCREEN_SCALE_FACTORS();
+    void environment_QT_USE_PHYSICAL_DPI();
     void screenAt_data();
     void screenAt();
     void screenGeometry_data();
@@ -187,6 +188,7 @@ void tst_QHighDpi::cleanup()
     // in order to avoid getting confusing follow-on errors on test failures.
     qunsetenv("QT_SCALE_FACTOR");
     qunsetenv("QT_SCREEN_SCALE_FACTORS");
+    qunsetenv("QT_USE_PHYSICAL_DPI");
 }
 
 void tst_QHighDpi::qhighdpiscaling_data()
@@ -273,6 +275,31 @@ void tst_QHighDpi::environment_QT_SCREEN_SCALE_FACTORS()
     }
 }
 
+void tst_QHighDpi::environment_QT_USE_PHYSICAL_DPI()
+{
+    qputenv("QT_USE_PHYSICAL_DPI", "1");
+
+    QList<qreal> dpiValues { 96, 144, 192 };
+    std::unique_ptr<QGuiApplication> app(createStandardOffscreenApp(dpiValues));
+
+    // Verify that the device pixel ratio is computed as physicalDpi / baseDpi.
+    // (which in practice uses physicalSize since this is what QPlatformScreen provides)
+
+    // The default QPlatformScreen::physicalSize() implementation (which QOffscreenScreen
+    // currerently uses) assumes a default DPI of 100 and calculates a fake physical size
+    // based on that value. Use DPI 100 here as well: if you have changed the default value
+    // in QPlatformScreen and get a test failure then update the value below.
+    const qreal platformScreenDefualtDpi = 100;
+    qreal expextedDpr = (platformScreenDefualtDpi / qreal(standardBaseDpi));
+
+    for (QScreen *screen : app->screens()) {
+        QCOMPARE(screen->devicePixelRatio(), expextedDpr);
+        QCOMPARE(screen->logicalDotsPerInch(), 96);
+        QWindow window(screen);
+        QCOMPARE(window.devicePixelRatio(), expextedDpr);
+    }
+}
+
 void tst_QHighDpi::minimumDpr()
 {
     QList<qreal> dpiValues { 40, 60, 95 };