Screen attached property: expose devicePixelRatio property

Change-Id: I08b22766b3e389b7d27ca4c56729f550b0647a08
Reviewed-by: Jens Bache-Wiig <jensbw@gmail.com>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>

2 files changed, 21 insertions, 0 deletions

diff --git a/src/quick/items/qquickscreen.cpp b/src/quick/items/qquickscreen.cpp
index 926ac7b4ee..8ac5a1e292 100644
--- a/src/quick/items/qquickscreen.cpp
+++ b/src/quick/items/qquickscreen.cpp
@@ -142,6 +142,15 @@ QT_BEGIN_NAMESPACE
     The number of physical pixels per millimeter.
 */
 /*!
+    \qmlattachedproperty real Screen::devicePixelRatio
+    \readonly
+    \since 5.4
+
+    The ratio between physical pixels and device-independent pixels for the screen.
+
+    Common values are 1.0 on normal displays and 2.0 on Apple "retina" displays.
+*/
+/*!
     \qmlattachedproperty Qt::ScreenOrientation Screen::primaryOrientation
     \readonly
 
@@ -260,6 +269,13 @@ qreal QQuickScreenAttached::pixelDensity() const
     return m_screen->physicalDotsPerInch() / 25.4;
 }
 
+qreal QQuickScreenAttached::devicePixelRatio() const
+{
+    if (!m_screen)
+        return 1.0;
+    return m_screen->devicePixelRatio();
+}
+
 Qt::ScreenOrientation QQuickScreenAttached::primaryOrientation() const
 {
     if (!m_screen)
@@ -340,6 +356,8 @@ void QQuickScreenAttached::screenChanged(QScreen *screen)
             emit logicalPixelDensityChanged();
         if (!oldScreen || screen->physicalDotsPerInch() != oldScreen->physicalDotsPerInch())
             emit pixelDensityChanged();
+        if (!oldScreen || screen->devicePixelRatio() != oldScreen->devicePixelRatio())
+            emit devicePixelRatioChanged();
 
         connect(screen, SIGNAL(geometryChanged(QRect)),
                 this, SIGNAL(widthChanged()));
diff --git a/src/quick/items/qquickscreen_p.h b/src/quick/items/qquickscreen_p.h
index d661cc6f56..257b18cfe0 100644
--- a/src/quick/items/qquickscreen_p.h
+++ b/src/quick/items/qquickscreen_p.h
@@ -57,6 +57,7 @@ class Q_AUTOTEST_EXPORT QQuickScreenAttached : public QObject
     Q_PROPERTY(int desktopAvailableHeight READ desktopAvailableHeight NOTIFY desktopGeometryChanged)
     Q_PROPERTY(qreal logicalPixelDensity READ logicalPixelDensity NOTIFY logicalPixelDensityChanged)
     Q_PROPERTY(qreal pixelDensity READ pixelDensity NOTIFY pixelDensityChanged)
+    Q_PROPERTY(qreal devicePixelRatio READ devicePixelRatio NOTIFY devicePixelRatioChanged)
     // TODO Qt 6 Rename primaryOrientation to orientation
     Q_PROPERTY(Qt::ScreenOrientation primaryOrientation READ primaryOrientation NOTIFY primaryOrientationChanged)
     // TODO Qt 6 Remove this orientation -> incomplete device orientation -> better use OrientationSensor
@@ -74,6 +75,7 @@ public:
     int desktopAvailableHeight() const;
     qreal logicalPixelDensity() const;
     qreal pixelDensity() const;
+    qreal devicePixelRatio() const;
     Qt::ScreenOrientation primaryOrientation() const;
     Qt::ScreenOrientation orientation() const;
     Qt::ScreenOrientations orientationUpdateMask() const;
@@ -91,6 +93,7 @@ Q_SIGNALS:
     void desktopGeometryChanged();
     void logicalPixelDensityChanged();
     void pixelDensityChanged();
+    void devicePixelRatioChanged();
     void primaryOrientationChanged();
     void orientationChanged();
     void orientationUpdateMaskChanged();