2 files changed, 42 insertions, 45 deletions

diff --git a/src/gui/kernel/qhighdpiscaling.cpp b/src/gui/kernel/qhighdpiscaling.cpp
index 93fcb1a216..0fea416404 100644
--- a/src/gui/kernel/qhighdpiscaling.cpp
+++ b/src/gui/kernel/qhighdpiscaling.cpp
@@ -452,52 +452,30 @@ QDpi QHighDpiScaling::logicalDpi()
     return m_logicalDpi;
 }
 
-qreal QHighDpiScaling::factor(const QScreen *screen)
+QHighDpiScaling::ScaleAndOrigin QHighDpiScaling::scaleAndOrigin(const QPlatformScreen *platformScreen, QPoint *nativePosition)
 {
-    // Fast path for when scaling in Qt is not used at all.
     if (!m_active)
-        return qreal(1.0);
-
-    // The effective factor for a given screen is the product of the
-    // screen and global sub-factors
-    qreal factor = m_factor;
-    if (screen)
-        factor *= screenSubfactor(screen->handle());
-    return factor;
+        return { qreal(1), QPoint() };
+    const QPlatformScreen *actualScreen = nativePosition ?
+        platformScreen->screenForPosition(*nativePosition) : platformScreen;
+    return { m_factor * screenSubfactor(actualScreen), actualScreen->geometry().topLeft() };
 }
 
-qreal QHighDpiScaling::factor(const QPlatformScreen *platformScreen)
+QHighDpiScaling::ScaleAndOrigin QHighDpiScaling::scaleAndOrigin(const QScreen *screen, QPoint *nativePosition)
 {
     if (!m_active)
-        return qreal(1.0);
-
-    return m_factor * screenSubfactor(platformScreen);
+        return { qreal(1), QPoint() };
+    if (!screen)
+        return { m_factor, QPoint() }; // the global factor
+    return scaleAndOrigin(screen->handle(), nativePosition);
 }
 
-qreal QHighDpiScaling::factor(const QWindow *window)
+QHighDpiScaling::ScaleAndOrigin QHighDpiScaling::scaleAndOrigin(const QWindow *window, QPoint *nativePosition)
 {
     if (!m_active)
-        return qreal(1.0);
-
-    return factor(window ? window->screen() : QGuiApplication::primaryScreen());
-}
-
-QPoint QHighDpiScaling::origin(const QScreen *screen)
-{
-    return screen->geometry().topLeft();
-}
-
-QPoint QHighDpiScaling::origin(const QPlatformScreen *platformScreen)
-{
-    return platformScreen->geometry().topLeft();
-}
-
-QPoint QHighDpiScaling::origin(const QWindow *window)
-{
-    if (window && window->isTopLevel() && window->screen())
-        return window->screen()->geometry().topLeft();
-
-    return QPoint(0, 0);
+        return { qreal(1), QPoint() };
+    QScreen *screen = window ? window->screen() : QGuiApplication::primaryScreen();
+    return scaleAndOrigin(screen, nativePosition);
 }
 
 #endif //QT_NO_HIGHDPISCALING
diff --git a/src/gui/kernel/qhighdpiscaling_p.h b/src/gui/kernel/qhighdpiscaling_p.h
index 525e3fe78e..3410c1d345 100644
--- a/src/gui/kernel/qhighdpiscaling_p.h
+++ b/src/gui/kernel/qhighdpiscaling_p.h
@@ -78,14 +78,23 @@ public:
     static void setScreenFactor(QScreen *window, qreal factor);
 
     static bool isActive() { return m_active; }
-    static qreal factor(const QWindow *window);
-    static qreal factor(const QScreen *screen);
-    static qreal factor(const QPlatformScreen *platformScreen);
-    static QPoint origin(const QScreen *screen);
-    static QPoint origin(const QPlatformScreen *platformScreen);
-    static QPoint origin(const QWindow *window);
-    static QPoint mapPositionToNative(const QPoint &pos, const QPlatformScreen *platformScreen);
+
+    struct ScaleAndOrigin
+    {
+        qreal factor;
+        QPoint origin;
+    };
+    static ScaleAndOrigin scaleAndOrigin(const QPlatformScreen *platformScreen, QPoint *nativePosition = nullptr);
+    static ScaleAndOrigin scaleAndOrigin(const QScreen *screen, QPoint *nativePosition = nullptr);
+    static ScaleAndOrigin scaleAndOrigin(const QWindow *platformScreen, QPoint *nativePosition = nullptr);
+
+    template<typename C>
+    static qreal factor(C *context, QPoint *nativePosition = nullptr) {
+        return scaleAndOrigin(context, nativePosition).factor;
+    }
+
     static QPoint mapPositionFromNative(const QPoint &pos, const QPlatformScreen *platformScreen);
+    static QPoint mapPositionToNative(const QPoint &pos, const QPlatformScreen *platformScreen);
     static QPoint mapPositionToGlobal(const QPoint &pos, const QPoint &windowGlobalPosition, const QWindow *window);
     static QPoint mapPositionFromGlobal(const QPoint &pos, const QPoint &windowGlobalPosition, const QWindow *window);
     static QDpi logicalDpi();
@@ -166,16 +175,26 @@ inline QRegion scale(const QRegion &region, qreal scaleFactor, QPoint origin = Q
     return scaled;
 }
 
+template <typename T>
+inline QPoint position(T) { return QPoint(); }
+inline QPoint position(QPoint point) { return point; }
+inline QPoint position(QPointF point) { return point.toPoint(); }
+inline QPoint position(QRect rect) { return rect.center(); }
+inline QPoint position(QRectF rect) { return rect.center().toPoint(); }
+
 template <typename T, typename C>
 T fromNativePixels(const T &value, const C *context)
 {
-    return scale(value, qreal(1) / QHighDpiScaling::factor(context), QHighDpiScaling::origin(context));
+    QPoint nativePosition = position(value);
+    QHighDpiScaling::ScaleAndOrigin so = QHighDpiScaling::scaleAndOrigin(context, &nativePosition);
+    return scale(value, qreal(1) / so.factor, so.origin);
 }
 
 template <typename T, typename C>
 T toNativePixels(const T &value, const C *context)
 {
-    return scale(value, QHighDpiScaling::factor(context), QHighDpiScaling::origin(context));
+    QHighDpiScaling::ScaleAndOrigin so = QHighDpiScaling::scaleAndOrigin(context);
+    return scale(value, so.factor, so.origin);
 }
 
 template <typename T, typename C>