5 files changed, 30 insertions, 4 deletions

diff --git a/src/corelib/kernel/qcoreevent.cpp b/src/corelib/kernel/qcoreevent.cpp
index bc54a2ae74..044128998b 100644
--- a/src/corelib/kernel/qcoreevent.cpp
+++ b/src/corelib/kernel/qcoreevent.cpp
@@ -278,6 +278,7 @@ QT_BEGIN_NAMESPACE
     \omitvalue FutureCallOut
     \omitvalue NativeGesture
     \omitvalue WindowChangeInternal
+    \omitvalue ScreenChangeInternal
 */
 
 /*!
diff --git a/src/corelib/kernel/qcoreevent.h b/src/corelib/kernel/qcoreevent.h
index cd7689f842..bd5a5187e3 100644
--- a/src/corelib/kernel/qcoreevent.h
+++ b/src/corelib/kernel/qcoreevent.h
@@ -281,6 +281,7 @@ public:
         ApplicationStateChange = 214,
 
         WindowChangeInternal = 215,             // internal for QQuickWidget
+        ScreenChangeInternal = 216,
 
         // 512 reserved for Qt Jambi's MetaCall event
         // 513 reserved for Qt Jambi's DeleteOnMainThread event
diff --git a/src/widgets/kernel/qopenglwidget.cpp b/src/widgets/kernel/qopenglwidget.cpp
index 8f7751618d..4eee4e526d 100644
--- a/src/widgets/kernel/qopenglwidget.cpp
+++ b/src/widgets/kernel/qopenglwidget.cpp
@@ -1061,6 +1061,10 @@ bool QOpenGLWidget::event(QEvent *e)
                 d->recreateFbo();
         }
         break;
+    case QEvent::ScreenChangeInternal:
+        if (d->initialized && d->paintDevice->devicePixelRatio() != devicePixelRatio())
+            d->recreateFbo();
+        break;
     default:
         break;
     }
diff --git a/src/widgets/kernel/qwidgetwindow.cpp b/src/widgets/kernel/qwidgetwindow.cpp
index b255bc16f9..dccd7ae2c8 100644
--- a/src/widgets/kernel/qwidgetwindow.cpp
+++ b/src/widgets/kernel/qwidgetwindow.cpp
@@ -99,7 +99,7 @@ QWidgetWindow::QWidgetWindow(QWidget *widget)
         setSurfaceType(QSurface::RasterGLSurface);
     }
     connect(m_widget, &QObject::objectNameChanged, this, &QWidgetWindow::updateObjectName);
-    connect(this, SIGNAL(screenChanged(QScreen*)), this, SLOT(repaintWindow()));
+    connect(this, SIGNAL(screenChanged(QScreen*)), this, SLOT(handleScreenChange()));
 }
 
 QWidgetWindow::~QWidgetWindow()
@@ -558,8 +558,27 @@ void QWidgetWindow::updateGeometry()
     m_widget->data->fstrut_dirty = false;
 }
 
-// Invalidates the backing store buffer and repaints immediately.
-// ### Qt 5.4: replace with QUpdateWindowRequestEvent.
+static void sendScreenChangeRecursively(QWidget *widget)
+{
+    QEvent e(QEvent::ScreenChangeInternal);
+    QApplication::sendEvent(widget, &e);
+    QWidgetPrivate *d = QWidgetPrivate::get(widget);
+    for (int i = 0; i < d->children.size(); ++i) {
+        QWidget *w = qobject_cast<QWidget *>(d->children.at(i));
+        if (w)
+            sendScreenChangeRecursively(w);
+    }
+}
+
+void QWidgetWindow::handleScreenChange()
+{
+    // Send an event recursively to the widget and its children.
+    sendScreenChangeRecursively(m_widget);
+
+    // Invalidate the backing store buffer and repaint immediately.
+    repaintWindow();
+}
+
 void QWidgetWindow::repaintWindow()
 {
     if (!m_widget->isVisible() || !m_widget->updatesEnabled())
diff --git a/src/widgets/kernel/qwidgetwindow_p.h b/src/widgets/kernel/qwidgetwindow_p.h
index be2adddff5..87ad7a4bd4 100644
--- a/src/widgets/kernel/qwidgetwindow_p.h
+++ b/src/widgets/kernel/qwidgetwindow_p.h
@@ -101,9 +101,10 @@ protected:
 
 private slots:
     void updateObjectName();
-    void repaintWindow();
+    void handleScreenChange();
 
 private:
+    void repaintWindow();
     void updateGeometry();
     void updateNormalGeometry();