3 files changed, 24 insertions, 0 deletions

diff --git a/src/compositor/compositor_api/qwaylandquickitem.cpp b/src/compositor/compositor_api/qwaylandquickitem.cpp
index 8480db6f4..7f0685fcf 100644
--- a/src/compositor/compositor_api/qwaylandquickitem.cpp
+++ b/src/compositor/compositor_api/qwaylandquickitem.cpp
@@ -1169,12 +1169,14 @@ void QWaylandQuickItem::updateWindow()
 
     if (d->connectedWindow) {
         disconnect(d->connectedWindow, &QQuickWindow::beforeSynchronizing, this, &QWaylandQuickItem::beforeSync);
+        disconnect(d->connectedWindow, &QQuickWindow::screenChanged, this, &QWaylandQuickItem::updateSize);
     }
 
     d->connectedWindow = newWindow;
 
     if (d->connectedWindow) {
         connect(d->connectedWindow, &QQuickWindow::beforeSynchronizing, this, &QWaylandQuickItem::beforeSync, Qt::DirectConnection);
+        connect(d->connectedWindow, &QQuickWindow::screenChanged, this, &QWaylandQuickItem::updateSize); // new screen may have new dpr
     }
 
     if (compositor() && d->connectedWindow) {
@@ -1182,6 +1184,25 @@ void QWaylandQuickItem::updateWindow()
         Q_ASSERT(output);
         d->view->setOutput(output);
     }
+
+    updateSize(); // because scaleFactor depends on devicePixelRatio, which may be different for the new window
+}
+
+void QWaylandQuickItem::updateOutput()
+{
+    Q_D(QWaylandQuickItem);
+    if (d->view->output() == d->connectedOutput)
+        return;
+
+    if (d->connectedOutput)
+        disconnect(d->connectedOutput, &QWaylandOutput::scaleFactorChanged, this, &QWaylandQuickItem::updateSize);
+
+    d->connectedOutput = d->view->output();
+
+    if (d->connectedOutput)
+        connect(d->connectedOutput, &QWaylandOutput::scaleFactorChanged, this, &QWaylandQuickItem::updateSize);
+
+    updateSize();
 }
 
 void QWaylandQuickItem::beforeSync()
diff --git a/src/compositor/compositor_api/qwaylandquickitem.h b/src/compositor/compositor_api/qwaylandquickitem.h
index aac88236c..653440aed 100644
--- a/src/compositor/compositor_api/qwaylandquickitem.h
+++ b/src/compositor/compositor_api/qwaylandquickitem.h
@@ -160,6 +160,7 @@ private Q_SLOTS:
     void updateSize();
     void updateBuffer(bool hasBuffer);
     void updateWindow();
+    void updateOutput();
     void beforeSync();
     void handleSubsurfaceAdded(QWaylandSurface *childSurface);
     void handleSubsurfacePosition(const QPoint &pos);
diff --git a/src/compositor/compositor_api/qwaylandquickitem_p.h b/src/compositor/compositor_api/qwaylandquickitem_p.h
index ee8ea5442..51b41c9f6 100644
--- a/src/compositor/compositor_api/qwaylandquickitem_p.h
+++ b/src/compositor/compositor_api/qwaylandquickitem_p.h
@@ -128,6 +128,7 @@ public:
         QObject::connect(view.data(), &QWaylandView::surfaceChanged, q, &QWaylandQuickItem::handleSurfaceChanged);
         QObject::connect(view.data(), &QWaylandView::surfaceDestroyed, q, &QWaylandQuickItem::surfaceDestroyed);
         QObject::connect(view.data(), &QWaylandView::outputChanged, q, &QWaylandQuickItem::outputChanged);
+        QObject::connect(view.data(), &QWaylandView::outputChanged, q, &QWaylandQuickItem::updateOutput);
         QObject::connect(view.data(), &QWaylandView::bufferLockedChanged, q, &QWaylandQuickItem::bufferLockedChanged);
         QObject::connect(view.data(), &QWaylandView::allowDiscardFrontBufferChanged, q, &QWaylandQuickItem::allowDiscardFrontBuffer);
 
@@ -174,6 +175,7 @@ public:
     QMatrix4x4 lastMatrix;
 
     QQuickWindow *connectedWindow = nullptr;
+    QWaylandOutput *connectedOutput = nullptr;
     QWaylandSurface::Origin origin = QWaylandSurface::OriginTopLeft;
     QPointer<QObject> subsurfaceHandler;
     QVector<QWaylandSeat *> touchingSeats;