Compositor: Fix coordinate system inconsistencies

Several properties were using pixel coordinates and surface coordinates without
converting.

[ChangeLog][Compositor] QWaylandSurface::destinationSize has been added which
returns the size of the surface that will be displayed on the screen in surface
coordinates.

[ChangeLog][Compositor] Fixed a bug where QWaylandSurface::inputRegionContains
would return true for some points outside surfaces with buffer scale > 1.

[ChangeLog][Compositor] Fixed a bug which caused ShellSurfaceItems for surfaces
with buffer scale > 1 to move too much when resizing interactively.

It also gets rid of all calls to QWaylandSurface::size, which confusingly
returns the size of the surface's buffer in pixel coordinates. Most properties
now use destionationSize's surface coordinates consistently. Hopefully,
QWaylandSurface::size can be renamed or removed in Qt 6.

Change-Id: I007256a8df7759cf74fbfd51624fa1f90c083336
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

12 files changed, 93 insertions, 54 deletions

diff --git a/src/compositor/compositor_api/qwaylandpointer.cpp b/src/compositor/compositor_api/qwaylandpointer.cpp
index 77e736a58..96263e0c2 100644
--- a/src/compositor/compositor_api/qwaylandpointer.cpp
+++ b/src/compositor/compositor_api/qwaylandpointer.cpp
@@ -239,7 +239,7 @@ uint QWaylandPointer::sendMouseReleaseEvent(Qt::MouseButton button)
 
 /*!
  * Sets the current mouse focus to \a view and sends a mouse move event to it with the
- * local position \a localPos and output space position \a outputSpacePos.
+ * local position \a localPos in surface coordinates and output space position \a outputSpacePos.
  */
 void QWaylandPointer::sendMouseMoveEvent(QWaylandView *view, const QPointF &localPos, const QPointF &outputSpacePos)
 {
@@ -253,7 +253,7 @@ void QWaylandPointer::sendMouseMoveEvent(QWaylandView *view, const QPointF &loca
     if (view) {
         // We adjust if the mouse position is on the edge
         // to work around Qt's event propagation
-        QSizeF size(view->surface()->size());
+        QSizeF size(view->surface()->destinationSize());
         if (d->localPosition.x() == size.width())
             d->localPosition.rx() -= 0.01;
         if (d->localPosition.y() == size.height())
@@ -294,7 +294,7 @@ QWaylandView *QWaylandPointer::mouseFocus() const
 }
 
 /*!
- * Returns the current local position of the QWaylandPointer.
+ * Returns the current local position of the QWaylandPointer in surface coordinates.
  */
 QPointF QWaylandPointer::currentLocalPosition() const
 {
diff --git a/src/compositor/compositor_api/qwaylandquickitem.cpp b/src/compositor/compositor_api/qwaylandquickitem.cpp
index 6be5701ff..8e1b84921 100644
--- a/src/compositor/compositor_api/qwaylandquickitem.cpp
+++ b/src/compositor/compositor_api/qwaylandquickitem.cpp
@@ -886,7 +886,7 @@ void QWaylandQuickItem::handleSurfaceChanged()
     if (d->oldSurface) {
         disconnect(d->oldSurface, &QWaylandSurface::hasContentChanged, this, &QWaylandQuickItem::surfaceMappedChanged);
         disconnect(d->oldSurface, &QWaylandSurface::parentChanged, this, &QWaylandQuickItem::parentChanged);
-        disconnect(d->oldSurface, &QWaylandSurface::sizeChanged, this, &QWaylandQuickItem::updateSize);
+        disconnect(d->oldSurface, &QWaylandSurface::destinationSizeChanged, this, &QWaylandQuickItem::updateSize);
         disconnect(d->oldSurface, &QWaylandSurface::bufferScaleChanged, this, &QWaylandQuickItem::updateSize);
         disconnect(d->oldSurface, &QWaylandSurface::configure, this, &QWaylandQuickItem::updateBuffer);
         disconnect(d->oldSurface, &QWaylandSurface::redraw, this, &QQuickItem::update);
@@ -903,7 +903,7 @@ void QWaylandQuickItem::handleSurfaceChanged()
     if (QWaylandSurface *newSurface = d->view->surface()) {
         connect(newSurface, &QWaylandSurface::hasContentChanged, this, &QWaylandQuickItem::surfaceMappedChanged);
         connect(newSurface, &QWaylandSurface::parentChanged, this, &QWaylandQuickItem::parentChanged);
-        connect(newSurface, &QWaylandSurface::sizeChanged, this, &QWaylandQuickItem::updateSize);
+        connect(newSurface, &QWaylandSurface::destinationSizeChanged, this, &QWaylandQuickItem::updateSize);
         connect(newSurface, &QWaylandSurface::bufferScaleChanged, this, &QWaylandQuickItem::updateSize);
         connect(newSurface, &QWaylandSurface::configure, this, &QWaylandQuickItem::updateBuffer);
         connect(newSurface, &QWaylandSurface::redraw, this, &QQuickItem::update);
@@ -992,7 +992,7 @@ void QWaylandQuickItem::updateSize()
 
     QSize size(0, 0);
     if (surface())
-        size = surface()->size() * (d->scaleFactor() / surface()->bufferScale());
+        size = surface()->destinationSize() * d->scaleFactor();
 
     setImplicitSize(size.width(), size.height());
     if (d->sizeFollowsSurface)
@@ -1061,11 +1061,11 @@ bool QWaylandQuickItem::inputRegionContains(const QPointF &localPosition)
 QPointF QWaylandQuickItem::mapToSurface(const QPointF &point) const
 {
     Q_D(const QWaylandQuickItem);
-    if (!surface() || surface()->size().isEmpty())
+    if (!surface() || surface()->destinationSize().isEmpty())
         return point / d->scaleFactor();
 
-    qreal xScale = width() / surface()->size().width() * surface()->bufferScale();
-    qreal yScale = height() / surface()->size().height() * surface()->bufferScale();
+    qreal xScale = width() / surface()->destinationSize().width();
+    qreal yScale = height() / surface()->destinationSize().height();
 
     return QPointF(point.x() / xScale, point.y() / yScale);
 }
@@ -1077,11 +1077,11 @@ QPointF QWaylandQuickItem::mapToSurface(const QPointF &point) const
 QPointF QWaylandQuickItem::mapFromSurface(const QPointF &point) const
 {
     Q_D(const QWaylandQuickItem);
-    if (!surface() || surface()->size().isEmpty())
+    if (!surface() || surface()->destinationSize().isEmpty())
         return point * d->scaleFactor();
 
-    qreal xScale = width() / surface()->size().width() * surface()->bufferScale();
-    qreal yScale = height() / surface()->size().height() * surface()->bufferScale();
+    qreal xScale = width() / surface()->destinationSize().width();
+    qreal yScale = height() / surface()->destinationSize().height();
 
     return QPointF(point.x() * xScale, point.y() * yScale);
 }
diff --git a/src/compositor/compositor_api/qwaylandsurface.cpp b/src/compositor/compositor_api/qwaylandsurface.cpp
index 13ae28220..79b2a9d4e 100644
--- a/src/compositor/compositor_api/qwaylandsurface.cpp
+++ b/src/compositor/compositor_api/qwaylandsurface.cpp
@@ -234,19 +234,21 @@ void QWaylandSurfacePrivate::surface_commit(Resource *)
 
     // Needed in order to know whether we want to emit signals later
     QSize oldBufferSize = bufferSize;
+    QSize oldDestinationSize = destinationSize;
     bool oldHasContent = hasContent;
     int oldBufferScale = bufferScale;
 
     // Update all internal state
     if (pending.buffer.hasBuffer() || pending.newlyAttached)
         bufferRef = pending.buffer;
+    bufferScale = pending.bufferScale;
     bufferSize = bufferRef.size();
-    damage = pending.damage.intersected(QRect(QPoint(), bufferSize));
+    destinationSize = pending.destinationSize.isEmpty() ? bufferSize / bufferScale : pending.destinationSize;
+    damage = pending.damage.intersected(QRect(QPoint(), destinationSize));
     hasContent = bufferRef.hasContent();
-    bufferScale = pending.bufferScale;
     frameCallbacks << pendingFrameCallbacks;
-    inputRegion = pending.inputRegion.intersected(QRect(QPoint(), bufferSize));
-    opaqueRegion = pending.opaqueRegion.intersected(QRect(QPoint(), bufferSize));
+    inputRegion = pending.inputRegion.intersected(QRect(QPoint(), destinationSize));
+    opaqueRegion = pending.opaqueRegion.intersected(QRect(QPoint(), destinationSize));
     QPoint offsetForNextFrame = pending.offset;
 
     // Clear per-commit state
@@ -274,6 +276,9 @@ void QWaylandSurfacePrivate::surface_commit(Resource *)
     if (oldBufferScale != bufferScale)
         emit q->bufferScaleChanged();
 
+    if (oldDestinationSize != destinationSize)
+        emit q->destinationSizeChanged();
+
     if (oldHasContent != hasContent)
         emit q->hasContentChanged();
 
@@ -448,15 +453,46 @@ bool QWaylandSurface::hasContent() const
 }
 
 /*!
+ * \qmlproperty size QtWaylandCompositor::WaylandSurface::destinationSize
+ *
+ * This property holds the size of this WaylandSurface in surface coordinates.
+ *
+ * If you want the size in pixels, multiply this size with \l bufferScale.
+ *
+ * \sa bufferScale
+ */
+
+/*!
+ * \property QWaylandSurface::destinationSize
+ *
+ * This property holds the size of this WaylandSurface in surface coordinates.
+ *
+ * If you want the size in pixels, multiply this size with \l bufferScale.
+ *
+ * \sa bufferScale
+ */
+QSize QWaylandSurface::destinationSize() const
+{
+    Q_D(const QWaylandSurface);
+    return d->destinationSize;
+}
+
+/*!
  * \qmlproperty size QtWaylandCompositor::WaylandSurface::size
  *
- * This property holds the WaylandSurface's size in pixels.
+ * This property holds the size of the current buffer of this WaylandSurface in pixels,
+ * not in surface coordinates.
+ *
+ * For the size in surface coordinates, use \l destinationSize instead.
  */
 
 /*!
  * \property QWaylandSurface::size
  *
- * This property holds the QWaylandSurface's size in pixels.
+ * This property holds the size of the current buffer of this QWaylandSurface in pixels,
+ * not in surface coordinates.
+ *
+ * For the size in surface coordinates, use \l destinationSize instead.
  */
 QSize QWaylandSurface::size() const
 {
diff --git a/src/compositor/compositor_api/qwaylandsurface.h b/src/compositor/compositor_api/qwaylandsurface.h
index c208c16d4..243aebd11 100644
--- a/src/compositor/compositor_api/qwaylandsurface.h
+++ b/src/compositor/compositor_api/qwaylandsurface.h
@@ -81,7 +81,8 @@ class Q_WAYLAND_COMPOSITOR_EXPORT QWaylandSurface : public QWaylandObject
     Q_OBJECT
     Q_DECLARE_PRIVATE(QWaylandSurface)
     Q_PROPERTY(QWaylandClient *client READ client CONSTANT)
-    Q_PROPERTY(QSize size READ size NOTIFY sizeChanged)
+    Q_PROPERTY(QSize destinationSize READ destinationSize NOTIFY destinationSizeChanged)
+    Q_PROPERTY(QSize size READ size NOTIFY sizeChanged) // Qt 6: Remove or replace with destinationSize
     Q_PROPERTY(int bufferScale READ bufferScale NOTIFY bufferScaleChanged)
     Q_PROPERTY(Qt::ScreenOrientation contentOrientation READ contentOrientation NOTIFY contentOrientationChanged)
     Q_PROPERTY(QWaylandSurface::Origin origin READ origin NOTIFY originChanged)
@@ -110,6 +111,7 @@ public:
 
     bool hasContent() const;
 
+    QSize destinationSize() const;
     QSize size() const;
     int bufferScale() const;
 
@@ -155,6 +157,7 @@ Q_SIGNALS:
     void damaged(const QRegion &rect);
     void parentChanged(QWaylandSurface *newParent, QWaylandSurface *oldParent);
     void childAdded(QWaylandSurface *child);
+    void destinationSizeChanged();
     void sizeChanged();
     void bufferScaleChanged();
     void offsetForNextFrame(const QPoint &offset);
diff --git a/src/compositor/compositor_api/qwaylandsurface_p.h b/src/compositor/compositor_api/qwaylandsurface_p.h
index df868de63..b34367801 100644
--- a/src/compositor/compositor_api/qwaylandsurface_p.h
+++ b/src/compositor/compositor_api/qwaylandsurface_p.h
@@ -152,6 +152,7 @@ public: //member variables
         bool newlyAttached;
         QRegion inputRegion;
         int bufferScale;
+        QSize destinationSize;
         QRegion opaqueRegion;
     } pending;
 
@@ -166,6 +167,7 @@ public: //member variables
     QRegion inputRegion;
     QRegion opaqueRegion;
 
+    QSize destinationSize;
     QSize bufferSize;
     int bufferScale = 1;
     bool isCursorSurface = false;
diff --git a/src/compositor/extensions/qwaylandwlshellintegration.cpp b/src/compositor/extensions/qwaylandwlshellintegration.cpp
index a2b6b1224..99a2e7655 100644
--- a/src/compositor/extensions/qwaylandwlshellintegration.cpp
+++ b/src/compositor/extensions/qwaylandwlshellintegration.cpp
@@ -84,8 +84,7 @@ void WlShellIntegration::handleStartResize(QWaylandSeat *seat, QWaylandWlShellSu
     grabberState = GrabberState::Resize;
     resizeState.seat = seat;
     resizeState.resizeEdges = edges;
-    float scaleFactor = m_item->view()->output()->scaleFactor();
-    resizeState.initialSize = m_shellSurface->surface()->size() / scaleFactor;
+    resizeState.initialSize = m_shellSurface->surface()->destinationSize();
     resizeState.initialized = false;
 }
 
@@ -265,7 +264,7 @@ void WlShellIntegration::handleShellSurfaceDestroyed()
 
 void WlShellIntegration::handleSurfaceHasContentChanged()
 {
-    if (m_shellSurface && m_shellSurface->surface()->size().isEmpty()
+    if (m_shellSurface && m_shellSurface->surface()->destinationSize().isEmpty()
             && m_shellSurface->windowType() == Qt::WindowType::Popup) {
         handlePopupClosed();
     }
@@ -285,9 +284,8 @@ void WlShellIntegration::adjustOffsetForNextFrame(const QPointF &offset)
     if (!m_item->view()->isPrimary())
         return;
 
-    float scaleFactor = m_item->view()->output()->scaleFactor();
     QQuickItem *moveItem = m_item->moveItem();
-    moveItem->setPosition(moveItem->position() + offset * scaleFactor / devicePixelRatio());
+    moveItem->setPosition(moveItem->position() + m_item->mapFromSurface(offset));
 }
 
 bool WlShellIntegration::mouseMoveEvent(QMouseEvent *event)
diff --git a/src/compositor/extensions/qwaylandxdgshell.cpp b/src/compositor/extensions/qwaylandxdgshell.cpp
index bd332287e..d0df8f066 100644
--- a/src/compositor/extensions/qwaylandxdgshell.cpp
+++ b/src/compositor/extensions/qwaylandxdgshell.cpp
@@ -311,7 +311,7 @@ QRect QWaylandXdgSurfacePrivate::calculateFallbackWindowGeometry() const
 {
     // TODO: The unset window geometry should include subsurfaces as well, so this solution
     // won't work too well on those kinds of clients.
-    return QRect(QPoint(0, 0), m_surface->size() / m_surface->bufferScale());
+    return QRect(QPoint(), m_surface->destinationSize());
 }
 
 void QWaylandXdgSurfacePrivate::updateFallbackWindowGeometry()
@@ -510,7 +510,7 @@ void QWaylandXdgSurface::initialize(QWaylandXdgShell *xdgShell, QWaylandSurface
     d->init(resource.resource());
     setExtensionContainer(surface);
     d->m_windowGeometry = d->calculateFallbackWindowGeometry();
-    connect(surface, &QWaylandSurface::sizeChanged, this, &QWaylandXdgSurface::handleSurfaceSizeChanged);
+    connect(surface, &QWaylandSurface::destinationSizeChanged, this, &QWaylandXdgSurface::handleSurfaceSizeChanged);
     connect(surface, &QWaylandSurface::bufferScaleChanged, this, &QWaylandXdgSurface::handleBufferScaleChanged);
     emit shellChanged();
     emit surfaceChanged();
diff --git a/src/compositor/extensions/qwaylandxdgshellintegration.cpp b/src/compositor/extensions/qwaylandxdgshellintegration.cpp
index 9ec2810b2..3de52944b 100644
--- a/src/compositor/extensions/qwaylandxdgshellintegration.cpp
+++ b/src/compositor/extensions/qwaylandxdgshellintegration.cpp
@@ -73,7 +73,7 @@ XdgToplevelIntegration::XdgToplevelIntegration(QWaylandQuickShellSurfaceItem *it
     connect(m_xdgSurface->shell(), &QWaylandXdgShell::popupCreated, this, [item](QWaylandXdgPopup *popup, QWaylandXdgSurface *){
         handlePopupCreated(item, popup);
     });
-    connect(m_xdgSurface->surface(), &QWaylandSurface::sizeChanged, this, &XdgToplevelIntegration::handleSurfaceSizeChanged);
+    connect(m_xdgSurface->surface(), &QWaylandSurface::destinationSizeChanged, this, &XdgToplevelIntegration::handleSurfaceSizeChanged);
     connect(m_toplevel, &QObject::destroyed, this, &XdgToplevelIntegration::handleToplevelDestroyed);
 }
 
@@ -130,7 +130,7 @@ void XdgToplevelIntegration::handleStartResize(QWaylandSeat *seat, Qt::Edges edg
     resizeState.resizeEdges = edges;
     resizeState.initialWindowSize = m_xdgSurface->windowGeometry().size();
     resizeState.initialPosition = m_item->moveItem()->position();
-    resizeState.initialSurfaceSize = m_item->surface()->size();
+    resizeState.initialSurfaceSize = m_item->surface()->destinationSize();
     resizeState.initialized = false;
 }
 
@@ -247,14 +247,14 @@ void XdgToplevelIntegration::handleActivatedChanged()
 void XdgToplevelIntegration::handleSurfaceSizeChanged()
 {
     if (grabberState == GrabberState::Resize) {
-        qreal x = resizeState.initialPosition.x();
-        qreal y = resizeState.initialPosition.y();
+        qreal dx = 0;
+        qreal dy = 0;
         if (resizeState.resizeEdges & Qt::TopEdge)
-            y += resizeState.initialSurfaceSize.height() - m_item->surface()->size().height();
-
+            dy = resizeState.initialSurfaceSize.height() - m_item->surface()->destinationSize().height();
         if (resizeState.resizeEdges & Qt::LeftEdge)
-            x += resizeState.initialSurfaceSize.width() - m_item->surface()->size().width();
-        m_item->moveItem()->setPosition(QPointF(x, y));
+            dx = resizeState.initialSurfaceSize.width() - m_item->surface()->destinationSize().width();
+        QPointF offset = m_item->mapFromSurface({dx, dy});
+        m_item->moveItem()->setPosition(resizeState.initialPosition + offset);
     }
 }
 
diff --git a/src/compositor/extensions/qwaylandxdgshellv5.cpp b/src/compositor/extensions/qwaylandxdgshellv5.cpp
index a6e88aabb..2e3b76dc7 100644
--- a/src/compositor/extensions/qwaylandxdgshellv5.cpp
+++ b/src/compositor/extensions/qwaylandxdgshellv5.cpp
@@ -249,7 +249,7 @@ QRect QWaylandXdgSurfaceV5Private::calculateFallbackWindowGeometry() const
 {
     // TODO: The unset window geometry should include subsurfaces as well, so this solution
     // won't work too well on those kinds of clients.
-    return QRect(QPoint(0, 0), m_surface->size() / m_surface->bufferScale());
+    return QRect(QPoint(), m_surface->destinationSize());
 }
 
 void QWaylandXdgSurfaceV5Private::updateFallbackWindowGeometry()
@@ -837,7 +837,7 @@ void QWaylandXdgSurfaceV5::initialize(QWaylandXdgShellV5 *xdgShell, QWaylandSurf
     d->init(resource.resource());
     setExtensionContainer(surface);
     d->m_windowGeometry = d->calculateFallbackWindowGeometry();
-    connect(surface, &QWaylandSurface::sizeChanged, this, &QWaylandXdgSurfaceV5::handleSurfaceSizeChanged);
+    connect(surface, &QWaylandSurface::destinationSizeChanged, this, &QWaylandXdgSurfaceV5::handleSurfaceSizeChanged);
     connect(surface, &QWaylandSurface::bufferScaleChanged, this, &QWaylandXdgSurfaceV5::handleBufferScaleChanged);
     emit shellChanged();
     emit surfaceChanged();
diff --git a/src/compositor/extensions/qwaylandxdgshellv5integration.cpp b/src/compositor/extensions/qwaylandxdgshellv5integration.cpp
index d21aa4428..1d63632a3 100644
--- a/src/compositor/extensions/qwaylandxdgshellv5integration.cpp
+++ b/src/compositor/extensions/qwaylandxdgshellv5integration.cpp
@@ -71,7 +71,7 @@ XdgShellV5Integration::XdgShellV5Integration(QWaylandQuickShellSurfaceItem *item
     connect(m_xdgSurface, &QWaylandXdgSurfaceV5::unsetMaximized, this, &XdgShellV5Integration::handleUnsetMaximized);
     connect(m_xdgSurface, &QWaylandXdgSurfaceV5::maximizedChanged, this, &XdgShellV5Integration::handleMaximizedChanged);
     connect(m_xdgSurface, &QWaylandXdgSurfaceV5::activatedChanged, this, &XdgShellV5Integration::handleActivatedChanged);
-    connect(m_xdgSurface->surface(), &QWaylandSurface::sizeChanged, this, &XdgShellV5Integration::handleSurfaceSizeChanged);
+    connect(m_xdgSurface->surface(), &QWaylandSurface::destinationSizeChanged, this, &XdgShellV5Integration::handleSurfaceSizeChanged);
     connect(m_xdgSurface->shell(), &QWaylandXdgShellV5::xdgPopupCreated, this, [item](QWaylandXdgPopupV5 *popup){
         handlePopupCreated(item, popup);
     });
@@ -139,7 +139,7 @@ void XdgShellV5Integration::handleStartResize(QWaylandSeat *seat, QWaylandXdgSur
     resizeState.resizeEdges = edges;
     resizeState.initialWindowSize = m_xdgSurface->windowGeometry().size();
     resizeState.initialPosition = m_item->moveItem()->position();
-    resizeState.initialSurfaceSize = m_item->surface()->size();
+    resizeState.initialSurfaceSize = m_item->surface()->destinationSize();
     resizeState.initialized = false;
 }
 
@@ -194,14 +194,14 @@ void XdgShellV5Integration::handleActivatedChanged()
 void XdgShellV5Integration::handleSurfaceSizeChanged()
 {
     if (grabberState == GrabberState::Resize) {
-        qreal x = resizeState.initialPosition.x();
-        qreal y = resizeState.initialPosition.y();
+        qreal dx = 0;
+        qreal dy = 0;
         if (resizeState.resizeEdges & QWaylandXdgSurfaceV5::ResizeEdge::TopEdge)
-            y += resizeState.initialSurfaceSize.height() - m_item->surface()->size().height();
-
+            dy = resizeState.initialSurfaceSize.height() - m_item->surface()->destinationSize().height();
         if (resizeState.resizeEdges & QWaylandXdgSurfaceV5::ResizeEdge::LeftEdge)
-            x += resizeState.initialSurfaceSize.width() - m_item->surface()->size().width();
-        m_item->moveItem()->setPosition(QPointF(x, y));
+            dx = resizeState.initialSurfaceSize.width() - m_item->surface()->destinationSize().width();
+        QPointF offset = m_item->mapFromSurface({dx, dy});
+        m_item->moveItem()->setPosition(resizeState.initialPosition + offset);
     }
 }
 
diff --git a/src/compositor/extensions/qwaylandxdgshellv6.cpp b/src/compositor/extensions/qwaylandxdgshellv6.cpp
index 8338fe6e2..e6741bfbc 100644
--- a/src/compositor/extensions/qwaylandxdgshellv6.cpp
+++ b/src/compositor/extensions/qwaylandxdgshellv6.cpp
@@ -316,7 +316,7 @@ QRect QWaylandXdgSurfaceV6Private::calculateFallbackWindowGeometry() const
 {
     // TODO: The unset window geometry should include subsurfaces as well, so this solution
     // won't work too well on those kinds of clients.
-    return QRect(QPoint(0, 0), m_surface->size() / m_surface->bufferScale());
+    return QRect(QPoint(), m_surface->destinationSize());
 }
 
 void QWaylandXdgSurfaceV6Private::updateFallbackWindowGeometry()
@@ -515,7 +515,7 @@ void QWaylandXdgSurfaceV6::initialize(QWaylandXdgShellV6 *xdgShell, QWaylandSurf
     d->init(resource.resource());
     setExtensionContainer(surface);
     d->m_windowGeometry = d->calculateFallbackWindowGeometry();
-    connect(surface, &QWaylandSurface::sizeChanged, this, &QWaylandXdgSurfaceV6::handleSurfaceSizeChanged);
+    connect(surface, &QWaylandSurface::destinationSizeChanged, this, &QWaylandXdgSurfaceV6::handleSurfaceSizeChanged);
     connect(surface, &QWaylandSurface::bufferScaleChanged, this, &QWaylandXdgSurfaceV6::handleBufferScaleChanged);
     emit shellChanged();
     emit surfaceChanged();
diff --git a/src/compositor/extensions/qwaylandxdgshellv6integration.cpp b/src/compositor/extensions/qwaylandxdgshellv6integration.cpp
index 0dd8df6f8..66dbc6841 100644
--- a/src/compositor/extensions/qwaylandxdgshellv6integration.cpp
+++ b/src/compositor/extensions/qwaylandxdgshellv6integration.cpp
@@ -73,7 +73,7 @@ XdgToplevelV6Integration::XdgToplevelV6Integration(QWaylandQuickShellSurfaceItem
     connect(m_xdgSurface->shell(), &QWaylandXdgShellV6::popupCreated, this, [item](QWaylandXdgPopupV6 *popup, QWaylandXdgSurfaceV6 *){
         handlePopupCreated(item, popup);
     });
-    connect(m_xdgSurface->surface(), &QWaylandSurface::sizeChanged, this, &XdgToplevelV6Integration::handleSurfaceSizeChanged);
+    connect(m_xdgSurface->surface(), &QWaylandSurface::destinationSizeChanged, this, &XdgToplevelV6Integration::handleSurfaceSizeChanged);
     connect(m_toplevel, &QObject::destroyed, this, &XdgToplevelV6Integration::handleToplevelDestroyed);
 }
 
@@ -130,7 +130,7 @@ void XdgToplevelV6Integration::handleStartResize(QWaylandSeat *seat, Qt::Edges e
     resizeState.resizeEdges = edges;
     resizeState.initialWindowSize = m_xdgSurface->windowGeometry().size();
     resizeState.initialPosition = m_item->moveItem()->position();
-    resizeState.initialSurfaceSize = m_item->surface()->size();
+    resizeState.initialSurfaceSize = m_item->surface()->destinationSize();
     resizeState.initialized = false;
 }
 
@@ -247,14 +247,14 @@ void XdgToplevelV6Integration::handleActivatedChanged()
 void XdgToplevelV6Integration::handleSurfaceSizeChanged()
 {
     if (grabberState == GrabberState::Resize) {
-        qreal x = resizeState.initialPosition.x();
-        qreal y = resizeState.initialPosition.y();
+        qreal dx = 0;
+        qreal dy = 0;
         if (resizeState.resizeEdges & Qt::TopEdge)
-            y += resizeState.initialSurfaceSize.height() - m_item->surface()->size().height();
-
+            dy = resizeState.initialSurfaceSize.height() - m_item->surface()->destinationSize().height();
         if (resizeState.resizeEdges & Qt::LeftEdge)
-            x += resizeState.initialSurfaceSize.width() - m_item->surface()->size().width();
-        m_item->moveItem()->setPosition(QPointF(x, y));
+            dx = resizeState.initialSurfaceSize.width() - m_item->surface()->destinationSize().width();
+        QPointF offset = m_item->mapFromSurface({dx, dy});
+        m_item->moveItem()->setPosition(resizeState.initialPosition + offset);
     }
 }