Scale surface items by the buffer scale

As reported here [1] with a compositor that properly
handles HiDPI, surface item size is not scaled at all
resulting in windows twice the size on Retina.

Issue: #190
Issue: #218

[1] = https://bugreports.qt.io/browse/QTBUG-55303

src/server/shell/clientwindow.cpp

@@ -639,8 +639,9 @@ QPointF ClientWindow::randomPosition() const
     Q_D(const ClientWindow);
 
     // Surface size
-    const int w = d->surface->size().width();
-    const int h = d->surface->size().height();
+    const QSize surfaceSize = d->surface->size() / d->surface->bufferScale();
+    const int w = surfaceSize.width();
+    const int h = surfaceSize.height();
 
     // Find the output where the pointer is located, defaults
     // to the default output

src/waylandcompositor/compositor_api/qwaylandquickitem.cpp

@@ -877,7 +877,7 @@ void QWaylandQuickItem::updateSize()
 {
     Q_D(QWaylandQuickItem);
     if (d->sizeFollowsSurface && surface()) {
-        setSize(surface()->size() * (d->scaleFactor() / surface()->bufferScale()));
+        setSize(surface()->size() / d->scaleFactor());
     }
 }
 

src/waylandcompositor/compositor_api/qwaylandquickitem_p.h

@@ -155,7 +155,7 @@ class QWaylandQuickItemPrivate : public QQuickItemPrivate
     }
 
     bool shouldSendInputEvents() const { return view->surface() && inputEventsEnabled; }
-    int scaleFactor() const { return view->output() ? view->output()->scaleFactor() : 1; }
+    int scaleFactor() const { return view->surface() ? view->surface()->bufferScale() : 1; }
 
     static QMutex *mutex;