diff --git a/gestures.cpp b/gestures.cpp
--- a/gestures.cpp
+++ b/gestures.cpp
@@ -46,6 +46,9 @@
     setMinimumY(geometry.y());
     setMaximumX(geometry.x() + geometry.width());
     setMaximumY(geometry.y() + geometry.height());
+
+    Q_ASSERT(m_maximumX >= m_minimumX);
+    Q_ASSERT(m_maximumY >= m_minimumY);
 }
 
 qreal SwipeGesture::minimumDeltaReachedProgress(const QSizeF &delta) const
diff --git a/screenedge.cpp b/screenedge.cpp
--- a/screenedge.cpp
+++ b/screenedge.cpp
@@ -727,8 +727,7 @@
     , m_actionLeft(ElectricActionNone)
     , m_gestureRecognizer(new GestureRecognizer(this))
 {
-    QWidget w;
-    m_cornerOffset = (w.physicalDpiX() + w.physicalDpiY() + 5) / 6;
+    m_cornerOffset = (Screens::self()->physicalDpiX(0) + Screens::self()->physicalDpiX(0) + 5) / 6;
 
     connect(workspace(), &Workspace::clientRemoved, this, &ScreenEdges::deleteEdgeForClient);
 }
diff --git a/screens.h b/screens.h
--- a/screens.h
+++ b/screens.h
@@ -146,6 +146,9 @@
 
     virtual Qt::ScreenOrientation orientation(int screen) const;
 
+    int physicalDpiX(int screen) const;
+    int physicalDpiY(int screen) const;
+
 public Q_SLOTS:
     void reconfigure();
 
diff --git a/screens.cpp b/screens.cpp
--- a/screens.cpp
+++ b/screens.cpp
@@ -229,4 +229,14 @@
     m_config = config;
 }
 
+int Screens::physicalDpiX(int screen) const
+{
+    return size(screen).width() / physicalSize(screen).width() * qreal(25.4);
+}
+
+int Screens::physicalDpiY(int screen) const
+{
+    return size(screen).height() / physicalSize(screen).height() * qreal(25.4);
+}
+
 } // namespace