diff --git a/effects/slideback/slideback.cpp b/effects/slideback/slideback.cpp
index e7313c0cbf..a3bbe2ed67 100644
--- a/effects/slideback/slideback.cpp
+++ b/effects/slideback/slideback.cpp
@@ -307,8 +307,11 @@ bool SlideBackEffect::intersects(EffectWindow* windowUnder, const QRect &windowO
 EffectWindowList SlideBackEffect::usableWindows(const EffectWindowList & allWindows)
 {
     EffectWindowList retList;
+    auto isWindowVisible = [] (const EffectWindow *window) {
+        return window && effects->virtualScreenGeometry().intersects(window->geometry());
+    };
     foreach (EffectWindow * tmp, allWindows) {
-        if (isWindowUsable(tmp)) {
+        if (isWindowUsable(tmp) && isWindowVisible(tmp)) {
             retList.append(tmp);
         }
     }
diff --git a/libkwineffects/kwinglutils.cpp b/libkwineffects/kwinglutils.cpp
index 8f7ce38ca0..11a8163ea3 100644
--- a/libkwineffects/kwinglutils.cpp
+++ b/libkwineffects/kwinglutils.cpp
@@ -128,11 +128,19 @@ static QString formatGLError(GLenum err)
 bool checkGLError(const char* txt)
 {
     GLenum err = glGetError();
+    if (err == GL_CONTEXT_LOST) {
+        qCWarning(LIBKWINGLUTILS) << "GL error: context lost";
+        return true;
+    }
     bool hasError = false;
     while (err != GL_NO_ERROR) {
         qCWarning(LIBKWINGLUTILS) << "GL error (" << txt << "): " << formatGLError(err);
         hasError = true;
         err = glGetError();
+        if (err == GL_CONTEXT_LOST) {
+            qCWarning(LIBKWINGLUTILS) << "GL error: context lost";
+            break;
+        }
     }
     return hasError;
 }
diff --git a/plugins/platforms/x11/standalone/edge.cpp b/plugins/platforms/x11/standalone/edge.cpp
index f4331fabc5..700d086849 100644
--- a/plugins/platforms/x11/standalone/edge.cpp
+++ b/plugins/platforms/x11/standalone/edge.cpp
@@ -110,18 +110,20 @@ void WindowBasedEdge::doStartApproaching()
     }
     m_approachWindow.unmap();
     Cursor *cursor = Cursor::self();
-    connect(cursor, SIGNAL(posChanged(QPoint)), SLOT(updateApproaching(QPoint)));
+#ifndef KWIN_UNIT_TEST
+    m_cursorPollingConnection = connect(cursor, &Cursor::posChanged, this, &WindowBasedEdge::updateApproaching);
+#endif
     cursor->startMousePolling();
 }
 
 void WindowBasedEdge::doStopApproaching()
 {
-    if (!activatesForPointer()) {
+    if (!m_cursorPollingConnection) {
         return;
     }
-    Cursor *cursor = Cursor::self();
-    disconnect(cursor, SIGNAL(posChanged(QPoint)), this, SLOT(updateApproaching(QPoint)));
-    cursor->stopMousePolling();
+    disconnect(m_cursorPollingConnection);
+    m_cursorPollingConnection = QMetaObject::Connection();
+    Cursor::self()->stopMousePolling();
     m_approachWindow.map();
 }
 
diff --git a/plugins/platforms/x11/standalone/edge.h b/plugins/platforms/x11/standalone/edge.h
index 980c8b3ae8..6934b7dcbd 100644
--- a/plugins/platforms/x11/standalone/edge.h
+++ b/plugins/platforms/x11/standalone/edge.h
@@ -61,6 +61,7 @@ private:
     void createApproachWindow();
     Xcb::Window m_window;
     Xcb::Window m_approachWindow;
+    QMetaObject::Connection m_cursorPollingConnection;
 };
 
 inline quint32 WindowBasedEdge::window() const