6 files changed, 50 insertions, 1 deletions
diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 2e6000625e..077084b80f 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -2801,6 +2801,27 @@ bool QGuiApplication::isSavingSession() const
     return d->is_saving_session;
 }
 
+/*!
+    \since 5.2
+
+    Function that can be used to sync Qt state with the Window Systems state.
+
+    This function will first empty Qts events by calling QCoreApplication::processEvents(),
+    then the platform plugin will sync up with the windowsystem, and finally Qts events
+    will be delived by another call to QCoreApplication::processEvents();
+
+    This function is timeconsuming and its use is discouraged.
+*/
+void QGuiApplication::sync()
+{
+    QCoreApplication::processEvents();
+    if (QGuiApplicationPrivate::platform_integration
+            && QGuiApplicationPrivate::platform_integration->hasCapability(QPlatformIntegration::SyncState)) {
+        QGuiApplicationPrivate::platform_integration->sync();
+        QCoreApplication::processEvents();
+    }
+}
+
 void QGuiApplicationPrivate::commitData()
 {
     Q_Q(QGuiApplication);
diff --git a/src/gui/kernel/qguiapplication.h b/src/gui/kernel/qguiapplication.h
index bd42f18418..0089d48fa6 100644
--- a/src/gui/kernel/qguiapplication.h
+++ b/src/gui/kernel/qguiapplication.h
@@ -155,6 +155,7 @@ public:
     bool isSavingSession() const;
 #endif
 
+    static void sync();
 Q_SIGNALS:
     void fontDatabaseChanged();
     void screenAdded(QScreen *screen);
diff --git a/src/gui/kernel/qplatformintegration.cpp b/src/gui/kernel/qplatformintegration.cpp
index 49ac7836cb..e583606e41 100644
--- a/src/gui/kernel/qplatformintegration.cpp
+++ b/src/gui/kernel/qplatformintegration.cpp
@@ -435,4 +435,19 @@ QPlatformSessionManager *QPlatformIntegration::createPlatformSessionManager(cons
 }
 #endif
 
+/*!
+   \since 5.2
+
+   Function to sync the platform integrations state with the window system.
+
+   This is often implemented as a roundtrip from the platformintegration to the window system.
+
+   This function should not call QWindowSystemInterface::flushWindowSystemEvents() or
+   QCoreApplication::processEvents()
+*/
+void QPlatformIntegration::sync()
+{
+
+}
+
 QT_END_NAMESPACE
diff --git a/src/gui/kernel/qplatformintegration.h b/src/gui/kernel/qplatformintegration.h
index d3189f8641..4be675a37a 100644
--- a/src/gui/kernel/qplatformintegration.h
+++ b/src/gui/kernel/qplatformintegration.h
@@ -94,7 +94,8 @@ public:
         ForeignWindows,
         NonFullScreenWindows,
         NativeWidgets,
-        WindowManagement
+        WindowManagement,
+        SyncState
     };
 
     virtual ~QPlatformIntegration() { }
@@ -162,6 +163,8 @@ public:
 #ifndef QT_NO_SESSIONMANAGER
     virtual QPlatformSessionManager *createPlatformSessionManager(const QString &id, const QString &key) const;
 #endif
+
+    virtual void sync();
 protected:
     void screenAdded(QPlatformScreen *screen);
 };
diff --git a/src/plugins/platforms/xcb/qxcbintegration.cpp b/src/plugins/platforms/xcb/qxcbintegration.cpp
index 6b5ea93638..d794065d45 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.cpp
+++ b/src/plugins/platforms/xcb/qxcbintegration.cpp
@@ -282,6 +282,7 @@ bool QXcbIntegration::hasCapability(QPlatformIntegration::Capability cap) const
     case WindowMasks: return true;
     case MultipleWindows: return true;
     case ForeignWindows: return true;
+    case SyncState: return true;
     default: return QPlatformIntegration::hasCapability(cap);
     }
 }
@@ -458,4 +459,11 @@ QPlatformSessionManager *QXcbIntegration::createPlatformSessionManager(const QSt
 }
 #endif
 
+void QXcbIntegration::sync()
+{
+    for (int i = 0; i < m_connections.size(); i++) {
+        m_connections.at(i)->sync();
+    }
+}
+
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/xcb/qxcbintegration.h b/src/plugins/platforms/xcb/qxcbintegration.h
index 79fb1965c4..6ae23125c8 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.h
+++ b/src/plugins/platforms/xcb/qxcbintegration.h
@@ -106,6 +106,7 @@ public:
     QPlatformSessionManager *createPlatformSessionManager(const QString &id, const QString &key) const Q_DECL_OVERRIDE;
 #endif
 
+    void sync();
 private:
     QList<QXcbConnection *> m_connections;