diff -up qt-everywhere-opensource-src-4.8.5/src/gui/kernel/qapplication_x11.cpp.QTBUG-21900 qt-everywhere-opensource-src-4.8.5/src/gui/kernel/qapplication_x11.cpp

--- qt-everywhere-opensource-src-4.8.5/src/gui/kernel/qapplication_x11.cpp.QTBUG-21900	2013-05-30 16:18:05.000000000 -0500

+++ qt-everywhere-opensource-src-4.8.5/src/gui/kernel/qapplication_x11.cpp	2013-06-09 11:53:45.891771748 -0500

@@ -818,6 +818,27 @@ static Bool qt_sync_request_scanner(Disp

 #endif

 #endif // QT_NO_XSYNC

+struct qt_configure_event_data

+{

+    WId window;

+    WId parent;

+};

+

+static Bool qt_configure_event_scanner(Display*, XEvent *event, XPointer arg)

+{

+    qt_configure_event_data *data =

+        reinterpret_cast<qt_configure_event_data*>(arg);

+    if (event->type == ConfigureNotify &&

+        event->xconfigure.window == data->window) {

+        return true;

+    } else if (event->type == ReparentNotify &&

+               event->xreparent.window == data->window) {

+        data->parent = event->xreparent.parent;

+    }

+

+    return false;

+}

+

 static void qt_x11_create_intern_atoms()

 {

     const char *names[QX11Data::NAtoms];

@@ -5302,8 +5323,11 @@ bool QETWidget::translateConfigEvent(con

         if (d->extra->compress_events) {

             // ConfigureNotify compression for faster opaque resizing

             XEvent otherEvent;

-            while (XCheckTypedWindowEvent(X11->display, internalWinId(), ConfigureNotify,

-                                          &otherEvent)) {

+            qt_configure_event_data configureData;

+            configureData.window = internalWinId();

+            configureData.parent = d->topData()->parentWinId;

+            while (XCheckIfEvent(X11->display, &otherEvent,

+                                 &qt_configure_event_scanner, (XPointer)&configureData)) {

                 if (qt_x11EventFilter(&otherEvent))

                     continue;

@@ -5316,13 +5340,19 @@ bool QETWidget::translateConfigEvent(con

                 newSize.setWidth(otherEvent.xconfigure.width);

                 newSize.setHeight(otherEvent.xconfigure.height);

+                trust = isVisible()

+                        && (configureData.parent == XNone ||

+                            configureData.parent == QX11Info::appRootWindow());

+

                 if (otherEvent.xconfigure.send_event || trust) {

                     newCPos.rx() = otherEvent.xconfigure.x +

                                    otherEvent.xconfigure.border_width;

                     newCPos.ry() = otherEvent.xconfigure.y +

                                    otherEvent.xconfigure.border_width;

                     isCPos = true;

-                }

+                } else {

+                    isCPos = false;

+               }

             }

 #ifndef QT_NO_XSYNC

             qt_sync_request_event_data sync_event;

@@ -5335,9 +5365,14 @@ bool QETWidget::translateConfigEvent(con

         }

         if (!isCPos) {

-            // we didn't get an updated position of the toplevel.

-            // either we haven't moved or there is a bug in the window manager.

-            // anyway, let's query the position to be certain.

+            // If the last configure event didn't have a trustable position,

+            // it's necessary to query, see ICCCM 4.24:

+            //

+            //  Any real ConfigureNotify event on a top-level window implies

+            //  that the window’s position on the root may have changed, even

+            //  though the event reports that the window’s position in its

+            //  parent is unchanged because the window may have been reparented.

+

             int x, y;

             Window child;

             XTranslateCoordinates(X11->display, internalWinId(),