patch 1:
--- qt-opensource-4.8.0.old/src/gui/kernel/qapplication_x11.cpp	2011-12-16 03:22:33.918428374 -0500
+++ qt-opensource-4.8.0.new/src/gui/kernel/qapplication_x11.cpp	2011-12-27 06:39:22.852191952 -0500
@@ -4244,6 +4244,12 @@ bool QETWidget::translateMouseEvent(cons
                     && (nextEvent.xclient.message_type == ATOM(_QT_SCROLL_DONE) ||
                     (nextEvent.xclient.message_type == ATOM(WM_PROTOCOLS) &&
                      (Atom)nextEvent.xclient.data.l[0] == ATOM(_NET_WM_SYNC_REQUEST))))) {
+                // As we may run through a significant number of a large class of non-MotionNotify
+                // events here, without returning to the event loop, just before processing nextEvent,
+                // pass it through QAbstractEventDispatcher::filterEvent().  Note that this issue may
+                // exist elsewhere, wherever events are compressed in a similar manner.
+                if (QAbstractEventDispatcher::instance()->filterEvent(&nextEvent))
+                    continue;
                 qApp->x11ProcessEvent(&nextEvent);
                 continue;
             } else if (nextEvent.type != MotionNotify ||
---

patch 2:
--- qt-opensource-4.8.0.old/src/gui/kernel/qapplication_x11.cpp	2011-12-16 03:22:33.918428374 -0500
+++ qt-opensource-4.8.0.new/src/gui/kernel/qapplication_x11.cpp	2011-12-27 06:21:28.510129894 -0500
@@ -4230,28 +4230,17 @@ bool QETWidget::translateMouseEvent(cons
             return false;
 
         XMotionEvent lastMotion = event->xmotion;
-        while(XPending(X11->display))  { // compress mouse moves
-            XNextEvent(X11->display, &nextEvent);
-            if (nextEvent.type == ConfigureNotify
-                || nextEvent.type == PropertyNotify
-                || nextEvent.type == Expose
-                || nextEvent.type == GraphicsExpose
-                || nextEvent.type == NoExpose
-                || nextEvent.type == KeymapNotify
-                || ((nextEvent.type == EnterNotify || nextEvent.type == LeaveNotify)
-                    && qt_button_down == this)
-                || (nextEvent.type == ClientMessage
-                    && (nextEvent.xclient.message_type == ATOM(_QT_SCROLL_DONE) ||
-                    (nextEvent.xclient.message_type == ATOM(WM_PROTOCOLS) &&
-                     (Atom)nextEvent.xclient.data.l[0] == ATOM(_NET_WM_SYNC_REQUEST))))) {
-                qApp->x11ProcessEvent(&nextEvent);
-                continue;
-            } else if (nextEvent.type != MotionNotify ||
-                       nextEvent.xmotion.window != event->xmotion.window ||
-                       nextEvent.xmotion.state != event->xmotion.state) {
-                XPutBackEvent(X11->display, &nextEvent);
+        // Compress any additional (same window, same state, contiguous) MotionNotify
+        // events immediately following this one.  This appears to work, but may have
+        // negative side effects such as increased event processing due to sub-optimal
+        // compression:
+        while (XPending(X11->display)) {
+            XPeekEvent(X11->display, &nextEvent);
+            if (nextEvent.type != MotionNotify ||
+                nextEvent.xmotion.window != event->xmotion.window ||
+                nextEvent.xmotion.state  != event->xmotion.state)
                 break;
-            }
+            XNextEvent(X11->display, &nextEvent);
             if (!qt_x11EventFilter(&nextEvent)
                 && !x11Event(&nextEvent)) // send event through filter
                 lastMotion = nextEvent.xmotion;
---

patch 3:
--- qt-opensource-4.8.0.old/src/gui/kernel/qapplication_x11.cpp	2011-12-16 03:22:33.918428374 -0500
+++ qt-opensource-4.8.0.new/src/gui/kernel/qapplication_x11.cpp	2011-12-27 18:08:38.625333252 -0500
@@ -4230,27 +4230,17 @@ bool QETWidget::translateMouseEvent(cons
             return false;
 
         XMotionEvent lastMotion = event->xmotion;
-        while(XPending(X11->display))  { // compress mouse moves
+        // Compress any additional (same window, same state, not nessarily contiguous)
+        // MotionNotify events without disturbing other events.  This appears to work,
+        // but may have negative side effects due to the out-of-order event processing
+        QList<XEvent> saved_events;
+        while (XPending(X11->display)) {
             XNextEvent(X11->display, &nextEvent);
-            if (nextEvent.type == ConfigureNotify
-                || nextEvent.type == PropertyNotify
-                || nextEvent.type == Expose
-                || nextEvent.type == GraphicsExpose
-                || nextEvent.type == NoExpose
-                || nextEvent.type == KeymapNotify
-                || ((nextEvent.type == EnterNotify || nextEvent.type == LeaveNotify)
-                    && qt_button_down == this)
-                || (nextEvent.type == ClientMessage
-                    && (nextEvent.xclient.message_type == ATOM(_QT_SCROLL_DONE) ||
-                    (nextEvent.xclient.message_type == ATOM(WM_PROTOCOLS) &&
-                     (Atom)nextEvent.xclient.data.l[0] == ATOM(_NET_WM_SYNC_REQUEST))))) {
-                qApp->x11ProcessEvent(&nextEvent);
+            if (nextEvent.type != MotionNotify ||
+                nextEvent.xmotion.window != event->xmotion.window ||
+                nextEvent.xmotion.state  != event->xmotion.state) {
+                saved_events.append(nextEvent);
                 continue;
-            } else if (nextEvent.type != MotionNotify ||
-                       nextEvent.xmotion.window != event->xmotion.window ||
-                       nextEvent.xmotion.state != event->xmotion.state) {
-                XPutBackEvent(X11->display, &nextEvent);
-                break;
             }
             if (!qt_x11EventFilter(&nextEvent)
                 && !x11Event(&nextEvent)) // send event through filter
@@ -4258,6 +4248,10 @@ bool QETWidget::translateMouseEvent(cons
             else
                 break;
         }
+        foreach (XEvent ev, saved_events)
+            XPutBackEvent(X11->display, (XEvent*)&ev);
+        saved_events.clear();
+
         type = QEvent::MouseMove;
         pos.rx() = lastMotion.x;
         pos.ry() = lastMotion.y;