diff -r dee5afe5301f -r 3f74d0d4af4c src/gui/kernel/qcocoaview_mac.mm
--- a/src/gui/kernel/qcocoaview_mac.mm	Mon Mar 15 12:43:09 2010 +0200
+++ b/src/gui/kernel/qcocoaview_mac.mm	Thu Apr 08 14:19:33 2010 +0300
@@ -520,10 +520,11 @@
 - (void)drawRect:(NSRect)aRect
 {
     if (QApplicationPrivate::graphicsSystem() != 0) {
-        if (QWidgetBackingStore *bs = qwidgetprivate->maybeBackingStore())
-            bs->markDirty(qwidget->rect(), qwidget);
-        qwidgetprivate->syncBackingStore(qwidget->rect());
-        return;
+        if (QWidgetBackingStore *bs = qwidgetprivate->maybeBackingStore()) {
+            // Drawing is handled on the window level
+            // See qcocoasharedwindowmethods_mac_p.
+            return;
+        }
     }
     CGContextRef cg = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
     qwidgetprivate->hd = cg;
@@ -827,6 +828,7 @@
         deltaZ = qBound(-120, int([theEvent deltaZ] * 10000), 120);
     }
 
+#ifndef QT_NO_WHEELEVENT
     if (deltaX != 0) {
         QWheelEvent qwe(qlocal, qglobal, deltaX, buttons, keyMods, Qt::Horizontal);
         qt_sendSpontaneousEvent(widgetToGetMouse, &qwe);
@@ -867,6 +869,8 @@
             wheelOK = qwe2.isAccepted();
         }
     }
+#endif //QT_NO_WHEELEVENT
+
     if (!wheelOK) {
         return [super scrollWheel:theEvent];
     }
@@ -1403,7 +1407,7 @@
 
     // setup the data
     QMacPasteboard dragBoard((CFStringRef) NSDragPboard, QMacPasteboardMime::MIME_DND);
-    dragPrivate()->data->setData(QLatin1String("application/x-qt-mime-type-name"), QByteArray());
+    dragPrivate()->data->setData(QLatin1String("application/x-qt-mime-type-name"), QByteArray("dummy"));
     dragBoard.setMimeData(dragPrivate()->data);
 
     // create the image