diff -r dee5afe5301f -r 3f74d0d4af4c src/gui/kernel/qwidget_mac.mm
--- a/src/gui/kernel/qwidget_mac.mm	Mon Mar 15 12:43:09 2010 +0200
+++ b/src/gui/kernel/qwidget_mac.mm	Thu Apr 08 14:19:33 2010 +0300
@@ -152,6 +152,7 @@
 static OSWindowRef qt_root_win = 0;
 QWidget *mac_mouse_grabber = 0;
 QWidget *mac_keyboard_grabber = 0;
+extern QPointer<QWidget> qt_button_down; //qapplication_mac.cpp
 
 #ifndef QT_MAC_USE_COCOA
 #ifdef QT_NAMESPACE
@@ -565,6 +566,25 @@
 }
 #endif
 
+#ifdef QT_MAC_USE_COCOA
+void qt_mac_set_needs_display(QWidget *widget, QRegion region)
+{
+    NSView *theNSView = qt_mac_nativeview_for(widget);
+    if (region.isEmpty()) {
+        [theNSView setNeedsDisplay:YES];
+        return;
+    }
+
+    QVector<QRect> rects = region.rects();
+    for (int i = 0; i<rects.count(); ++i) {
+        const QRect &rect = rects.at(i);
+        NSRect nsrect = NSMakeRect(rect.x(), rect.y(), rect.width(), rect.height());
+        [theNSView setNeedsDisplayInRect:nsrect];
+    }
+
+}
+#endif
+
 inline static bool updateRedirectedToGraphicsProxyWidget(QWidget *widget, const QRect &rect)
 {
     if (!widget)
@@ -847,7 +867,6 @@
                                                            & ~Qt::WindowMaximized));
                 QApplication::sendSpontaneousEvent(widget, &e);
             }
-            extern QPointer<QWidget> qt_button_down; //qapplication_mac.cpp
             qt_button_down = 0;
         } else if(ekind == kEventWindowCollapsed) {
             if (!widget->isMinimized()) {
@@ -875,7 +894,6 @@
             //we send a hide to be like X11/Windows
             QEvent e(QEvent::Hide);
             QApplication::sendSpontaneousEvent(widget, &e);
-            extern QPointer<QWidget> qt_button_down; //qapplication_mac.cpp
             qt_button_down = 0;
         } else if(ekind == kEventWindowToolbarSwitchMode) {
             macSendToolbarChangeEvent(widget);
@@ -1249,6 +1267,11 @@
                 if (widget->isVisible() && widget->updatesEnabled()) { //process the actual paint event.
                     if(widget->testAttribute(Qt::WA_WState_InPaintEvent))
                         qWarning("QWidget::repaint: Recursive repaint detected");
+                    if (widget->isWindow() && !widget->d_func()->isOpaque
+                        && !widget->testAttribute(Qt::WA_MacBrushedMetal)) {
+                        QRect qrgnRect = qrgn.boundingRect();
+                        CGContextClearRect(cg, CGRectMake(qrgnRect.x(), qrgnRect.y(), qrgnRect.width(), qrgnRect.height()));
+                    }
 
                     QPoint redirectionOffset(0, 0);
                     QWidget *tl = widget->window();
@@ -1299,13 +1322,6 @@
                             widget->d_func()->restoreRedirected();
                     }
 
-                    if (widget->isWindow() && !widget->d_func()->isOpaque
-                           && !widget->testAttribute(Qt::WA_MacBrushedMetal)) {
-                        QRect qrgnRect = qrgn.boundingRect();
-                        CGContextClearRect(cg, CGRectMake(qrgnRect.x(), qrgnRect.y(), qrgnRect.width(), qrgnRect.height()));
-                    }
-
-
                     if(!HIObjectIsOfClass((HIObjectRef)hiview, kObjectQWidget))
                         CallNextEventHandler(er, event);
 
@@ -1502,7 +1518,6 @@
             if (widget) {
                 qt_event_request_window_change(widget);
                 if (!HIViewIsVisible(HIViewRef(widget->winId()))) {
-                    extern QPointer<QWidget> qt_button_down; //qapplication_mac.cpp
                     if (widget == qt_button_down)
                         qt_button_down = 0;
                 }
@@ -1511,7 +1526,6 @@
         break; }
     case kEventClassMouse: {
         bool send_to_app = false;
-        extern QPointer<QWidget> qt_button_down; //qapplication_mac.cpp
         if(qt_button_down)
             send_to_app = true;
         if(send_to_app) {
@@ -3388,7 +3402,6 @@
     Q_Q(QWidget);
     if((q->windowType() == Qt::Desktop)) //you can't hide the desktop!
         return;
-
     QMacCocoaAutoReleasePool pool;
     if(q->isWindow()) {
         OSWindowRef window = qt_mac_window_for(q);
@@ -4456,8 +4469,20 @@
         }
     }
 
+    // ### Scroll the dirty regions as well, the following is not correct.
+    QRegion displayRegion = r.isNull() ? dirtyOnWidget : (dirtyOnWidget & r);
+    const QVector<QRect> &rects = dirtyOnWidget.rects();
+    const QVector<QRect>::const_iterator end = rects.end();
+    QVector<QRect>::const_iterator it = rects.begin();
+    while (it != end) {
+	const QRect rect = *it;
+	const NSRect dirtyRect = NSMakeRect(rect.x() + dx, rect.y() + dy,
+		rect.width(), rect.height());
+	[view setNeedsDisplayInRect:dirtyRect];
+	++it;
+    }
+
     NSSize deltaSize = NSMakeSize(dx, dy);
-    [view translateRectsNeedingDisplayInRect:scrollRect by:deltaSize];
     [view scrollRect:scrollRect by:deltaSize];
     [view setNeedsDisplayInRect:deltaXRect];
     [view setNeedsDisplayInRect:deltaYRect];
@@ -4657,8 +4682,10 @@
     if (!q->testAttribute(Qt::WA_WState_Created) || !extra)
         return;
 
-    if (extra->hasMask && extra->maskBits.size() != q->size()) {
-        extra->maskBits = QImage(q->size(), QImage::Format_Mono);
+    if (extra->hasMask) {
+        if(extra->maskBits.size() != q->size()) {
+            extra->maskBits = QImage(q->size(), QImage::Format_Mono);
+        }
         extra->maskBits.fill(QColor(Qt::color1).rgba());
         extra->maskBits.setNumColors(2);
         extra->maskBits.setColor(0, QColor(Qt::color0).rgba());