fix scrollwheel issues. make sure we reset origin before calling GlobalToLocal() and xlate local mouse coord into widget-relative coords for gecko. r=bryner/sr=sfraser/a=shaver. bug#125570

widget/src/mac/nsMacEventHandler.cpp

@@ -148,6 +148,12 @@ HandleScrollEvent ( EventMouseWheelAxis inAxis, PRBool inByLine, PRInt32 inDelta
   if ( !inByLine )
     scrollEvent.scrollFlags |= nsMouseScrollEvent::kIsFullPage;
   
+  // convert window-relative (local) mouse coordinates to widget-relative
+  // coords for Gecko.
+  nsPoint widgetOrigin(0, 0);
+  inWidget->ConvertToDeviceCoordinates(widgetOrigin.x, widgetOrigin.y);
+  nsPoint mouseLocRelativeToWidget(inMouseLoc.h - widgetOrigin.x, inMouseLoc.v - widgetOrigin.y);
+		
   scrollEvent.eventStructType = NS_MOUSE_SCROLL_EVENT;
   scrollEvent.isShift = PR_FALSE;
   scrollEvent.isControl = PR_FALSE;
@@ -155,8 +161,8 @@ HandleScrollEvent ( EventMouseWheelAxis inAxis, PRBool inByLine, PRInt32 inDelta
   scrollEvent.isAlt = PR_FALSE;
 	scrollEvent.message = NS_MOUSE_SCROLL;
   scrollEvent.delta = inDelta;
-	scrollEvent.point.x = inMouseLoc.h;
-	scrollEvent.point.y = inMouseLoc.v;
+	scrollEvent.point.x = mouseLocRelativeToWidget.x;
+	scrollEvent.point.y = mouseLocRelativeToWidget.y;
 	scrollEvent.time = PR_IntervalNow();
 	scrollEvent.widget = inWidget;
 	scrollEvent.nativeMsg = nsnull;

widget/src/mac/nsMacWindow.cpp

@@ -644,8 +644,9 @@ nsMacWindow :: ScrollEventHandler ( EventHandlerCallRef inHandlerChain, EventRef
   if ( err1 == noErr && err2 == noErr && err3 == noErr ) {
     nsMacWindow* self = NS_REINTERPRET_CAST(nsMacWindow*, userData);
     if ( self ) {
-      // convert mouse to local coordinates since that's how gecko wants them
+      // convert mouse to local coordinates since that's how the event handler wants them
       StPortSetter portSetter(self->mWindowPtr);
+      StOriginSetter originSetter(self->mWindowPtr);
       ::GlobalToLocal(&mouseLoc);
       self->mMacEventHandler->Scroll ( axis, delta, mouseLoc );
     }