QWidget on top of gstreamer

[Marco Trapanese]

Hi,

with this code:

Widget::Widget(QWidget *parent) : QWidget(parent), ui(new Ui::Widget) {
     ui->setupUi(this);
     setAttribute(Qt::WA_NativeWindow, true);
     gst_init(NULL, NULL);
     GstElement *pipeline = gst_pipeline_new ("xvoverlay");
     GstElement *src = gst_element_factory_make ("videotestsrc", NULL);
     GstElement *sink = gst_element_factory_make ("ximagesink", NULL);
     gst_bin_add_many (GST_BIN (pipeline), src, sink, NULL);
     gst_element_link (src, sink);
     gst_video_overlay_set_window_handle (GST_VIDEO_OVERLAY(sink), 
ui->widget->winId());
     GstStateChangeReturn ret = gst_element_set_state (pipeline, 
GST_STATE_PLAYING);
}
I see the video test on a QWidget.
Now I want to put over that other widgets with some transparencies.
I get this effect:

http://oi44.tinypic.com/2q9e4wi.jpg

How to get the transparency work also for the area above the video?
I'm working on Debian Jessie 32-bit.

Thanks!
Marco