QDrag setPixmap failed with "XBM" format

[alfa_wu]

Hi all,
I got trouble when QDrag setPixmap with "XBM" format.(X11 env.)
You can reproduce it by modify exmaple ~qt4.x.src/examples/draganddrop/draggableicons/dragwidget.cpp
Replace Line #110 ( drag->setPixmap(pixmap); ) with

{
        static unsigned char drag_bits[] = {
       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
       0x00, 0x7f, 0x00, 0x00, 0x41, 0x00, 0x00, 0x41, 0x00, 0xff, 0xc1, 0x0f,
       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0xf0, 0x0f,
       0x40, 0x10, 0x00, 0x40, 0x10, 0x00, 0xc0, 0x1f, 0x00, 0x00, 0x00, 0x00,
       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
 
        QBitmap pixmap = QBitmap::fromData(
                        QSize(20, 20), drag_bits, QImage::Format_Mono);
         pixmap.setMask(QPixmap::grabWidget(this).createHeuristicMask(true));
        drag->setPixmap((QPixmap)pixmap);
 
}

{
        static unsigned char drag_bits[] = {
       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
       0x00, 0x7f, 0x00, 0x00, 0x41, 0x00, 0x00, 0x41, 0x00, 0xff, 0xc1, 0x0f,
       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0xf0, 0x0f,
       0x40, 0x10, 0x00, 0x40, 0x10, 0x00, 0xc0, 0x1f, 0x00, 0x00, 0x00, 0x00,
       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

        QBitmap pixmap = QBitmap::fromData(
                        QSize(20, 20), drag_bits, QImage::Format_Mono);
         pixmap.setMask(QPixmap::grabWidget(this).createHeuristicMask(true));
        drag->setPixmap((QPixmap)pixmap);

}

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When we start dragging,
we can find the icon is not xbm format, it become color not mono.
And draggable icon contain background color

Does anyone can help me?
I need mono draggable icon.(XBM format)