Starts a loader widget on the inputed widget.
        
        :param      widget          | <QWidget>
        
        :return     <XLoaderWidget>

def start(widget, processEvents=True, style=None, movie=None):
        """
        Starts a loader widget on the inputed widget.
        
        :param      widget          | <QWidget>
        
        :return     <XLoaderWidget>
        """
        if style is None:
            style = os.environ.get('PROJEXUI_LOADER_STYLE', 'gray')
        
        # there is a bug with the way the loader is handled in a splitter,
        # so bypass it
        parent = widget.parent()
        while isinstance(parent, QSplitter):
            parent = parent.parent()
        
        # retrieve the loader widget
        loader = getattr(widget, '_private_xloader_widget', None)
        if not loader:
            loader = XLoaderWidget(parent, style)
            
            # make sure that if the widget is destroyed, the loader closes
            widget.destroyed.connect(loader.deleteLater)
            
            setattr(widget, '_private_xloader_widget', loader)
            setattr(widget, '_private_xloader_count', 0)
            
            loader.move(widget.pos())
            if widget.isVisible():
                loader.show()
            
            if movie:
                loader.setMovie(movie)
            
            widget.installEventFilter(loader)
        else:
            count = getattr(widget, '_private_xloader_count', 0)
            setattr(widget, '_private_xloader_count', count + 1)
        
        loader.resize(widget.size())
        return loader