Calculate actual widget width based on given margins.

def calculate_width_widget(width, margin = None, margin_left = None, margin_right = None):
        """
        Calculate actual widget width based on given margins.
        """
        if margin_left is None:
            margin_left = margin
        if margin_right is None:
            margin_right = margin
        if margin_left is not None:
            width -= int(margin_left)
        if margin_right is not None:
            width -= int(margin_right)
        return width if width > 0 else None