"""Widgets are placed on fixed position as specified in `sizereq`.

    Align hints (kwargs to :meth:`add`):

        * halign = 'left' (default) | 'right' | 'fill' | 'center'

        * valign = 'top' (default) | 'bottom' | 'fill' | 'center'

    """

    def __init__(self):

        Layout.__init__(self)

        self._widget_hints = {}  # Widget : (halign, valign)

    def add(self, widget, *args, **kwargs):

        Layout.add(self, widget)

        assert len(args) == 0, \

            "FixedLayout does not support positional hint args: %s" % args

        assert all(key in ('halign', 'valign') for key in kwargs.keys()), \

            "Unsupported hints: %s" % tuple(kwargs.keys())

        halign = kwargs.get('halign', 'left')

        valign = kwargs.get('valign', 'top')

        self._widget_hints[widget] = (halign, valign)

    def update(self, w, h):

            halign, valign = self._widget_hints[widget]

            px, py = widget.posreq

            sw, sh = widget.sizereq

            if halign == 'right':   px = w - px

            if valign == 'bottom':  py = h - py

            if halign == 'fill':    px = 0; sw = w

            if valign == 'fill':    py = 0; sh = h

            if halign == 'center':  px = (w - sw) // 2

            if valign == 'center':  py = (h - sh) // 2

            widget.resize(sw, sh)

            widget.pos.update(px, py)