from .layout import Layout

class AnchorLayout(Layout):

    """Anchor widgets to borders of container."""

    def __init__(self):

        Layout.__init__(self)

        self.register_hints(

            'halign', make_select('left', 'right', 'fill', 'center'),

            'valign', make_select('top', 'bottom', 'fill', 'center'),

            'margin', Borders,

            )

    def on_resize(self, ev):

        for child in self._get_children():

            reqw = max(child.sizereq.w, child.sizemin.w)

            reqh = max(child.sizereq.h, child.sizemin.h)

            ha = child.hint_value('halign')

            va = child.hint_value('valign')

            margin = child.hint_value('margin')

            if ha == 'left':

                x = margin.l

                w = reqw

            if ha == 'right':

                x = self.width - margin.r - reqw

                w = reqw

            if ha == 'fill':

                x = margin.l

                w = self.width - margin.l - margin.r

            if ha == 'center':

                x = (self.width - reqw) // 2

                w = reqw

            if va == 'top':

                y = margin.t

                h = reqh

            if va == 'bottom':

                y = self.height - margin.b - reqh

                h = reqh

            if va == 'fill':

                y = margin.t

                h = self.height - margin.t - margin.b

            if va == 'center':

                y = (self.height - reqh) // 2

                h = reqh

            child._pos.update(x=x, y=y)

            child._size.update(w=w, h=h)

            child._view_size.update(w=w, h=h)

    def move_child(self, child, x=None, y=None):

        """Move child inside container by adjusting its margin.

        Operation is supported only for one-side anchors:

            left, right, top, bottom

        No move on axis where align is set to

            center, fill

        """

        if not child in self.children:

            raise ValueError('AnchorLayout.move(): Cannot move foreign child.')

        margin = child.hint_value('margin')

        newx = None

        if x is not None:

            ha = child.hint_value('halign')

            ofsx = x - child.x

            if ha == 'left':

                margin.l += ofsx

                newx = margin.l

            elif ha == 'right':

                margin.r -= ofsx

                newx = self.width - margin.r - child.sizereq.w

        newy = None

        if y is not None:

            va = child.hint_value('valign')

            ofsy = y - child.y

            if va == 'top':

                margin.t += ofsy

                newy = margin.t

            elif va == 'bottom':

                margin.b -= ofsy

                newy = self.height - margin.b - child.sizereq.h

        child._pos.update(x=newx, y=newy)