'''
Anchor Layout
=============
.. only:: html
.. image:: images/anchorlayout.gif
:align: right
.. only:: latex
.. image:: images/anchorlayout.png
:align: right
The :class:`AnchorLayout` aligns its children to a border (top, bottom,
left, right) or center.
To draw a button in the lower-right corner::
layout = AnchorLayout(
anchor_x='right', anchor_y='bottom')
btn = Button(text='Hello World')
layout.add_widget(btn)
'''
__all__ = ('AnchorLayout', )
from kivy.uix.layout import Layout
from kivy.properties import OptionProperty, VariableListProperty
[docs]class AnchorLayout(Layout):
'''Anchor layout class. See the module documentation for more information.
'''
padding = VariableListProperty([0, 0, 0, 0])
'''Padding between the widget box and its children, in pixels:
[padding_left, padding_top, padding_right, padding_bottom].
padding also accepts a two argument form [padding_horizontal,
padding_vertical] and a one argument form [padding].
:attr:`padding` is a :class:`~kivy.properties.VariableListProperty` and
defaults to [0, 0, 0, 0].
'''
anchor_x = OptionProperty('center', options=(
'left', 'center', 'right'))
'''Horizontal anchor.
:attr:`anchor_x` is an :class:`~kivy.properties.OptionProperty` and
defaults to 'center'. It accepts values of 'left', 'center' or
'right'.
'''
anchor_y = OptionProperty('center', options=(
'top', 'center', 'bottom'))
'''Vertical anchor.
:attr:`anchor_y` is an :class:`~kivy.properties.OptionProperty` and
defaults to 'center'. It accepts values of 'top', 'center' or
'bottom'.
'''
def __init__(self, **kwargs):
super(AnchorLayout, self).__init__(**kwargs)
fbind = self.fbind
update = self._trigger_layout
fbind('children', update)
fbind('parent', update)
fbind('padding', update)
fbind('anchor_x', update)
fbind('anchor_y', update)
fbind('size', update)
fbind('pos', update)
[docs] def do_layout(self, *largs):
_x, _y = self.pos
width = self.width
height = self.height
anchor_x = self.anchor_x
anchor_y = self.anchor_y
pad_left, pad_top, pad_right, pad_bottom = self.padding
for c in self.children:
x, y = _x, _y
cw, ch = c.size
shw, shh = c.size_hint
shw_min, shh_min = c.size_hint_min
shw_max, shh_max = c.size_hint_max
if shw is not None:
cw = shw * (width - pad_left - pad_right)
if shw_min is not None and cw < shw_min:
cw = shw_min
elif shw_max is not None and cw > shw_max:
cw = shw_max
if shh is not None:
ch = shh * (height - pad_top - pad_bottom)
if shh_min is not None and ch < shh_min:
ch = shh_min
elif shh_max is not None and ch > shh_max:
ch = shh_max
if anchor_x == 'left':
x = x + pad_left
elif anchor_x == 'right':
x = x + width - (cw + pad_right)
else:
x = x + (width - pad_right + pad_left - cw) / 2
if anchor_y == 'bottom':
y = y + pad_bottom
elif anchor_y == 'top':
y = y + height - (ch + pad_top)
else:
y = y + (height - pad_top + pad_bottom - ch) / 2
c.pos = x, y
c.size = cw, ch
