Quick search

Table Of Contents

Source code for kivy.uix.boxlayout

Box Layout

.. only:: html

    .. image:: images/boxlayout.gif
        :align: right

.. only:: latex

    .. image:: images/boxlayout.png
        :align: right

:class:`BoxLayout` arranges children in a vertical or horizontal box.

To position widgets above/below each other, use a vertical BoxLayout::

    layout = BoxLayout(orientation='vertical')
    btn1 = Button(text='Hello')
    btn2 = Button(text='World')

To position widgets next to each other, use a horizontal BoxLayout. In this
example, we use 10 pixel spacing between children; the first button covers
70% of the horizontal space, the second covers 30%::

    layout = BoxLayout(spacing=10)
    btn1 = Button(text='Hello', size_hint=(.7, 1))
    btn2 = Button(text='World', size_hint=(.3, 1))

Position hints are partially working, depending on the orientation:

* If the orientation is `vertical`: `x`, `right` and `center_x` will be used.
* If the orientation is `horizontal`: `y`, `top` and `center_y` will be used.

You can check the `examples/widgets/boxlayout_poshint.py` for a live example.

.. note::

    The `size_hint` uses the available space after subtracting all the
    fixed-size widgets. For example, if you have a layout that is 800px
    wide, and add three buttons like this::

        btn1 = Button(text='Hello', size=(200, 100), size_hint=(None, None))
        btn2 = Button(text='Kivy', size_hint=(.5, 1))
        btn3 = Button(text='World', size_hint=(.5, 1))

    The first button will be 200px wide as specified, the second and third
    will be 300px each, e.g. (800-200) * 0.5

.. versionchanged:: 1.4.1
    Added support for `pos_hint`.


__all__ = ('BoxLayout', )

from kivy.uix.layout import Layout
from kivy.properties import (NumericProperty, OptionProperty,
                             VariableListProperty, ReferenceListProperty)

[docs]class BoxLayout(Layout): '''Box layout class. See module documentation for more information. ''' spacing = NumericProperty(0) '''Spacing between children, in pixels. :attr:`spacing` is a :class:`~kivy.properties.NumericProperty` and defaults to 0. ''' padding = VariableListProperty([0, 0, 0, 0]) '''Padding between layout box and children: [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]. .. versionchanged:: 1.7.0 Replaced NumericProperty with VariableListProperty. :attr:`padding` is a :class:`~kivy.properties.VariableListProperty` and defaults to [0, 0, 0, 0]. ''' orientation = OptionProperty('horizontal', options=( 'horizontal', 'vertical')) '''Orientation of the layout. :attr:`orientation` is an :class:`~kivy.properties.OptionProperty` and defaults to 'horizontal'. Can be 'vertical' or 'horizontal'. ''' minimum_width = NumericProperty(0) '''Automatically computed minimum width needed to contain all children. .. versionadded:: 1.10.0 :attr:`minimum_width` is a :class:`~kivy.properties.NumericProperty` and defaults to 0. It is read only. ''' minimum_height = NumericProperty(0) '''Automatically computed minimum height needed to contain all children. .. versionadded:: 1.10.0 :attr:`minimum_height` is a :class:`~kivy.properties.NumericProperty` and defaults to 0. It is read only. ''' minimum_size = ReferenceListProperty(minimum_width, minimum_height) '''Automatically computed minimum size needed to contain all children. .. versionadded:: 1.10.0 :attr:`minimum_size` is a :class:`~kivy.properties.ReferenceListProperty` of (:attr:`minimum_width`, :attr:`minimum_height`) properties. It is read only. ''' def __init__(self, **kwargs): super(BoxLayout, self).__init__(**kwargs) update = self._trigger_layout fbind = self.fbind fbind('spacing', update) fbind('padding', update) fbind('children', update) fbind('orientation', update) fbind('parent', update) fbind('size', update) fbind('pos', update) def _iterate_layout(self, sizes): # optimize layout by preventing looking at the same attribute in a loop len_children = len(sizes) padding_left, padding_top, padding_right, padding_bottom = self.padding spacing = self.spacing orientation = self.orientation padding_x = padding_left + padding_right padding_y = padding_top + padding_bottom # calculate maximum space used by size_hint stretch_sum = 0. has_bound = False hint = [None] * len_children # min size from all the None hint, and from those with sh_min minimum_size_bounded = 0 if orientation == 'horizontal': minimum_size_y = 0 minimum_size_none = padding_x + spacing * (len_children - 1) for i, ((w, h), (shw, shh), _, (shw_min, shh_min), (shw_max, _)) in enumerate(sizes): if shw is None: minimum_size_none += w else: hint[i] = shw if shw_min: has_bound = True minimum_size_bounded += shw_min elif shw_max is not None: has_bound = True stretch_sum += shw if shh is None: minimum_size_y = max(minimum_size_y, h) elif shh_min: minimum_size_y = max(minimum_size_y, shh_min) minimum_size_x = minimum_size_bounded + minimum_size_none minimum_size_y += padding_y else: minimum_size_x = 0 minimum_size_none = padding_y + spacing * (len_children - 1) for i, ((w, h), (shw, shh), _, (shw_min, shh_min), (_, shh_max)) in enumerate(sizes): if shh is None: minimum_size_none += h else: hint[i] = shh if shh_min: has_bound = True minimum_size_bounded += shh_min elif shh_max is not None: has_bound = True stretch_sum += shh if shw is None: minimum_size_x = max(minimum_size_x, w) elif shw_min: minimum_size_x = max(minimum_size_x, shw_min) minimum_size_y = minimum_size_bounded + minimum_size_none minimum_size_x += padding_x self.minimum_size = minimum_size_x, minimum_size_y # do not move the w/h get above, it's likely to change on above line selfx = self.x selfy = self.y if orientation == 'horizontal': stretch_space = max(0.0, self.width - minimum_size_none) dim = 0 else: stretch_space = max(0.0, self.height - minimum_size_none) dim = 1 if has_bound: # make sure the size_hint_min/max are not violated if stretch_space < 1e-9: # there's no space, so just set to min size or zero stretch_sum = stretch_space = 1. for i, val in enumerate(sizes): sh = val[1][dim] if sh is None: continue sh_min = val[3][dim] if sh_min is not None: hint[i] = sh_min else: hint[i] = 0. # everything else is zero else: # hint gets updated in place self.layout_hint_with_bounds( stretch_sum, stretch_space, minimum_size_bounded, (val[3][dim] for val in sizes), (elem[4][dim] for elem in sizes), hint) if orientation == 'horizontal': x = padding_left + selfx size_y = self.height - padding_y for i, (sh, ((w, h), (_, shh), pos_hint, _, _)) in enumerate( zip(reversed(hint), reversed(sizes))): cy = selfy + padding_bottom if sh: w = max(0., stretch_space * sh / stretch_sum) if shh: h = max(0, shh * size_y) for key, value in pos_hint.items(): posy = value * size_y if key == 'y': cy += posy elif key == 'top': cy += posy - h elif key == 'center_y': cy += posy - (h / 2.) yield len_children - i - 1, x, cy, w, h x += w + spacing else: y = padding_bottom + selfy size_x = self.width - padding_x for i, (sh, ((w, h), (shw, _), pos_hint, _, _)) in enumerate( zip(hint, sizes)): cx = selfx + padding_left if sh: h = max(0., stretch_space * sh / stretch_sum) if shw: w = max(0, shw * size_x) for key, value in pos_hint.items(): posx = value * size_x if key == 'x': cx += posx elif key == 'right': cx += posx - w elif key == 'center_x': cx += posx - (w / 2.) yield i, cx, y, w, h y += h + spacing def do_layout(self, *largs): children = self.children if not children: l, t, r, b = self.padding self.minimum_size = l + r, t + b return for i, x, y, w, h in self._iterate_layout( [(c.size, c.size_hint, c.pos_hint, c.size_hint_min, c.size_hint_max) for c in children]): c = children[i] c.pos = x, y shw, shh = c.size_hint if shw is None: if shh is not None: c.height = h else: if shh is None: c.width = w else: c.size = (w, h) def add_widget(self, widget, index=0): widget.fbind('pos_hint', self._trigger_layout) return super(BoxLayout, self).add_widget(widget, index) def remove_widget(self, widget): widget.funbind('pos_hint', self._trigger_layout) return super(BoxLayout, self).remove_widget(widget)