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Source code for kivy.uix.tabbedpanel

'''
TabbedPanel
===========

.. image:: images/tabbed_panel.jpg
    :align: right

.. versionadded:: 1.3.0


The `TabbedPanel` widget manages different widgets in tabs, with a header area
for the actual tab buttons and a content area for showing the current tab
content.

The :class:`TabbedPanel` provides one default tab.

Simple example
--------------

.. include:: ../../examples/widgets/tabbedpanel.py
    :literal:

.. note::

    A new class :class:`TabbedPanelItem` has been introduced in 1.5.0 for
    convenience. So now one can simply add a :class:`TabbedPanelItem` to a
    :class:`TabbedPanel` and `content` to the :class:`TabbedPanelItem`
    as in the example provided above.

Customize the Tabbed Panel
--------------------------

You can choose the position in which the tabs are displayed::

    tab_pos = 'top_mid'

An individual tab is called a TabbedPanelHeader. It is a special button
containing a `content` property. You add the TabbedPanelHeader first, and set
its `content` property separately::

    tp = TabbedPanel()
    th = TabbedPanelHeader(text='Tab2')
    tp.add_widget(th)

An individual tab, represented by a TabbedPanelHeader, needs its content set.
This content can be any widget. It could be a layout with a deep
hierarchy of widgets, or it could be an individual widget, such as a label or a
button::

    th.content = your_content_instance

There is one "shared" main content area active at any given time, for all
the tabs. Your app is responsible for adding the content of individual tabs
and for managing them, but it's not responsible for content switching. The
tabbed panel handles switching of the main content object as per user action.

There is a default tab added when the tabbed panel is instantiated.
Tabs that you add individually as above, are added in addition to the default
tab. Thus, depending on your needs and design, you will want to customize the
default tab::

    tp.default_tab_text = 'Something Specific To Your Use'


The default tab machinery requires special consideration and management.
Accordingly, an `on_default_tab` event is provided for associating a callback::

    tp.bind(default_tab = my_default_tab_callback)

It's important to note that by default, :attr:`default_tab_cls` is of type
:class:`TabbedPanelHeader` and thus has the same properties as other tabs.

Since 1.5.0, it is now possible to disable the creation of the
:attr:`default_tab` by setting :attr:`do_default_tab` to False.

Tabs and content can be removed in several ways::

    tp.remove_widget(widget/tabbed_panel_header)
    or
    tp.clear_widgets() # to clear all the widgets in the content area
    or
    tp.clear_tabs() # to remove the TabbedPanelHeaders

To access the children of the tabbed panel, use content.children::

    tp.content.children

To access the list of tabs::

    tp.tab_list

To change the appearance of the main tabbed panel content::

    background_color = (1, 0, 0, .5) #50% translucent red
    border = [0, 0, 0, 0]
    background_image = 'path/to/background/image'

To change the background of a individual tab, use these two properties::

    tab_header_instance.background_normal = 'path/to/tab_head/img'
    tab_header_instance.background_down = 'path/to/tab_head/img_pressed'

A TabbedPanelStrip contains the individual tab headers. To change the
appearance of this tab strip, override the canvas of TabbedPanelStrip.
For example, in the kv language:

.. code-block:: kv

    <TabbedPanelStrip>
        canvas:
            Color:
                rgba: (0, 1, 0, 1) # green
            Rectangle:
                size: self.size
                pos: self.pos

By default the tabbed panel strip takes its background image and color from the
tabbed panel's background_image and background_color.

'''

__all__ = ('StripLayout', 'TabbedPanel', 'TabbedPanelContent',
           'TabbedPanelHeader', 'TabbedPanelItem', 'TabbedPanelStrip',
           'TabbedPanelException')

from functools import partial
from kivy.clock import Clock
from kivy.compat import string_types
from kivy.factory import Factory
from kivy.uix.togglebutton import ToggleButton
from kivy.uix.widget import Widget
from kivy.uix.scatter import Scatter
from kivy.uix.scrollview import ScrollView
from kivy.uix.gridlayout import GridLayout
from kivy.uix.floatlayout import FloatLayout
from kivy.logger import Logger
from kivy.metrics import dp
from kivy.properties import ObjectProperty, StringProperty, OptionProperty, \
    ListProperty, NumericProperty, AliasProperty, BooleanProperty, \
    ColorProperty


[docs]class TabbedPanelException(Exception): '''The TabbedPanelException class. ''' pass
[docs]class TabbedPanelHeader(ToggleButton): '''A Base for implementing a Tabbed Panel Head. A button intended to be used as a Heading/Tab for a TabbedPanel widget. You can use this TabbedPanelHeader widget to add a new tab to a TabbedPanel. ''' content = ObjectProperty(None, allownone=True) '''Content to be loaded when this tab header is selected. :attr:`content` is an :class:`~kivy.properties.ObjectProperty` and defaults to None. ''' # only allow selecting the tab if not already selected
[docs] def on_touch_down(self, touch): if self.state == 'down': # dispatch to children, not to self for child in self.children: child.dispatch('on_touch_down', touch) return else: super(TabbedPanelHeader, self).on_touch_down(touch)
def on_release(self, *largs): # Tabbed panel header is a child of tab_strib which has a # `tabbed_panel` property if self.parent: self.parent.tabbed_panel.switch_to(self) else: # tab removed before we could switch to it. Switch back to # previous tab self.panel.switch_to(self.panel.current_tab)
[docs]class TabbedPanelItem(TabbedPanelHeader): '''This is a convenience class that provides a header of type TabbedPanelHeader and links it with the content automatically. Thus facilitating you to simply do the following in kv language: .. code-block:: kv <TabbedPanel>: # ...other settings TabbedPanelItem: BoxLayout: Label: text: 'Second tab content area' Button: text: 'Button that does nothing' .. versionadded:: 1.5.0 '''
[docs] def add_widget(self, widget, *args, **kwargs): self.content = widget if not self.parent: return panel = self.parent.tabbed_panel if panel.current_tab == self: panel.switch_to(self)
[docs] def remove_widget(self, *args, **kwargs): self.content = None if not self.parent: return panel = self.parent.tabbed_panel if panel.current_tab == self: panel.remove_widget(*args, **kwargs)
[docs]class TabbedPanelStrip(GridLayout): '''A strip intended to be used as background for Heading/Tab. This does not cover the blank areas in case the tabs don't cover the entire width/height of the TabbedPanel(use :class:`StripLayout` for that). ''' tabbed_panel = ObjectProperty(None) '''Link to the panel that the tab strip is a part of. :attr:`tabbed_panel` is an :class:`~kivy.properties.ObjectProperty` and defaults to None . '''
[docs]class StripLayout(GridLayout): ''' The main layout that is used to house the entire tabbedpanel strip including the blank areas in case the tabs don't cover the entire width/height. .. versionadded:: 1.8.0 ''' border = ListProperty([4, 4, 4, 4]) '''Border property for the :attr:`background_image`. :attr:`border` is a :class:`~kivy.properties.ListProperty` and defaults to [4, 4, 4, 4] ''' background_image = StringProperty( 'atlas://data/images/defaulttheme/action_view') '''Background image to be used for the Strip layout of the TabbedPanel. :attr:`background_image` is a :class:`~kivy.properties.StringProperty` and defaults to a transparent image. '''
[docs]class TabbedPanelContent(FloatLayout): '''The TabbedPanelContent class. ''' pass
[docs]class TabbedPanel(GridLayout): '''The TabbedPanel class. See module documentation for more information. ''' background_color = ColorProperty([1, 1, 1, 1]) '''Background color, in the format (r, g, b, a). :attr:`background_color` is a :class:`~kivy.properties.ColorProperty` and defaults to [1, 1, 1, 1]. .. versionchanged:: 2.0.0 Changed from :class:`~kivy.properties.ListProperty` to :class:`~kivy.properties.ColorProperty`. ''' border = ListProperty([16, 16, 16, 16]) '''Border used for :class:`~kivy.graphics.vertex_instructions.BorderImage` graphics instruction, used itself for :attr:`background_image`. Can be changed for a custom background. It must be a list of four values: (bottom, right, top, left). Read the BorderImage instructions for more information. :attr:`border` is a :class:`~kivy.properties.ListProperty` and defaults to (16, 16, 16, 16) ''' background_image = StringProperty('atlas://data/images/defaulttheme/tab') '''Background image of the main shared content object. :attr:`background_image` is a :class:`~kivy.properties.StringProperty` and defaults to 'atlas://data/images/defaulttheme/tab'. ''' background_disabled_image = StringProperty( 'atlas://data/images/defaulttheme/tab_disabled') '''Background image of the main shared content object when disabled. .. versionadded:: 1.8.0 :attr:`background_disabled_image` is a :class:`~kivy.properties.StringProperty` and defaults to 'atlas://data/images/defaulttheme/tab'. ''' strip_image = StringProperty( 'atlas://data/images/defaulttheme/action_view') '''Background image of the tabbed strip. .. versionadded:: 1.8.0 :attr:`strip_image` is a :class:`~kivy.properties.StringProperty` and defaults to a empty image. ''' strip_border = ListProperty([4, 4, 4, 4]) '''Border to be used on :attr:`strip_image`. .. versionadded:: 1.8.0 :attr:`strip_border` is a :class:`~kivy.properties.ListProperty` and defaults to [4, 4, 4, 4]. ''' _current_tab = ObjectProperty(None) def get_current_tab(self): return self._current_tab current_tab = AliasProperty(get_current_tab, None, bind=('_current_tab', )) '''Links to the currently selected or active tab. .. versionadded:: 1.4.0 :attr:`current_tab` is an :class:`~kivy.AliasProperty`, read-only. ''' tab_pos = OptionProperty( 'top_left', options=('left_top', 'left_mid', 'left_bottom', 'top_left', 'top_mid', 'top_right', 'right_top', 'right_mid', 'right_bottom', 'bottom_left', 'bottom_mid', 'bottom_right')) '''Specifies the position of the tabs relative to the content. Can be one of: `left_top`, `left_mid`, `left_bottom`, `top_left`, `top_mid`, `top_right`, `right_top`, `right_mid`, `right_bottom`, `bottom_left`, `bottom_mid`, `bottom_right`. :attr:`tab_pos` is an :class:`~kivy.properties.OptionProperty` and defaults to 'top_left'. ''' tab_height = NumericProperty('40dp') '''Specifies the height of the tab header. :attr:`tab_height` is a :class:`~kivy.properties.NumericProperty` and defaults to 40. ''' tab_width = NumericProperty('100dp', allownone=True) '''Specifies the width of the tab header. :attr:`tab_width` is a :class:`~kivy.properties.NumericProperty` and defaults to 100. ''' bar_width = NumericProperty('2dp') '''Width of the horizontal scroll bar. The width is interpreted as a height for the horizontal bar. .. versionadded:: 2.2.0 :attr:`bar_width` is a :class:`~kivy.properties.NumericProperty` and defaults to 2. ''' scroll_type = OptionProperty(['content'], options=(['content'], ['bars'], ['bars', 'content'], ['content', 'bars'])) '''Sets the type of scrolling to use for the content of the scrollview. Available options are: ['content'], ['bars'], ['bars', 'content']. .. versionadded:: 2.2.0 :attr:`scroll_type` is an :class:`~kivy.properties.OptionProperty` and defaults to ['content']. ''' do_default_tab = BooleanProperty(True) '''Specifies whether a default_tab head is provided. .. versionadded:: 1.5.0 :attr:`do_default_tab` is a :class:`~kivy.properties.BooleanProperty` and defaults to 'True'. ''' default_tab_text = StringProperty('Default tab') '''Specifies the text displayed on the default tab header. :attr:`default_tab_text` is a :class:`~kivy.properties.StringProperty` and defaults to 'default tab'. ''' default_tab_cls = ObjectProperty(TabbedPanelHeader) '''Specifies the class to use for the styling of the default tab. .. versionadded:: 1.4.0 .. warning:: `default_tab_cls` should be subclassed from `TabbedPanelHeader` :attr:`default_tab_cls` is an :class:`~kivy.properties.ObjectProperty` and defaults to `TabbedPanelHeader`. If you set a string, the :class:`~kivy.factory.Factory` will be used to resolve the class. .. versionchanged:: 1.8.0 The :class:`~kivy.factory.Factory` will resolve the class if a string is set. ''' def get_tab_list(self): if self._tab_strip: return self._tab_strip.children return 1. tab_list = AliasProperty(get_tab_list, None) '''List of all the tab headers. :attr:`tab_list` is an :class:`~kivy.properties.AliasProperty` and is read-only. ''' content = ObjectProperty(None) '''This is the object holding (current_tab's content is added to this) the content of the current tab. To Listen to the changes in the content of the current tab, you should bind to current_tabs `content` property. :attr:`content` is an :class:`~kivy.properties.ObjectProperty` and defaults to 'None'. ''' _default_tab = ObjectProperty(None, allow_none=True) def get_def_tab(self): return self._default_tab def set_def_tab(self, new_tab): if not issubclass(new_tab.__class__, TabbedPanelHeader): raise TabbedPanelException('`default_tab_class` should be\ subclassed from `TabbedPanelHeader`') if self._default_tab == new_tab: return oltab = self._default_tab self._default_tab = new_tab self.remove_widget(oltab) self._original_tab = None self.switch_to(new_tab) new_tab.state = 'down' default_tab = AliasProperty(get_def_tab, set_def_tab, bind=('_default_tab', )) '''Holds the default tab. .. Note:: For convenience, the automatically provided default tab is deleted when you change default_tab to something else. As of 1.5.0, this behavior has been extended to every `default_tab` for consistency and not just the automatically provided one. :attr:`default_tab` is an :class:`~kivy.properties.AliasProperty`. ''' def get_def_tab_content(self): return self.default_tab.content def set_def_tab_content(self, *l): self.default_tab.content = l[0] default_tab_content = AliasProperty(get_def_tab_content, set_def_tab_content) '''Holds the default tab content. :attr:`default_tab_content` is an :class:`~kivy.properties.AliasProperty`. ''' _update_top_ev = _update_tab_ev = _update_tabs_ev = None def __init__(self, **kwargs): # these variables need to be initialized before the kv lang is # processed setup the base layout for the tabbed panel self._childrens = [] self._tab_layout = StripLayout(rows=1) self.rows = 1 self._tab_strip = TabbedPanelStrip( tabbed_panel=self, rows=1, size_hint=(None, None), height=self.tab_height, width=self.tab_width) self._partial_update_scrollview = None self.content = TabbedPanelContent() self._current_tab = self._original_tab \ = self._default_tab = TabbedPanelHeader() super(TabbedPanel, self).__init__(**kwargs) self.fbind('size', self._reposition_tabs) if not self.do_default_tab: Clock.schedule_once(self._switch_to_first_tab) return self._setup_default_tab() self.switch_to(self.default_tab)
[docs] def switch_to(self, header, do_scroll=False): '''Switch to a specific panel header. .. versionchanged:: 1.10.0 If used with `do_scroll=True`, it scrolls to the header's tab too. :meth:`switch_to` cannot be called from within the :class:`TabbedPanel` or its subclass' ``__init__`` method. If that is required, use the ``Clock`` to schedule it. See `discussion <https://github.com/kivy/kivy/issues/3493#issuecomment-121567969>`_ for full example. ''' header_content = header.content self._current_tab.state = 'normal' header.state = 'down' self._current_tab = header self.clear_widgets() if header_content is None: return # if content has a previous parent remove it from that parent parent = header_content.parent if parent: parent.remove_widget(header_content) self.add_widget(header_content) if do_scroll: tabs = self._tab_strip tabs.parent.scroll_to(header)
def clear_tabs(self, *l): self_tabs = self._tab_strip self_tabs.clear_widgets() if self.do_default_tab: self_default_tab = self._default_tab self_tabs.add_widget(self_default_tab) self_tabs.width = self_default_tab.width self._reposition_tabs()
[docs] def add_widget(self, widget, *args, **kwargs): content = self.content if content is None: return parent = widget.parent if parent: parent.remove_widget(widget) if widget in (content, self._tab_layout): super(TabbedPanel, self).add_widget(widget, *args, **kwargs) elif isinstance(widget, TabbedPanelHeader): self_tabs = self._tab_strip self_tabs.add_widget(widget, *args, **kwargs) widget.group = '__tab%r__' % self_tabs.uid self.on_tab_width() else: widget.pos_hint = {'x': 0, 'top': 1} self._childrens.append(widget) content.disabled = self.current_tab.disabled content.add_widget(widget, *args, **kwargs)
[docs] def remove_widget(self, widget, *args, **kwargs): content = self.content if content is None: return if widget in (content, self._tab_layout): super(TabbedPanel, self).remove_widget(widget, *args, **kwargs) elif isinstance(widget, TabbedPanelHeader): if not (self.do_default_tab and widget is self._default_tab): self_tabs = self._tab_strip self_tabs.width -= widget.width self_tabs.remove_widget(widget) if widget.state == 'down' and self.do_default_tab: self._default_tab.on_release() self._reposition_tabs() else: Logger.info('TabbedPanel: default tab! can\'t be removed.\n' + 'Change `default_tab` to a different tab.') else: if widget in self._childrens: self._childrens.remove(widget) if widget in content.children: content.remove_widget(widget, *args, **kwargs)
[docs] def clear_widgets(self, *args, **kwargs): if self.content: self.content.clear_widgets(*args, **kwargs)
def on_strip_image(self, instance, value): if not self._tab_layout: return self._tab_layout.background_image = value def on_strip_border(self, instance, value): if not self._tab_layout: return self._tab_layout.border = value def on_do_default_tab(self, instance, value): if not value: dft = self.default_tab if dft in self.tab_list: self.remove_widget(dft) self._switch_to_first_tab() self._default_tab = self._current_tab else: self._current_tab.state = 'normal' self._setup_default_tab() def on_default_tab_text(self, *args): self._default_tab.text = self.default_tab_text def on_tab_width(self, *l): ev = self._update_tab_ev if ev is None: ev = self._update_tab_ev = Clock.create_trigger( self._update_tab_width, 0) ev() def on_tab_height(self, *l): self._tab_layout.height = self._tab_strip.height = self.tab_height self._reposition_tabs() def on_tab_pos(self, *l): # ensure canvas self._reposition_tabs() def _setup_default_tab(self): if self._default_tab in self.tab_list: return content = self._default_tab.content _tabs = self._tab_strip cls = self.default_tab_cls if isinstance(cls, string_types): cls = Factory.get(cls) if not issubclass(cls, TabbedPanelHeader): raise TabbedPanelException('`default_tab_class` should be\ subclassed from `TabbedPanelHeader`') # no need to instantiate if class is TabbedPanelHeader if cls != TabbedPanelHeader: self._current_tab = self._original_tab = self._default_tab = cls() default_tab = self.default_tab if self._original_tab == self.default_tab: default_tab.text = self.default_tab_text default_tab.height = self.tab_height default_tab.group = '__tab%r__' % _tabs.uid default_tab.state = 'down' default_tab.width = self.tab_width if self.tab_width else 100 default_tab.content = content tl = self.tab_list if default_tab not in tl: _tabs.add_widget(default_tab, len(tl)) if default_tab.content: self.clear_widgets() self.add_widget(self.default_tab.content) else: Clock.schedule_once(self._load_default_tab_content) self._current_tab = default_tab def _switch_to_first_tab(self, *l): ltl = len(self.tab_list) - 1 if ltl > -1: self._current_tab = dt = self._original_tab \ = self.tab_list[ltl] self.switch_to(dt) def _load_default_tab_content(self, dt): if self.default_tab: self.switch_to(self.default_tab) def _reposition_tabs(self, *l): ev = self._update_tabs_ev if ev is None: ev = self._update_tabs_ev = Clock.create_trigger( self._update_tabs, 0) ev() def _update_tabs(self, *l): self_content = self.content if not self_content: return # cache variables for faster access tab_pos = self.tab_pos tab_layout = self._tab_layout tab_layout.clear_widgets() scrl_v = ScrollView(size_hint=(None, 1), always_overscroll=False, bar_width=self.bar_width, scroll_type=self.scroll_type) tabs = self._tab_strip parent = tabs.parent if parent: parent.remove_widget(tabs) scrl_v.add_widget(tabs) scrl_v.pos = (0, 0) self_update_scrollview = self._update_scrollview # update scrlv width when tab width changes depends on tab_pos if self._partial_update_scrollview is not None: tabs.unbind(width=self._partial_update_scrollview) self._partial_update_scrollview = partial( self_update_scrollview, scrl_v) tabs.bind(width=self._partial_update_scrollview) # remove all widgets from the tab_strip super(TabbedPanel, self).clear_widgets() tab_height = self.tab_height widget_list = [] tab_list = [] pos_letter = tab_pos[0] if pos_letter == 'b' or pos_letter == 't': # bottom or top positions # one col containing the tab_strip and the content self.cols = 1 self.rows = 2 # tab_layout contains the scrollview containing tabs and two blank # dummy widgets for spacing tab_layout.rows = 1 tab_layout.cols = 3 tab_layout.size_hint = (1, None) tab_layout.height = (tab_height + tab_layout.padding[1] + tab_layout.padding[3] + dp(2)) self_update_scrollview(scrl_v) if pos_letter == 'b': # bottom if tab_pos == 'bottom_mid': tab_list = (Widget(), scrl_v, Widget()) widget_list = (self_content, tab_layout) else: if tab_pos == 'bottom_left': tab_list = (scrl_v, Widget(), Widget()) elif tab_pos == 'bottom_right': # add two dummy widgets tab_list = (Widget(), Widget(), scrl_v) widget_list = (self_content, tab_layout) else: # top if tab_pos == 'top_mid': tab_list = (Widget(), scrl_v, Widget()) elif tab_pos == 'top_left': tab_list = (scrl_v, Widget(), Widget()) elif tab_pos == 'top_right': tab_list = (Widget(), Widget(), scrl_v) widget_list = (tab_layout, self_content) elif pos_letter == 'l' or pos_letter == 'r': # left or right positions # one row containing the tab_strip and the content self.cols = 2 self.rows = 1 # tab_layout contains two blank dummy widgets for spacing # "vertically" and the scatter containing scrollview # containing tabs tab_layout.rows = 3 tab_layout.cols = 1 tab_layout.size_hint = (None, 1) tab_layout.width = tab_height scrl_v.height = tab_height self_update_scrollview(scrl_v) # rotate the scatter for vertical positions rotation = 90 if tab_pos[0] == 'l' else -90 sctr = Scatter(do_translation=False, rotation=rotation, do_rotation=False, do_scale=False, size_hint=(None, None), auto_bring_to_front=False, size=scrl_v.size) sctr.add_widget(scrl_v) lentab_pos = len(tab_pos) # Update scatter's top when its pos changes. # Needed for repositioning scatter to the correct place after its # added to the parent. Use clock_schedule_once to ensure top is # calculated after the parent's pos on canvas has been calculated. # This is needed for when tab_pos changes to correctly position # scatter. Without clock.schedule_once the positions would look # fine but touch won't translate to the correct position if tab_pos[lentab_pos - 4:] == '_top': # on positions 'left_top' and 'right_top' sctr.bind(pos=partial(self._update_top, sctr, 'top', None)) tab_list = (sctr, ) elif tab_pos[lentab_pos - 4:] == '_mid': # calculate top of scatter sctr.bind(pos=partial(self._update_top, sctr, 'mid', scrl_v.width)) tab_list = (Widget(), sctr, Widget()) elif tab_pos[lentab_pos - 7:] == '_bottom': tab_list = (Widget(), Widget(), sctr) if pos_letter == 'l': widget_list = (tab_layout, self_content) else: widget_list = (self_content, tab_layout) # add widgets to tab_layout add = tab_layout.add_widget for widg in tab_list: add(widg) # add widgets to self add = self.add_widget for widg in widget_list: add(widg) def _update_tab_width(self, *l): if self.tab_width: for tab in self.tab_list: tab.size_hint_x = 1 tsw = self.tab_width * len(self._tab_strip.children) else: # tab_width = None tsw = 0 for tab in self.tab_list: if tab.size_hint_x: # size_hint_x: x/.xyz tab.size_hint_x = 1 # drop to default tab_width tsw += 100 else: # size_hint_x: None tsw += tab.width self._tab_strip.width = tsw self._reposition_tabs() def _update_top(self, *args): sctr, top, scrl_v_width, x, y = args ev = self._update_top_ev if ev is not None: ev.cancel() ev = self._update_top_ev = Clock.schedule_once( partial(self._updt_top, sctr, top, scrl_v_width), 0) def _updt_top(self, sctr, top, scrl_v_width, *args): if top[0] == 't': sctr.top = self.top else: sctr.top = self.top - (self.height - scrl_v_width) / 2 def _update_scrollview(self, scrl_v, *l): self_tab_pos = self.tab_pos self_tabs = self._tab_strip if self_tab_pos[0] == 'b' or self_tab_pos[0] == 't': # bottom or top scrl_v.width = min(self.width, self_tabs.width) # required for situations when scrl_v's pos is calculated # when it has no parent scrl_v.top += 1 scrl_v.top -= 1 else: # left or right scrl_v.width = min(self.height, self_tabs.width) self_tabs.pos = (0, 0)