text: '''
  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
  
  
  class TabbedPanelException(Exception):
      '''The TabbedPanelException class.
      '''
      pass
  
  
  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
      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)
  
  
  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
      '''
  
      def add_widget(self, widget, index=0):
          self.content = widget
          if not self.parent:
              return
          panel = self.parent.tabbed_panel
          if panel.current_tab == self:
              panel.switch_to(self)
  
      def remove_widget(self, widget):
          self.content = None
          if not self.parent:
              return
          panel = self.parent.tabbed_panel
          if panel.current_tab == self:
              panel.remove_widget(widget)
  
  
  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 .
      '''
  
  
  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.
      '''
  
  
  class TabbedPanelContent(FloatLayout):
      '''The TabbedPanelContent class.
      '''
      pass
  
  
  class TabbedPanel(GridLayout):
      '''The TabbedPanel class. See module documentation for more information.
      '''
  
      background_color = ListProperty([1, 1, 1, 1])
      '''Background color, in the format (r, g, b, a).
  
      :attr:`background_color` is a :class:`~kivy.properties.ListProperty` and
      defaults to [1, 1, 1, 1].
      '''
  
      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: (top, right, bottom, 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.
      '''
  
      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 behaviour 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)
  
      def switch_to(self, header, do_scroll=False):
          '''Switch to a specific panel header.
  
          .. versionchanged:: 1.9.2
  
          If used with `do_scroll=True`, it scrolls
          to the header's tab too.
          '''
          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()
  
      def add_widget(self, widget, index=0):
          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, index)
          elif isinstance(widget, TabbedPanelHeader):
              self_tabs = self._tab_strip
              self_tabs.add_widget(widget, index)
              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, index)
  
      def remove_widget(self, widget):
          content = self.content
          if content is None:
              return
          if widget in (content, self._tab_layout):
              super(TabbedPanel, self).remove_widget(widget)
          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:
              self._childrens.pop(widget, None)
              if widget in content.children:
                  content.remove_widget(widget)
  
      def clear_widgets(self, **kwargs):
          content = self.content
          if content is None:
              return
          if kwargs.get('do_super', False):
              super(TabbedPanel, self).clear_widgets()
          else:
              content.clear_widgets()
  
      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))
          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
          self.clear_widgets(do_super=True)
          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 ot 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 it's 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)
  