tabbedpanel.py

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

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

.. versionadded:: 1.3.0

.. warning::

    This widget is still experimental, and its API is subject to change in a
    future version.

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

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

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

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

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

You can choose the direction 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 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 of the widget choices. It could be a layout with a deep
hierarchy of widget, or it could be an indivual widget, such as a label or
button::

    th.content = your_content_instance

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

There is always 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, including its text::

    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(on_default_tab = my_default_tab_callback)

Tabs and content can be removed in several ways::

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

.. warning::
    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::

    <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__ = ('TabbedPanel', 'TabbedPanelContent', 'TabbedPanelHeader',
    'TabbedPanelStrip', 'TabbedPanelException')

from functools import partial
from kivy.clock import Clock
from kivy.uix.togglebutton import ToggleButton
from kivy.uix.image import Image
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.properties import ObjectProperty, StringProperty, OptionProperty, \
        ListProperty, NumericProperty, AliasProperty


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 TabbedPanel widget.

    You can use this TabbedPanelHeader widget to add a new tab to TabbedPanel.
    '''

    content = ObjectProperty(None)
    '''Content to be loaded when this tab header is selected.

    :data:`content` is a :class:`~kivy.properties.ObjectProperty` default
    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, *l):
        parent = self.parent
        while parent is not None and not isinstance(parent, TabbedPanel):
            parent = parent.parent
        if not parent:
            return
        parent.switch_to(self)


class TabbedPanelStrip(GridLayout):
    '''A strip intended to be used as background for Heading/Tab.
    '''
    tabbed_panel = ObjectProperty(None)
    '''link to the panel that tab strip is a part of.

    :data:`tabbed_panel` is a :class:`~kivy.properties.ObjectProperty` default
    to None .
    '''


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).

    :data:`background_color` is a :class:`~kivy.properties.ListProperty`,
    default 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 :data:`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.

    :data:`border` is a :class:`~kivy.properties.ListProperty`,
    default to (16, 16, 16, 16)
    '''

    background_image = StringProperty('atlas://data/images/defaulttheme/tab')
    '''Background image of the main shared content object.

    :data:`background_image` is a :class:`~kivy.properties.StringProperty`,
    default to 'atlas://data/images/defaulttheme/tab'.
    '''

    def get_current_tab(self):
        return self._current_tab

    current_tab = AliasProperty(get_current_tab, None)
    '''Links to the currently select or active tab.

    .. versionadded:: 1.4.0

    :data:`current_tab` is a :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`.

    :data:`tab_pos` is a :class:`~kivy.properties.OptionProperty`,
    default to 'bottom_mid'.
    '''

    tab_height = NumericProperty(40)
    '''Specifies the height of the tab header.

    :data:`tab_height` is a :class:`~kivy.properties.NumericProperty`,
    default to 40.
    '''

    tab_width = NumericProperty(100, allownone=True)
    '''Specifies the width of the tab header.

    :data:`tab_width` is a :class:`~kivy.properties.NumericProperty`,
    default to 100.
    '''

    default_tab_text = StringProperty('Default tab')
    '''Specifies the text displayed on the default tab header.

    :data:`default_tab_text` is a :class:`~kivy.properties.StringProperty`,
    default 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`

    :data:`default_tab_cls` is a :class:`~kivy.properties.ObjectProperty`,
    default to `TabbedPanelHeader`.
    '''

    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.

    :data:`tab_list` is a :class:`~kivy.properties.AliasProperty`, and is
    read-only.
    '''

    content = ObjectProperty(None)
    '''This is the object holding the content of the current tab.

    :data:`content` is a :class:`~kivy.properties.ObjectProperty`,
    default to 'None'.
    '''

    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
        if hasattr(self, '_original_tab') and self._original_tab == oltab:
            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)
    '''Holds the default tab.

    .. Note:: For convenience, the automatically provided default tab is deleted
    when you change default_tab to something else.

    :data:`default_tab` is a :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.

    :data:`default_tab_content` is a :class:`~kivy.properties.AliasProperty`
    '''

    def __init__(self, **kwargs):
        self._tab_layout = GridLayout(rows = 1)
        self._bk_img = Image(
            source=self.background_image, allow_stretch=True,
            keep_ratio=False, color=self.background_color)
        self._tab_strip = _tabs = TabbedPanelStrip(tabbed_panel=self,
            rows=1, cols=99, size_hint=(None, None),\
            height=self.tab_height, width=self.tab_width)

        self._partial_update_scrollview = None
        self.content = content = TabbedPanelContent()

        self._current_tab = default_tab = self._original_tab\
            = self._default_tab = TabbedPanelHeader()
        super(TabbedPanel, self).__init__(**kwargs)

        content = self._default_tab.content
        cls = self.default_tab_cls
        if not issubclass(cls, TabbedPanelHeader):
            raise TabbedPanelException('`default_tab_class` should be\
                subclassed from `TabbedPanelHeader`')

        if cls != type(default_tab):
            self._default_tab = cls()
        default_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
        self.on_tab_pos()

    def _load_default_tab_content(self, dt):
        self.switch_to(self.default_tab)

    def on_default_tab_text(self, *args):
        self._default_tab.text = self.default_tab_text

    def switch_to(self, header):
        '''Switch to a specific panel header.
        '''
        header_content = header.content
        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)

    def add_widget(self, widget, index=0):
        content = self.content
        if content is None:
            return
        if widget == content or widget == self._tab_layout:
            super(TabbedPanel, self).add_widget(widget, index)
        elif isinstance(widget, TabbedPanelHeader):
            self_tabs = self._tab_strip
            self_tabs.add_widget(widget)
            widget.group = '__tab%r__' % self_tabs.uid
            self.on_tab_width()
        else:
            widget.pos_hint = {'x': 0, 'top': 1}
            content.add_widget(widget, index)

    def remove_widget(self, widget):
        content = self.content
        if content is None:
            return
        if widget == content or widget == self._tab_layout:
            super(TabbedPanel, self).remove_widget(widget)
        elif isinstance(widget, TabbedPanelHeader):
            if widget != self._default_tab:
                self_tabs = self._tab_strip
                self_tabs.width -= widget.width
                self_tabs.remove_widget(widget)
                if widget.state == 'down':
                    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:
            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 clear_tabs(self, *l):
        self_tabs = self._tab_strip
        self_tabs.clear_widgets()
        self_default_tab = self._default_tab
        self_tabs.add_widget(self_default_tab)
        self_tabs.width = self_default_tab.width
        self.reposition_tabs()

    def reposition_tabs(self, *l):
        Clock.unschedule(self.on_tab_pos)
        Clock.schedule_once(self.on_tab_pos, 0)

    def on_background_image(self, *l):
        self._bk_img.source = self.background_image

    def on_background_color(self, *l):
        if self.content is None:
            return
        self._bk_img.color = self.background_color

    def on_tab_width(self, *l):
        Clock.unschedule(self.update_tab_width)
        Clock.schedule_once(self.update_tab_width, 0)

    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 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):
        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
        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
            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_top(self, *args):
        sctr, top, scrl_v_width, x, y = args
        Clock.unschedule(partial(self._updt_top, sctr, top, scrl_v_width))
        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)