app.py

'''
Application
===========

The :class:`App` class is the base for creating Kivy applications.
Think of it as your main entry point into the Kivy run loop. In most
cases, you subclass this class and make your own app. You create an
instance of your specific app class and then, when you are ready to
start the application's life cycle, you call your instance's
:meth:`App.run` method.


Creating an Application
-----------------------

Method using build() override
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To initialize your app with a widget tree, override the :meth:`~App.build`
method in your app class and return the widget tree you constructed.

Here's an example of a very simple application that just shows a button:

.. include:: ../../examples/application/app_with_build.py
   :literal:

The file is also available in the examples folder at
:file:`kivy/examples/application/app_with_build.py`.

Here, no widget tree was constructed (or if you will, a tree with only
the root node).


Method using kv file
~~~~~~~~~~~~~~~~~~~~

You can also use the :doc:`api-kivy.lang` for creating applications. The
.kv can contain rules and root widget definitions at the same time. Here
is the same example as the Button one in a kv file.

Contents of 'test.kv':

.. include:: ../../examples/application/test.kv
   :literal:

Contents of 'main.py':

.. include:: ../../examples/application/app_with_kv.py
   :literal:

See :file:`kivy/examples/application/app_with_kv.py`.

The relationship between main.py and test.kv is explained in
:meth:`App.load_kv`.

.. _Application configuration:

Application configuration
-------------------------

Use the configuration file
~~~~~~~~~~~~~~~~~~~~~~~~~~

Your application might need its own configuration file. The
:class:`App` class handles 'ini' files automatically if you add
the section key-value pair to the :meth:`App.build_config` method using the
`config` parameter (an instance of :class:`~kivy.config.ConfigParser`)::

    class TestApp(App):
        def build_config(self, config):
            config.setdefaults('section1', {
                'key1': 'value1',
                'key2': '42'
            })

As soon as you add one section to the config, a file is created on the
disk (see :attr:`~App.get_application_config` for its location) and
named based your class name. "TestApp" will give a config file named
"test.ini" with the content::

    [section1]
    key1 = value1
    key2 = 42

The "test.ini" will be automatically loaded at runtime and you can access the
configuration in your :meth:`App.build` method::

    class TestApp(App):
        def build_config(self, config):
            config.setdefaults('section1', {
                'key1': 'value1',
                'key2': '42'
            })

        def build(self):
            config = self.config
            return Label(text='key1 is %s and key2 is %d' % (
                config.get('section1', 'key1'),
                config.getint('section1', 'key2')))

Create a settings panel
~~~~~~~~~~~~~~~~~~~~~~~

Your application can have a settings panel to let your user configure some of
your config tokens. Here is an example done in the KinectViewer example
(available in the examples directory):

    .. image:: images/app-settings.jpg
        :align: center

You can add your own panels of settings by extending
the :meth:`App.build_settings` method.
Check the :class:`~kivy.uix.settings.Settings` about how to create a panel,
because you need a JSON file / data first.

Let's take as an example the previous snippet of TestApp with custom
config. We could create a JSON like this::

    [
        { "type": "title",
          "title": "Test application" },

        { "type": "options",
          "title": "My first key",
          "desc": "Description of my first key",
          "section": "section1",
          "key": "key1",
          "options": ["value1", "value2", "another value"] },

        { "type": "numeric",
          "title": "My second key",
          "desc": "Description of my second key",
          "section": "section1",
          "key": "key2" }
    ]

Then, we can create a panel using this JSON to automatically create all the
options and link them to our :attr:`App.config` ConfigParser instance::

    class TestApp(App):
        # ...
        def build_settings(self, settings):
            jsondata = """... put the json data here ..."""
            settings.add_json_panel('Test application',
                self.config, data=jsondata)

That's all! Now you can press F1 (default keystroke) to toggle the
settings panel or press the "settings" key on your android device. You
can manually call :meth:`App.open_settings` and
:meth:`App.close_settings` if you want to handle this manually. Every
change in the panel is automatically saved in the config file.

You can also use :meth:`App.build_settings` to modify properties of
the settings panel. For instance, the default panel has a sidebar for
switching between json panels whose width defaults to 200dp. If you'd
prefer this to be narrower, you could add::

    settings.interface.menu.width = dp(100)

to your :meth:`build_settings` method.

You might want to know when a config value has been changed by the
user in order to adapt or reload your UI. You can then overload the
:meth:`on_config_change` method::

    class TestApp(App):
        # ...
        def on_config_change(self, config, section, key, value):
            if config is self.config:
                token = (section, key)
                if token == ('section1', 'key1'):
                    print('Our key1 has been changed to', value)
                elif token == ('section1', 'key2'):
                    print('Our key2 has been changed to', value)

The Kivy configuration panel is added by default to the settings
instance. If you don't want this panel, you can declare your Application as
follows::

    class TestApp(App):
        use_kivy_settings = False
        # ...

This only removes the Kivy panel but does not stop the settings instance
from appearing. If you want to prevent the settings instance from appearing
altogether, you can do this::

    class TestApp(App):
        def open_settings(self, *largs):
            pass

.. versionadded:: 1.0.7

Profiling with on_start and on_stop
-----------------------------------

It is often useful to profile python code in order to discover locations to
optimise. The standard library profilers
(http://docs.python.org/2/library/profile.html) provides multiple options for
profiling code. For profiling the entire program, the natural
approaches of using profile as a module or profile's run method does not work
with Kivy. It is however, possible to use :meth:`App.on_start` and
:meth:`App.on_stop` methods::

    import cProfile

    class MyApp(App):
        def on_start(self):
            self.profile = cProfile.Profile()
            self.profile.enable()

        def on_stop(self):
            self.profile.disable()
            self.profile.dump_stats('myapp.profile')

This will create a file called `myapp.profile` when you exit your app.

Customising layout
------------------

You can choose different settings widget layouts by setting
:attr:`App.settings_cls`. By default, this is a
:class:`~kivy.uix.settings.Settings` class which provides the pictured
sidebar layout, but you could set it to any of the other layouts
provided in :mod:`kivy.uix.settings` or create your own. See the
module documentation for :mod:`kivy.uix.settings` for more
information.

You can customise how the settings panel is displayed by
overriding :meth:`App.display_settings` which is called before
displaying the settings panel on the screen. By default, it
simply draws the panel on top of the window, but you could modify it
to (for instance) show the settings in a
:class:`~kivy.uix.popup.Popup` or add it to your app's
:class:`~kivy.uix.screenmanager.ScreenManager` if you are using
one. If you do so, you should also modify :meth:`App.close_settings`
to exit the panel appropriately. For instance, to have the settings
panel appear in a popup you can do::

    def display_settings(self, settings):
        try:
            p = self.settings_popup
        except AttributeError:
            self.settings_popup = Popup(content=settings,
                                        title='Settings',
                                        size_hint=(0.8, 0.8))
            p = self.settings_popup
        if p.content is not settings:
            p.content = settings
        p.open()

    def close_settings(self, *args):
        try:
            p = self.settings_popup
            p.dismiss()
        except AttributeError:
            pass # Settings popup doesn't exist

Finally, if you want to replace the current settings panel widget, you
can remove the internal references to it using
:meth:`App.destroy_settings`. If you have modified
:meth:`App.display_settings`, you should be careful to detect if the
settings panel has been replaced.

Pause mode
----------

.. versionadded:: 1.1.0

On tablets and phones, the user can switch at any moment to another
application. By default, your application will close and the
:meth:`App.on_stop` event will be fired.

If you support Pause mode, when switching to another application, your
application will wait indefinitely until the user
switches back to your application. There is an issue with OpenGL on Android
devices: it is not guaranteed that the OpenGL ES Context will be restored when
your app resumes. The mechanism for restoring all the OpenGL data is not yet
implemented in Kivy.

The currently implemented Pause mechanism is:

    #. Kivy checks every frame if Pause mode is activated by the Operating
       System due to the user switching to another application, a phone
       shutdown or any other reason.
    #. :meth:`App.on_pause` is called:
    #. If False is returned, then :meth:`App.on_stop` is called.
    #. If True is returned (default case), the application will sleep until
       the OS resumes our App.
    #. When the app is resumed, :meth:`App.on_resume` is called.
    #. If our app memory has been reclaimed by the OS, then nothing will be
       called.

Here is a simple example of how on_pause() should be used::

   class TestApp(App):

      def on_pause(self):
         # Here you can save data if needed
         return True

      def on_resume(self):
         # Here you can check if any data needs replacing (usually nothing)
         pass

.. warning::

    Both `on_pause` and `on_stop` must save important data because after
    `on_pause` is called, `on_resume` may not be called at all.

'''

__all__ = ('App', )

import os
from inspect import getfile
from os.path import dirname, join, exists, sep, expanduser, isfile
from kivy.config import ConfigParser
from kivy.base import runTouchApp, stopTouchApp
from kivy.compat import string_types
from kivy.factory import Factory
from kivy.logger import Logger
from kivy.event import EventDispatcher
from kivy.lang import Builder
from kivy.resources import resource_find
from kivy.utils import platform as core_platform
from kivy.uix.widget import Widget
from kivy.properties import ObjectProperty, StringProperty
from kivy.setupconfig import USE_SDL2


platform = core_platform


class App(EventDispatcher):
    ''' Application class, see module documentation for more information.

    :Events:
        `on_start`:
            Fired when the application is being started (before the
            :func:`~kivy.base.runTouchApp` call.
        `on_stop`:
            Fired when the application stops.
        `on_pause`:
            Fired when the application is paused by the OS.
        `on_resume`:
            Fired when the application is resumed from pause by the OS. Beware:
            you have no guarantee that this event will be fired after the
            `on_pause` event has been called.

    .. versionchanged:: 1.7.0
        Parameter `kv_file` added.

    .. versionchanged:: 1.8.0
        Parameters `kv_file` and `kv_directory` are now properties of App.
    '''

    title = StringProperty(None)
    '''
    Title of your application. You can set this as follows::

        class MyApp(App):
            def build(self):
                self.title = 'Hello world'

    .. versionadded:: 1.0.5

    .. versionchanged:: 1.8.0
        `title` is now a :class:`~kivy.properties.StringProperty`. Don't
        set the title in the class as previously stated in the documentation.

    .. note::

        For Kivy < 1.8.0, you can set this as follows::

            class MyApp(App):
                title = 'Custom title'

        If you want to dynamically change the title, you can do::

            from kivy.base import EventLoop
            EventLoop.window.title = 'New title'

    '''

    icon = StringProperty(None)
    '''Icon of your application.
    The icon can be located in the same directory as your main file. You can
    set this as follows::

        class MyApp(App):
            def build(self):
                self.icon = 'myicon.png'

    .. versionadded:: 1.0.5

    .. versionchanged:: 1.8.0
        `icon` is now a :class:`~kivy.properties.StringProperty`. Don't set the
        icon in the class as previously stated in the documentation.

    .. note::

        For Kivy prior to 1.8.0, you need to set this as follows::

            class MyApp(App):
                icon = 'customicon.png'

         Recommended 256x256 or 1024x1024? for GNU/Linux and Mac OSX
         32x32 for Windows7 or less. <= 256x256 for windows 8
         256x256 does work (on Windows 8 at least), but is scaled
         down and doesn't look as good as a 32x32 icon.
    '''

    use_kivy_settings = True
    '''.. versionadded:: 1.0.7

    If True, the application settings will also include the Kivy settings. If
    you don't want the user to change any kivy settings from your settings UI,
    change this to False.
    '''

    settings_cls = ObjectProperty(None)
    '''.. versionadded:: 1.8.0

    The class used to construct the settings panel and
    the instance passed to :meth:`build_config`. You should
    use either :class:`~kivy.uix.settings.Settings` or one of the provided
    subclasses with different layouts
    (:class:`~kivy.uix.settings.SettingsWithSidebar`,
    :class:`~kivy.uix.settings.SettingsWithSpinner`,
    :class:`~kivy.uix.settings.SettingsWithTabbedPanel`,
    :class:`~kivy.uix.settings.SettingsWithNoMenu`). You can also create your
    own Settings subclass. See the documentation
    of :mod:`~kivy.uix.settings.Settings` for more information.

    :attr:`~App.settings_cls` is an :class:`~kivy.properties.ObjectProperty`
    and defaults to :class:`~kivy.uix.settings.SettingsWithSpinner` which
    displays settings panels with a spinner to switch between them. If you set
    a string, the :class:`~kivy.factory.Factory` will be used to resolve the
    class.

    '''

    kv_directory = StringProperty(None)
    '''Path of the directory where application kv is stored, defaults to None

    .. versionadded:: 1.8.0

    If a kv_directory is set, it will be used to get the initial kv file. By
    default, the file is assumed to be in the same directory as the current App
    definition file.
    '''

    kv_file = StringProperty(None)
    '''Filename of the Kv file to load, defaults to None.

    .. versionadded:: 1.8.0

    If a kv_file is set, it will be loaded when the application starts. The
    loading of the "default" kv file will be prevented.
    '''

    # Return the current running App instance
    _running_app = None

    __events__ = ('on_start', 'on_stop', 'on_pause', 'on_resume')

    def __init__(self, **kwargs):
        App._running_app = self
        self._app_directory = None
        self._app_name = None
        self._app_settings = None
        self._app_window = None
        super(App, self).__init__(**kwargs)
        self.built = False

        #: Options passed to the __init__ of the App
        self.options = kwargs

        #: Returns an instance of the :class:`~kivy.config.ConfigParser` for
        #: the application configuration. You can use this to query some config
        #: tokens in the :meth:`build` method.
        self.config = None

        #: The *root* widget returned by the :meth:`build` method or by the
        #: :meth:`load_kv` method if the kv file contains a root widget.
        self.root = None

    def build(self):
        '''Initializes the application; it will be called only once.
        If this method returns a widget (tree), it will be used as the root
        widget and added to the window.

        :return:
            None or a root :class:`~kivy.uix.widget.Widget` instance
            if no self.root exists.'''

        if not self.root:
            return Widget()

    def build_config(self, config):
        '''.. versionadded:: 1.0.7

        This method is called before the application is initialized to
        construct your :class:`~kivy.config.ConfigParser` object. This
        is where you can put any default section / key / value for your
        config. If anything is set, the configuration will be
        automatically saved in the file returned by
        :meth:`get_application_config`.

        :Parameters:
            `config`: :class:`~kivy.config.ConfigParser`
                Use this to add default section / key / value items

        '''

    def build_settings(self, settings):
        '''.. versionadded:: 1.0.7

        This method is called when the user (or you) want to show the
        application settings. It is called once when the settings panel
        is first opened, after which the panel is cached. It may be
        called again if the cached settings panel is removed by
        :meth:`destroy_settings`.

        You can use this method to add settings panels and to
        customise the settings widget e.g. by changing the sidebar
        width. See the module documentation for full details.

        :Parameters:
            `settings`: :class:`~kivy.uix.settings.Settings`
                Settings instance for adding panels

        '''

    def load_kv(self, filename=None):
        '''This method is invoked the first time the app is being run if no
        widget tree has been constructed before for this app.
        This method then looks for a matching kv file in the same directory as
        the file that contains the application class.

        For example, say you have a file named main.py that contains::

            class ShowcaseApp(App):
                pass

        This method will search for a file named `showcase.kv` in
        the directory that contains main.py. The name of the kv file has to be
        the lowercase name of the class, without the 'App' postfix at the end
        if it exists.

        You can define rules and a root widget in your kv file::

            <ClassName>: # this is a rule
                ...

            ClassName: # this is a root widget
                ...

        There must be only one root widget. See the :doc:`api-kivy.lang`
        documentation for more information on how to create kv files. If your
        kv file contains a root widget, it will be used as self.root, the root
        widget for the application.

        .. note::

            This function is called from :meth:`run`, therefore, any widget
            whose styling is defined in this kv file and is created before
            :meth:`run` is called (e.g. in `__init__`), won't have its styling
            applied. Note that :meth:`build` is called after :attr:`load_kv`
            has been called.
        '''
        # Detect filename automatically if it was not specified.
        if filename:
            filename = resource_find(filename)
        else:
            try:
                default_kv_directory = dirname(getfile(self.__class__))
                if default_kv_directory == '':
                    default_kv_directory = '.'
            except TypeError:
                # if it's a builtin module.. use the current dir.
                default_kv_directory = '.'

            kv_directory = self.kv_directory or default_kv_directory
            clsname = self.__class__.__name__.lower()
            if (clsname.endswith('app') and
                    not isfile(join(kv_directory, '%s.kv' % clsname))):
                clsname = clsname[:-3]
            filename = join(kv_directory, '%s.kv' % clsname)

        # Load KV file
        Logger.debug('App: Loading kv <{0}>'.format(filename))
        rfilename = resource_find(filename)
        if rfilename is None or not exists(rfilename):
            Logger.debug('App: kv <%s> not found' % filename)
            return False
        root = Builder.load_file(rfilename)
        if root:
            self.root = root
        return True

    def get_application_name(self):
        '''Return the name of the application.
        '''
        if self.title is not None:
            return self.title
        clsname = self.__class__.__name__
        if clsname.endswith('App'):
            clsname = clsname[:-3]
        return clsname

    def get_application_icon(self):
        '''Return the icon of the application.
        '''
        if not resource_find(self.icon):
            return ''
        else:
            return resource_find(self.icon)

    def get_application_config(self, defaultpath='%(appdir)s/%(appname)s.ini'):
        '''.. versionadded:: 1.0.7

        .. versionchanged:: 1.4.0
            Customized the default path for iOS and Android platforms. Added a
            defaultpath parameter for desktop OS's (not applicable to iOS
            and Android.)

        Return the filename of your application configuration. Depending
        on the platform, the application file will be stored in
        different locations:

            - on iOS: <appdir>/Documents/.<appname>.ini
            - on Android: /sdcard/.<appname>.ini
            - otherwise: <appdir>/<appname>.ini

        When you are distributing your application on Desktops, please
        note that if the application is meant to be installed
        system-wide, the user might not have write-access to the
        application directory. If you want to store user settings, you
        should overload this method and change the default behavior to
        save the configuration file in the user directory. ::

            class TestApp(App):
                def get_application_config(self):
                    return super(TestApp, self).get_application_config(
                        '~/.%(appname)s.ini')

        Some notes:

        - The tilda '~' will be expanded to the user directory.
        - %(appdir)s will be replaced with the application :attr:`directory`
        - %(appname)s will be replaced with the application :attr:`name`
        '''

        if platform == 'android':
            defaultpath = '/sdcard/.%(appname)s.ini'
        elif platform == 'ios':
            defaultpath = '~/Documents/%(appname)s.ini'
        elif platform == 'win':
            defaultpath = defaultpath.replace('/', sep)
        return expanduser(defaultpath) % {
            'appname': self.name, 'appdir': self.directory}

    @property
    def root_window(self):
        '''.. versionadded:: 1.9.0

        Returns the root window instance used by :meth:`run`.
        '''
        return self._app_window

    def load_config(self):
        '''(internal) This function is used for returning a ConfigParser with
        the application configuration. It's doing 3 things:

            #. Creating an instance of a ConfigParser
            #. Loading the default configuration by calling
               :meth:`build_config`, then
            #. If it exists, it loads the application configuration file,
               otherwise it creates one.

        :return:
            :class:`~kivy.config.ConfigParser` instance
        '''
        try:
            config = ConfigParser.get_configparser('app')
        except KeyError:
            config = None
        if config is None:
            config = ConfigParser(name='app')
        self.config = config
        self.build_config(config)
        # if no sections are created, that's mean the user don't have
        # configuration.
        if len(config.sections()) == 0:
            return
        # ok, the user have some sections, read the default file if exist
        # or write it !
        filename = self.get_application_config()
        if filename is None:
            return config
        Logger.debug('App: Loading configuration <{0}>'.format(filename))
        if exists(filename):
            try:
                config.read(filename)
            except:
                Logger.error('App: Corrupted config file, ignored.')
                config.name = ''
                try:
                    config = ConfigParser.get_configparser('app')
                except KeyError:
                    config = None
                if config is None:
                    config = ConfigParser(name='app')
                self.config = config
                self.build_config(config)
                pass
        else:
            Logger.debug('App: First configuration, create <{0}>'.format(
                filename))
            config.filename = filename
            config.write()
        return config

    @property
    def directory(self):
        '''.. versionadded:: 1.0.7

        Return the directory where the application lives.
        '''
        if self._app_directory is None:
            try:
                self._app_directory = dirname(getfile(self.__class__))
                if self._app_directory == '':
                    self._app_directory = '.'
            except TypeError:
                # if it's a builtin module.. use the current dir.
                self._app_directory = '.'
        return self._app_directory

    @property
    def user_data_dir(self):
        '''
        .. versionadded:: 1.7.0

        Returns the path to the directory in the users file system which the
        application can use to store additional data.

        Different platforms have different conventions with regards to where
        the user can store data such as preferences, saved games and settings.
        This function implements these conventions. The <app_name> directory
        is created when the property is called, unless it already exists.

        On iOS, `~/Documents/<app_name>` is returned (which is inside the
        app's sandbox).

        On Android, `/sdcard/<app_name>` is returned.

        On Windows, `%APPDATA%/<app_name>` is returned.

        On OS X, `~/Library/Application Support/<app_name>` is returned.

        On Linux, `$XDG_CONFIG_HOME/<app_name>` is returned.
        '''
        data_dir = ""
        if platform == 'ios':
            data_dir = join('~/Documents', self.name)
        elif platform == 'android':
            data_dir = join('/sdcard', self.name)
        elif platform == 'win':
            data_dir = os.path.join(os.environ['APPDATA'], self.name)
        elif platform == 'macosx':
            data_dir = '~/Library/Application Support/{}'.format(self.name)
        else:  # _platform == 'linux' or anything else...:
            data_dir = os.environ.get('XDG_CONFIG_HOME', '~/.config')
            data_dir = join(data_dir, self.name)
        data_dir = expanduser(data_dir)
        if not exists(data_dir):
            os.mkdir(data_dir)
        return data_dir

    @property
    def name(self):
        '''.. versionadded:: 1.0.7

        Return the name of the application based on the class name.
        '''
        if self._app_name is None:
            clsname = self.__class__.__name__
            if clsname.endswith('App'):
                clsname = clsname[:-3]
            self._app_name = clsname.lower()
        return self._app_name

    def run(self):
        '''Launches the app in standalone mode.
        '''
        if not self.built:
            self.load_config()
            self.load_kv(filename=self.kv_file)
            root = self.build()
            if root:
                self.root = root
        if self.root:
            if not isinstance(self.root, Widget):
                Logger.critical('App.root must be an _instance_ of Widget')
                raise Exception('Invalid instance in App.root')
            from kivy.core.window import Window
            Window.add_widget(self.root)

        # Check if the window is already created
        from kivy.base import EventLoop
        window = EventLoop.window
        if window:
            self._app_window = window
            window.set_title(self.get_application_name())
            icon = self.get_application_icon()
            if icon:
                window.set_icon(icon)
            self._install_settings_keys(window)
        else:
            Logger.critical("Application: No window is created."
                            " Terminating application run.")
            return

        self.dispatch('on_start')
        runTouchApp()
        self.stop()

    def stop(self, *largs):
        '''Stop the application.

        If you use this method, the whole application will stop by issuing
        a call to :func:`~kivy.base.stopTouchApp`.
        '''
        self.dispatch('on_stop')
        stopTouchApp()

        # Clear the window children
        if self._app_window:
            for child in self._app_window.children:
                self._app_window.remove_widget(child)

    def on_start(self):
        '''Event handler for the `on_start` event which is fired after
        initialization (after build() has been called) but before the
        application has started running.
        '''
        pass

    def on_stop(self):
        '''Event handler for the `on_stop` event which is fired when the
        application has finished running (i.e. the window is about to be
        closed).
        '''
        pass

    def on_pause(self):
        '''Event handler called when Pause mode is requested. You should
        return True if your app can go into Pause mode, otherwise
        return False and your application will be stopped (the default).

        You cannot control when the application is going to go into this mode.
        It's determined by the Operating System and mostly used for mobile
        devices (android/ios) and for resizing.

        The default return value is True.

        .. versionadded:: 1.1.0
        '''
        return True

    def on_resume(self):
        '''Event handler called when your application is resuming from
        the Pause mode.

        .. versionadded:: 1.1.0

        .. warning::

            When resuming, the OpenGL Context might have been damaged / freed.
            This is where you can reconstruct some of your OpenGL state
            e.g. FBO content.
        '''
        pass

    @staticmethod
    def get_running_app():
        '''Return the currently running application instance.

        .. versionadded:: 1.1.0
        '''
        return App._running_app

    def on_config_change(self, config, section, key, value):
        '''Event handler fired when a configuration token has been changed by
        the settings page.
        '''
        pass

    def open_settings(self, *largs):
        '''Open the application settings panel. It will be created the very
        first time, or recreated if the previously cached panel has been
        removed by :meth:`destroy_settings`. The settings panel will be
        displayed with the
        :meth:`display_settings` method, which by default adds the
        settings panel to the Window attached to your application. You
        should override that method if you want to display the
        settings panel differently.

        :return:
            True if the settings has been opened.

        '''
        if self._app_settings is None:
            self._app_settings = self.create_settings()
        displayed = self.display_settings(self._app_settings)
        if displayed:
            return True
        return False

    def display_settings(self, settings):
        '''.. versionadded:: 1.8.0

        Display the settings panel. By default, the panel is drawn directly
        on top of the window. You can define other behaviour by overriding
        this method, such as adding it to a ScreenManager or Popup.

        You should return True if the display is successful, otherwise False.

        :Parameters:
            `settings`: :class:`~kivy.uix.settings.Settings`
                You can modify this object in order to modify the settings
                display.

        '''
        win = self._app_window
        if not win:
            raise Exception('No windows are set on the application, you cannot'
                            ' open settings yet.')
        if settings not in win.children:
            win.add_widget(settings)
            return True
        return False

    def close_settings(self, *largs):
        '''Close the previously opened settings panel.

        :return:
            True if the settings has been closed.
        '''
        win = self._app_window
        settings = self._app_settings
        if win is None or settings is None:
            return
        if settings in win.children:
            win.remove_widget(settings)
            return True
        return False

    def create_settings(self):
        '''Create the settings panel. This method will normally
        be called only one time per
        application life-time and the result is cached internally,
        but it may be called again if the cached panel is removed
        by :meth:`destroy_settings`.

        By default, it will build a settings panel according to
        :attr:`settings_cls`, call :meth:`build_settings`, add a Kivy panel if
        :attr:`use_kivy_settings` is True, and bind to
        on_close/on_config_change.

        If you want to plug your own way of doing settings, without the Kivy
        panel or close/config change events, this is the method you want to
        overload.

        .. versionadded:: 1.8.0
        '''
        if self.settings_cls is None:
            from kivy.uix.settings import SettingsWithSpinner
            self.settings_cls = SettingsWithSpinner
        elif isinstance(self.settings_cls, string_types):
            self.settings_cls = Factory.get(self.settings_cls)
        s = self.settings_cls()
        self.build_settings(s)
        if self.use_kivy_settings:
            s.add_kivy_panel()
        s.bind(on_close=self.close_settings,
               on_config_change=self._on_config_change)
        return s

    def destroy_settings(self):
        '''.. versionadded:: 1.8.0

        Dereferences the current settings panel if one
        exists. This means that when :meth:`App.open_settings` is next
        run, a new panel will be created and displayed. It doesn't
        affect any of the contents of the panel, but lets you (for
        instance) refresh the settings panel layout if you have
        changed the settings widget in response to a screen size
        change.

        If you have modified :meth:`~App.open_settings` or
        :meth:`~App.display_settings`, you should be careful to
        correctly detect if the previous settings widget has been
        destroyed.

        '''
        if self._app_settings is not None:
            self._app_settings = None

    #
    # privates
    #

    def _on_config_change(self, *largs):
        self.on_config_change(*largs[1:])

    def _install_settings_keys(self, window):
        window.bind(on_keyboard=self._on_keyboard_settings)

    def _on_keyboard_settings(self, window, *largs):
        key = largs[0]
        setting_key = 282  # F1

        # android hack, if settings key is pygame K_MENU
        if platform == 'android' and not USE_SDL2:
            import pygame
            setting_key = pygame.K_MENU

        if key == setting_key:
            # toggle settings panel
            if not self.open_settings():
                self.close_settings()
            return True
        if key == 27:
            return self.close_settings()

    def on_title(self, instance, title):
        if self._app_window:
            self._app_window.set_title(title)

    def on_icon(self, instance, icon):
        if self._app_window:
            self._app_window.set_icon(self.get_application_icon())