Parses the command line parameters and decide if dbus methods
    should be called or not. If there is already a guake instance
    running it will be used and a True value will be returned,
    otherwise, false will be returned.

def main():
    """Parses the command line parameters and decide if dbus methods
    should be called or not. If there is already a guake instance
    running it will be used and a True value will be returned,
    otherwise, false will be returned.
    """
    # Force to xterm-256 colors for compatibility with some old command line programs
    os.environ["TERM"] = "xterm-256color"

    # Force use X11 backend underwayland
    os.environ["GDK_BACKEND"] = "x11"

    # do not use version keywords here, pbr might be slow to find the version of Guake module
    parser = OptionParser()
    parser.add_option(
        '-V',
        '--version',
        dest='version',
        action='store_true',
        default=False,
        help=_('Show Guake version number and exit')
    )

    parser.add_option(
        '-v',
        '--verbose',
        dest='verbose',
        action='store_true',
        default=False,
        help=_('Enable verbose logging')
    )

    parser.add_option(
        '-f',
        '--fullscreen',
        dest='fullscreen',
        action='store_true',
        default=False,
        help=_('Put Guake in fullscreen mode')
    )

    parser.add_option(
        '-t',
        '--toggle-visibility',
        dest='show_hide',
        action='store_true',
        default=False,
        help=_('Toggles the visibility of the terminal window')
    )

    parser.add_option(
        '--show',
        dest="show",
        action='store_true',
        default=False,
        help=_('Shows Guake main window')
    )

    parser.add_option(
        '--hide',
        dest='hide',
        action='store_true',
        default=False,
        help=_('Hides Guake main window')
    )

    parser.add_option(
        '-p',
        '--preferences',
        dest='show_preferences',
        action='store_true',
        default=False,
        help=_('Shows Guake preference window')
    )

    parser.add_option(
        '-a',
        '--about',
        dest='show_about',
        action='store_true',
        default=False,
        help=_('Shows Guake\'s about info')
    )

    parser.add_option(
        '-n',
        '--new-tab',
        dest='new_tab',
        action='store',
        default='',
        help=_('Add a new tab (with current directory set to NEW_TAB)')
    )

    parser.add_option(
        '-s',
        '--select-tab',
        dest='select_tab',
        action='store',
        default='',
        help=_('Select a tab (SELECT_TAB is the index of the tab)')
    )

    parser.add_option(
        '-g',
        '--selected-tab',
        dest='selected_tab',
        action='store_true',
        default=False,
        help=_('Return the selected tab index.')
    )

    parser.add_option(
        '-l',
        '--selected-tablabel',
        dest='selected_tablabel',
        action='store_true',
        default=False,
        help=_('Return the selected tab label.')
    )

    parser.add_option(
        '--split-vertical',
        dest='split_vertical',
        action='store_true',
        default=False,
        help=_('Split the selected tab vertically.')
    )

    parser.add_option(
        '--split-horizontal',
        dest='split_horizontal',
        action='store_true',
        default=False,
        help=_('Split the selected tab horizontally.')
    )

    parser.add_option(
        '-e',
        '--execute-command',
        dest='command',
        action='store',
        default='',
        help=_('Execute an arbitrary command in the selected tab.')
    )

    parser.add_option(
        '-i',
        '--tab-index',
        dest='tab_index',
        action='store',
        default='0',
        help=_('Specify the tab to rename. Default is 0. Can be used to select tab by UUID.')
    )

    parser.add_option(
        '--bgcolor',
        dest='bgcolor',
        action='store',
        default='',
        help=_('Set the hexadecimal (#rrggbb) background color of '
               'the selected tab.')
    )

    parser.add_option(
        '--fgcolor',
        dest='fgcolor',
        action='store',
        default='',
        help=_('Set the hexadecimal (#rrggbb) foreground color of the '
               'selected tab.')
    )

    parser.add_option(
        '--change-palette',
        dest='palette_name',
        action='store',
        default='',
        help=_('Change Guake palette scheme')
    )

    parser.add_option(
        '--rename-tab',
        dest='rename_tab',
        metavar='TITLE',
        action='store',
        default='',
        help=_(
            'Rename the specified tab by --tab-index. Reset to default if TITLE is '
            'a single dash "-".'
        )
    )

    parser.add_option(
        '-r',
        '--rename-current-tab',
        dest='rename_current_tab',
        metavar='TITLE',
        action='store',
        default='',
        help=_('Rename the current tab. Reset to default if TITLE is a '
               'single dash "-".')
    )

    parser.add_option(
        '-q',
        '--quit',
        dest='quit',
        action='store_true',
        default=False,
        help=_('Says to Guake go away =(')
    )

    parser.add_option(
        '-u',
        '--no-startup-script',
        dest='execute_startup_script',
        action='store_false',
        default=True,
        help=_('Do not execute the start up script')
    )

    parser.add_option(
        '--save-preferences',
        dest='save_preferences',
        action='store',
        default=None,
        help=_('Save Guake preferences to this filename')
    )

    parser.add_option(
        '--restore-preferences',
        dest='restore_preferences',
        action='store',
        default=None,
        help=_('Restore Guake preferences from this file')
    )

    parser.add_option(
        '--support',
        dest='support',
        action='store_true',
        default=False,
        help=_('Show support infomations')
    )

    # checking mandatory dependencies
    import gi

    try:
        gi.require_version('Gtk', '3.0')
        gi.require_version('Gdk', '3.0')
    except ValueError:
        print("[ERROR] Unable to start Guake, missing mandatory dependency: GtK 3.0")
        sys.exit(1)

    try:
        gi.require_version('Vte', '2.91')  # vte-0.42
    except ValueError:
        print("[ERROR] Unable to start Guake, missing mandatory dependency: Vte >= 0.42")
        sys.exit(1)

    try:
        gi.require_version('Keybinder', '3.0')
    except ValueError:
        print("[ERROR] Unable to start Guake, missing mandatory dependency: Keybinder 3")
        sys.exit(1)

    options = parser.parse_args()[0]
    if options.version:
        from guake import gtk_version
        from guake import guake_version
        from guake import vte_version
        from guake import vte_runtime_version
        print('Guake Terminal: {}'.format(guake_version()))
        print('VTE: {}'.format(vte_version()))
        print('VTE runtime: {}'.format(vte_runtime_version()))
        print('Gtk: {}'.format(gtk_version()))
        sys.exit(0)

    if options.save_preferences and options.restore_preferences:
        parser.error('options --save-preferences and --restore-preferences are mutually exclusive')
    if options.save_preferences:
        save_preferences(options.save_preferences)
        sys.exit(0)
    elif options.restore_preferences:
        restore_preferences(options.restore_preferences)
        sys.exit(0)

    if options.support:
        print_support()
        sys.exit(0)

    import dbus

    from guake.dbusiface import DBUS_NAME
    from guake.dbusiface import DBUS_PATH
    from guake.dbusiface import DbusManager
    from guake.guake_logging import setupLogging

    instance = None

    # Trying to get an already running instance of guake. If it is not
    # possible, lets create a new instance. This function will return
    # a boolean value depending on this decision.
    try:
        bus = dbus.SessionBus()
        remote_object = bus.get_object(DBUS_NAME, DBUS_PATH)
        already_running = True
    except dbus.DBusException:
        # can now configure the logging
        setupLogging(options.verbose)

        # COLORTERM is an environment variable set by some terminal emulators such as
        # gnome-terminal.
        # To avoid confusing applications running inside Guake, clean up COLORTERM at startup.
        if "COLORTERM" in os.environ:
            del os.environ['COLORTERM']

        log.info("Guake not running, starting it")
        # late loading of the Guake object, to speed up dbus comm
        from guake.guake_app import Guake
        instance = Guake()
        remote_object = DbusManager(instance)
        already_running = False

    only_show_hide = True

    if options.fullscreen:
        remote_object.fullscreen()

    if options.show:
        remote_object.show_from_remote()

    if options.hide:
        remote_object.hide_from_remote()

    if options.show_preferences:
        remote_object.show_prefs()
        only_show_hide = options.show

    if options.new_tab:
        remote_object.add_tab(options.new_tab)
        only_show_hide = options.show

    if options.select_tab:
        selected = int(options.select_tab)
        tab_count = int(remote_object.get_tab_count())
        if 0 <= selected < tab_count:
            remote_object.select_tab(selected)
        else:
            sys.stderr.write('invalid index: %d\n' % selected)
        only_show_hide = options.show

    if options.selected_tab:
        selected = remote_object.get_selected_tab()
        sys.stdout.write('%d\n' % selected)
        only_show_hide = options.show

    if options.selected_tablabel:
        selectedlabel = remote_object.get_selected_tablabel()
        sys.stdout.write('%s\n' % selectedlabel)
        only_show_hide = options.show

    if options.split_vertical:
        remote_object.v_split_current_terminal()
        only_show_hide = options.show

    if options.split_horizontal:
        remote_object.h_split_current_terminal()
        only_show_hide = options.show

    if options.command:
        remote_object.execute_command(options.command)
        only_show_hide = options.show

    if options.tab_index and options.rename_tab:
        try:
            remote_object.rename_tab_uuid(str(uuid.UUID(options.tab_index)), options.rename_tab)
        except ValueError:
            remote_object.rename_tab(int(options.tab_index), options.rename_tab)
        only_show_hide = options.show

    if options.bgcolor:
        remote_object.set_bgcolor(options.bgcolor)
        only_show_hide = options.show

    if options.fgcolor:
        remote_object.set_fgcolor(options.fgcolor)
        only_show_hide = options.show

    if options.palette_name:
        remote_object.change_palette_name(options.palette_name)
        only_show_hide = options.show

    if options.rename_current_tab:
        remote_object.rename_current_tab(options.rename_current_tab)
        only_show_hide = options.show

    if options.show_about:
        remote_object.show_about()
        only_show_hide = options.show

    if options.quit:
        try:
            remote_object.quit()
            return True
        except dbus.DBusException:
            return True

    if already_running and only_show_hide:
        # here we know that guake was called without any parameter and
        # it is already running, so, lets toggle its visibility.
        remote_object.show_hide()

    if options.execute_startup_script:
        if not already_running:
            startup_script = instance.settings.general.get_string("startup-script")
            if startup_script:
                log.info("Calling startup script: %s", startup_script)
                pid = subprocess.Popen([startup_script],
                                       shell=True,
                                       stdin=None,
                                       stdout=None,
                                       stderr=None,
                                       close_fds=True)
                log.info("Startup script started with pid: %s", pid)
                # Please ensure this is the last line !!!!
    else:
        log.info("--no-startup-script argument defined, so don't execute the startup script")
    if already_running:
        log.info("Guake is already running")
    return already_running