anim.py

#!/usr/bin/python3
#
# Copyright (C) 2007-2009, Joseph C. Lee
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

from gi.repository import GLib

# Animation timer interval (in msec)
_TIMER_INTERVAL = 20


class Anim(object):
    """Manages an animation."""
    def __init__(self, update_func, end_anim_func):
        """update_func is a function returns True if the animation should
           continue, False otherwise.  end_anim_func is a function that takes a
           boolean indicating whether the animation was stopped prematurely."""
        self._update_func = update_func
        self._end_anim_func = end_anim_func
        self._animating = False

    def start(self):
        self._animating = True
        self._update_func()
        GLib.timeout_add(_TIMER_INTERVAL, self._timer)

    def stop(self):
        if self._animating:
            self._end_anim(anim_stopped=True)

    def _timer(self):
        if not self._animating:
            return False
        if self._update_func():
            return True
        self._end_anim(anim_stopped=False)
        return False

    def _end_anim(self, anim_stopped):
        self._animating = False
        self._end_anim_func(anim_stopped=anim_stopped)