sugar-toolkit-gtk3/sugar/graphics/timeline.py

# Copyright (C) 2006, Red Hat, Inc.
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the
# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
# Boston, MA 02111-1307, USA.

import gobject

class _Tag:
    def __init__(self, name, start_frame, end_frame):
        self.name = name
        self.start_frame = start_frame
        self.end_frame = end_frame

class TimelineObserver:
    def __init__(self, observer):
        self._observer = observer

    def next_frame(self, tag, current_frame, n_frames):
        try:
            method = getattr(self._observer, 'do_' + tag)
        except AttributeError:
            method = None

        if method:
            method(current_frame, n_frames)

class Timeline:
    def __init__(self, observer):
        self._fps = 12
        self._tags = []
        self._name_to_tag = {}
        self._current_frame = 0
        self._timeout_sid = 0
        self._observer = TimelineObserver(observer)

    def add_tag(self, name, start_frame, end_frame):
        tag = _Tag(name, start_frame, end_frame)
        self._tags.append(tag)
        self._name_to_tag[name] = tag 

    def remove_tag(self, name):
        tag = self._tags[name]
        self._tags.remove(tag)
        del self._tags[name]

    def _next_frame(self, tag, frame):
        n_frames = tag.end_frame - tag.start_frame + 1
        self._observer.next_frame(tag.name, frame, n_frames)

    def goto(self, tag_name, end_frame=False):
        self.pause()

        tag = self._name_to_tag[tag_name]
        if end_frame:
            self._current_frame = tag.end_frame
        else:
            self._current_frame = tag.start_frame

        self._next_frame(tag, self._current_frame)

    def on_tag(self, name):
        tag = self._name_to_tag[name]
        return (tag.start_frame <= self._current_frame and \
                tag.end_frame >= self._current_frame)

    def _get_tags_for_frame(self, frame):
        result = []
        for tag in self._tags:
            if tag.start_frame <= frame and tag.end_frame >= frame:
                result.append(tag)
        return result

    def _timeout_cb(self, end_frame):
        for tag in self._get_tags_for_frame(self._current_frame):
            cur_frame = self._current_frame - tag.start_frame
            self._next_frame(tag, cur_frame)

        if self._current_frame < end_frame:
            self._current_frame += 1
            return True
        else:
            return False

    def play(self, start_tag=None, stop_tag=None):
        self.pause()

        if start_tag == None:
            start = 0
        else:
            start = self._name_to_tag[start_tag].start_frame

        if stop_tag == None:
            end = self._tags[len(self._tags) - 1].end_frame
        else:
            end = self._name_to_tag[stop_tag].end_frame

        self._current_frame = start

        interval = 1000 / self._fps
        self._timeout_sid = gobject.timeout_add(
                        interval, self._timeout_cb, end)

    def pause(self):
        if self._timeout_sid > 0:
            gobject.source_remove(self._timeout_sid)