Simple timeline API.

Use it to implement the frame key logic.

1 files changed, 87 insertions, 0 deletions

diff --git a/sugar/canvas/Timeline.py b/sugar/canvas/Timeline.py
new file mode 100644
index 0000000..333484e
--- /dev/null
+++ b/sugar/canvas/Timeline.py
@@ -0,0 +1,87 @@
+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)
+			method(current_frame, n_frames)
+		except:
+			pass
+
+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.start_frame - tag.end_frame
+		self._observer.next_frame(tag.name, frame, n_frames)
+
+	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.stop()
+
+		if start_tag == None:
+			start = self._tags[0].start_frame
+		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 stop(self):
+		if self._timeout_sid > 0:
+			gobject.source_remove(self._timeout_sid)