[Matplotlib-users] What is Artist._animated used for in Matplotlib

[Yuri Sukhov]

Hi all,

I am writing my own Animation class for Matplotlib in order to use
event-based animation and it's unclear how Artist._animated and associated
set_animated() function affect rendering.

My animation should use blitting and I took existing FuncAnimation class as
a reference for my implementation. In this class _init_draw and _draw_frame
methods, among other things, set _animated = True for each artist in
self._drawn_artists if blitting is enabled:

for a in self._drawn_artists:
    a.set_animated(self._blit)

What is the reason for this operation? In what cases Artist._animated is
used, and how it affects rendering with or without blitting? I have tested
my implementation and I don't see any difference in behaviour with or
without set_animated():

class DataAnimation(Animation):
    def __init__(self, fig, *args, **kwargs):
        super(DataAnimation, self).__init__(fig, event_source=event_source,
*args, **kwargs)

    def new_frame_seq(self):
        return itertools.count()

    def _init_draw(self):
        self._drawn_artists = plot.init()
        for artist in self._drawn_artists:  # <- do we need this?
            artist.set_animated(self._blit)

    def _draw_frame(self, frame_data):
        self._drawn_artists = plot.updated_artists
        for artist in self._drawn_artists:  # <- do we need this?
            artist.set_animated(self._blit)

Thanks!

Yuri.
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