[Matplotlib-devel] Confusion about draw_artist

[Matthew Brett]

Hi,

Sorry to keep displaying my confusion on this one but...

On Wed, Jan 4, 2017 at 6:58 PM, Thomas Caswell <tcaswell at gmail.com> wrote:
> Unless you have flagged the artist as `animated` (via `set_animated` or by
> kwarg), it will be drawn as part of the next re-draw.

Adding `set_animated` doesn't help in the example above;

fig, ax = plt.subplots(1, 1)
ax.set_animated(True)
im = plt.imshow([[1, 2], [3, 4]])
fig.canvas.draw()
ax.draw_artist(im)

> You are better off
> just changing the `fig.canvas.draw()` to `fig.canvas.draw_idle()` and
> letting the GUI decide when to re-draw things.

Changing to `fig.canvas.draw_idle()` above doesn't prevent the error
from `draw_artist`, but I guess I should not have expected it would.
So I guess my question is - how do I use `draw_artist` in this case?
Is there any way to make sure that the renderer is cached first?

> If you want to get any performance gain from animated artists + draw_artist
> you will need to use blitting (which will work with the OSX backend in 2.0).

Yup, the real code does use blitting, but thanks for the reminder,

Cheers,

Matthew