Simplify repeat_delay and fix support for it when using iterable frames.

anntzer · anntzer · commit a264c0fb0b42 · 2020-11-05T21:16:45.000+01:00
- Simplify the implementation of `repeat_delay`: instead of switching
  callbacks back and forth, just set the timer interval at each
  iteration to either the normal delay or the end-of-loop delay.

- Fix support for `repeat_delay` when `frames` is an iterable: the
  previous implementation handled looping in `iter_frames` and therefore
  `_step` never saw the end of the iterable.  Instead, just iterate
  through `frames` once in `iter_frames`, but still `tee` the iterable
  so that `_step` can take care of repeating the animation.

Can be checked with
```python
import matplotlib.pyplot as plt
import matplotlib.animation as animation

fig, ax = plt.subplots()
line, = ax.plot(range(10))

def animate(i):
    line.set_ydata(range(i, i + 10))  # update the data.
    return line,

ani = animation.FuncAnimation(
    fig, animate, frames=range(5), interval=1000, repeat_delay=2000, blit=True, save_count=50)
plt.show()
```
Previously repeat_delay would not be applied.
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -1433,27 +1433,12 @@ def _step(self, *args):
         if not still_going and self.repeat:
             self._init_draw()
             self.frame_seq = self.new_frame_seq()
-            self.event_source.remove_callback(self._step)
-            self.event_source.add_callback(self._loop_delay)
             self.event_source.interval = self._repeat_delay
             return True
         else:
+            self.event_source.interval = self._interval
             return still_going
 
-    def _stop(self, *args):
-        # If we stop in the middle of a loop delay (which is relatively likely
-        # given the potential pause here), remove the loop_delay callback as
-        # well.
-        self.event_source.remove_callback(self._loop_delay)
-        super()._stop()
-
-    def _loop_delay(self, *args):
-        # Reset the interval and change callbacks after the delay.
-        self.event_source.remove_callback(self._loop_delay)
-        self.event_source.interval = self._interval
-        self.event_source.add_callback(self._step)
-        Animation._step(self)
-
 
 class ArtistAnimation(TimedAnimation):
     """
@@ -1633,10 +1618,10 @@ def __init__(self, fig, func, frames=None, init_func=None, fargs=None,
             self._iter_gen = frames
         elif np.iterable(frames):
             if kwargs.get('repeat', True):
+                self._tee_from = frames
                 def iter_frames(frames=frames):
-                    while True:
-                        this, frames = itertools.tee(frames, 2)
-                        yield from this
+                    this, self._tee_from = itertools.tee(self._tee_from, 2)
+                    yield from this
                 self._iter_gen = iter_frames
             else:
                 self._iter_gen = lambda: iter(frames)
