FuncAnimation fails to display with interval 0 on Tkagg backend #18236

Bug report

Bug summary

This is a continuation of sorts of #8107. I think the root cause is that, in Tcl, self-rescheduling after 0 callbacks exclude all other callbacks because after 0 events are prepended to the event queue. See this and this from the Tcl wiki. It looks straightforward to augment TimerTk with that after idle {after 0 ...} incantation but I haven't gotten that far yet.

PR (likely) forthcoming, especially if the problem is reproduced by others in this issue.

Code for reproduction

run examples/animation/simple_anim.py but set the interval kwarg to 0 or any float x where 0 <= x < 1.

Actual outcome

Expected outcome

Matplotlib version

• Operating system: Win10
• Matplotlib version: master
• Matplotlib backend (print(matplotlib.get_backend())): Tkagg
• Python version: 3.8
• Jupyter version (if applicable):
• Other libraries:

installed from git & setup.py develop