Bug summary

When using blitting together with a draw_event callback, backend behavior differs between TkAgg and QtAgg.

Specifically:
fig.canvas.draw_artist(...) is backend-dependent and unreliable.
ax.draw_artist(...) works consistently across backends but still
Under TkAgg, using blitting with a draw_event callback causes visible flickering and repeated redraws.
The same code behaves smoothly under QtAgg, without flickering.

This indicates a backend-specific issue in TkAgg, where draw_event interactions interfere with blitting and trigger unnecessary redraw cycles, rather than a documentation problem.

Code for reproduction

import matplotlib
matplotlib.use("TkAgg") 

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0, 2 * np.pi, 200)

fig, ax = plt.subplots()
(line,) = ax.plot(x, np.sin(x), animated=True)

def on_draw(event):
    print("draw_event fired")
    ax.draw_artist(line)

fig.canvas.mpl_connect("draw_event", on_draw)

plt.show(block=False)
plt.pause(0.1)

bg = fig.canvas.copy_from_bbox(fig.bbox)

for i in range(50):
    fig.canvas.restore_region(bg)
    line.set_ydata(np.sin(x + i * 0.2))
    ax.draw_artist(line)
    fig.canvas.blit(fig.bbox)
    fig.canvas.flush_events()
    plt.pause(0.05)

Actual outcome

When running the above script with TkAgg, the figure visibly flickers and redraws repeatedly during the animation.
The draw_event callback appears to be triggered more aggressively, interfering with blitting and causing unnecessary redraw cycles.

Expected outcome

Blitting combined with a draw_event callback should behave consistently across backends.
Specifically: Using ax.draw_artist(...) inside a draw_event callback should not trigger additional full redraws.
The animation should render smoothly without flickering or flashing.
The number of draw_event callbacks should be comparable across backends (TkAgg and QtAgg).

Additional information

No response

Operating system

Windows 10 / Windows 11

Matplotlib Version

import matplotlib; print(matplotlib.version)

Matplotlib Backend

TkAgg, QtAgg

Python version

python --version

Jupyter version

jupyter notebook version

Installation

pip