CallbackRegistry should not silently drop duplicate callbacks #20210
Description
Bug report
Bug summary
Currently, if a same function is connected twice to the same signal and same callbackregisry, the second connection is silently dropped, per
matplotlib/lib/matplotlib/cbook/__init__.py
Lines 208 to 210 in b6a6414
This seems not so nice and a bit surprising (as in #15785 (comment)); we should deprecate that behavior and either
- (preferred) just always perform the connection, even if duplicated; it's the user's job to keep track of duplicates if they want; or
- (less preferred) add something like
keep_duplicates={None,True,False}where None (default) raises an exception for duplicates, True keeps them, False drops them.
Code for reproduction
for _ in range(2): gcf().canvas.mpl_connect("button_press_event", print)
show()and click on the canvas.
Actual outcome
The event is printed once.
Expected outcome
The event is printed twice.
Matplotlib version
- Operating system: linux
- Matplotlib version (
import matplotlib; print(matplotlib.__version__)): HEAD (3.4.x+) - Matplotlib backend (
print(matplotlib.get_backend())): any - Python version: 39
- Jupyter version (if applicable):
- Other libraries: