Displaying annotations when an event callback runs

Hi,
I want to display annotations when an event callback runs
I tried:

cds1= ColumnDataSource(data=dict(x_start=, y_start=[*], x_end=, y_end= ))
p.add_layout(Arrow(end=VeeHead(size=8), line_color=“grey”, source=cds1, x_start=‘x_start’, y_start=‘y_start’, x_end=‘x_end’, y_end=‘y_end’))

in callback:
cds1.data=dict(x_start=x_start_arr, y_start=y_start_arr, x_end=x_end_arr, y_end=y_end_arr )

I expected all arrows to be seen, when I injected data into cds1.data. But none of them are seen.

What am I doing wrong?

regards

Hi @ahmettemiz88

A few things to check/confirm quickly. If these do not uncover the problem, you’ll probably be asked to provide more information including a minimum reproducible example of what is not working.

1. From the data assignment statement, I surmise you’re using a Python callback. If so, you need to be running bokeh as a server via bokeh serve ... See this part of the documentation that makes it explicit
   https://docs.bokeh.org/en/latest/docs/reference/events.html?highlight=on_event

Alternatively it is possible to trigger Python code to run when events happen, in the context of a Bokeh application running on a Bokeh server. This can accomplished by passing an event class, and a callback function to the the on_event() method. The callback should accept a single argument event , which will be passed the concrete event object that triggered the callback.

2. If you are running as a bokeh server and using a callback such as on_event(), what is the event you’ve registered with the callback and do you see the callback actually being invoked?