Call back isn't triggering?

Dash Python
2

Hi @vily,

import plotly.express as px
from dash import Input, Output, Dash, dcc, html, no_update
from skimage import data
import json

img = data.chelsea()
fig = px.imshow(img)
fig.update_layout(dragmode="drawrect")

app = Dash(__name__)
app.layout = html.Div(
    [
        html.H3("Drag and draw rectangle annotations"),
        dcc.Graph(id="graph-picture", figure=fig),
        dcc.Markdown("Characteristics of shapes"),
        html.Pre(id="annotations-data"),
    ]
)


@app.callback(
    Output("annotations-data", "children"),
    Input("graph-picture", "relayoutData"),
    prevent_initial_call=True,
)
def on_new_annotation(relayout_data):
    if "shapes" in relayout_data:
        return json.dumps(relayout_data["shapes"], indent=2)
    else:
        return no_update


if __name__ == "__main__":
    app.run_server(debug=True)

And everything is working fine on my side.