provide loading Indicator during plotly rendering

[Yokogawa-Akshay]

I have created a simple dash app, which renders a scatter plot using plotly express, I have used the dcc.Loading to wrap the component which displays the plot upon a simple button click.

But during the initial rendering the indicator stops displaying once the component is ready with its data, but the plot is not yet rendered and displayed to the user.

Is there any way to show a loading spinner or any loading indicator which can be displayed until the plot is rendered? Or anything within the dcc.Graph component which can show this loading indicator until the plot is rendered completly

I have searched around the plotly documentation and not seem find anything suitable.

The CSV file being consumed is around 250 mb and the delay after the loading indicator stops and the plot to render is around a second or 2, but this might increase once the files being consumed are also increasing in size.

import time
import dash
from dash import dcc, html
from dash.dependencies import Input, Output
import plotly.express as px
import pandas as pd
import numpy as np

df = pd.read_csv(
    '2m Sales Records.csv',
    index_col=0)

app = dash.Dash(__name__)

app.layout = html.Div([
    html.Button('Update Plot', id='update-button', n_clicks=0),
    html.Div([
        dcc.Loading(
            id="loading",
            type="default",
            fullscreen=True,
            children=[
                html.Div(id='graph-container')
            ]
        )
    ])
])


@app.callback(
    Output('graph-container', 'children'),
    [Input('update-button', 'n_clicks')]
)
def update_plot(n_clicks):
    x_column = 'Units Sold'
    y_column = 'Total Profit'

    if n_clicks > 0:
        fig = px.scatter(df, x=x_column, y=y_column, title='Scatter Plot')
        fig.update_traces(textposition='top center')

        return dcc.Graph(id='volcano-plot', figure=fig)

    return html.Div()


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

The CSV file with about 2million records:
2m-Sales-Records.zip

Video Sample:

Plot_loading.mp4