Scattergl points disappear when reaching a certain threshold in size difference

I noticed, that in Scattergl points start to disappear from the graph when resizing and reaching certain thresholds in size difference.

Minimal example:

from dash import Dash, html, dcc, callback
from dash.dependencies import Input, Output
import plotly.graph_objects as go
from plotly.graph_objs import Scattergl
import numpy as np
import pandas as pd


np.random.seed(41)
x = np.random.uniform(-10, 10, 10)
y = np.random.uniform(-10, 10, 10)
sizes = np.random.uniform(0, 1000, 10)

df = pd.DataFrame({
    'x': x,
    'y': y,
    'sizes': sizes
})

app = Dash(__name__)

app.layout = html.Div([
    dcc.Slider(min=13, max=14, value=1, id='slider-sizes', step=0.1),
    dcc.Graph(id='graph', style={"width": "100vw", "height": "80vh"}),
])


def update_marker_sizes(fig, size):
    for trace in fig.data:
        if 'marker' in trace and 'size' in trace.marker:
            trace.marker.size = [s * size for s in trace.marker.size]
    return fig


@callback(
    Output('graph', 'figure'),
    Input('slider-sizes', 'value')
)
def update_graph(size):
    figure = go.Figure(data=Scattergl(x=df["x"], y=df["y"], mode='markers',
                                      marker=dict(size=df['sizes']*size, sizemode='area')))
    print(f"{50*'-'}\nslider size:{size}")
    num_points = sum(
        len(trace['x']) for trace in figure.full_figure_for_development()['data'] if
        len(trace["x"]) > 1)
    print(f"num points in dev data (x): {num_points}")

    minsize, maxsize = float("inf"), float("-inf")
    for trace in figure.data:
        if hasattr(trace, 'marker') and hasattr(trace.marker, 'size'):
            if len(trace.marker.size) > 1:
                print(f"num points in data: {len(trace.marker.size)}")
            minsize = min(minsize, min(trace.marker.size))
            maxsize = max(maxsize, max(trace.marker.size))
    print(f"min: {minsize}, max: {maxsize}, diff: {maxsize - minsize}")

    return figure


if __name__ == '__main__':
    app.run_server(debug=True, port=8000)

The points are still present in the underlying data structure:

Output:

--------------------------------------------------
slider size:13.5
num points in dev data (x): 10
num points in data: 10
min: 1350.4235691765416, max: 10008.250444470288, diff: 8657.826875293747
--------------------------------------------------
slider size:13.6
num points in dev data (x): 10
num points in data: 10
min: 1360.4267067259975, max: 10082.385632947846, diff: 8721.958926221849
--------------------------------------------------
slider size:13.5
num points in dev data (x): 10
num points in data: 10
min: 1350.4235691765416, max: 10008.250444470288, diff: 8657.826875293747
--------------------------------------------------

Visually, this is what happens:

Inizia eseguendo l’esempio minimo di Dash riportato nell’issue e variando lo slider intorno alle soglie di dimensione segnalate. Traccia il percorso di rendering di Scattergl per determinare perché i punti scompaiono nonostante rimangano nei dati, quindi verifica che tutti i punti restino visibili nell’intero intervallo di dimensioni che riproduce il problema.