Can lasso select work with a go.Scattermap in a go.FigureWidget?

📊 Plotly Python
1

Hello,

In a Shiny for Python app, I have a go.Scattermap wrapped in a go.FigureWidget, and with a function on_map_select() registered as callback to mapwidget.data[0]. There is only one trace in the figure.

The callback is being called OK for single point selections as well as box selections.
However, for lasso selections the callback is not invoked. No crash or error.

In the Shiny UI, both box and lasso selections appear to behave similarly, highlighting the markers within the selected area.

Bug or missing feature? Anyone experienced something similar?

Plotly 6.2.0, Python 3.12, Shiny 1.2.1, Windows 11.
Plotly 6.1.1 and ScatterMapBox also tried, same behaviour.
The map has around 140 markers (have seen posts where this number was relevant).

pseudo-code:

mapfigure = InitMap(CatchmentDF) (function returning a Figure)
mapwidget = go.FigureWidget(mapfigure)
mapwidget.data[0].on_selection(on_map_select)

def on_map_select(trace, points, selector): Non-reactive callback function

2

Update: The callback is actually called even for a Lasso select if only one point is selected, but not if two or more points are within the lasso.

Working minimal example:

from shiny import ui, App
from shinywidgets import render_plotly, output_widget
import plotly.graph_objects as go
import geopandas as gpd
import random

app_ui = ui.page_fluid(output_widget("MapPlot", height="600px"))    # Shiny UI with one item MapPlot

def server(input, output, session):
    
    @render_plotly
    def MapPlot():  # Function to render a Plotly map with random points
        points = gpd.points_from_xy(x=[random.uniform(5, 12) for _ in range(25)],
                                    y=[random.uniform(59, 63) for _ in range(25)])
        gdf = gpd.GeoDataFrame(geometry=points, crs=4326)
        mapfigure = go.Figure(go.Scattermap(lat = gdf.geometry.y, lon = gdf.geometry.x))
        mapfigure.update_geos(projection_type="mercator")
        mapfigure = mapfigure.update_layout(map_style="open-street-map", 
                                            clickmode='event+select',
                                            map_zoom = 3.9,
                                            map_center = {"lat": 61, "lon": 18})
        mapwidget = go.FigureWidget(mapfigure)
        mapwidget.data[0].on_selection(on_map_select)
        return mapwidget

    def on_map_select(trace, points, selector): # Callback responding to map selections
        if len(points.point_inds) == 1:
            print(f"on_map_select() detects a single selected point with index {points.point_inds[0]}")
        else:
            print(f"on_map_select() detects {len(points.point_inds)} selected points, selector is {selector}")

app = App(app_ui, server)