Support hv.Overlay as input to inspect_points

[droumis]

Is your feature request related to a problem? Please describe.

inspect_points does not support overlays and must be used with a single element.

Describe the solution you'd like

Allow users to run insepect_points on an overlay, including multi_y Overlay.

Describe alternatives you've considered

Alternative is for users to define a custom class that runs the inspect_points _process on each of the Overlay's elements. However, this does not work for a multi_y Overlay, tracked as a related issue here.

Here is a simplish code example of using a custom class to iterate over an Overlay:

Code

import numpy as np
import pandas as pd
import holoviews as hv
from holoviews.streams import Tap
from holoviews.operation.datashader import datashade, inspect_points
import panel as pn

hv.extension('bokeh')
pn.extension('tabulator')

np.random.seed(42)
x = np.linspace(0, 10, 100)
y1 = np.sin(x) + np.random.normal(0, 0.1, 100)
y2 = np.cos(x) + np.random.normal(0, 0.1, 100)
df1 = pd.DataFrame({'x': x, 'y': y1, 'source': 'sin-red'})
df2 = pd.DataFrame({'x': x, 'y': y2, 'source': 'cos-blue'})

curve1 = datashade(hv.Curve(df1, kdims='x', vdims=['y', 'source']), cmap='red')
curve2 = datashade(hv.Curve(df2, kdims='x', vdims=['y', 'source']), cmap='blue')

overlay = (curve1 * curve2).opts(width=600)

class CustomInspectPoints(inspect_points):
    def _process(self, element, key=None):
        if isinstance(element, hv.Overlay):
            print(f'Overlay: {element}')
            hits = []
            tap_point = hv.Points([])
            for el in element.values():
                processed = super()._process(el)
                if not self.hits.empty:
                    tap_point = processed
                hits.append(self.hits)
            self.hits = pd.concat(hits, ignore_index=True)
            return tap_point
        return super()._process(element, key=key)

inspector = CustomInspectPoints.instance(pixels=10, streams=[Tap])
inspection = inspector(overlay).opts(hv.opts.Points(color='black', marker='circle', 
                                    size=8, fill_alpha=.1, line_alpha=.8))

def create_tap_table(hits):
    if hits is None or hits.empty:
        return pn.pane.Markdown("No points selected")
    return pn.widgets.Tabulator(hits[['x', 'y', 'source']], show_index=False)

tap_table = pn.bind(create_tap_table, hits=inspector.param.hits)

pn.Column(inspection * overlay, tap_table).servable()

GMT20240812-180736_Clip_inspect_overlay.mp4