enh: Support selector and ds.summary for geom_aggregator

[hoxbro]

Resolves #6736
Resolves #6739

Mostly factoring out logic in aggregate to also use for geom_aggregate. Not sure if I like the new method name, but just wanted to push this before it was lost in a stash. Know at least one test is failing because of change of NdOverlay to ImageStack.

Also fixes a bug where __index__ data was not sent to the frontend when hover_tooltips were used, so it would not hide tooltips.

And handle ds.by cases like what has been done aggregate.

Summary

import datashader as ds

import holoviews as hv
from holoviews.operation.datashader import rasterize

hv.extension("bokeh")

rects = hv.Rectangles(
    [
        (0, 0, 1, 1, 128, 100, 200),
        (2, 3, 4, 6, 100, 50, 80),
        (0.5, 2, 1.5, 4, 20, 200, 120),
        (2, 1, 3.5, 2.5, 110, 40, 240),
    ],
    kdims=[
        hv.Dimension("x0"),
        hv.Dimension("y0"),
        hv.Dimension("x1"),
        hv.Dimension("y1"),
    ],
    vdims=[
        hv.Dimension("r"),
        hv.Dimension("g"),
        hv.Dimension("b"),
    ],
)
rasterize(
    rects,
    aggregator=ds.summary(
        r=ds.where(ds.max("x0"), "r"),
        g=ds.where(ds.max("x0"), "g"),
        b=ds.where(ds.max("x0"), "b"),
    ),
).opts(tools=["hover"])

Screencast.From.2025-11-24.19-06-59.mp4

Selector

import datashader as ds
import numpy as np
import pandas as pd

import holoviews as hv
from holoviews.operation.datashader import datashade, dynspread, rasterize

hv.extension("bokeh")

# Set default hover tools on various plot types
hv.opts.defaults(tools=["hover"])

rects = hv.Rectangles(
    [(0, 0, 1, 1), (2, 3, 4, 6), (0.5, 2, 1.5, 4), (2, 1, 3.5, 2.5)],
    kdims=[
        hv.Dimension("Time"),
        hv.Dimension("y0"),
        hv.Dimension("x1"),
        hv.Dimension("y1"),
    ],
)

rects = datashade(rects, aggregator=ds.count(), selector=ds.min("Time"))
rects.opts(hover_tooltips=["Time"])
rects

Screencast.From.2025-11-24.19-07-53.mp4

Simple

import datashader as ds

import holoviews as hv
from holoviews.operation.datashader import rasterize

hv.extension("bokeh")

rects = hv.Rectangles(
    [
        (0, 0, 1, 1, 128, 100, 200),
        (2, 3, 4, 6, 100, 50, 80),
        (0.5, 2, 1.5, 4, 20, 200, 120),
        (2, 1, 3.5, 2.5, 110, 40, 240),
    ],
    kdims=[
        hv.Dimension("x0"),
        hv.Dimension("y0"),
        hv.Dimension("x1"),
        hv.Dimension("y1"),
    ],
    vdims=[
        hv.Dimension("r"),
        hv.Dimension("g"),
        hv.Dimension("b"),
    ],
)
rasterize(rects, aggregator=ds.max("x0")).opts(tools=["hover"])

Screencast.From.2025-11-24.19-08-25.mp4

[codecov]

Codecov Report

❌ Patch coverage is 97.94521% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.11%. Comparing base (1f0d3cf) to head (0fbc2b0).
⚠️ Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
holoviews/operation/datashader.py	97.19%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #6743       +/-   ##
===========================================
+ Coverage   21.18%   89.11%   +67.92%     
===========================================
  Files         335      341        +6     
  Lines       72706    73241      +535     
===========================================
+ Hits        15404    65268    +49864     
+ Misses      57302     7973    -49329     

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[hoxbro]

This is duplicated, but I think it is OK.

[philippjfr]

Let's merge after the patch release.

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.