CSS styles misalign with frozen_columns in Panel’s Tabulator

Panel
1

ALL software version info

(this library, plus any other relevant software, e.g. bokeh, python, notebook, OS, browser, etc should be added within the dropdown below.)

Software Version Info 
Panel Version: 1.7.0
Python Version: 3.10.17
OS: Linux (AWS)
Browser: Firefox 138.0.3 (aarch64)
Pandas: 2.2.3

Description of expected behavior and the observed behavior

Expected Behavior

  • Styles (e.g. font color, background color) should align with the correct cells.
  • Freezing a column should not impact visual styling alignment.

Actual Behavior

  • With frozen_columns=[0], all cell styles are offset one column to the right.
  • Without frozen columns, styles apply correctly.
  • styled_fz.style and styled.style objects appear identical and correct.
  • Applying .style.background_gradient (which uses matplotlib) does align correctly as following issue #6675, which was fixed with #7792 — maybe bug is limited to custom styling with style.map and style.apply.

Complete, minimal, self-contained example code that reproduces the issue

  • Reproducible in both Jupyter notebooks and when serving via panel serve.
import numpy as np
import pandas as pd
import panel as pn

pn.extension('tabulator')

# Seed and sample data
np.random.seed(42)
style_df = pd.DataFrame(np.random.randn(4, 5), columns=list('ABCDE'))

# Styling functions
def color_negative_red(val):
    return 'color: red' if val < 0 else 'color: black'

def highlight_max(s):
    is_max = s == s.max()
    return ['background-color: yellow' if v else '' for v in is_max]

# Tabulator widgets
styled_fz = pn.widgets.Tabulator(style_df, frozen_columns=[0])
styled = pn.widgets.Tabulator(style_df)

# Apply styling
styled.style.map(color_negative_red).apply(highlight_max)
styled_fz.style.map(color_negative_red).apply(highlight_max)

# Layout to compare output
pn.Column(
    "NO FROZEN COL",
    styled,
    "FROZEN COL",
    styled_fz,
    "Style Object: Frozen",
    styled_fz.style,
    "Style Object: Non-Frozen",
    styled.style,
)

Stack traceback and/or browser JavaScript console output

N/A

Screenshots or screencasts of the bug in action

Image

2

If you want to keep the same order for your column and want to have some frozen columns, you should use :

styled_fz = pn.widgets.Tabulator(style_df, frozen_columns=["index", "A"])

If you want to have the index and the A column frozen.