[BUG]: `hoverlabel.align` is ignored in `hovermode: "x unified"`

[stdedos]

Description

layout.hoverlabel.align (and trace-level hoverlabel.align) has no effect when hovermode is 'x unified' or 'y unified'. Row text in the unified label is always left-aligned.

Reported on the forum: https://community.plotly.com/t/hoverlabel-align-right-is-not-honored-in-hovermode-x-unified/97717

Repro

import plotly.graph_objects as go

people = ["Person A", "Person B", "Person C"]

fig = go.Figure()
for name, values in {
    "Series 1": [3944, 2810, 1675],
    "Series 2": [-266, -1020, -85],
    "Series 3": [-44, -310, -7],
    "Series 4": [-43, -5, -390],
}.items():
    fig.add_trace(go.Bar(x=people, y=values, name=name, hovertemplate="%{y:,.0f} €<extra></extra>"))

# --- secondary-axis line: delete this block to test without it ---
fig.add_trace(go.Scatter(
    x=people, y=[0.91, 0.62, 0.785], name="Ratio",
    mode="lines+markers", yaxis="y2", line=dict(color="black"),
    hovertemplate="%{y:.1%}<extra></extra>",
))
fig.update_layout(yaxis2=dict(overlaying="y", side="right", tickformat=".0%"))
# --- end ---

fig.update_layout(
    barmode="relative",
    separators=". ",
    hovermode="x unified",
    hoverlabel=dict(align="right"),
    # Same with
    # hoverlabel_align="right",
)
fig.show()

Expected: values right-aligned within the unified label.
Actual: left-aligned.

Screenshots/Video

Steps to reproduce

Reports must include steps to reproduce the issue. Alternatively, you can use codepen, jsfiddle or jsbin to share your example. Please use the latest (un-minified) version of plotly.js in your report unless not applicable.

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Notes

This does appear to be a bug in plotly.js. The label is hardcoded to use 'start'.

---

It seems to lead to a 9 year old code (standardize on attr over style for text-anchor · plotly/plotly.js@3ad11f6 · GitHub).

[camdecoster]

Thanks for the report! This would be a good first issue for someone to dig into if they're interested.

[MannXo]

I'll work on this one , can I get assigned?

[camdecoster]

I'll take a look at your PR, but in the future could you please describe the solution you're planning on in the issue before creating a PR?