plotly / plotly/plotly.py

[BUG]: Mixed bar orientations hide one bar on initial render, but restyle renders correctly

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bug P3 size: 3
Dominant language
Python
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Description

Description

A figure with two go.Bar traces renders differently depending on when the second
trace is changed from horizontal to vertical.

If fig.data[1].orientation = "v" is set before the first render, one red vertical
bar is missing or clipped. If the same base figure is rendered first and the same
orientation value is applied later with Plotly.restyle, all three red bars are
visible.

Screenshots/Video
Image Image
Steps to reproduce
import io

import plotly
import plotly.graph_objects as go
import plotly.io as pio
from PIL import Image, ImageChops
from playwright.sync_api import sync_playwright

print(f"Plotly version: {plotly.__version__}")

fig = go.Figure(
    [
        go.Bar(name="a", orientation="h", x=[1, 3, 2], y=[0, 1, 2]),
        go.Bar(name="b", orientation="h", x=[3, 2, 1], y=[0, 1, 2]),
    ]
)
fig.update_layout(xaxis_title="value", yaxis_title="index", legend_title_text="variable")

# plot1.png: set orientation before the first render.
fig.data[1].orientation = "v"
assert fig.data[1].orientation == "v"
html1 = pio.to_html(fig, full_html=True, include_plotlyjs="cdn")

# plot2.png: render first, then apply the same value with Plotly.restyle.
fig.data[1].orientation = "h"
html2 = pio.to_html(fig, full_html=True, include_plotlyjs="cdn")
html2 = html2.replace(
    "</body>",
    """
<script>
window.addEventListener("DOMContentLoaded", () => {
    const plotEl = document.getElementsByClassName("plotly-graph-div")[0];
    setTimeout(() => {
        Plotly.restyle(plotEl, {"orientation": "v"}, [1]);
    }, 1000);
});
</script>
</body>""",
)

with sync_playwright() as playwright:
    browser = playwright.chromium.launch(
        headless=True,
        args=["--no-sandbox", "--disable-dev-shm-usage", "--disable-gpu"],
    )
    page = browser.new_page(viewport={"width": 1200, "height": 800})

    page.set_content(html1)
    page.wait_for_timeout(1500)
    img1 = page.screenshot(path="plot1.png")

    page.set_content(html2)
    page.wait_for_timeout(2000)
    img2 = page.screenshot(path="plot2.png")

    browser.close()

diff = ImageChops.difference(
    Image.open(io.BytesIO(img1)).convert("RGB"),
    Image.open(io.BytesIO(img2)).convert("RGB"),
)
assert diff.getbbox() is not None, "Screenshots are unexpectedly identical."
print("Saved plot1.png and plot2.png")
```### Notes

_Add info here that doesn't fit in the other sections._

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Run the provided Python and Playwright reproduction and compare the initial-render screenshot with the Plotly.restyle result. Trace the bar rendering path for mixed horizontal and vertical orientations; done means both renderings show all three red bars without clipping or differences caused by render timing.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, playwright, python
Domain
data-visualization, frontend
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
45/100

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