plotly / plotly/plotly.js

[BUG]: forced minimum tick spacing (box/violin/candlestick/ohlc) leaks between figures on the same graph div

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bug P2 size: 1
Dominant language
JavaScript
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Merged PRs (30d)
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Description

Description

Box, violin, candlestick and ohlc traces ask their position axis for a minimum tick spacing, so that each box gets a tick of its own rather than ticks at meaningless in-between positions. That forcing is silently lost whenever the figure is drawn into a graph div that already held a different figure — so Plotly.react, restyle, addTraces and friends can produce different ticks than Plotly.newPlot of the exact same figure.

It goes the other way too: a graph div that once held a box plot keeps the forced spacing after you react to a trace type that never asked for it.

Steps to reproduce
var boxFig = {
    data: [{type: 'box', x: [1, 1, 2, 2, 3, 3], y: [1, 2, 3, 4, 5, 6]}],
    layout: {width: 700, height: 400}
};
var scatterFig = {data: [{y: [1, 2, 3]}], layout: {width: 700, height: 400}};

// x ticks: 1, 2, 3  — correct, one per box
Plotly.newPlot(gd, boxFig);

// x ticks: 0.5, 1, 1.5, 2, 2.5, 3, 3.5  — same figure, half the ticks land between boxes
Plotly.newPlot(gd, scatterFig).then(function() { return Plotly.react(gd, boxFig); });

It is most visible on a date axis. Five daily candles at width: 1000, reached by reacting from a line chart over the same dates:

newPlot:  Jan 1 | Jan 2 | Jan 3 | Jan 4 | Jan 5
react:    12:00 Dec 31, 2023 | 00:00 Jan 1, 2024 | 12:00 | 00:00 Jan 2, 2024 | 12:00 | ...

Every second tick falls in the gap between two candles, and the axis now starts on the day before the data.

Notes

Axes.minDtick keeps its state in ax._minDtick / ax._forceTick0, with three meanings: undefined (nothing forced yet — adopt this trace's spacing), a positive number (a forcing is in effect), and 0 (forcing cancelled — by non-grouped bars, or by scatter/heatmap calc — and sticky, so a later trace can't reinstate it).

The reset back to undefined between passes sits at the bottom of setConvert, but it can't take effect on a real axis: setConvert runs while supplyDefaults builds the new _fullLayout, where those keys don't exist yet, and relinkPrivateKeys then copies the old values back onto it. So whichever figure the graph div held first decides the forcing for every figure after it. newPlot escapes it only because it starts from an empty _fullLayout.

Found by a sweep comparing react against newPlot of the same figure — 7 of 12 divergences traced back here.

Fix proposed in #7950, which moves the reset into ax.clearCalc(), alongside the equivalent relink cleanup doCalcdata already does for shared color axes.

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

Start by inspecting Axes.minDtick and the setConvert, ax.clearCalc, and doCalcdata entry points mentioned in the issue. Reproduce the difference between Plotly.newPlot and Plotly.react with the provided box and scatter figures, then verify that forced tick spacing is reset between figures and that both paths produce the same ticks.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript
Domain
data-visualization
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Quiet
Clarity
Clearly specified
Newbie friendliness
65/100

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