[Compatibility]: Legacy LineChart data point x-positions shifted in v7 (getXMaxValues off-by-one vs v6)

[gimi-anders]

Version that worked

react-native-chart-kit 6.12.3

Version that regressed

7.0.1

Component

LineChart (legacy root import)

Legacy props and data

<LineChart
  data={{ labels: [], datasets: [{ data: [10, 20, 15, 30, 25, 40] }] }}
  width={400}
  height={125}
  style={{ paddingRight: 10 }}
  chartConfig={{ propsForDots: { r: "6" } }}
  bezier
  transparent
/>

What happens

In v6, dot i was rendered at:

cx = paddingRight + i * (width - paddingRight) / data.length

In v7, the same legacy LineChart renders it at:

cx = paddingRight + i * (chartWidth - paddingRight) / (data.length - 1)

Two changes cause this:

1. getXMaxValues returns Math.max(data.length - 1, 1) in v7 (src/charts/line/LineChart.tsx), where v6 returned data.length. This spreads the points across the full width, shifting every point except the first.
2. A new getChartRightPadding subtracts dot radius (min 4px) from the drawing width.

With the sample above (6 points, width 400, paddingRight 10), v6 spaced dots 65px apart; v7 spaces them ~76.8px apart — the last dot shifts ~59px. Any app that overlays custom markers/labels on the legacy chart using the v6 formula (a common workaround since the chart exposes no point positions) gets misaligned overlays.

Before and after screenshots

Will be added in a follow-up comment.

Did you try compatibility props?

Not available for this chart

Expected compatibility behavior

The migration docs (docs/migration/from-v1.md) say: "Keep migrated charts on the legacy package path when they rely on old spacing during a transition." So we expect the legacy root import to keep v6's exact point positions. The new spreading behavior may be nicer as a default, but it belongs to the v2 API — or behind an opt-in prop — not a silent change in the compat layer.

Additional notes

No warnings or errors — the chart renders fine, only positions changed. This blocks upgrading to v7 for us, since our screen overlays interactive markers on the data points.

[gimi-anders]

Before (the white active dot is correctly placed)

After (the issue is that the white active dot is misplaced)