fix: re-nice linear axis with the real plot-area length after layout

[g1f9]

Problem

When a cartesian linear (value) axis uses a function tick.tickCount (i.e. the tick count depends on the axis length), the ticks come out too dense and the niced ceiling too low compared to the real plot area.

The root cause is already flagged by a TODO in linear-axis-mixin.ts (setLinearScaleNice):

if (rangeSize === 1 && this._option) {
  // TODO: need to be optimized, when the range is not updated, use the size of view
  const isX = isXAxis(this._orient);
  rangeSize = isX ? this._option.getChartViewRect().width : this._option.getChartViewRect().height;
}

setLinearScaleNice runs before layout, while scale.range() is still the initial [0, 1] (rangeSize === 1). In that case it falls back to the whole chart viewRect to estimate the axis length. But viewRect is larger than the real plot area (it still includes title / legend / opposite axis / padding), so:

• the axisLength passed to tickCount(...) is too large → tickCount too large → ticks too dense;
• the niced domain ceiling ends up lower than it should be.

After layout the scale range is updated to the real plot-area length (onLayoutEnd → updateScaleRange), but the nice computation is never re-run, so the wrong tick count / ceiling persists.

Fix

CartesianLinearAxis.onLayoutEnd now re-runs the domain + nice computation once, after the scale range reflects the real plot-area pixel length:

• It only takes effect when tick.tickCount is a function (length-dependent). Fixed tickCount, forceTickCount, and the default count are range-independent and are left untouched → no behavior change for existing users.
• A cached "last nice axis length" (_lastNiceAxisLength) skips the recompute when the axis length hasn't changed, guarding against redundant work / re-entrancy across multiple layout passes.

Scope / safety

• No-op unless tick.tickCount is a function.
• Reuses the existing updateScaleDomain() path (the same path used when series data changes), so domain extensions, zero, soft min/max, axis breaks, etc. are all preserved.

Known limitation

The axis space is allocated during layout using the pre-layout tick labels; if re-nicing produces a wider ceiling label, the axis width is not re-measured afterwards. In practice the niced ceiling label width is essentially unchanged, and this matches the trade-off already implied by the existing TODO.

[xuefei1313]

CODE REVIEW REPORT

Files reviewed: 3
Recommendation: COMMENT

MEDIUM

1. packages/vchart/src/component/axis/cartesian/linear-axis.ts:89

reTransformDomainByLayout() is executed from onLayoutEnd(). This can refresh tick/axis attributes before the chart-level layoutEnd handlers run, but it still happens after layout bounds have already been measured in getBoundsInRect(). If the re-niced domain changes the ceiling label or formatter output width, axis allocation / autoIndent will still be based on the old pre-layout ticks and may clip or squeeze the plot area. The PR body also calls out this limitation. A more robust place would be after updateScaleRange() but before computeData('range') and bounds measurement, or otherwise trigger a relayout when the re-niced domain actually changes.

2. packages/vchart/src/component/axis/mixin/linear-axis-mixin.ts:164

This adds subtle lifecycle behavior without a regression test. Please add a focused case under packages/vchart/__tests__/unit/component/cartesian/axis/linear-axis.test.ts: mock collectData, make getChartViewRect().height larger than the real layout rect height, use a function tick.tickCount that records axisLength, and assert that after onLayoutEnd() the domain/tick count is based on the real axis length rather than the full chart viewRect.

Verification: inspected PR metadata, full diff, related axis layout/event lifecycle, and ran git diff --check origin/develop...origin/pr-4594 with no output. Full test suite was not run.