feat(chart): improve adaptive waveform layout

src/utils/domain.test.ts

@@ -0,0 +1,28 @@
+import { describe, expect, it } from 'vitest'
+
+import { buildMinorTicks } from './domain'
+
+describe('buildMinorTicks', () => {
+  it('preserves the existing behavior when no domain is provided', () => {
+    expect(buildMinorTicks([0, 10, 20], 5)).toEqual([2, 4, 6, 8, 12, 14, 16, 18])
+  })
+
+  it('fills the partial interval after the final major tick', () => {
+    const majorTicks = Array.from({ length: 13 }, (_, index) => -8000 + index * 1000)
+
+    expect(buildMinorTicks(majorTicks, 5, [-8000, 4990.3]).slice(-4)).toEqual([
+      4200, 4400, 4600, 4800,
+    ])
+  })
+
+  it('fills both edge intervals and excludes the domain endpoints', () => {
+    const ticks = buildMinorTicks([-7000, -6000, -5000], 5, [-7950, -4100])
+
+    expect(ticks).toEqual([
+      -7800, -7600, -7400, -7200, -6800, -6600, -6400, -6200, -5800, -5600, -5400,
+      -5200, -4800, -4600, -4400, -4200,
+    ])
+    expect(ticks).not.toContain(-7950)
+    expect(ticks).not.toContain(-4100)
+  })
+})

src/utils/domain.ts

@@ -17,13 +17,34 @@ export function paddedDomain(values: number[]): [number, number] {
  * 在主刻度之间生成次要刻度
  * @param values 主刻度值数组
  * @param subdivisions 细分数量，默认 5
+ * @param domain 可选的可见域，用于补齐首尾不完整主刻度区间内的次要刻度
  * @returns 次要刻度值数组
  */
-export function buildMinorTicks(values: number[], subdivisions = 5): number[] {
-  return values.flatMap((value, index) => {
-    const nextValue = values[index + 1]
+export function buildMinorTicks(
+  values: number[],
+  subdivisions = 5,
+  domain?: readonly [number, number],
+): number[] {
+  let intervalBoundaries = values
+
+  if (domain && values.length >= 2) {
+    const first = values[0]
+    const second = values[1]
+    const last = values[values.length - 1]
+    const previous = values[values.length - 2]
+    intervalBoundaries = [first - (second - first), ...values, last + (last - previous)]
+  }
+
+  const minorTicks = intervalBoundaries.flatMap((value, index) => {
+    const nextValue = intervalBoundaries[index + 1]
     if (nextValue === undefined) return []
     const step = (nextValue - value) / subdivisions
     return Array.from({ length: subdivisions - 1 }, (_, minorIndex) => value + step * (minorIndex + 1))
   })
+
+  if (!domain) return minorTicks
+
+  const domainMinimum = Math.min(...domain)
+  const domainMaximum = Math.max(...domain)
+  return minorTicks.filter((tick) => tick > domainMinimum && tick < domainMaximum)
 }