feat(chart): add series styling and visibility controls

src/core/rendering.test.ts

@@ -1,7 +1,11 @@
 import { describe, expect, it } from 'vitest'
 
 import type { WaveformPoint } from '../types'
-import { resolveWaveformRenderingOptions, selectRenderablePoints } from './rendering'
+import {
+  resolveWaveformRenderingOptions,
+  selectDecorationPoints,
+  selectRenderablePoints,
+} from './rendering'
 
 describe('waveform rendering selection', () => {
   const points = Array.from({ length: 10_000 }, (_, index): WaveformPoint => ({
@@ -37,7 +41,85 @@ describe('waveform rendering selection', () => {
 
   it('normalizes invalid rendering options to stable defaults', () => {
     expect(
-      resolveWaveformRenderingOptions({ downsampleThreshold: -1, maxPointsPerPixel: 0 }),
-    ).toEqual({ downsample: true, downsampleThreshold: 2_000, maxPointsPerPixel: 4 })
+      resolveWaveformRenderingOptions({
+        downsampleThreshold: -1,
+        maxPointsPerPixel: 0,
+        pointMinSpacing: -1,
+        errorBarMinSpacing: Number.POSITIVE_INFINITY,
+      }),
+    ).toEqual({
+      downsample: true,
+      downsampleThreshold: 2_000,
+      maxPointsPerPixel: 4,
+      pointMinSpacing: 10,
+      errorBarMinSpacing: 12,
+    })
+  })
+
+  it('accepts custom decoration spacing and uses zero to disable it', () => {
+    expect(resolveWaveformRenderingOptions({ pointMinSpacing: 6, errorBarMinSpacing: 0 })).toEqual({
+      downsample: true,
+      downsampleThreshold: 2_000,
+      maxPointsPerPixel: 4,
+      pointMinSpacing: 6,
+      errorBarMinSpacing: 0,
+    })
+  })
+
+  it('selects evenly distributed source points for dense decorations', () => {
+    const selected = selectDecorationPoints(points, [0, 9_999], 100, 10, true)
+
+    expect(selected.length).toBeLessThanOrEqual(12)
+    expect(selected[0]).toBe(points[0])
+    expect(selected.at(-1)).toBe(points.at(-1))
+    expect(selected.every((point) => points.includes(point))).toBe(true)
+  })
+
+  it('clips decorations exactly to the visible domain and preserves sparse points', () => {
+    const sparsePoints = [
+      { x: 0, y: 0 },
+      { x: 40, y: 1 },
+      { x: 80, y: 2 },
+      { x: 120, y: 3 },
+    ]
+
+    expect(selectDecorationPoints(sparsePoints, [40, 80], 100, 10, true)).toEqual([
+      sparsePoints[1],
+      sparsePoints[2],
+    ])
+  })
+
+  it('supports filtering decoration candidates and disabling sampling', () => {
+    const errorPoints = Array.from({ length: 100 }, (_, index) => ({
+      x: index,
+      y: index,
+      error: index % 10 === 0 ? 1 : 0,
+    }))
+    const hasError = (point: WaveformPoint) => (point.error ?? 0) > 0
+
+    expect(selectDecorationPoints(errorPoints, [0, 99], 100, 12, true, hasError)).toHaveLength(10)
+    expect(selectDecorationPoints(errorPoints, [0, 99], 100, 12, false)).toHaveLength(100)
+    expect(selectDecorationPoints(errorPoints, [0, 99], 100, 0, true)).toHaveLength(100)
+  })
+
+  it('prefers priority candidates within dense decoration buckets', () => {
+    const priorityPoints = Array.from({ length: 100 }, (_, index) => ({
+      x: index,
+      y: index,
+      error: index % 20 === 1 ? 1 : 0,
+    }))
+    const hasError = (point: WaveformPoint) => (point.error ?? 0) > 0
+    const selected = selectDecorationPoints(
+      priorityPoints,
+      [0, 99],
+      100,
+      20,
+      true,
+      undefined,
+      hasError,
+    )
+
+    expect(selected.filter(hasError)).toEqual(priorityPoints.filter(hasError))
+    expect(selected.length).toBeLessThanOrEqual(Math.ceil(100 / 20) + 2)
   })
 })