Cover breakable fit mode cache

Author: chenglou

src/layout.test.ts

@@ -10,8 +10,10 @@ const LINE_HEIGHT = 19
 
 type LayoutModule = typeof import('./layout.ts')
 type LineBreakModule = typeof import('./line-break.ts')
+type MeasurementModule = typeof import('./measurement.ts')
 type RichInlineModule = typeof import('./rich-inline.ts')
 type AnalysisModule = typeof import('./analysis.ts')
+type SegmentMetrics = ReturnType<MeasurementModule['getSegmentMetrics']>
 
 let prepare: LayoutModule['prepare']
 let prepareWithSegments: LayoutModule['prepareWithSegments']
@@ -27,6 +29,7 @@ let countPreparedLines: LineBreakModule['countPreparedLines']
 let measurePreparedLineGeometry: LineBreakModule['measurePreparedLineGeometry']
 let stepPreparedLineGeometry: LineBreakModule['stepPreparedLineGeometry']
 let walkPreparedLines: LineBreakModule['walkPreparedLines']
+let getSegmentBreakableFitAdvances: MeasurementModule['getSegmentBreakableFitAdvances']
 let prepareRichInline: RichInlineModule['prepareRichInline']
 let materializeRichInlineLineRange: RichInlineModule['materializeRichInlineLineRange']
 let measureRichInlineStats: RichInlineModule['measureRichInlineStats']
@@ -262,10 +265,11 @@ class TestOffscreenCanvas {
 
 beforeAll(async () => {
   Reflect.set(globalThis, 'OffscreenCanvas', TestOffscreenCanvas)
-  const [analysisMod, mod, lineBreakMod, richInlineMod] = await Promise.all([
+  const [analysisMod, mod, lineBreakMod, measurementMod, richInlineMod] = await Promise.all([
     import('./analysis.ts'),
     import('./layout.ts'),
     import('./line-break.ts'),
+    import('./measurement.ts'),
     import('./rich-inline.ts'),
   ])
   ;({ isCJK } = analysisMod)
@@ -282,6 +286,7 @@ beforeAll(async () => {
     setLocale,
   } = mod)
   ;({ countPreparedLines, measurePreparedLineGeometry, stepPreparedLineGeometry, walkPreparedLines } = lineBreakMod)
+  ;({ getSegmentBreakableFitAdvances } = measurementMod)
   ;({ prepareRichInline, materializeRichInlineLineRange, measureRichInlineStats, walkRichInlineLineRanges } = richInlineMod)
 })
 
@@ -290,6 +295,25 @@ beforeEach(() => {
   clearCache()
 })
 
+describe('measurement invariants', () => {
+  test('breakable fit cache distinguishes fit modes', () => {
+    const metrics: SegmentMetrics = { width: 80, containsCJK: false }
+    const cache = new Map<string, SegmentMetrics>([
+      ['a', { width: 10, containsCJK: false }],
+      ['b', { width: 20, containsCJK: false }],
+      ['c', { width: 30, containsCJK: false }],
+      ['ab', { width: 35, containsCJK: false }],
+      ['bc', { width: 60, containsCJK: false }],
+      ['abc', metrics],
+    ])
+
+    expect(getSegmentBreakableFitAdvances('abc', metrics, cache, 0, 'sum-graphemes')).toEqual([10, 20, 30])
+    expect(getSegmentBreakableFitAdvances('abc', metrics, cache, 0, 'pair-context')).toEqual([10, 25, 40])
+    expect(getSegmentBreakableFitAdvances('abc', metrics, cache, 0, 'segment-prefixes')).toEqual([10, 25, 45])
+    expect(getSegmentBreakableFitAdvances('abc', metrics, cache, 0, 'sum-graphemes')).toEqual([10, 20, 30])
+  })
+})
+
 describe('prepare invariants', () => {
   test('whitespace-only input stays empty', () => {
     const prepared = prepare('  \t\n  ', FONT)