fix(subtitles): preserve lyric selection and deduplicate secondary text

- Seek sidebar selections past overlapping karaoke exit spans
- Collapse duplicate long ASS lines and omit reconstructed sign grids

src/core/services/index.ts

@@ -52,6 +52,7 @@ export { syncYomitanDefaultAnkiServer } from './tokenizer/yomitan-parser-runtime
 export { createSubtitleProcessingController } from './subtitle-processing-controller';
 export {
   resolveSanitizedSubtitleSeekCommand,
+  subtitleCueListSeekTime,
   subtitleCueSeekTime,
 } from './subtitle-cue-navigation';
 export { createFrequencyDictionaryLookup } from './frequency-dictionary';

src/core/services/secondary-subtitle-line-identity.ts

@@ -0,0 +1,15 @@
+const MIN_FLATTENED_DUPLICATE_LENGTH = 16;
+const TERMINAL_SENTENCE_PUNCTUATION = /[.!?。！？…⋯]+$/gu;
+
+/**
+ * Identifies long lines that become duplicates when positioned ASS events are
+ * flattened into the secondary subtitle bar. Short dialogue stays distinct.
+ */
+export function flattenedSecondarySubtitleLineIdentity(text: string): string | null {
+  const identity = text
+    .normalize('NFKC')
+    .replace(/\s+/gu, '')
+    .replace(TERMINAL_SENTENCE_PUNCTUATION, '');
+
+  return identity.length >= MIN_FLATTENED_DUPLICATE_LENGTH ? identity : null;
+}

src/core/services/subtitle-cue-navigation.test.ts

@@ -2,6 +2,7 @@ import assert from 'node:assert/strict';
 import test from 'node:test';
 import {
   resolveSanitizedSubtitleSeekCommand,
+  subtitleCueListSeekTime,
   subtitleCueSeekTime,
 } from './subtitle-cue-navigation';
 
@@ -85,3 +86,23 @@ test('sidebar cue seeks share the boundary-safe sanitized cue timestamp', () =>
   assert.equal(subtitleCueSeekTime({ startTime: 1, endTime: 2, text: 'line' }), 1.08);
   assert.equal(subtitleCueSeekTime({ startTime: 1, endTime: 1.04, text: 'short' }), 1.03);
 });
+
+test('sidebar cue selection clears an overlapping previous lyric', () => {
+  const cues = [
+    { startTime: 1, endTime: 3.4, text: 'previous lyric' },
+    { startTime: 3, endTime: 5, text: 'selected lyric' },
+  ];
+
+  assert.equal(subtitleCueListSeekTime(cues, cues[1]!), 3.48);
+});
+
+test('sidebar cue selection remains inside a short cue when overlap cannot be cleared', () => {
+  const cues = [
+    { startTime: 1, endTime: 3.4, text: 'previous lyric' },
+    { startTime: 3, endTime: 3.2, text: 'selected lyric' },
+  ];
+
+  const seekTime = subtitleCueListSeekTime(cues, cues[1]!);
+  assert.ok(seekTime >= 3.19);
+  assert.ok(seekTime < cues[1]!.endTime);
+});

src/core/services/subtitle-cue-navigation.ts

@@ -42,6 +42,36 @@ export function subtitleCueSeekTime(cue: SubtitleCue): number {
   );
 }
 
+/**
+ * Choose a stable point inside a selected cue. Karaoke lines can overlap while the
+ * previous line animates out, so a sidebar selection should clear that overlap when
+ * the selected cue has enough time remaining.
+ */
+export function subtitleCueListSeekTime(
+  cues: readonly SubtitleCue[],
+  selectedCue: SubtitleCue,
+): number {
+  const groups = groupCueBoundaries(cues);
+  const selectedGroupIndex = groups.findIndex(
+    (group) =>
+      selectedCue.startTime >= group.startTime &&
+      selectedCue.startTime - group.startTime <= CUE_START_GROUP_TOLERANCE_SECONDS,
+  );
+  const previousGroupEndTime =
+    selectedGroupIndex > 0 ? groups[selectedGroupIndex - 1]?.endTime : undefined;
+  if (previousGroupEndTime === undefined || previousGroupEndTime <= selectedCue.startTime) {
+    return subtitleCueSeekTime(selectedCue);
+  }
+
+  return Math.max(
+    selectedCue.startTime,
+    Math.min(
+      selectedCue.endTime - CUE_END_GUARD_SECONDS,
+      previousGroupEndTime + CUE_BOUNDARY_SEEK_OFFSET_SECONDS,
+    ),
+  );
+}
+
 /**
  * Translate mpv subtitle-line navigation onto parsed cues. Generated ASS karaoke can
  * contain hundreds of subtitle events for one visible line, while the parsed list has

src/core/services/subtitle-cue-parser.ts

@@ -10,6 +10,7 @@ import { hasAssAnimationEvidence, mergeDuplicateCues } from './subtitle-cue-dedu
 
 export type AssCueLayout =
   | { kind: 'positioned'; sourceOrder: number; y: number }
+  | { kind: 'fragment-grid'; sourceOrder: number }
   | { kind: 'source-order'; sourceOrder: number };
 
 export interface SubtitleCue {
@@ -210,6 +211,7 @@ const MIN_FRAGMENT_LINE_EVENTS = 8;
 const MIN_FRAGMENT_LINE_PARTS = 4;
 const MAX_FRAGMENT_MEDIAN_LENGTH = 4;
 const MAX_FRAGMENT_LINE_TIMING_VARIANCE_SECONDS = 2;
+const MAX_FRAGMENT_LINE_VERTICAL_SPAN = 48;
 
 function parseAssTimestamp(raw: string): number | null {
   const match = ASS_TIMING_PATTERN.exec(raw.trim());
@@ -385,6 +387,30 @@ interface AssFragmentPart {
   text: string;
 }
 
+function reconstructedAssFragmentLayout(
+  parts: readonly AssFragmentPart[],
+  owner: AnnotatedSubtitleCue,
+): AssCueLayout | undefined {
+  let positionedPartCount = 0;
+  let minimumY = Infinity;
+  let maximumY = -Infinity;
+  for (const part of parts) {
+    const layout = part.cue.assLayout;
+    if (layout?.kind !== 'positioned') continue;
+    positionedPartCount += 1;
+    minimumY = Math.min(minimumY, layout.y);
+    maximumY = Math.max(maximumY, layout.y);
+  }
+
+  if (
+    positionedPartCount >= MIN_FRAGMENT_LINE_PARTS &&
+    maximumY - minimumY > MAX_FRAGMENT_LINE_VERTICAL_SPAN
+  ) {
+    return { kind: 'fragment-grid', sourceOrder: owner.order };
+  }
+  return owner.assLayout;
+}
+
 interface AssFragmentTimingCluster {
   events: AnnotatedSubtitleCue[];
   minStartTime: number;
@@ -515,6 +541,7 @@ function reconstructAssFragmentLine(
     source: 'reconstructed-ass',
     animationStartTime,
     animationEndTime,
+    assLayout: reconstructedAssFragmentLayout(parts, owner),
     overrides: [],
     overrideSignature: '',
   };