Fix ReplacingCuesResolver.discardCuesBeforeTimeUs to retain active cue

The method previously discarded the cue that was active at `timeUs`,
meaning it had started before but had not ended by `timeUs`.

Issue: #1939

PiperOrigin-RevId: 702707611
(cherry picked from commit e927d7b)

RELEASENOTES.md

@@ -38,6 +38,13 @@
         when provided while processing `onOutputFormatChanged`
         ([#1371](https://github.com/androidx/media/pull/1371)).
 *   Text:
+    *   Stop eagerly loading all subtitle files configured with
+        `MediaItem.Builder.setSubtitleConfigurations`, and instead only load one
+        if it is selected by track selection
+        ([#1721](https://github.com/androidx/media/issues/1721)).
+    *   Fix bug in `ReplacingCuesResolver.discardCuesBeforeTimeUs` where the cue
+        active at `timeUs` (started before but not yet ended) was incorrectly
+        discarded ([#1939](https://github.com/androidx/media/issues/1939)).
 *   Metadata:
 *   Image:
 *   DRM:

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/text/ReplacingCuesResolver.java

@@ -80,9 +80,15 @@ public ImmutableList<Cue> getCuesAtTimeUs(long timeUs) {
   @Override
   public void discardCuesBeforeTimeUs(long timeUs) {
     int indexToDiscardTo = getIndexOfCuesStartingAfter(timeUs);
-    if (indexToDiscardTo > 0) {
-      cuesWithTimingList.subList(0, indexToDiscardTo).clear();
+    if (indexToDiscardTo == 0) {
+      // Either the first cue starts after timeUs, or the cues list is empty.
+      return;
+    }
+    CuesWithTiming lastCueToDiscard = cuesWithTimingList.get(indexToDiscardTo - 1);
+    if (lastCueToDiscard.endTimeUs == C.TIME_UNSET || lastCueToDiscard.endTimeUs >= timeUs) {
+      indexToDiscardTo--;
     }
+    cuesWithTimingList.subList(0, indexToDiscardTo).clear();
   }
 
   @Override
@@ -142,7 +148,7 @@ public void clear() {
 
   /**
    * Returns the index of the first {@link CuesWithTiming} in {@link #cuesWithTimingList} where
-   * {@link CuesWithTiming#startTimeUs} is strictly less than {@code timeUs}.
+   * {@link CuesWithTiming#startTimeUs} is strictly greater than {@code timeUs}.
    *
    * <p>Returns the size of {@link #cuesWithTimingList} if all cues are before timeUs
    */

libraries/exoplayer/src/test/java/androidx/media3/exoplayer/text/ReplacingCuesResolverTest.java

@@ -217,6 +217,47 @@ public void discardCuesBeforeTimeUs() {
     assertThat(replacingCuesResolver.getNextCueChangeTimeUs(4_999_990)).isEqualTo(6_000_000);
   }
 
+  @Test
+  public void discardCuesBeforeTimeUs_retainsActiveCueWithSetDuration() {
+    ReplacingCuesResolver replacingCuesResolver = new ReplacingCuesResolver();
+    CuesWithTiming activeCue =
+        new CuesWithTiming(FIRST_CUES, /* startTimeUs= */ 3_000_000, /* durationUs= */ 4_000_000);
+    CuesWithTiming laterCue =
+        new CuesWithTiming(SECOND_CUES, /* startTimeUs= */ 8_000_000, /* durationUs= */ 2_000_000);
+    replacingCuesResolver.addCues(activeCue, /* currentPositionUs= */ 5_000_000);
+    replacingCuesResolver.addCues(laterCue, /* currentPositionUs= */ 5_000_000);
+
+    // Discard cues before 5_000_000. activeCue should remain active because it ends at 7_000_000.
+    replacingCuesResolver.discardCuesBeforeTimeUs(5_000_000);
+
+    // Query at a time within activeCue's range to verify it's still there.
+    assertThat(replacingCuesResolver.getCuesAtTimeUs(6_000_000)).isEqualTo(FIRST_CUES);
+    // Ensure that laterCue is unaffected.
+    assertThat(replacingCuesResolver.getCuesAtTimeUs(9_000_000)).isEqualTo(SECOND_CUES);
+  }
+
+  @Test
+  public void discardCuesBeforeTimeUs_retainsActiveCueWithUnsetDuration() {
+    ReplacingCuesResolver replacingCuesResolver = new ReplacingCuesResolver();
+    CuesWithTiming activeCue =
+        new CuesWithTiming(
+            FIRST_CUES, /* startTimeUs= */ 3_000_000, /* durationUs= */ C.TIME_UNSET);
+    CuesWithTiming laterCue =
+        new CuesWithTiming(SECOND_CUES, /* startTimeUs= */ 8_000_000, /* durationUs= */ 2_000_000);
+    replacingCuesResolver.addCues(activeCue, /* currentPositionUs= */ 5_000_000);
+    replacingCuesResolver.addCues(laterCue, /* currentPositionUs= */ 5_000_000);
+
+    // Discard cues before 5_000_000. activeCue should remain active because its
+    // duration is unset, meaning it should remain visible until replaced by a subsequent cue
+    // starting at 8_000_000.
+    replacingCuesResolver.discardCuesBeforeTimeUs(5_000_000);
+
+    // Query at a time within activeCue's range to verify it's still there.
+    assertThat(replacingCuesResolver.getCuesAtTimeUs(6_000_000)).isEqualTo(FIRST_CUES);
+    // Ensure that laterCue is unaffected.
+    assertThat(replacingCuesResolver.getCuesAtTimeUs(9_000_000)).isEqualTo(SECOND_CUES);
+  }
+
   @Test
   public void clear_clearsAllCues() {
     ReplacingCuesResolver replacingCuesResolver = new ReplacingCuesResolver();