From 2f18b47d95b79f5e8109e155c8ff36c190569569 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=81lvaro=20Velad=20Galv=C3=A1n?= <ladvan91@hotmail.com>
Date: Fri, 14 Mar 2025 14:01:28 +0100
Subject: [PATCH] fix: Update region observer with new rules for small regions
 (#8275)

This is necessary because some EMSG and ID3 events might not fire
because the endTime is equal to or very close to the startTime.

Related to https://github.com/shaka-project/shaka-player/pull/8012
---
 lib/media/region_observer.js       | 11 +++++++-
 test/media/region_observer_unit.js | 45 +++++++++++++++++-------------
 2 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/lib/media/region_observer.js b/lib/media/region_observer.js
index d6ffa7673..a519378e2 100644
--- a/lib/media/region_observer.js
+++ b/lib/media/region_observer.js
@@ -96,7 +96,16 @@ shaka.media.RegionObserver = class extends shaka.util.FakeEventTarget {
       {
         weWere: BEFORE_THE_REGION,
         weAre: AFTER_THE_REGION,
-        invoke: (region, seeking) => this.onEvent_('skip', region, seeking),
+        invoke: (region, seeking) => {
+          if (seeking) {
+            this.onEvent_('skip', region, seeking);
+          } else {
+            // This is the case of regions whose duration is smaller than the
+            // resolution of our polling.
+            this.onEvent_('enter', region, seeking);
+            this.onEvent_('exit', region, seeking);
+          }
+        },
       },
       {
         weWere: AFTER_THE_REGION,
diff --git a/test/media/region_observer_unit.js b/test/media/region_observer_unit.js
index fd9c43627..d572c3514 100644
--- a/test/media/region_observer_unit.js
+++ b/test/media/region_observer_unit.js
@@ -113,25 +113,29 @@ describe('RegionObserver', () => {
     expect(onExitRegion).toHaveBeenCalledOnceMoreWith([region, false]);
   });
 
-  it('fires skip event when we enter and leave region in one move', () => {
-    const region = createRegion('my-region', 5, 10);
-    timeline.addRegion(region);
+  it('fires start and end events when we enter and leave region in one move',
+      () => {
+        const region = createRegion('my-region', 5, 10);
+        timeline.addRegion(region);
 
-    // Make sure we are before the region starts.
-    poll(observer,
-        /* timeInSeconds= */ 4,
-        /* seeking= */ false);
-    expect(onSkipRegion).not.toHaveBeenCalled();
+        // Make sure we are before the region starts.
+        poll(observer,
+            /* timeInSeconds= */ 4,
+            /* seeking= */ false);
+        expect(onEnterRegion).not.toHaveBeenCalled();
+        expect(onExitRegion).not.toHaveBeenCalled();
+        expect(onSkipRegion).not.toHaveBeenCalled();
 
-    // Make sure we call |onSkip| when we move so far that we skip over the
-    // region.
-    poll(observer,
-        /* timeInSeconds= */ 15,
-        /* seeking= */ false);
-    expect(onSkipRegion).toHaveBeenCalledOnceMoreWith([region, false]);
-  });
+        // Make sure we call |onEnter| and |onExit|
+        poll(observer,
+            /* timeInSeconds= */ 15,
+            /* seeking= */ false);
+        expect(onEnterRegion).toHaveBeenCalledOnceMoreWith([region, false]);
+        expect(onExitRegion).toHaveBeenCalledOnceMoreWith([region, false]);
+        expect(onSkipRegion).not.toHaveBeenCalled();
+      });
 
-  it('fires skip events for zero-duration regions', () => {
+  it('fires start and end events for zero-duration regions', () => {
     // Make a region with no duration.
     const region = createRegion('my-region', 5, 5);
     timeline.addRegion(region);
@@ -140,14 +144,17 @@ describe('RegionObserver', () => {
     poll(observer,
         /* timeInSeconds= */ 4,
         /* seeking= */ false);
+    expect(onEnterRegion).not.toHaveBeenCalled();
+    expect(onExitRegion).not.toHaveBeenCalled();
     expect(onSkipRegion).not.toHaveBeenCalled();
 
-    // Make sure we call |onSkip| when we move so far that we skip over the
-    // region.
+    // Make sure we call |onEnter| and |onExit|
     poll(observer,
         /* timeInSeconds= */ 10,
         /* seeking= */ false);
-    expect(onSkipRegion).toHaveBeenCalledOnceMoreWith([region, false]);
+    expect(onEnterRegion).toHaveBeenCalledOnceMoreWith([region, false]);
+    expect(onExitRegion).toHaveBeenCalledOnceMoreWith([region, false]);
+    expect(onSkipRegion).not.toHaveBeenCalled();
   });
 
   // We want to simulate a "normal" case of overlapping regions. For this we