From 15a8baee0307f8c9cec7c0ba174e111d4df2d0ac Mon Sep 17 00:00:00 2001
From: Matthew Olsson <matthewcolsson@gmail.com>
Date: Thu, 23 May 2024 19:17:52 -0700
Subject: [PATCH] LibWeb: Save time for animationcancel event before
 transitioning to idle

The if statement in the dispatch implies we are in the idle state, so of
course the active time will always be undefined. If this was cancelled
via a call to cancel(), we can save the time at that point. Otherwise,
just send 0.
---
 .../sending-animationcancel-event-crash.txt   |  1 +
 .../sending-animationcancel-event-crash.html  | 27 +++++++++++++++++++
 .../Libraries/LibWeb/Animations/Animation.cpp |  4 +++
 .../Libraries/LibWeb/Animations/Animation.h   |  3 +++
 Userland/Libraries/LibWeb/DOM/Document.cpp    |  5 ++--
 5 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 Tests/LibWeb/Text/expected/css/sending-animationcancel-event-crash.txt
 create mode 100644 Tests/LibWeb/Text/input/css/sending-animationcancel-event-crash.html

diff --git a/Tests/LibWeb/Text/expected/css/sending-animationcancel-event-crash.txt b/Tests/LibWeb/Text/expected/css/sending-animationcancel-event-crash.txt
new file mode 100644
index 00000000000..be36d109cd5
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/css/sending-animationcancel-event-crash.txt
@@ -0,0 +1 @@
+   PASS! (Didn't crash)
diff --git a/Tests/LibWeb/Text/input/css/sending-animationcancel-event-crash.html b/Tests/LibWeb/Text/input/css/sending-animationcancel-event-crash.html
new file mode 100644
index 00000000000..dfa5b6856c7
--- /dev/null
+++ b/Tests/LibWeb/Text/input/css/sending-animationcancel-event-crash.html
@@ -0,0 +1,27 @@
+<!-- https://github.com/SerenityOS/serenity/issues/24424 -->
+<style>
+    @keyframes anim {
+        to {
+            width: 200px;
+        }
+    }
+
+    div {
+        animation: anim 1s;
+    }
+</style>
+<div id="foo"></div>
+<script src="../include.js"></script>
+<script>
+    asyncTest(done => {
+        const foo = document.getElementById("foo");
+        const anim = foo.getAnimations()[0];
+        foo.addEventListener("animationcancel", () => {
+            println("PASS! (Didn't crash)");
+            done();
+        });
+        requestAnimationFrame(() => {
+            anim.cancel();
+        });
+    });
+</script>
diff --git a/Userland/Libraries/LibWeb/Animations/Animation.cpp b/Userland/Libraries/LibWeb/Animations/Animation.cpp
index a2a654d7f14..f4fbac63707 100644
--- a/Userland/Libraries/LibWeb/Animations/Animation.cpp
+++ b/Userland/Libraries/LibWeb/Animations/Animation.cpp
@@ -470,6 +470,10 @@ void Animation::cancel(ShouldInvalidate should_invalidate)
     // 3. Make animation’s start time unresolved.
     m_start_time = {};
 
+    // This time is needed for dispatching the animationcancel DOM event
+    if (auto effect = m_effect)
+        m_saved_cancel_time = effect->active_time_using_fill(Bindings::FillMode::Both);
+
     if (should_invalidate == ShouldInvalidate::Yes)
         invalidate_effect();
 }
diff --git a/Userland/Libraries/LibWeb/Animations/Animation.h b/Userland/Libraries/LibWeb/Animations/Animation.h
index f9678d09d77..c06e5010e65 100644
--- a/Userland/Libraries/LibWeb/Animations/Animation.h
+++ b/Userland/Libraries/LibWeb/Animations/Animation.h
@@ -108,6 +108,8 @@ public:
 
     unsigned int global_animation_list_order() const { return m_global_animation_list_order; }
 
+    auto release_saved_cancel_time() { return move(m_saved_cancel_time); }
+
 protected:
     Animation(JS::Realm&);
 
@@ -194,6 +196,7 @@ private:
 
     Optional<double> m_saved_play_time;
     Optional<double> m_saved_pause_time;
+    Optional<double> m_saved_cancel_time;
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index b6cd64091ee..1b70bc46153 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -2103,8 +2103,9 @@ void Document::dispatch_events_for_animation_if_necessary(JS::NonnullGCPtr<Anima
         }
 
         if (current_phase == Animations::AnimationEffect::Phase::Idle && previous_phase != Animations::AnimationEffect::Phase::Idle && previous_phase != Animations::AnimationEffect::Phase::After) {
-            // FIXME: Use the active time "at the moment it was cancelled"
-            dispatch_event(HTML::EventNames::animationcancel, effect->active_time_using_fill(Bindings::FillMode::Both).value());
+            // FIXME: Calculate a non-zero time when the animation is cancelled by means other than calling cancel()
+            auto cancel_time = animation->release_saved_cancel_time().value_or(0.0);
+            dispatch_event(HTML::EventNames::animationcancel, cancel_time);
         }
     }
     effect->set_previous_phase(current_phase);