From ec5950da0693afddc8c0fa92c22e353d47d69584 Mon Sep 17 00:00:00 2001
From: SGavrl <277843151+SGavrl@users.noreply.github.com>
Date: Sun, 26 Jul 2026 14:27:29 +0000
Subject: [PATCH] dom: deliver standalone event target listeners

---
 crates/obscura-js/js/bootstrap.js        | 98 +++++++++++++++++++++++-
 crates/obscura-js/src/runtime.rs         | 56 ++++++++++++++
 render-repros/checks.json                |  3 +
 render-repros/eventtarget-lifecycle.html | 41 ++++++++++
 4 files changed, 197 insertions(+), 1 deletion(-)
 create mode 100644 render-repros/eventtarget-lifecycle.html

diff --git a/crates/obscura-js/js/bootstrap.js b/crates/obscura-js/js/bootstrap.js
index bcf25de..1397e85 100644
--- a/crates/obscura-js/js/bootstrap.js
+++ b/crates/obscura-js/js/bootstrap.js
@@ -753,6 +753,94 @@ function _shallowCloneNode(node) {
   return el;
 }
 
+// EventTarget listener state belongs to the JS wrapper rather than the backing
+// DOM node.  This is also what makes `new EventTarget()` and subclasses used by
+// framework schedulers work: those targets deliberately have no native node id.
+const _eventTargetListeners = new WeakMap();
+function _eventCapture(options) {
+  return typeof options === "boolean" ? options : !!(options && options.capture);
+}
+function _eventTargetAdd(target, type, callback, options) {
+  if (callback == null) return;
+  const isFunction = typeof callback === "function";
+  if (!isFunction && typeof callback.handleEvent !== "function") return;
+  type = String(type);
+  const capture = _eventCapture(options);
+  const signal = options && typeof options === "object" ? options.signal : null;
+  if (signal && signal.aborted) return;
+  let byType = _eventTargetListeners.get(target);
+  if (!byType) {
+    byType = new Map();
+    _eventTargetListeners.set(target, byType);
+  }
+  let listeners = byType.get(type);
+  if (!listeners) {
+    listeners = [];
+    byType.set(type, listeners);
+  }
+  if (listeners.some((entry) => entry.callback === callback && entry.capture === capture)) return;
+  const entry = {
+    callback,
+    capture,
+    once: !!(options && typeof options === "object" && options.once),
+    passive: !!(options && typeof options === "object" && options.passive),
+    signal,
+    abortHandler: null,
+  };
+  listeners.push(entry);
+  if (signal && typeof signal.addEventListener === "function") {
+    entry.abortHandler = () => _eventTargetRemove(target, type, callback, capture);
+    signal.addEventListener("abort", entry.abortHandler, { once: true });
+  }
+}
+function _eventTargetRemove(target, type, callback, options) {
+  const byType = _eventTargetListeners.get(target);
+  if (!byType) return;
+  type = String(type);
+  const listeners = byType.get(type);
+  if (!listeners) return;
+  const capture = _eventCapture(options);
+  for (let i = 0; i < listeners.length; i++) {
+    const entry = listeners[i];
+    if (entry.callback !== callback || entry.capture !== capture) continue;
+    listeners.splice(i, 1);
+    if (entry.signal && entry.abortHandler && typeof entry.signal.removeEventListener === "function") {
+      entry.signal.removeEventListener("abort", entry.abortHandler);
+    }
+    break;
+  }
+  if (listeners.length === 0) byType.delete(type);
+  if (byType.size === 0) _eventTargetListeners.delete(target);
+}
+function _eventTargetDispatch(target, event) {
+  if (!event || typeof event.type === "undefined") {
+    throw new TypeError("Failed to execute 'dispatchEvent' on 'EventTarget': parameter 1 is not of type 'Event'.");
+  }
+  if (String(event.type) === "") {
+    throw new DOMException("The event's type was not specified.", "InvalidStateError");
+  }
+  if (!event.target) event.target = target;
+  event.currentTarget = target;
+  event.eventPhase = 2;
+  const listeners = (_eventTargetListeners.get(target)?.get(String(event.type)) || []).slice();
+  for (const entry of listeners) {
+    const current = _eventTargetListeners.get(target)?.get(String(event.type));
+    if (!current || !current.includes(entry)) continue;
+    if (entry.once) _eventTargetRemove(target, event.type, entry.callback, entry.capture);
+    const callback = entry.callback;
+    try {
+      if (typeof callback === "function") callback.call(target, event);
+      else callback.handleEvent.call(callback, event);
+    } catch (error) {
+      console.error(error);
+    }
+    if (event._immediatePropagationStopped) break;
+  }
+  event.currentTarget = null;
+  event.eventPhase = 0;
+  return !event.defaultPrevented;
+}
+
 class Node {
   static ELEMENT_NODE = 1;
   static ATTRIBUTE_NODE = 2;
@@ -1033,7 +1121,15 @@ class Node {
     return true;
   }
   isSameNode(other) { return other && this._nid === other._nid; }
-  addEventListener() {} removeEventListener() {} dispatchEvent() { return true; }
+  addEventListener(type, callback, options) {
+    _eventTargetAdd(this, type, callback, options);
+  }
+  removeEventListener(type, callback, options) {
+    _eventTargetRemove(this, type, callback, options);
+  }
+  dispatchEvent(event) {
+    return _eventTargetDispatch(this, event);
+  }
 }
 class CharacterData extends Node {
   get data() {
diff --git a/crates/obscura-js/src/runtime.rs b/crates/obscura-js/src/runtime.rs
index 12b5df3..7c58f30 100644
--- a/crates/obscura-js/src/runtime.rs
+++ b/crates/obscura-js/src/runtime.rs
@@ -4457,4 +4457,60 @@ mod tests {
             .unwrap();
         assert_eq!(result, serde_json::json!(["menu", "true"]));
     }
+
+    /// Framework schedulers commonly subclass EventTarget for their own
+    /// lifecycle events. These targets have no backing DOM node, but must
+    /// still deliver callbacks (including object, once, and signal listeners).
+    #[test]
+    fn standalone_event_target_delivers_framework_lifecycle_events() {
+        let mut rt = setup_runtime("<div></div>");
+        let result = rt
+            .evaluate(
+                r#"
+                const TypedEventTarget = class extends EventTarget {};
+                const target = new TypedEventTarget();
+                const calls = [];
+                const removed = () => calls.push("removed");
+                const controller = new AbortController();
+                const node = { id: "canvas-ref" };
+
+                target.addEventListener("insert", (event) => calls.push(event.node.id));
+                target.addEventListener("insert", { handleEvent() { calls.push("object"); } });
+                target.addEventListener("insert", () => calls.push("once"), { once: true });
+                target.addEventListener("insert", removed);
+                target.removeEventListener("insert", removed);
+                target.addEventListener("insert", () => calls.push("aborted"), {
+                    signal: controller.signal,
+                });
+                controller.abort();
+
+                const first = new Event("insert", { cancelable: true });
+                first.node = node;
+                const firstResult = target.dispatchEvent(first);
+                const second = new Event("insert");
+                second.node = node;
+                const secondResult = target.dispatchEvent(second);
+                return [
+                    target instanceof EventTarget,
+                    calls,
+                    firstResult,
+                    secondResult,
+                    first.target === target,
+                    first.currentTarget === null,
+                ];
+                "#,
+            )
+            .unwrap();
+        assert_eq!(
+            result,
+            serde_json::json!([
+                true,
+                ["canvas-ref", "object", "once", "canvas-ref", "object"],
+                true,
+                true,
+                true,
+                true
+            ])
+        );
+    }
 }
diff --git a/render-repros/checks.json b/render-repros/checks.json
index f085560..f991a67 100644
--- a/render-repros/checks.json
+++ b/render-repros/checks.json
@@ -53,6 +53,9 @@
     {"name": "max padding uses actual viewport", "color": "#c2255c", "x": 60, "y": 240, "width": 20, "height": 40},
     {"name": "round quantizes nested custom property math", "color": "#2f9e44", "x": 0, "y": 300, "width": 250, "height": 40}
   ],
+  "eventtarget-lifecycle": [
+    {"name": "framework lifecycle EventTarget completes", "color": "#18723a", "x": 0, "y": 0, "width": 420, "height": 120}
+  ],
   "flex-whitespace-items": [
     {"name": "direct flex sidebar starts at container edge", "color": "#1971c2", "x": 0, "y": 0, "width": 225, "height": 180},
     {"name": "direct flex body keeps its intended inset", "color": "#2b8a3e", "x": 225, "y": 0, "width": 675, "height": 200},
diff --git a/render-repros/eventtarget-lifecycle.html b/render-repros/eventtarget-lifecycle.html
new file mode 100644
index 0000000..382a6a1
--- /dev/null
+++ b/render-repros/eventtarget-lifecycle.html
@@ -0,0 +1,41 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <title>EventTarget lifecycle</title>
+  <style>
+    body { margin: 0; font: 18px sans-serif; }
+    #result {
+      box-sizing: border-box;
+      width: 420px;
+      height: 120px;
+      padding: 32px;
+      background: #a22;
+      color: white;
+    }
+    #result.passed { background: #18723a; }
+  </style>
+</head>
+<body>
+  <div id="result">lifecycle pending</div>
+  <script type="module">
+    const result = document.getElementById("result");
+    class LifecycleTarget extends EventTarget {}
+    const lifecycle = new LifecycleTarget();
+    let insertedNode = null;
+    lifecycle.addEventListener("insert", (event) => {
+      insertedNode = event.node;
+    });
+    const event = new Event("insert");
+    event.node = result;
+    lifecycle.dispatchEvent(event);
+
+    if (insertedNode === result) {
+      result.textContent = "framework lifecycle completed";
+      result.className = "passed";
+    } else {
+      result.textContent = "framework lifecycle stalled";
+    }
+  </script>
+</body>
+</html>