1 files changed, 35 insertions, 0 deletions
diff --git a/dom/bindings/CallbackInterface.cpp b/dom/bindings/CallbackInterface.cpp
new file mode 100644
index 0000000000..b000ea22d1
--- /dev/null
+++ b/dom/bindings/CallbackInterface.cpp
@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/CallbackInterface.h"
+#include "jsapi.h"
+#include "js/CallAndConstruct.h"  // JS::IsCallable
+#include "js/CharacterEncoding.h"
+#include "js/PropertyAndElement.h"  // JS_GetProperty, JS_GetPropertyById
+#include "mozilla/dom/BindingUtils.h"
+#include "nsPrintfCString.h"
+
+namespace mozilla::dom {
+
+bool CallbackInterface::GetCallableProperty(
+    BindingCallContext& cx, JS::Handle<jsid> aPropId,
+    JS::MutableHandle<JS::Value> aCallable) {
+  JS::Rooted<JSObject*> obj(cx, CallbackKnownNotGray());
+  if (!JS_GetPropertyById(cx, obj, aPropId, aCallable)) {
+    return false;
+  }
+  if (!aCallable.isObject() || !JS::IsCallable(&aCallable.toObject())) {
+    JS::Rooted<JSString*> propId(cx, aPropId.toString());
+    JS::UniqueChars propName = JS_EncodeStringToUTF8(cx, propId);
+    nsPrintfCString description("Property '%s'", propName.get());
+    cx.ThrowErrorMessage<MSG_NOT_CALLABLE>(description.get());
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace mozilla::dom