GUIProxy: Support property introspection for debugging

This commit enables proper property enumeration and inspection for GUI
proxy objects in debugging sessions using the SpiderMonkey Debugger API.

Interface (IGUIProxyObject):
- Added a pure virtual method getPropsNames() to expose cached property
  names from the GUI object implementation.

Proxy handler (JSI_GUIProxy):
- Implemented ownPropertyKeys() to enumerate all visible properties of
  the proxy, including: -- Built-in GUI fields: "name", "parent",
  "children". -- Dynamic settings stored in m_Settings. -- Script event
  handlers prefixed with "on" from m_ScriptHandlers. -- Function
  properties returned by getPropsNames().
- Implemented getOwnPropertyDescriptor() to synthesize descriptors for
  debugger queries: -- Returns undefined if the property is not defined.
  -- Returns a read-only enumerable descriptor otherwise.
- Both methods are marked final and override SpiderMonkey's
  BaseProxyHandler.

Why:
- SpiderMonkey’s Debugger API requires ownPropertyKeys and
  getOwnPropertyDescriptor for proxy objects to be introspectable in dev
  tools like VS Code.
- Without these, properties of GUI objects are hidden during debugging.
- This change improves the developer experience by making all meaningful
  GUI object fields visible and explorable at runtime.

source/gui/Scripting/JSInterface_GUIProxy.h

@@ -101,6 +101,7 @@ public:
 	// @return the JSFunction matching @param name. Must call has() first as it can assume existence.
 	virtual JSObject* get(const std::string& name) const = 0;
 	virtual bool setFunction(const ScriptRequest& rq, const std::string& name, JSFunction* function) = 0;
+	virtual std::vector<std::string_view> getPropsNames() const = 0;
 };
 
 /**
@@ -177,24 +178,17 @@ protected:
 	// The following methods are not provided by BaseProxyHandler.
 	// We provide defaults that do nothing (some raise JS exceptions).
 
-	// The JS code will see undefined when querying a property descriptor.
-	virtual bool getOwnPropertyDescriptor(JSContext*, JS::HandleObject /*proxy*/, JS::HandleId,
-		JS::MutableHandle<mozilla::Maybe<JS::PropertyDescriptor>>) const override
-	{
-		return true;
-	}
+	virtual bool getOwnPropertyDescriptor(JSContext* cx, JS::HandleObject proxy, JS::HandleId id, JS::MutableHandle<mozilla::Maybe<JS::PropertyDescriptor>> desc) const override final;
+
 	// Throw an exception is JS code attempts defining a property.
 	virtual bool defineProperty(JSContext*, JS::HandleObject /*proxy*/, JS::HandleId,
 		JS::Handle<JS::PropertyDescriptor>, JS::ObjectOpResult& /*result*/) const override
 	{
 		return false;
 	}
-	// No accessible properties.
-	virtual bool ownPropertyKeys(JSContext*, JS::HandleObject /*proxy*/,
-		JS::MutableHandleIdVector) const override
-	{
-		return true;
-	}
+
+	virtual bool ownPropertyKeys(JSContext* cx, JS::HandleObject proxy, JS::MutableHandleIdVector props) const override final;
+
 	// Nothing to enumerate.
 	virtual bool enumerate(JSContext*, JS::HandleObject /*proxy*/,
 		JS::MutableHandleIdVector /*props*/) const override

source/gui/Scripting/JSInterface_GUIProxy_impl.h

@@ -104,6 +104,17 @@ public:
 		return true;
 	}
 
+	virtual std::vector<std::string_view> getPropsNames() const override
+	{
+		std::vector<std::string_view> result;
+		result.reserve(m_Functions.size());
+
+		for (const auto& [key, value] : m_Functions)
+			result.emplace_back(key);
+
+		return result;
+	}
+
 protected:
 	std::unordered_map<std::string, JS::PersistentRootedObject> m_Functions;
 };
@@ -344,4 +355,83 @@ bool JSI_GUIProxy<T>::delete_(JSContext* cx, JS::HandleObject proxy, JS::HandleI
 	LOGERROR("Only event handlers can be deleted from GUI objects!");
 	return result.fail(JSMSG_BAD_PROP_ID);
 }
+
+template<typename T>
+bool JSI_GUIProxy<T>::ownPropertyKeys(JSContext* cx, JS::HandleObject proxy, JS::MutableHandleIdVector props) const
+{
+	ScriptRequest rq(cx);
+
+	T* e = IGUIProxyObject::FromPrivateSlot<T>(proxy.get());
+	if (!e)
+		return false;
+
+	// Add common properties.
+	static constexpr std::array<const char*, 3> keys = {
+		"name",
+		"parent",
+		"children"
+	};
+
+	for (const char* key : keys)
+	{
+		JS::RootedString str(cx, JS_NewStringCopyZ(cx, key));
+		if (!str)
+			return false;
+
+		JS::RootedId id(cx);
+		if (!JS_StringToId(cx, str, &id))
+			return false;
+
+		if (!props.append(id))
+			return false;
+	}
+
+	// Add settings.
+	for (const auto& [name, setting] : e->m_Settings)
+	{
+		JS::RootedString str(cx, JS_NewStringCopyZ(cx, name.c_str()));
+		JS::RootedId id(cx);
+		if (!str || !JS_StringToId(cx, str, &id) || !props.append(id))
+			return false;
+	}
+
+	// Add script handlers.
+	for (const auto& [name, scriptHandler] : e->m_ScriptHandlers)
+	{
+		JS::RootedString str(cx, JS_NewStringCopyZ(cx, fmt::format("on{}", name).c_str()));
+		JS::RootedId id(cx);
+		if (!str || !JS_StringToId(cx, str, &id) || !props.append(id))
+			return false;
+	}
+
+	// Add properties from the cache.
+	using PropertyCache = typename PropCache::type;
+	const PropertyCache* data = static_cast<const PropertyCache*>(static_cast<const GUIProxyProps*>(js::GetProxyReservedSlot(proxy, 0).toPrivate()));
+	for (const auto& key : data->getPropsNames()) {
+		JS::RootedString str(cx, JS_NewStringCopyZ(cx, key.data()));
+		JS::RootedId id(cx);
+		if (!str || !JS_StringToId(cx, str, &id) || !props.append(id))
+			return false;
+	}
+
+	return true;
+}
+
+template<typename T>
+bool JSI_GUIProxy<T>::getOwnPropertyDescriptor(JSContext* cx, JS::HandleObject proxy, JS::HandleId id, JS::MutableHandle<mozilla::Maybe<JS::PropertyDescriptor>> desc) const
+{
+	JS::RootedValue value(cx);
+
+	if (!this->get(cx, proxy, JS::UndefinedHandleValue, id, &value))
+		return false;
+
+	if (value.isUndefined())
+	{
+		desc.set(mozilla::Nothing());
+		return true;
+	}
+
+	desc.set(mozilla::Some(JS::PropertyDescriptor::Data(value, JSPROP_ENUMERATE | JSPROP_READONLY)));
+	return true;
+}
 #endif // INCLUDED_JSI_GUIPROXY_IMP