Method callback_closure

gi/function.cpp:302–413

This is our main entry point for ffi_closure callbacks. ffi_prep_closure() is * doing pure magic and replaces the original function call with this one which * gives us the ffi arguments, a place to store the return value and our use * data. In other words, everything we need to call the JS function and get the * return value back. */

 * return value back.
 */
void GjsCallbackTrampoline::callback_closure(GIArgument** args, void* result) {
    GI::StackTypeInfo ret_type;

    // Fill in the result with some hopefully neutral value
    m_info.load_return_type(&ret_type);
    if (ret_type.tag() != GI_TYPE_TAG_VOID) {
        GIArgument argument = {};
        gjs_arg_unset(&argument);
        set_return_ffi_arg_from_gi_argument(ret_type, result, &argument);
    }

    if (G_UNLIKELY(!is_valid())) {
        warn_about_illegal_js_callback(
            "during shutdown",
            "destroying a Clutter actor or GTK widget with ::destroy signal "
            "connected, or using the destroy(), dispose(), or remove() vfuncs",
            true);
        return;
    }

    JSContext* cx = this->cx();
    GjsContextPrivate* gjs = GjsContextPrivate::from_cx(cx);
    if (JS::RuntimeHeapIsCollecting()) {
        warn_about_illegal_js_callback(
            "during garbage collection",
            "destroying a Clutter actor or GTK widget with ::destroy signal "
            "connected, or using the destroy(), dispose(), or remove() vfuncs",
            true);
        return;
    }

    if (G_UNLIKELY(!gjs->is_owner_thread())) {
        warn_about_illegal_js_callback("on a different thread",
                                       "an API not intended to be used in JS",
                                       false);
        return;
    }

    JSAutoRealm ar{cx, callable()};

    unsigned n_args = m_info.n_args();

    auto cleanup = mozilla::MakeScopeExit([this, gjs]() {
        if (this->m_scope == GI_SCOPE_TYPE_ASYNC) {
            // We don't release the trampoline here as we've an extra ref that
            // has been set in gjs_marshal_callback_in()
            gjs_debug_closure("Saving async closure for gc cleanup %p", this);
            gjs->async_closure_enqueue_for_gc(this);
        }
        gjs->schedule_gc_if_needed();
    });

    JS::RootedObject this_object{cx};
    unsigned c_args_offset = 0;
    GObject* gobj = nullptr;
    if (m_is_vfunc) {
        gobj = G_OBJECT(gjs_arg_get<GObject*>(args[0]));
        if (gobj) {