From 282bd37e5c9dbc1bba4fe349fc7868643a54164b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ignacio=20Rold=C3=A1n=20Etcheverry?= Date: Fri, 28 Oct 2022 22:59:13 +0200 Subject: C#: Remove need for reflection to invoking callable delegates We aim to make the C# API reflection-free, mainly for concerns about performance, and to be able to target NativeAOT in refletion-free mode, which reduces the binary size. One of the main usages of reflection still left was the dynamic invokation of callable delegates, and for some time I wasn't sure I would find an alternative solution that I'd be happy with. The new solution uses trampoline functions to invoke the delegates: ``` static void Trampoline(object delegateObj, NativeVariantPtrArgs args, out godot_variant ret) { if (args.Count != 1) throw new ArgumentException($"Callable expected 1 arguments but received {args.Count}."); string res = ((Func)delegateObj)( VariantConversionCallbacks.GetToManagedCallback()(args[0]) ); ret = VariantConversionCallbacks.GetToVariantCallback()(res); } Callable.CreateWithUnsafeTrampoline((int num) => "Foo" + num, &Trampoline); ``` Of course, this is too much boilerplate for user code. To improve this, the `Callable.From` methods were added. These are overloads that take `Action` and `Func` delegates, which covers the most common use cases: lambdas and method groups: ``` // Lambda Callable.From((int num) => "Foo" + num); // Method group string AppendNum(int num) => "Foo" + num; Callable.From(AppendNum); ``` Unfortunately, due to limitations in the C# language, implicit conversions from delegates to `Callable` are not supported. `Callable.From` does not support custom delegates. These should be uncommon, but the Godot C# API actually uses them for event signals. As such, the bindings generator was updated to generate trampoline functions for event signals. It was also optimized to use `Action` instead of a custom delegate for parameterless signals, which removes the need for the trampoline functions for those signals. The change to reflection-free invokation removes one of the last needs for `ConvertVariantToManagedObjectOfType`. The only remaining usage is from calling script constructors with parameters from the engine (`CreateManagedForGodotObjectScriptInstance`). Once that one is made reflection-free, `ConvertVariantToManagedObjectOfType` can be removed. --- modules/mono/managed_callable.cpp | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'modules/mono/managed_callable.cpp') diff --git a/modules/mono/managed_callable.cpp b/modules/mono/managed_callable.cpp index 0c2c533090..28edc41d98 100644 --- a/modules/mono/managed_callable.cpp +++ b/modules/mono/managed_callable.cpp @@ -92,7 +92,7 @@ void ManagedCallable::call(const Variant **p_arguments, int p_argcount, Variant ERR_FAIL_COND(delegate_handle.value == nullptr); GDMonoCache::managed_callbacks.DelegateUtils_InvokeWithVariantArgs( - delegate_handle, p_arguments, p_argcount, &r_return_value); + delegate_handle, trampoline, p_arguments, p_argcount, &r_return_value); r_call_error.error = Callable::CallError::CALL_OK; } @@ -106,7 +106,8 @@ void ManagedCallable::release_delegate_handle() { // Why you do this clang-format... /* clang-format off */ -ManagedCallable::ManagedCallable(GCHandleIntPtr p_delegate_handle, ObjectID p_object_id) : delegate_handle(p_delegate_handle), object_id(p_object_id) { +ManagedCallable::ManagedCallable(GCHandleIntPtr p_delegate_handle, void *p_trampoline, ObjectID p_object_id) : + delegate_handle(p_delegate_handle), trampoline(p_trampoline), object_id(p_object_id) { #ifdef GD_MONO_HOT_RELOAD { MutexLock lock(instances_mutex); -- cgit v1.2.3