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/glue/runtime_interop.cpp | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'modules/mono/glue/runtime_interop.cpp') diff --git a/modules/mono/glue/runtime_interop.cpp b/modules/mono/glue/runtime_interop.cpp index 2717b945f6..e20a88076a 100644 --- a/modules/mono/glue/runtime_interop.cpp +++ b/modules/mono/glue/runtime_interop.cpp @@ -447,15 +447,16 @@ void godotsharp_packed_string_array_add(PackedStringArray *r_dest, const String r_dest->append(*p_element); } -void godotsharp_callable_new_with_delegate(GCHandleIntPtr p_delegate_handle, const Object *p_object, Callable *r_callable) { +void godotsharp_callable_new_with_delegate(GCHandleIntPtr p_delegate_handle, void *p_trampoline, + const Object *p_object, Callable *r_callable) { // TODO: Use pooling for ManagedCallable instances. ObjectID objid = p_object ? p_object->get_instance_id() : ObjectID(); - CallableCustom *managed_callable = memnew(ManagedCallable(p_delegate_handle, objid)); + CallableCustom *managed_callable = memnew(ManagedCallable(p_delegate_handle, p_trampoline, objid)); memnew_placement(r_callable, Callable(managed_callable)); } bool godotsharp_callable_get_data_for_marshalling(const Callable *p_callable, - GCHandleIntPtr *r_delegate_handle, Object **r_object, StringName *r_name) { + GCHandleIntPtr *r_delegate_handle, void **r_trampoline, Object **r_object, StringName *r_name) { if (p_callable->is_custom()) { CallableCustom *custom = p_callable->get_custom(); CallableCustom::CompareEqualFunc compare_equal_func = custom->get_compare_equal_func(); @@ -463,18 +464,21 @@ bool godotsharp_callable_get_data_for_marshalling(const Callable *p_callable, if (compare_equal_func == ManagedCallable::compare_equal_func_ptr) { ManagedCallable *managed_callable = static_cast(custom); *r_delegate_handle = managed_callable->get_delegate(); + *r_trampoline = managed_callable->get_trampoline(); *r_object = nullptr; memnew_placement(r_name, StringName()); return true; } else if (compare_equal_func == SignalAwaiterCallable::compare_equal_func_ptr) { SignalAwaiterCallable *signal_awaiter_callable = static_cast(custom); *r_delegate_handle = { nullptr }; + *r_trampoline = nullptr; *r_object = ObjectDB::get_instance(signal_awaiter_callable->get_object()); memnew_placement(r_name, StringName(signal_awaiter_callable->get_signal())); return true; } else if (compare_equal_func == EventSignalCallable::compare_equal_func_ptr) { EventSignalCallable *event_signal_callable = static_cast(custom); *r_delegate_handle = { nullptr }; + *r_trampoline = nullptr; *r_object = ObjectDB::get_instance(event_signal_callable->get_object()); memnew_placement(r_name, StringName(event_signal_callable->get_signal())); return true; @@ -482,11 +486,13 @@ bool godotsharp_callable_get_data_for_marshalling(const Callable *p_callable, // Some other CallableCustom. We only support ManagedCallable. *r_delegate_handle = { nullptr }; + *r_trampoline = nullptr; *r_object = nullptr; memnew_placement(r_name, StringName()); return false; } else { *r_delegate_handle = { nullptr }; + *r_trampoline = nullptr; *r_object = ObjectDB::get_instance(p_callable->get_object_id()); memnew_placement(r_name, StringName(p_callable->get_method())); return true; -- cgit v1.2.3