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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<int, string>)delegateObj)(
VariantConversionCallbacks.GetToManagedCallback<int>()(args[0])
);
ret = VariantConversionCallbacks.GetToVariantCallback<string>()(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.
77 lines
3.7 KiB
C++
77 lines
3.7 KiB
C++
/*************************************************************************/
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/* managed_callable.h */
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/*************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* https://godotengine.org */
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/*************************************************************************/
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/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur. */
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/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md). */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/*************************************************************************/
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#ifndef MANAGED_CALLABLE_H
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#define MANAGED_CALLABLE_H
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#include "core/os/mutex.h"
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#include "core/templates/self_list.h"
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#include "core/variant/callable.h"
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#include "mono_gc_handle.h"
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class ManagedCallable : public CallableCustom {
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friend class CSharpLanguage;
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GCHandleIntPtr delegate_handle;
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void *trampoline = nullptr;
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ObjectID object_id;
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#ifdef GD_MONO_HOT_RELOAD
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SelfList<ManagedCallable> self_instance = this;
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static SelfList<ManagedCallable>::List instances;
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static RBMap<ManagedCallable *, Array> instances_pending_reload;
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static Mutex instances_mutex;
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#endif
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public:
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uint32_t hash() const override;
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String get_as_text() const override;
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CompareEqualFunc get_compare_equal_func() const override;
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CompareLessFunc get_compare_less_func() const override;
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ObjectID get_object() const override;
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void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, Callable::CallError &r_call_error) const override;
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_FORCE_INLINE_ GCHandleIntPtr get_delegate() const { return delegate_handle; }
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_FORCE_INLINE_ void *get_trampoline() const { return trampoline; }
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static bool compare_equal(const CallableCustom *p_a, const CallableCustom *p_b);
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static bool compare_less(const CallableCustom *p_a, const CallableCustom *p_b);
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static constexpr CompareEqualFunc compare_equal_func_ptr = &ManagedCallable::compare_equal;
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static constexpr CompareEqualFunc compare_less_func_ptr = &ManagedCallable::compare_less;
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void release_delegate_handle();
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ManagedCallable(GCHandleIntPtr p_delegate_handle, void *p_trampoline, ObjectID p_object_id);
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~ManagedCallable();
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};
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#endif // MANAGED_CALLABLE_H
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