Add support for getting argument count from Callables

Author: AThousandShips

gdextension/gdextension_interface.h

@@ -442,6 +442,8 @@ typedef GDExtensionBool (*GDExtensionCallableCustomLessThan)(void *callable_user
 
 typedef void (*GDExtensionCallableCustomToString)(void *callable_userdata, GDExtensionBool *r_is_valid, GDExtensionStringPtr r_out);
 
+typedef GDExtensionInt (*GDExtensionCallableCustomGetArgumentCount)(void *callable_userdata, GDExtensionBool *r_is_valid);
+
 typedef struct {
 	/* Only `call_func` and `token` are strictly required, however, `object_id` should be passed if its not a static method.
 	 *
@@ -471,7 +473,40 @@ typedef struct {
 	GDExtensionCallableCustomLessThan less_than_func;
 
 	GDExtensionCallableCustomToString to_string_func;
-} GDExtensionCallableCustomInfo;
+} GDExtensionCallableCustomInfo; // Deprecated. Use GDExtensionCallableCustomInfo2 instead.
+
+typedef struct {
+	/* Only `call_func` and `token` are strictly required, however, `object_id` should be passed if its not a static method.
+	 *
+	 * `token` should point to an address that uniquely identifies the GDExtension (for example, the
+	 * `GDExtensionClassLibraryPtr` passed to the entry symbol function.
+	 *
+	 * `hash_func`, `equal_func`, and `less_than_func` are optional. If not provided both `call_func` and
+	 * `callable_userdata` together are used as the identity of the callable for hashing and comparison purposes.
+	 *
+	 * The hash returned by `hash_func` is cached, `hash_func` will not be called more than once per callable.
+	 *
+	 * `is_valid_func` is necessary if the validity of the callable can change before destruction.
+	 *
+	 * `free_func` is necessary if `callable_userdata` needs to be cleaned up when the callable is freed.
+	 */
+	void *callable_userdata;
+	void *token;
+
+	GDObjectInstanceID object_id;
+
+	GDExtensionCallableCustomCall call_func;
+	GDExtensionCallableCustomIsValid is_valid_func;
+	GDExtensionCallableCustomFree free_func;
+
+	GDExtensionCallableCustomHash hash_func;
+	GDExtensionCallableCustomEqual equal_func;
+	GDExtensionCallableCustomLessThan less_than_func;
+
+	GDExtensionCallableCustomToString to_string_func;
+
+	GDExtensionCallableCustomGetArgumentCount get_argument_count_func;
+} GDExtensionCallableCustomInfo2;
 
 /* SCRIPT INSTANCE EXTENSION */
 
@@ -2450,6 +2485,7 @@ typedef GDExtensionScriptInstanceDataPtr (*GDExtensionInterfaceObjectGetScriptIn
 /**
  * @name callable_custom_create
  * @since 4.2
+ * @deprecated in Godot 4.3. Use `callable_custom_create2` instead.
  *
  * Creates a custom Callable object from a function pointer.
  *
@@ -2460,6 +2496,19 @@ typedef GDExtensionScriptInstanceDataPtr (*GDExtensionInterfaceObjectGetScriptIn
  */
 typedef void (*GDExtensionInterfaceCallableCustomCreate)(GDExtensionUninitializedTypePtr r_callable, GDExtensionCallableCustomInfo *p_callable_custom_info);
 
+/**
+ * @name callable_custom_create2
+ * @since 4.3
+ *
+ * Creates a custom Callable object from a function pointer.
+ *
+ * Provided struct can be safely freed once the function returns.
+ *
+ * @param r_callable A pointer that will receive the new Callable.
+ * @param p_callable_custom_info The info required to construct a Callable.
+ */
+typedef void (*GDExtensionInterfaceCallableCustomCreate2)(GDExtensionUninitializedTypePtr r_callable, GDExtensionCallableCustomInfo2 *p_callable_custom_info);
+
 /**
  * @name callable_custom_get_userdata
  * @since 4.2

include/godot_cpp/godot.hpp

@@ -167,7 +167,7 @@ extern "C" GDExtensionInterfaceObjectGetInstanceFromId gdextension_interface_obj
 extern "C" GDExtensionInterfaceObjectGetInstanceId gdextension_interface_object_get_instance_id;
 extern "C" GDExtensionInterfaceObjectHasScriptMethod gdextension_interface_object_has_script_method;
 extern "C" GDExtensionInterfaceObjectCallScriptMethod gdextension_interface_object_call_script_method;
-extern "C" GDExtensionInterfaceCallableCustomCreate gdextension_interface_callable_custom_create;
+extern "C" GDExtensionInterfaceCallableCustomCreate2 gdextension_interface_callable_custom_create2;
 extern "C" GDExtensionInterfaceCallableCustomGetUserData gdextension_interface_callable_custom_get_userdata;
 extern "C" GDExtensionInterfaceRefGetObject gdextension_interface_ref_get_object;
 extern "C" GDExtensionInterfaceRefSetObject gdextension_interface_ref_set_object;

include/godot_cpp/variant/callable_custom.hpp

@@ -41,6 +41,7 @@ class Object;
 class CallableCustomBase {
 public:
 	virtual ObjectID get_object() const = 0;
+	virtual int get_argument_count(bool &r_is_valid) const;
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, GDExtensionCallError &r_call_error) const = 0;
 	virtual ~CallableCustomBase() {}
 };

include/godot_cpp/variant/callable_method_pointer.hpp

@@ -73,6 +73,11 @@ class CallableCustomMethodPointer : public CallableCustomMethodPointerBase {
 		return ObjectID(data.instance->get_instance_id());
 	}
 
+	virtual int get_argument_count(bool &r_is_valid) const override {
+		r_is_valid = true;
+		return sizeof...(P);
+	}
+
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, GDExtensionCallError &r_call_error) const override {
 		call_with_variant_args(data.instance, data.method, p_arguments, p_argcount, r_call_error);
 	}
@@ -110,6 +115,11 @@ class CallableCustomMethodPointerRet : public CallableCustomMethodPointerBase {
 		return ObjectID(data.instance->get_instance_id());
 	}
 
+	virtual int get_argument_count(bool &r_is_valid) const override {
+		r_is_valid = true;
+		return sizeof...(P);
+	}
+
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, GDExtensionCallError &r_call_error) const override {
 		call_with_variant_args_ret(data.instance, data.method, p_arguments, p_argcount, r_return_value, r_call_error);
 	}
@@ -147,6 +157,11 @@ class CallableCustomMethodPointerRetC : public CallableCustomMethodPointerBase {
 		return ObjectID(data.instance->get_instance_id());
 	}
 
+	virtual int get_argument_count(bool &r_is_valid) const override {
+		r_is_valid = true;
+		return sizeof...(P);
+	}
+
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, GDExtensionCallError &r_call_error) const override {
 		call_with_variant_args_retc(data.instance, data.method, p_arguments, p_argcount, r_return_value, r_call_error);
 	}
@@ -182,6 +197,11 @@ class CallableCustomStaticMethodPointer : public CallableCustomMethodPointerBase
 		return ObjectID();
 	}
 
+	virtual int get_argument_count(bool &r_is_valid) const override {
+		r_is_valid = true;
+		return sizeof...(P);
+	}
+
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, GDExtensionCallError &r_call_error) const override {
 		call_with_variant_args_static_ret(data.method, p_arguments, p_argcount, r_return_value, r_call_error);
 		r_return_value = Variant();
@@ -218,6 +238,11 @@ class CallableCustomStaticMethodPointerRet : public CallableCustomMethodPointerB
 		return ObjectID();
 	}
 
+	virtual int get_argument_count(bool &r_is_valid) const override {
+		r_is_valid = true;
+		return sizeof...(P);
+	}
+
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, GDExtensionCallError &r_call_error) const override {
 		call_with_variant_args_static_ret(data.method, p_arguments, p_argcount, r_return_value, r_call_error);
 	}

src/godot.cpp

@@ -173,7 +173,7 @@ GDExtensionInterfaceObjectGetInstanceFromId gdextension_interface_object_get_ins
 GDExtensionInterfaceObjectGetInstanceId gdextension_interface_object_get_instance_id = nullptr;
 GDExtensionInterfaceObjectHasScriptMethod gdextension_interface_object_has_script_method = nullptr;
 GDExtensionInterfaceObjectCallScriptMethod gdextension_interface_object_call_script_method = nullptr;
-GDExtensionInterfaceCallableCustomCreate gdextension_interface_callable_custom_create = nullptr;
+GDExtensionInterfaceCallableCustomCreate2 gdextension_interface_callable_custom_create2 = nullptr;
 GDExtensionInterfaceCallableCustomGetUserData gdextension_interface_callable_custom_get_userdata = nullptr;
 GDExtensionInterfaceRefGetObject gdextension_interface_ref_get_object = nullptr;
 GDExtensionInterfaceRefSetObject gdextension_interface_ref_set_object = nullptr;
@@ -413,7 +413,7 @@ GDExtensionBool GDExtensionBinding::init(GDExtensionInterfaceGetProcAddress p_ge
 	LOAD_PROC_ADDRESS(object_get_instance_id, GDExtensionInterfaceObjectGetInstanceId);
 	LOAD_PROC_ADDRESS(object_has_script_method, GDExtensionInterfaceObjectHasScriptMethod);
 	LOAD_PROC_ADDRESS(object_call_script_method, GDExtensionInterfaceObjectCallScriptMethod);
-	LOAD_PROC_ADDRESS(callable_custom_create, GDExtensionInterfaceCallableCustomCreate);
+	LOAD_PROC_ADDRESS(callable_custom_create2, GDExtensionInterfaceCallableCustomCreate2);
 	LOAD_PROC_ADDRESS(callable_custom_get_userdata, GDExtensionInterfaceCallableCustomGetUserData);
 	LOAD_PROC_ADDRESS(ref_get_object, GDExtensionInterfaceRefGetObject);
 	LOAD_PROC_ADDRESS(ref_set_object, GDExtensionInterfaceRefSetObject);

src/variant/callable_custom.cpp

@@ -35,6 +35,11 @@
 
 namespace godot {
 
+int CallableCustomBase::get_argument_count(bool &r_is_valid) const {
+	r_is_valid = false;
+	return 0;
+}
+
 static void callable_custom_call(void *p_userdata, const GDExtensionConstVariantPtr *p_args, GDExtensionInt p_argument_count, GDExtensionVariantPtr r_return, GDExtensionCallError *r_error) {
 	CallableCustom *callable_custom = (CallableCustom *)p_userdata;
 	callable_custom->call((const Variant **)p_args, p_argument_count, *(Variant *)r_return, *r_error);
@@ -84,13 +89,21 @@ static GDExtensionBool callable_custom_less_than_func(void *p_a, void *p_b) {
 	return func_a(a, b);
 }
 
+static GDExtensionInt custom_callable_get_argument_count_func(void *p_userdata, GDExtensionBool *r_is_valid) {
+	CallableCustom *callable_custom = (CallableCustom *)p_userdata;
+	bool valid = false;
+	int ret = callable_custom->get_argument_count(valid);
+	*r_is_valid = valid;
+	return ret;
+}
+
 bool CallableCustom::is_valid() const {
 	// The same default implementation as in Godot.
 	return ObjectDB::get_instance(get_object());
 }
 
 Callable::Callable(CallableCustom *p_callable_custom) {
-	GDExtensionCallableCustomInfo info = {};
+	GDExtensionCallableCustomInfo2 info = {};
 	info.callable_userdata = p_callable_custom;
 	info.token = internal::token;
 	info.object_id = p_callable_custom->get_object();
@@ -101,8 +114,9 @@ Callable::Callable(CallableCustom *p_callable_custom) {
 	info.equal_func = &callable_custom_equal_func;
 	info.less_than_func = &callable_custom_less_than_func;
 	info.to_string_func = &callable_custom_to_string;
+	info.get_argument_count_func = &custom_callable_get_argument_count_func;
 
-	::godot::internal::gdextension_interface_callable_custom_create(_native_ptr(), &info);
+	::godot::internal::gdextension_interface_callable_custom_create2(_native_ptr(), &info);
 }
 
 CallableCustom *Callable::get_custom() const {

src/variant/callable_method_pointer.cpp

@@ -77,6 +77,14 @@ static GDExtensionBool custom_callable_mp_less_than_func(void *p_a, void *p_b) {
 	return memcmp(a->get_comp_ptr(), b->get_comp_ptr(), a->get_comp_size() * 4) < 0;
 }
 
+static GDExtensionInt custom_callable_mp_get_argument_count_func(void *p_userdata, GDExtensionBool *r_is_valid) {
+	CallableCustomMethodPointerBase *callable_method_pointer = (CallableCustomMethodPointerBase *)p_userdata;
+	bool valid = false;
+	int ret = callable_method_pointer->get_argument_count(valid);
+	*r_is_valid = valid;
+	return ret;
+}
+
 void CallableCustomMethodPointerBase::_setup(uint32_t *p_base_ptr, uint32_t p_ptr_size) {
 	comp_ptr = p_base_ptr;
 	comp_size = p_ptr_size / 4;
@@ -93,7 +101,7 @@ void CallableCustomMethodPointerBase::_setup(uint32_t *p_base_ptr, uint32_t p_pt
 namespace internal {
 
 Callable create_callable_from_ccmp(CallableCustomMethodPointerBase *p_callable_method_pointer) {
-	GDExtensionCallableCustomInfo info = {};
+	GDExtensionCallableCustomInfo2 info = {};
 	info.callable_userdata = p_callable_method_pointer;
 	info.token = internal::token;
 	info.object_id = p_callable_method_pointer->get_object();
@@ -103,9 +111,10 @@ Callable create_callable_from_ccmp(CallableCustomMethodPointerBase *p_callable_m
 	info.hash_func = &custom_callable_mp_hash;
 	info.equal_func = &custom_callable_mp_equal_func;
 	info.less_than_func = &custom_callable_mp_less_than_func;
+	info.get_argument_count_func = &custom_callable_mp_get_argument_count_func;
 
 	Callable callable;
-	::godot::internal::gdextension_interface_callable_custom_create(callable._native_ptr(), &info);
+	::godot::internal::gdextension_interface_callable_custom_create2(callable._native_ptr(), &info);
 	return callable;
 }
 

test/project/main.gd

@@ -102,6 +102,7 @@ func _ready():
 	# mp_callable() with void method.
 	var mp_callable: Callable = example.test_callable_mp()
 	assert_equal(mp_callable.is_valid(), true)
+	assert_equal(mp_callable.get_argument_count(), 3)
 	mp_callable.call(example, "void", 36)
 	assert_equal(custom_signal_emitted, ["unbound_method1: Example - void", 36])
 
@@ -117,14 +118,17 @@ func _ready():
 
 	# mp_callable() with return value.
 	var mp_callable_ret: Callable = example.test_callable_mp_ret()
+	assert_equal(mp_callable_ret.get_argument_count(), 3)
 	assert_equal(mp_callable_ret.call(example, "test", 77), "unbound_method2: Example - test - 77")
 
 	# mp_callable() with const method and return value.
 	var mp_callable_retc: Callable = example.test_callable_mp_retc()
+	assert_equal(mp_callable_retc.get_argument_count(), 3)
 	assert_equal(mp_callable_retc.call(example, "const", 101), "unbound_method3: Example - const - 101")
 
 	# mp_callable_static() with void method.
 	var mp_callable_static: Callable = example.test_callable_mp_static()
+	assert_equal(mp_callable_static.get_argument_count(), 3)
 	mp_callable_static.call(example, "static", 83)
 	assert_equal(custom_signal_emitted, ["unbound_static_method1: Example - static", 83])
 
@@ -140,6 +144,7 @@ func _ready():
 
 	# mp_callable_static() with return value.
 	var mp_callable_static_ret: Callable = example.test_callable_mp_static_ret()
+	assert_equal(mp_callable_static_ret.get_argument_count(), 3)
 	assert_equal(mp_callable_static_ret.call(example, "static-ret", 84), "unbound_static_method2: Example - static-ret - 84")
 
 	# CallableCustom.
@@ -150,6 +155,7 @@ func _ready():
 	assert_equal(custom_callable.hash(), 27);
 	assert_equal(custom_callable.get_object(), null);
 	assert_equal(custom_callable.get_method(), "");
+	assert_equal(custom_callable.get_argument_count(), 2)
 	assert_equal(str(custom_callable), "<MyCallableCustom>");
 
 	# PackedArray iterators

test/src/example.cpp

@@ -49,6 +49,11 @@ class MyCallableCustom : public CallableCustom {
 		return ObjectID();
 	}
 
+	virtual int get_argument_count(bool &r_is_valid) const {
+		r_is_valid = true;
+		return 2;
+	}
+
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, GDExtensionCallError &r_call_error) const {
 		r_return_value = "Hi";
 		r_call_error.error = GDEXTENSION_CALL_OK;