feat: LuaCallable by illarn · Pull Request #224 · gilzoide/lua-gdextension

illarn · 2026-04-09T22:52:16Z

Goal

Make it possible to create callables for godot's signals from lua

Changes

Added a CallableCustom LuaCallable
Added a Callable constructor from a lua function
Added a test to the callable test
Added Callable from lua function constructor to lua definition generator

Known limitations

~~Binding arguments does nothing~~
~~No return values~~

~~These features do not contribute to this PR goal and are redundant since you can just use lua functions if you need this~~

TODO

Right now explicitly calling :call() on a LuaCallable freezes the game. While it's not intended to be used this way adding some error and/or a guard for this sounds reasonable. Or maybe a comment in the lua definition will be enough, not really sure

illarn · 2026-04-09T23:07:49Z

Builded and tested in a linux environment only

I didn't use include guards like other scripts I've seen and may've broken some other styling rules, so pls tell me if I have to change it

Also I've tried using a LuaCoroutine to solve a call freezing issue, but either I didn't understand how it's supposed to be used or did something wrong, anyways, it didn't work

And I did a somewhat hacky thing with the lua definition, since I didn't really have time to delve into this part, if I should have done it differently pls tell/change

gilzoide · 2026-04-12T19:38:01Z

+LuaCallable::~LuaCallable() {
+	_lua_func.unref();
+}


You don't really need to manually call unref, the Ref's destructor already does that, so a default destructor would be enough here.

gilzoide · 2026-04-12T19:40:45Z

+class LuaCallable : public CallableCustom {
+	Ref<LuaFunction> _lua_func;
+public:
+	explicit LuaCallable(sol::function func) : _lua_func{memnew(LuaFunction(func))} {};


Please use sol::protected_function here instead of sol::function, just like everywhere else in the code.

Also do not create a new LuaFunction here, use LuaObject::wrap_object<LuaFunction>(sol::protected_function f) instead.

gilzoide · 2026-04-12T19:45:03Z

 #include "Class.hpp"
 #include "VariantArguments.hpp"
 #include "convert_godot_lua.hpp"
+#include "godot_cpp/variant/callable.hpp"


Includes for 3rd party headers live in the block below and use angled brackets #include <godot_cpp/...>. In any case, I don't think you need this include here, Godot's Variant types are reachable by the other headers already included. But feel free to keep it, since it's used directly, just put it in the other block.

My bad, it's all auto-incudes from clangd. It's probably a good idea to add .clang-format for auto sorting and correct brackets, I can add it if you want

gilzoide · 2026-04-12T19:45:32Z

 #include <godot_cpp/classes/resource.hpp>
 #include <godot_cpp/classes/script.hpp>
 #include <godot_cpp/variant/utility_functions.hpp>
+#include "LuaCallable.hpp"


Includes for Lua GDExtension's own headers live in the block above and are sorted alphabetically.

gilzoide · 2026-04-12T19:47:06Z

+				return dictionary;
+			}
+		} else if (first_arg_type == sol::type::function) {
+			return LuaCallable::construct(args.get<sol::function>());


Use sol::protected_function instead of sol::function to match the rest of the code.

gilzoide · 2026-04-12T19:49:42Z

+#include "sol/forward.hpp"
+#include "sol/types.hpp"


You also don't really need these, VariantType.hpp already includes sol.hpp. It's ok to leave them here, but use angled brackets<> for 3rd party code instead of double quotes "" at least.

gilzoide · 2026-04-12T19:51:26Z

+	virtual CompareLessFunc get_compare_less_func() const override;
+	uint32_t hash() const override;
+	void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, GDExtensionCallError &r_call_error) const override;
+	static void register_lua(lua_State *L);


Why does it have this register_lua method? I don't really see this being called or even implemented in LuaCallable.cpp. Seems like it should be removed.

Yeah, you're right, it's leftovers from when I tested, I'll remove it

gilzoide · 2026-04-12T19:51:39Z

+	void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, GDExtensionCallError &r_call_error) const override;
+	static void register_lua(lua_State *L);
+	int get_argument_count(bool &r_is_valid) const override;
+	static Variant construct(sol::function func);


Also please use sol::protected_function here instead of sol::function.

gilzoide · 2026-04-12T19:57:22Z

+int LuaCallable::get_argument_count(bool &r_is_valid) const {
+	r_is_valid = true;
+	return 0;
+}


I don't think you need to override get_argument_count. CallableCustomBase::get_argument_count already does pretty much the same thing, although setting r_is_valid to false, which I think is the correct thing to do in this case (this argument count of 0 isn't really valid, the function may have more than 0 parameters, you could only know with a LuaDebug in Lua 5.2+).

gilzoide · 2026-04-12T20:04:02Z

Hi @illarn, thanks for the contribution!

I only checked the code for now and added some comments.

About these "known limitations", did you test if they only happen in Lua or if it happens in GDScript as well? I really don't think it's ok to have Callables that don't properly bind arguments or return values.

Also, the freezing issue should most likely be fixed before we let people use this functionality. I'll take a look into it here and let you know if I find the cause in my tests. Just by reading the code everything seems fine.

gilzoide · 2026-04-12T20:07:05Z

+local a = 1
+local custom_callable = Callable(function(val)
+	a = a + val
+	print(a == 6 and "Passed" or "Failed")
+end)
+custom_callable:call_deferred(5)


Automated tests should assert instead of only printing, the test runner only understands thrown errors and do not look into printed text.

Yeah, this test is not very good, I'll change it. I completely missed the Makefile, so I've run tests wrong, I'll do it properly now

There's no documentation of the test setup at all, so don't worry! Maybe I should have told you here as well, sorry about that. Just run make test and there you go (or run the command line from Makefile if you don't have make installed) 😄

gilzoide · 2026-04-12T20:14:48Z

I tested calling the LuaCallable here without :call, using the regular function call style (custom_callable(5) instead of custom_callable:call(5)) and it works fine. Using :call gives an error because it's calling Variant::call instead of Callable::call, which expects the method name as first argument, this error is likely what makes your game freeze. Lua uses Variants for simplicity instead of defining each variant type separately.

gilzoide · 2026-04-12T20:20:31Z

Also tested bind and returning values and it's all working fine:

local bound_callable = custom_callable:bind(5)
local result = bound_callable()
print(result)

illarn · 2026-04-12T20:28:37Z

Thank you for the feedback, I'll go fix it now

Also tested bind and returning values and it's all working fine:

Yeah, for me it also started working, I was sleepy and probably messed something up when testing it initially

illarn · 2026-04-12T22:33:47Z

I've pushed fixes, fixed everything from the comments, fixed the test and added a few more cases. I've also added callable from function to the README. Calling via () doesn't freeze, returning and binding arguments works, so I think everything should be ready now

illarn · 2026-04-13T11:33:56Z

I've added .clang-format, tried to make it as non-obstructive as possible, so it follows existing code style almost 1/1

gilzoide · 2026-04-14T01:08:34Z

Hey @illarn, thanks for the updates.

Everything looks fine now, I'll just let the CI do its thing before merging.

Just wanted to say that the bind you are making in the test doesn't really test anything. Callable.bind returns a copy of the callable with the bound arguments, you have to make the call from the returned Callable and not the original one!
Now that I'm rethinking, the last assert in the test might be broken 🤔

.clang-format is one of those little organization things that all projects should have, and yet I never have setup in my projects 😅 Thanks for bringing that in!

illarn · 2026-04-14T22:58:59Z

Just wanted to say that the bind you are making in the test doesn't really test anything. Callable.bind returns a copy of the callable with the bound arguments, you have to make the call from the returned Callable and not the original one!

fixed, forgot to commit this and lost in autostash when switching branches, lol (sorry for the wasted CI run)

gilzoide · 2026-04-20T18:06:32Z

Nice, now everything should work fine. Again, I'll just wait for the CI to do its thing and if everything is fine, merge afterwards.

Thanks again for the contribution!

illarn added 4 commits April 10, 2026 01:10

feat: LuaCallable

6140dbe

Merge branch 'main' of https://github.com/gilzoide/lua-gdextension

4be3b23

fix: fixed callable test

8b013ba

feat: callable from lua function lua ls definition

af6d7ea

illarn mentioned this pull request Apr 9, 2026

Lua functions can't be used as Callable #219

Closed

fixed brackets

25b1cec

gilzoide reviewed Apr 12, 2026

View reviewed changes

illarn added 5 commits April 13, 2026 00:15

fixes from the feedback

bf6fc53

fixed callable test

c908c65

included callable from lua function into README

d5a021b

removed leftover virtual from LuaCallable's methods

aba225e

removed excessive type specifier

adabff8

aded .clang-format

528d48a

fixed callable test

3b00277

gilzoide merged commit c41f076 into gilzoide:main Apr 20, 2026
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TODO

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