Add ability to bind an unbind arguments to Callable.

[reduz]

After the today's contributor meeting we decided to change the way arguments are bound and unbound to signals and other structures by doing this directly in Callable.

As such, its now possible to bind and unbind arguments directly from the Callable:

func myfunc(extraarg):
    print("hello",extraarg)

func myfunc2():
    print("hello")

func _ready():
#old style (remains supported for more flexibility, but no longer the recommended way)
    $Button.connect("pressed",this,"myfunc",["watsup"])
#new style
    $Button.pressed.connect( myfunc.bind("watsup") )
#unbinding also possible, discard the extra argument
    $AnimationPlayer.finished.connect( myfunc2.unbind(1) )

from C++, the callable_bind() functions were added, can be used like this:

button->connect(callable_bind( callable_mp(this,&MyClass::_myfunc), "watsup" ) );

The ability to pass an array in the connect() version that takes a callable, in both C++ and script languages will be removed, so these will have to be used from now on in Godot 4.0 (the connect method for Object will remain unchanged in case flexibility is desired)). This change will be done project wide in a subsequent pull request.

[akien-mga]

Suggested change

	}
	Callable Callable::unbind(int p_argcount) const {
	}
	Callable Callable::unbind(int p_argcount) const {

[akien-mga]

Missing copyright header.

[akien-mga]

And review spacing between functions (yes, I'll go pester clang-format devs about it again ;))

[akien-mga]

Missing copyright header.

[akien-mga]

Please try to get used to this comment style that the team agreed upon:

Suggested change

	//compare with the base callable, so binds can be ignored
	// Compare with the base callable, so binds can be ignored.

We can't rely on formatting tools for that, we have to be consistent in the code we write.

[reduz]

The problem is that this comment style is everywhere in the codebase, even in that file. I honestly just forget. We should try to ask the clang format guys to add support for this and pester them about it.

[akien-mga]

Would it be worth it (and possible) to add some sugar so we can define a Callable with binds directly? E.g. callable_mp_bind(this, &SceneTreeDock::_tool_selected, TOOL_NEW, false)?

[reduz]

its a bit difficult because callable_mp is a macro, I wonder if vararg macros are finally supported in C++17..

[reduz]

maybe someone with more C++17 fu can help me figure it out

[willnationsdev]

@AndreaCatania's fork has an ecs branch which has some examples of variadic templates, iirc. Example

[reduz]

I already implememted them in a couple of places, but it won't help here

[reduz]

Also callable_bind is ok, because there are other places where regular callables (not mp) are used, so a generic function needs to exist, so given this is not used super often, it may be ok to leave as is.

[KoBeWi]

Would be useful if the PR included also documentation. It's just two methods.

[reduz]

@KoBeWi can try after the next PR, since I will have to change the doc system due to the changes to builtin methods.

[Xrayez]

Would be useful if the PR included also documentation. It's just two methods.

I usually use the following command when there's no documentation written. 🙂

git log --since 3.2 --until master --pretty=format:"https://github.com/godotengine/godot/commit/%h %s" --author="Juan Linietsky"

Commits can then be followed by URLs specified by commits, leading to PRs with actual descriptions.

[aaronfranke]

Where is the documentation for this feature?

[2fd5]

Could unbind have unbind all option ? Like by passing -1 as an argument, so that I do not need to know how many arguments are defined for the signal. It is in relation to godotengine/godot-proposals#762 (comment)

[Jan-PieterInghels]

The old way of binding arguments to a callable via array is still shown in the documentation, on the gdscript basics page to be specific. CTRL+F "battlelog" and you'll see the old example.