Dont know how i missed this one, think ive set up my search tags a little wonky
(but i also see that theres no tag associated with the post, so ill get that added, just so others can find it easier)
nicely caught guys
heres my understanding with relation to the whole underscore thing.
the uderscores in either a function name or variable are as mentioned, just really a convention and wont force an error, just warnings.
pretty much comes down to the idea of virtual methods for the first part.
with the likes or _process and _ready, these are base methods that are internally created and used by godot and are intended to be overrided / exended by a script if the programmer decides that they want some additional functionality from these methods, through the convention of having a leading underscore.
if we dont use any one of these virtual methods in our script, no biggie, godot will do what it does and use their base functionality which we dont have to worry about in our scripts.
so, this is now where the method arguments come into play.
since for example, _process and _physics_process are virtual methods, these methods have whats called a signature. the signature defines or declares how the method or function has to be used and what arguments it requires, if any.
with say the base class of _process as per the docs it shows this does require something
so its expecting an argument, so by default ‘delta’ is popped in there if we use it in our scripts rather than ommit it.
as was mentioned, the underscore has another couple of convention uses. again these are just convention and not enforced.
the warning that you were getting is just that, a warning, basically the engine telling you that its base _process method has an parameter it uses, but you arent using it at all. so its informing you, if your sure about not using it then pop a _ before the parameter and ill ignore the fact that your not using it then
theres also the last convention that im aware of that uses the _ .
its the idea of private variables. now, godot doesnt have the understanding of public and private variables.
but as a convention, the _ can be used before variables, just to indicate or remind ourselves or others who read our code, that this variable is not intended to be used outwith this script it is declared in.