Add Object:IsClassNative to check whether a class is native

[robojumper]

In which we work our way into the innards of the UnrealScript virtual machine. Closes #767.

Original description below, see comments for current design:

Click to expand

// Must be called on a `Class` instance, i.e. if you have an X2AbilityTargetStyle and
// want to know whether it's native, check `TargetStyle.class.IsNative()`
final function bool IsNative()
{
	// This is the flag the UC VM uses to mark a class as native
	return (self.ObjectFlags.B & (1 << 26)) != 0;
}

You may call <SomeObject>.class.IsNative() to determine whether the class is native, or, if you are working with a class<_> already, skip the .class part.

Because I am a skeptical person and you should be too, here is a debug output that makes this implementation appear correct (interestingly enough, GetClassDefaultObjects yields objects for native classes first):

https://pastebin.com/acG9Jc0a

This may come in useful for #762.

[Xymanek]

Why not check if (class(self) != none) (or vice versa) and adjust the check automatically, so that you could call the method directly, without caring about "type of instance" that you are dealing with?

[robojumper]

I'm conflicted. On one hand, it's more "magic" and can clash with the mental model where objects and their classes are entirely separate things (see #477 (comment), where I got confused about this) and introduces an inconsistency with other functions in Object (see discussion I just linked).

On the other hand, the only kinds of Object that can have this flag set (and for which the function makes sense) are classes, but I can't add it to Class.uc because that doesn't exist.

Perhaps a

final static function bool ClassIsNative(Class klass)
{
	// This is the flag the UC VM uses to mark a class as native
	return (klass.ObjectFlags.B & (1 << 26)) != 0;
}

would be better?

[Xymanek]

Yeah, ClassIsNative resolves the confusion 👍

[MrNiceUK]

Assume that's "as well as", so you call IsNative() or IsClassNative() depending what you're dealing with?

[robojumper]

No, a static function ClassIsNative.

[Xymanek]

Needs a tracking issue

[Xymanek]

What about #765?

[Xymanek]

Please adjust the version info/check, now that the new approach is implemented

[robojumper]

Fixed. I hope.

[Xymanek]

Isn't this backwards incompatible? Since someone might be checking the engine version already

[robojumper]

Technically yes, but the only Engine feature we have is the AudioComponent WWise/SoundCue fix which I don't think anyone ever queried for.

[Xymanek]

I don't think anyone ever

So far this kind of thought was allowed only in extreme cases, particularly related to new features

[Xymanek]

Also, the matter of name collision still remains. I think naming the function CH_IsClassNative would be much safer option

---

Also 2: Shouldn't /// HL-Docs: ref:ComponentVersions be added to the DLC2 version?

[robojumper]

Addressed. I would still like to get rid of the Engine template because it's not useful and there is no mod that ever checked that Engine version (it only contained a single bugfix).

[Xymanek]

I mean, if you are so sure that no one ever checked the engine template, then I guess go ahead....