always-on-mouselook enabled by default

[neogeographica]

(Another of the "out-of-the-box experience" items from that email.)

The method of doing this isn't as obvious/trivial as some of the others, so I'll put this up for potential comments before changing anything.

I kind of like the way that Engoo handles this, with a new m_look cvar that essentially flips the sense of +mlook. In Engoo, if m_look is 1 then always-on-mouselook is enabled (and pressing a +mlook key would actually turn off mouselook rather than turning it on).

We could default m_look to 1 in reQuiem so that always-on-mouselook is enabled by default. This would differ from Engoo's behavior, which defaults it to 0.

Engoo implements the m_look behavior by replacing all occurrences of (in_mlook.state & 1) with ((in_mlook.state & 1) ^ ((int)m_look->value & 1)).

That would work, but at first glance it looks like we could handle things more efficiently by only checking the value of m_look if/when the +mlook key is pressed or released, i.e. make the IN_MLookDown and IN_MLookUp functions decide whether to call KeyUp or KeyDown depending on the value of m_look.

There might be some reason not to do that which I haven't noticed yet. Also I'd need to be careful about at least a couple of things:

• If lookspring is enabled, make sure it activates in the "mouselook deactivated" case specifically, as opposed to just the "key up" case.
• If the value of m_look is changed during play, the change callback would need to generate a KeyUp for any current KeyDowns, and vice-versa.

[neogeographica]

One solution in https://github.com/SpiritQuaddicted/reQuiem/commit/5164cc4c189ebf4a76940ed34ecf35af5eb88f0e on the m_look branch ... see the description of that commit for a bit of discussion. Comments on those alternatives welcome.

[neogeographica]

Pull request is out. The proposed functionality there is different than in the thoughts above... see the pull request comments.