Mod Support: Add a way for the server to know the skin-related client options

[Kaffeine]

Hi devs. I maintain a mod with player classes and the mod uses skins and colors to distinguish them. Maybe you've heard about Left 4 Dead or Team Fortress games; the mod I'm doing also has some Smoker, Spider, Boomer as well as Engineer, Soldier, Sniper classes (22 in total).

The set of available skins is a huge limiting factor, and right now the mod uses only standard teeworlds skins and nothing else, because if a skin is disabled, the fallback to default skin would ruin the gameplay.

If the server could know whether the client has 'Vanilla skins only' option ON, it can snap the most suitable skins.

E.g. for "vanilla only" and non-ddnet clients the game uses this skin for Ghost class.

For my custom infclass client it uses ghost skin by whis (ghost can be "invisible" and in that case I render it semitransparent, which has an issue with alpha blending but meh, it is better than nothing).

It is so unfortunate that I can't enable ghost skin for ghost classes for ddnet, because there is a number of players with that "vanilla skins only" option checked on.

I'm proposing to add some ClientPreferences (somehow similar to ServerCapabilities but those are not "Capabilities" in the strong sense) with version and flags. Something like that:

void CClient::SendPreferences(int Conn)
{
	CMsgPacker Msg(NETMSG_CLIENT_PREFERENCES, true);
	Msg.AddInt(CLIENTPREF_CURVERSION);
	int Flags = 0;
	if(Config()->m_ClVanillaSkinsOnly)
	{
		Flags |= CLIENTPREFFLAG_VANILLA_SKINS_ONLY;
	}
	Msg.AddInt(Flags);
	SendMsg(Conn, &Msg, MSGFLAG_VITAL);
}

I'd also like to have the client preferred language (can be null) here in ClientPreferences but it is a different topic.

[heinrich5991]

It seems to me that inferring which skins are available is brittle. Perhaps we could make the client accept skin files from the server? Maybe only fallback skin files?

[Kaffeine]

Server side skins would be an awesome superior solution. The only drawback is that I have no idea how to implement it.

[Kaffeine]

Closed in favor of #7297 (server-side skins)