Server: limit how far a mod may resize part of a skater for other players

- bone_scale_limit in ReSkateServer.json, and the bone-scale command:
  the most a bone may be scaled in the poses the server passes on, 1 to
  8, and its inverse the least. 1 shows every skater at the game's own
  proportions; 0 (the default, "bone-scale off") is no limit
- A "big head" mod sets one joint's scale in the body's bind pose
  (animation/dingo/cas_rsp_body_bind, the head from 1 to 4). The game
  applies it to the bone, and the bone's scale travels in every pose,
  which is how players without the mod see it. The game's own skeleton
  has no scaled joint, so 1 changes nothing for anyone else
- The player with the mod still sees it on their own screen: the server
  decides only what the others are sent
- Changing it sends whole states again, so nobody keeps a reference
  with the old sizes in it
- Dedicated servers only; a lobby's host has no such setting

Server/server_host.cpp

@@ -46,7 +46,7 @@ std::uint64_t nonce() {
 constexpr std::string_view help_text =
     "status | net [player] | players | say <text> | msg <player> <text> | msg-party <player> <text> | msg-admins <text> | kick <player> | ban <player or SteamID64> [name] | unban <SteamID64> | bans\n"
     "map <name, e.g. San Vansterdam> | maps | name <text> | password <text|off> | welcome <text|off> | listed on|off\n"
-    "voice on|off | voice-range <50-1000> | distances <full> <half> <half-return> <low> | crowd <n>|off | rate <KB/s>\n"
+    "voice on|off | voice-range <50-1000> | distances <full> <half> <half-return> <low> | crowd <n>|off | rate <KB/s> | bone-scale <1-8>|off\n"
     "placement everyone|admins|nobody | objects <number>|off | clear-objects | noclip on|off | nobail on|off | boosts on|off | tuning on|off\n"
     "tpall [player] | tphere <player> | votes [map|kick|tod on|off|<percent>] | vote-cancel\n"
     "map-pool [add|remove <map>|clear] | rotation [<minutes>|off]\n"
@@ -342,7 +342,11 @@ void Host::broadcast(const Packet &packet, bool reliable, bool fresh, std::uint6
         if (data.raw.empty()) {
             data.packet = packet;
             data.packet.pose_interval_us = interval;
-            if (packet.kind == PacketKind::pose) coarsen_rotations(data.packet.pose, pose_precision[precision]);
+            if (packet.kind == PacketKind::pose) {
+                // What a mod resized on its player's skater reaches the others only as far as the server allows.
+                if (config_.bone_scale_limit >= 1.f) limit_bone_scale(data.packet.pose, config_.bone_scale_limit);
+                coarsen_rotations(data.packet.pose, pose_precision[precision]);
+            }
             data.raw = encode(data.packet, true);
             data.wire = encode_wire_bytes(data.raw);
         }
@@ -1570,6 +1574,22 @@ std::string Host::command(std::string_view line, std::uint64_t admin) {
         return changed("Each player is sent at most " + std::to_string(config_.send_rate) + " KB/s" +
                        (applied ? "." : ": players who join from now on. Steam did not change the connections already open."));
     }
+    if (name == "bone-scale") {
+        // bone-scale <1-8>|off: how far a mod may resize part of a skater for the other players.
+        float value{};
+        const bool off = argument == "off" || argument == "0";
+        const auto parsed = std::from_chars(argument.data(), argument.data() + argument.size(), value);
+        if (!off && (parsed.ec != std::errc{} || parsed.ptr != argument.data() + argument.size() || !(value >= 1.f && value <= 8.f)))
+            return "bone-scale <1-8>|off: 1 shows every skater at the game's own proportions, off allows anything (now " +
+                   (config_.bone_scale_limit >= 1.f ? std::to_string(config_.bone_scale_limit).substr(0, 4) : std::string("off")) + ")";
+        config_.bone_scale_limit = off ? 0.f : value;
+        // Whole states go again so that nobody keeps a reference with the old sizes in it.
+        for (auto &[id, guest] : guests_)
+            for (const auto &[other, unused] : guests_) guest->sender.forget(other, PacketKind::pose);
+        return changed(off ? std::string("Mods may resize skaters' body parts freely.")
+                           : value == 1.f ? std::string("Skaters show at the game's own proportions: resized body parts are not passed on.")
+                                          : "Resized body parts show at up to " + std::to_string(value).substr(0, 4) + "x.");
+    }
     if (name == "crowd") {
         // crowd <poses a second>|off: the most one player is sent (crowd_limits).
         auto value = number(argument);