Replication

Sending one player a ConVar value of their own with ReplicateConVar, keeping it there, and reading ConVars from the client.

Some ConVars matter on the client as much as on the server. FCVAR_REPLICATED ConVars — sv_autobunnyhopping, sv_jump_impulse, mp_forcecamera, weapon_accuracy_nospread, … — are sent by the server to every client, and the client uses them for prediction, movement and UI. Normally everyone gets the same value. ReplicateConVar sends a single player a value of their own.

`ReplicateConVar`

A helper on CBasePlayerController (so on CCSPlayerController too, and on the script methodmaps of the same names):

CBasePlayerController.h

void ReplicateConVar(const char* pszConVar, const char* pszValue);

It builds a CNETMsg_SetConVar with the one name/value pair and sends it straight down that player's net channel. The value is always a string, as the client would parse it from the console: "1", "true", "301.9933".

plugin.cpp

#include "source2mod/schema/entity/classes/CCSPlayerController.h"

// Auto-bunnyhop for one player only.
void SetBhop(CCSPlayerController* player, bool enabled)
{
    player->ReplicateConVar("sv_autobunnyhopping", enabled ? "true" : "false");
}

Things to keep in mind:

Only the client's copy changes. The server's value is untouched, and anything the server decides with it still uses the server's value. For ConVars that are simulated on both sides — movement mostly — the server has to agree, or the client mispredicts.
The player must be connected. Without a net channel the call does nothing.
It does not survive a reconnect. A client that reconnects starts from the server's values again.

Keeping the value per player

If the ConVar is FCVAR_REPLICATED, the engine broadcasts the server's value to every client whenever it changes — which overwrites every per-player value you sent. FUNPLAY's plugins, which toggle bunnyhop, C4-anywhere and friends per player, handle this in three places:

Before sending, drop FCVAR_REPLICATED from the ConVar so a later change of the server value is not pushed over the per-player ones:

UTIL_RemoveConVarFlags("sv_autobunnyhopping", FCVAR_REPLICATED);
player->ReplicateConVar("sv_autobunnyhopping", state ? "true" : "false");

When the server value changes, send each player their value again (HOOK_CONVAR_CHANGE).
When a player (re)connects, send it again — player_connect_full is the usual place (see Game events).

bhop.cpp

static CConVarRef<bool> sv_autobunnyhopping("sv_autobunnyhopping");

static void UpdatePlayerBhop(CCSPlayerController* player, bool state)
{
    UTIL_RemoveConVarFlags("sv_autobunnyhopping", FCVAR_REPLICATED);

    // With bhop on for everybody there is nothing to override.
    if (!sv_autobunnyhopping.Get())
        player->ReplicateConVar("sv_autobunnyhopping", state ? "true" : "false");
}

// in Load()
HOOK_CONVAR_CHANGE([](ConVarRefAbstract* ref, CSplitScreenSlot slot, const char* pszNewValue, const char* pszOldValue)
{
    if (V_strcmp(ref->GetName(), "sv_autobunnyhopping") != 0)
        return;

    for (int i = 0; i < 64; i++)
        if (auto* player = CCSPlayerController::FromSlot(i))
            UpdatePlayerBhop(player, PlayerHasBhop(player)); // your own per-player state
});

HOOK_GAME_EVENT("player_connect_full", [](IGameEvent* event, bool post, bool& dontBroadcast) -> Action
{
    auto* player = static_cast<CCSPlayerController*>(event->GetPlayerController("userid"));
    if (player)
        UpdatePlayerBhop(player, PlayerHasBhop(player));
    return Action::Ignore;
}, true);

bhop.sp

CConVarRef sv_autobunnyhopping;

void UpdatePlayerBhop(CCSPlayerController player, bool state)
{
    sv_autobunnyhopping.Flags &= ~FCVAR_REPLICATED;

    // With bhop on for everybody there is nothing to override.
    if (!sv_autobunnyhopping.BoolValue)
        player.ReplicateConVar("sv_autobunnyhopping", state ? "true" : "false");
}

public void OnPluginStart()
{
    sv_autobunnyhopping = CConVarRef.Find("sv_autobunnyhopping");

    Source2ModConVars.HookConVarChange(OnConVarChanged);
    Source2ModEvents.HookGameEvent("player_connect_full", Event_PlayerConnectFull, true);
}

public void OnConVarChanged(ConVar convar, int slot, const char[] newValue, const char[] oldValue)
{
    char name[64];
    convar.GetName(name, sizeof(name));
    if (!Source2ModUtils.Equal(name, "sv_autobunnyhopping"))
        return;

    for (int i = 0; i < 64; i++)
    {
        CCSPlayerController player = CCSPlayerController.FromSlot(CPlayerSlot(i));
        if (player != NULL_ENTITY)
            UpdatePlayerBhop(player, PlayerHasBhop(player)); // your own per-player state
    }
}

public Source2ModAction Event_PlayerConnectFull(IGameEvent event, bool post, bool &dontBroadcast)
{
    CCSPlayerController player = event.GetPlayerController("userid");
    if (player != NULL_ENTITY)
        UpdatePlayerBhop(player, PlayerHasBhop(player));
    return Action_Ignore;
}

UTIL_RemoveConVarFlags and UTIL_AddConVarFlags are the by-name helpers from ISource2ModConVars.h; see ConVars. A script changes the flags on the ConVar handle's Flags instead.

Common uses

ConVar	Per-player effect
`sv_autobunnyhopping`	Hold-to-jump bunnyhopping for chosen players.
`mp_forcecamera`	What a dead player may spectate (FUNPLAY switches it per player on spawn, round start and round end).
`sv_cheats`	Lets a single client use client-side cheat commands — FUNPLAY's Inspect plugin does this. The server stays `sv_cheats 0`.
`sv_jump_impulse`, `sv_friction`, `weapon_accuracy_nospread`, `mp_plant_c4_anywhere`	Movement and weapon behaviour the client predicts; the server side has to match (see above).

Reading ConVars from a client

Source2Mod has no wrapper for asking a client for one of its ConVars. There are two ways, both engine-level:

User info. IVEngineServer2::GetClientConVarValue(CPlayerSlot, const char*) returns a value from the user info the client sends to the server — no round trip, but only for what the client puts there.
```
IVEngineServer2* engine = g_Source2ModAPI->GetEngineServer();
const char* value = engine->GetClientConVarValue(player->GetPlayerSlot(), "name_of_userinfo_cvar");
```
C++ only — scripts have no GetClientConVarValue; they use the cvar query below.
A cvar query. Send the client a CSVCMsg_GetCvarValue (fields cookie and cvar_name) and read the answer, a CCLCMsg_RespondCvarValue with the same cookie and a status (EQueryCvarValueStatus: value intact, not found, not a ConVar, protected). The reply arrives asynchronously; FUNPLAY's AntiCheat catches it with a KHook on CServerSideClientBase::ProcessRespondCvarValue. Sending messages is covered under Protobuf, hooking under Hooking. A script sends the query and catches the answer with Source2ModNetworkMessages — see Common messages.

`ReplicateConVar`

Keeping the value per player

Common uses

Reading ConVars from a client

See also

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