Events

"Something happened, run my code" means different things on a CS2 server, and Source2Mod has a different tool for each. This section covers the first two; the rest are linked below.

Game events

The game announces what happens in a match through game events — player_death, round_start, bomb_planted, player_connect_full, some 270 of them in all. Each is a named bag of typed fields (an IGameEvent) that the server fires and, usually, sends to every client too (that is how the killfeed and the round timer work).

HOOK_GAME_EVENT("player_death", [](IGameEvent* event, bool post, bool& dontBroadcast) -> Action
{
    auto* victim = static_cast<CCSPlayerController*>(event->GetPlayerController("userid"));
    // ...
    return Action::Ignore;
}, true);

Source2ModEvents.HookGameEvent("player_death", Event_PlayerDeath, true);

public Source2ModAction Event_PlayerDeath(IGameEvent event, bool post, bool &dontBroadcast)
{
    CCSPlayerController victim = event.GetPlayerController("userid");
    // ...
    return Action_Ignore;
}

With ISource2ModEvents you hook an event before or after the engine handles it, read and change its fields, keep it from the clients, cancel it, and fire events of your own — to everybody or to one player. See Game events, and the event reference for the fields of the ones you will use most.

Source2Mod listener callbacks

Source2Mod itself tells your plugin about the plugin system and the map lifecycle through ISource2ModListener: other plugins loading and unloading, "all plugins are loaded", map start (OnLevelInit) and map end (OnLevelShutdown), plus interface queries. You implement the interface and register it once with api->AddListener(this, this); a script registers nothing and defines public functions named after the Source2Mod_On* forwards instead. See Listeners.

Engine callbacks: clients and the frame

Player connection and the server frame are not listener callbacks. They are engine interface functions you hook with KHook, the way the sample plugin does:

KHOOK_VIRTUAL(m_hGameFrame, &ISource2Server::GameFrame, &g_pSource2Server, nullptr, &MyPlugin::Hook_GameFrame);
KHOOK_VIRTUAL(m_hClientDisconnect, &ISource2GameClients::ClientDisconnect, &g_pSource2GameClients, nullptr, &MyPlugin::Hook_ClientDisconnect);

C++ only — scripts get client connection and the frame as forwards (Source2Mod_OnClientConnect, Source2Mod_OnClientDisconnect, Source2Mod_OnGameFrame, …); see Listeners.

See Hooking for how these work. Many of these moments also have a game event — player_connect_full and player_disconnect are often all you need.

Entities and entity outputs

Entities being created, spawned and deleted (IEntityListener, ADD_ENTITY_LISTENER) and map logic firing outputs such as OnPressed or OnStartTouch (IEntityIOListener, ADD_ENTITY_IO_LISTENER) belong to ISource2ModEntities. See Entities.

Net messages, sounds, commands, ConVars

• Protobuf messages between server and clients (user messages, net messages) — Protobuf.
• Sounds being emitted — ISource2ModSounds.
• Commands and chat — ConVars & Commands.
• ConVar changes — HOOK_CONVAR_CHANGE.