rust-samp

Plugin anatomy

Every rust-samp plugin follows the same shape: a Rust type that implements SampPlugin, methods annotated with #[native], and a single initialize_plugin! invocation that wires it all together.

The `SampPlugin` trait

SampPlugin defines the plugin’s lifecycle. Every method is optional — the trait provides empty defaults.

pub trait SampPlugin {
    /// Called once after the server loads the plugin
    /// (`Load()` on SA-MP, `onLoad(ICore*)` on native Open Multiplayer).
    fn on_load(&mut self) {}

    /// Called when the server unloads the plugin.
    fn on_unload(&mut self) {}

    /// A Pawn script (`.amx`) was loaded.
    fn on_amx_load(&mut self, amx: &Amx) {}

    /// A Pawn script is being unloaded.
    fn on_amx_unload(&mut self, amx: &Amx) {}

    /// Periodic callback. Requires opting in via
    /// `samp::plugin::enable_tick()` (or `enable_tick_with(...)`).
    /// `TickContext::source` distinguishes SA-MP's main-loop tick
    /// from the SDK-owned Open Multiplayer timer; `TickContext::elapsed`
    /// is the wall-clock time since the previous dispatch.
    fn on_tick(&mut self, ctx: TickContext) {}

    /// Every Open Multiplayer component has finished initializing.
    /// Compiled only when the `samp-only` feature is **not** active.
    #[cfg(not(feature = "samp-only"))]
    fn on_omp_ready(&mut self) {}

    /// An Open Multiplayer component is being released.
    /// Compiled only when the `samp-only` feature is **not** active.
    #[cfg(not(feature = "samp-only"))]
    fn on_component_free(&mut self) {}
}

The two Open Multiplayer-only hooks exist only when the samp-only feature is not set. Plugins that must compile both with and without that feature should gate their overrides with #[cfg(not(feature = "samp-only"))].

See Native Open Multiplayer support for the full Open Multiplayer lifecycle and feature-flag matrix.

Because every method has a default, a plugin without overrides can use the derive instead of writing the impl by hand:

#[derive(SampPlugin, Default)]
struct MyPlugin;

#[derive(SampPlugin)] emits exactly impl SampPlugin for T {}. If a method needs custom logic (on_load, on_tick, …), write the impl by hand and drop the derive.

Plugin state

The plugin struct is mutable (&mut self), so it can hold state across calls:

struct MyPlugin {
    players_online: u32,
    sessions: Vec<String>,
}

impl SampPlugin for MyPlugin {
    fn on_load(&mut self) {
        self.players_online = 0;
        println!("Plugin ready.");
    }
}

Order of execution

initialize_plugin! { ... } — instantiate the plugin.
on_load — once, after the server loads the plugin.
on_amx_load — each time a Pawn script is loaded.
on_tick — repeatedly, while enabled.
on_amx_unload — each time a Pawn script is unloaded.
on_unload — once, before shutdown.

On native Open Multiplayer, on_omp_ready fires between on_load and the first on_amx_load, and on_component_free fires when any other component is released.

The `initialize_plugin!` macro

initialize_plugin! does three things:

Registers the plugin’s natives.
Constructs the plugin instance.
Emits every server-required entry point — SA-MP exports (Load, Unload, Supports, AmxLoad, AmxUnload, ProcessTick) and, by default, the Open Multiplayer ComponentEntryPoint.

Short form — `type: T`

For plugins without initialization logic. Uses Default::default() as the constructor:

#[derive(SampPlugin, Default)]
struct MyPlugin;

initialize_plugin!(
    type: MyPlugin,
    natives: [
        MyPlugin::function_a,
        MyPlugin::function_b,
    ],
);

Full form — constructor block

For plugins that need to set up logging, encoding, the server tick, or that build initial state:

initialize_plugin!(
    natives: [
        MyPlugin::function_a,
        MyPlugin::function_b,
    ],
    {
        samp::plugin::enable_tick();
        samp::encoding::set_default_encoding(samp::encoding::WINDOWS_1251);

        return MyPlugin {
            players_online: 0,
            sessions: Vec::new(),
        };
    }
);

The constructor block must end with return <instance>;. Any code preceding the return runs exactly once, when the server loads the plugin.

Native Open Multiplayer metadata

Native Open Multiplayer mode is the default: every build without the samp-only feature emits both the SA-MP exports and the ComponentEntryPoint. No extra configuration is required.

The component UID is resolved from three sources, in priority order:

uid: 0x..._u64 declared inside initialize_plugin!.
[package.metadata.samp] uid = "0x..." in Cargo.toml.
FNV-1a 64-bit hash of CARGO_PKG_NAME@CARGO_PKG_VERSION. The computed value is written back into Cargo.toml under [package.metadata.samp] on the next build, so subsequent builds reuse the same value.

To declare the metadata directly in Cargo.toml:

[package.metadata.samp]
uid     = "0x4D455550CAFEBABE"
name    = "MyPlugin"             # optional — default: CARGO_PKG_NAME
version = "1.0.0"                # optional — default: CARGO_PKG_VERSION

To declare it directly in code (macro values take precedence over Cargo.toml):

initialize_plugin!(
    uid: 0x4D455550CAFEBABE_u64,
    component_name: "MyPlugin",     // optional
    component_version: (1, 0, 0),   // optional
    natives: [MyPlugin::function_a],
    { return MyPlugin::new(); }
);

See Native Open Multiplayer support for the full explanation.

No natives

If the plugin only reacts to events:

// Short form
initialize_plugin!(type: MyPlugin, natives: []);

// Full form
initialize_plugin!(
    natives: [],
    { return MyPlugin; }
);

Enabling the periodic tick

By default on_tick is not called. Opt in inside the constructor block:

initialize_plugin!(
    natives: [],
    {
        samp::plugin::enable_tick();
        return MyPlugin::default();
    }
);

The two servers schedule the callback differently:

SA-MP — Supports::PROCESS_TICK is advertised and the server calls ProcessTick on every iteration of its main loop. The cadence is whatever the server is configured for; the SDK has no control over it.
Native Open Multiplayer — there is no native ProcessTick equivalent. The SDK queries ITimersComponent in on_ready and installs a repeating timer; its timeout dispatches on_tick. The interval is configurable.

For custom cadence or per-server control, use the explicit form:

use std::time::Duration;
use samp::plugin::{enable_tick_with, TickConfig};

// Both servers, but 100 ms on Open Multiplayer instead of 5 ms:
enable_tick_with(TickConfig::new().omp_interval(Duration::from_millis(100)));

// Shortcut: SA-MP only, no Open Multiplayer timer.
enable_tick_with(TickConfig::sa_mp_only());

// Shortcut: Open Multiplayer only, at the given interval.
enable_tick_with(TickConfig::omp_only(Duration::from_millis(50)));

TickContext::source (passed to on_tick) reports TickSource::SaMp or TickSource::OmpTimer, so the same method can branch on origin when needed.

Lifecycle diagrams

SA-MP

Server start
  └─ Plugin load
       ├─ initialize_plugin! { ... }    ← construct the instance
       ├─ on_load()
       ├─ Gamemode loaded → on_amx_load(amx)
       ├─ [loop] on_tick(ctx)               (if enabled — cadence dictated by the server)
       ├─ Gamemode unloaded → on_amx_unload(amx)
       └─ on_unload()
Server shutdown

Native Open Multiplayer

Server start
  └─ Plugin load (ComponentEntryPoint)
       ├─ initialize_plugin! { ... }    ← construct the instance
       ├─ on_load()                      ← from comp_on_load(ICore*)
       ├─ on_omp_ready()                 ← every component initialized
       ├─ Script loaded → on_amx_load(amx)
       ├─ [loop] on_tick(ctx)             (if enabled — SDK-owned ITimer at configured interval)
       ├─ on_component_free()             ← another component being released
       ├─ Script unloaded → on_amx_unload(amx)
       └─ on_unload()                    ← from comp_free
Server shutdown

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