Struct LaunchOptions 

pub struct LaunchOptions {

    pub path: PathBuf,
    pub version: String,
    pub authenticator: Authenticator,
    pub timeout_secs: u64,
    pub download_concurrency: u32,
    pub verify_concurrency: u32,
    pub memory: MemoryConfig,
    pub java: JavaOptions,
    pub loader: LoaderConfig,
    pub screen: ScreenConfig,
    pub verify: bool,
    pub game_args: Vec<String>,
    pub jvm_args: Vec<String>,
    pub instance: Option<String>,
    pub url: Option<String>,
    pub mcp: Option<String>,
    pub intel_enabled_mac: bool,
    pub bypass_offline: bool,
    pub skip_bundle_check: bool,
    pub force_ipv4: bool,
}

Complete configuration for a launcher session.

Pass to Launcher::new(). Every field except path, version, and authenticator has a sensible default so callers only need to set what differs from the defaults.

Fields

path: PathBuf

Absolute base path for all launcher data (libraries/, assets/, versions/, runtime/, …).

version: String

Minecraft version: concrete ("1.20.4") or alias ("latest_release" / "r" / "lr" / "latest_snapshot" / "s" / "ls").

authenticator: Authenticator

Authentication credentials — required.

timeout_secs: u64

HTTP request timeout in seconds (default: 10).

download_concurrency: u32

Concurrent download workers, clamped to 1–30 (default: 5).

verify_concurrency: u32

Concurrent SHA-1 verify workers, clamped to 1–16 (default: 4). Lower than download_concurrency to avoid disk seek thrashing on HDDs.

memory: MemoryConfig

java: JavaOptions

loader: LoaderConfig

screen: ScreenConfig

verify: bool

Re-verify SHA-1 integrity of every file after download (default: false).

game_args: Vec<String>

Extra arguments appended after the vanilla game arg list.

jvm_args: Vec<String>

Extra arguments prepended to the JVM arg list.

instance: Option<String>

Named instance for multi-instance support. When set, data lives under <path>/instances/<instance>/.

url: Option<String>

URL for custom additional assets (optional).

mcp: Option<String>

Path to a custom Minecraft JAR (mod compatibility parameter).

intel_enabled_mac: bool

macOS only: force x64 Java even on Apple Silicon (Rosetta 2).

bypass_offline: bool

Redirect Mojang auth endpoints to an invalid domain so offline multiplayer works without a valid session (default: false).

skip_bundle_check: bool

When true and gameData.json already exists on disk, skip the bundle integrity check and load directly from cache (fast launch). Falls through to the normal download path when the cache is absent. Default: false (always verify — current behaviour preserved).

force_ipv4: bool

Force all HTTP traffic over IPv4, ignoring DNS AAAA (IPv6) records.

Enable when downloads fail with connection errors (“error sending request”) on networks whose IPv6 route is broken even though IPv4 works — a frequent cause of failures that vanish under a VPN or in a browser (which does Happy Eyeballs; reqwest does not). Default: false.

Implementations

impl LaunchOptions

pub fn save_dir(&self) -> PathBuf

Directory where gameData.json is stored. Returns <path>/instances/<instance> when instanced, otherwise <path>.

pub fn loader_dir(&self, name: &str) -> PathBuf

Root directory for a specific mod loader’s files.

Returns <path>/loader/<name> unless loader.path is set explicitly.

pub fn clamped_concurrency(&self) -> u32

download_concurrency clamped to the valid range 1–64.

The upper bound matches the ceiling in [adaptive_concurrency], which further reduces the effective value based on available CPU cores.

pub fn clamped_verify_concurrency(&self) -> u32

verify_concurrency clamped to the valid range 1–16.

Trait Implementations

impl Clone for LaunchOptions

fn clone(&self) -> LaunchOptions

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LaunchOptions

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for LaunchOptions

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for LaunchOptions

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.