Struct AppCfg 

pub struct AppCfg {
    pub entry: Option<String>,
    pub id: Option<String>,
    pub kind: Option<AppKind>,
    pub locale: Option<LanguageIdentifier>,
    pub fallback_locale: Option<LanguageIdentifier>,
    pub single_instance: bool,
}

[app] block.

Fields

entry: Option<String>

Markup entry filename relative to the app dir. Defaults to main.lmn.

id: Option<String>

Stable identifier used for per-app state directories (window state, plugin caches). Falls back to the app directory name when absent.

kind: Option<AppKind>

Optional app-kind override ("markup" | "rust" | "cpp" | "python"). Optional and used only to override auto-detection: when absent, crate::app_kind::detect inspects the directory; when present, it wins. Lets an ambiguous directory (e.g. a Rust workspace member that should still run as pure markup) pin its build/run route.

locale: Option<LanguageIdentifier>

BCP-47 tag naming the locale the app starts in, e.g. "de-DE". Absent means “follow the OS”, falling back to en-US. The tag selects which locale/<tag>.ftl catalogue translatable="..." markup and the scripts’ t() builtin resolve against; every catalogue in the directory is loaded regardless. A tag that is not valid BCP-47 is a lumen.toml error.

fallback_locale: Option<LanguageIdentifier>

BCP-47 tag naming the locale a key missing from the active catalogue falls through to before the element’s own authored text. Defaults to en-US. Set it to the language the app’s source strings are written in, so an app authored in German does not probe an en-US catalogue it does not ship. Naming the active locale here leaves nothing to fall through to, so a miss goes straight to the authored text. A tag that is not valid BCP-47 is a lumen.toml error.

single_instance: bool

When true, a second launch of this app forwards its command-line arguments to the already-running instance and exits instead of opening a second window; the primary sees them as on_second_instance(args). Defaults to false: most apps are fine with more than one window open, and the lock has a real side effect (a bound socket / named pipe) that an app should opt into rather than acquire by surprise. Windowed runs only - a headless / --headless run never locks, so CI and the SDK’s non-interactive embedding never contend over one socket.

Trait Implementations

impl Clone for AppCfg

fn clone(&self) -> AppCfg

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for AppCfg

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

Formats the value using the given formatter.

impl Default for AppCfg

fn default() -> AppCfg

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for AppCfg

where AppCfg: Default,

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.