Library Modules

A Slint library module lets one Rust crate publish a set of .slint components and another crate import them through Cargo’s dependency system. The consumer writes import { Foo } from "@libname"; and Cargo’s build metadata tells the Slint compiler where to find the library source.

Note: Library modules are experimental. The publishing side requires the experimental-module-builds feature of slint-build, and the consumer side requires the experimental-library-module feature of the Slint compiler. Tracking issue: slint-ui/slint#154 ↗.

Publishing a library

A crate that provides a library compiles its .slint entry point in its build.rs and marks it as a library. This causes Cargo to emit DEP_* environment variables that downstream crates can read.

// build.rs of the publishing crate
fn main() {
    let config = slint_build::CompilerConfiguration::new()
        .as_library("mywidgets");
    slint_build::compile_with_config("ui/lib.slint", config).unwrap();
}

rust,no_run

The crate’s Cargo.toml must declare links = "mywidgets" so that Cargo forwards the metadata to dependent crates.

[package]
name = "mywidgets"
links = "mywidgets"

toml

Consuming a library

A crate that depends on the publishing crate imports its components with the @ prefix followed by the library name:

import { FancyButton } from "@mywidgets";

export component App inherits Window {
    FancyButton { text: "Click me"; }
}

slint

No extra build.rs configuration is needed on the consumer side: the Slint compiler discovers the library through the DEP_MYWIDGETS_SLINT_LIBRARY_* environment variables that Cargo forwards automatically for links dependencies.

Environment variables

When the publishing crate uses as_library("name"), its build script emits the following metadata, which Cargo exposes to dependents as DEP_NAME_*:

Variable	Meaning
SLINT_LIBRARY_NAME	The library name used in the @name import.
SLINT_LIBRARY_SOURCE	Absolute path to the library’s entry .slint file.
SLINT_LIBRARY_PACKAGE	The publishing crate’s package name.
SLINT_LIBRARY_MODULE	Optional Rust module path where the generated code lives.

Ad-hoc local libraries that do not need to travel across crates can still be registered directly with slint_build::CompilerConfiguration::with_library_paths. That API is stable and does not require the experimental feature.