slint-vcpkg

Experimental / work in progress. This registry is early and not yet battle-tested -- expect rough edges, breaking changes, and incomplete feature coverage (see "Known limitations" below). Feedback and issues welcome, but don't depend on stability yet.

An unofficial vcpkg registry for Slint, the declarative C++/Rust GUI toolkit. Provides slint and corrosion (the CMake/Rust integration Slint's C++ API is built with).

There is no official Slint vcpkg port yet -- see microsoft/vcpkg#33824 and slint-ui/slint#6085. The blocker has always been that vcpkg's CI forbids network access during builds, and a normal Slint build needs the network twice: once for CMake to fetch Corrosion, once for cargo to fetch crates.io dependencies. This registry resolves both:

• Corrosion is, as of v0.6, pure CMake with no Rust component of its own to build -- ports/corrosion installs it with zero network access and zero cargo invocations.
• Slint's own crate graph is vendored ahead of time (see "Adding a new version" below) and shipped as a pinned, hashed distfile, so the actual vcpkg install slint step runs cargo with --offline against a local vendor directory instead of crates.io.

Using this registry

Add it to your project's vcpkg-configuration.json:

{
  "default-registry": {
    "kind": "git",
    "repository": "https://github.com/microsoft/vcpkg",
    "baseline": "<a recent microsoft/vcpkg commit>"
  },
  "registries": [
    {
      "kind": "git",
      "repository": "<URL of this repository>",
      "baseline": "<a commit of this repository>",
      "packages": ["slint", "corrosion"]
    }
  ]
}

Then depend on slint from your vcpkg.json as usual. In your CMakeLists.txt:

find_package(Slint CONFIG REQUIRED)
target_link_libraries(main PRIVATE Slint::Slint)

Prerequisites

• A Rust toolchain (cargo/rustc 1.92+) on PATH. vcpkg does not manage Rust toolchains -- install one from https://rustup.rs.
• CMake 3.21+.
• Network access is not required at install time for the default feature set (interpreter, backend-winit, renderer-femtovg, accessibility, testing), thanks to the vendored-crates mechanism above.

slint is always built as a shared library, regardless of the triplet's default linkage (see "Implementation notes" below for why).

Known limitations

• backend-qt: requires Qt 5.15+ or 6.2+ separately installed and discoverable via CMAKE_PREFIX_PATH. Not provided by this registry.
• renderer-skia / renderer-skia-opengl / renderer-skia-vulkan: Skia is fetched by the skia-safe Rust crate's own build script (typically a prebuilt binary download), independently of cargo's normal crate-download mechanism. Vendoring crates.io sources does not cover this -- expect these features to still need network access. Not yet validated.
• gettext: requires gettext installed on the system. Not provided by this registry.
• backend-linuxkms: requires libseat installed on the system.
• Bare-metal/freestanding builds (SLINT_FEATURE_FREESTANDING upstream) are not exposed as a feature yet.
• The vendored-crates archive is built from Slint's full workspace Cargo.lock (includes examples/tests/etc., not just the api/cpp dependency graph) for simplicity, at the cost of a larger archive than strictly necessary.

Testing

test/smoketest is a minimal interpreter-based program that compiles a trivial .slint snippet, instantiates it, and reads a property back -- proving the installed package actually works, not just that it configured/compiled/linked. It needs no display server. CI runs it after every vcpkg install slint; to run it yourself against a local install:

cmake -S test/smoketest -B test/smoketest/build \
    -DCMAKE_TOOLCHAIN_FILE=<vcpkg-root>/scripts/buildsystems/vcpkg.cmake
cmake --build test/smoketest/build
./test/smoketest/build/slint_vcpkg_smoketest

Implementation notes / gotchas

Things that weren't obvious while building this, kept here so they don't get rediscovered the hard way:

• The vendor archive's paths already start with vendor/... (it's produced by tar-ing the directory cargo vendor creates). portfile.cmake extracts it into "${SOURCE_PATH}", not "${SOURCE_PATH}/vendor" -- extracting into the latter double-nests it into vendor/vendor/... and every crate lookup fails.
• cargo vendor must cover every optional dependency, not just the ones actually activated. Cargo needs a manifest for every optional dependency listed in Cargo.toml to resolve the full feature graph, even ones your enabled features never turn on. Slint's slint-cpp crate has ESP32-only optional deps (esp-backtrace, esp-println) that are irrelevant to every feature this port exposes, but omitting them from the vendor set still breaks --offline resolution outright. This is why vendor-crates.sh vendors the entire workspace Cargo.lock rather than trying to scope it down to just what api/cpp needs.
• vcpkg's default (static) triplet linkage breaks the build for consumers. Rust static libraries don't propagate their transitive system-library dependencies (e.g. fontconfig, pulled in by the fontique crate) through CMake's exported targets the way a normal C++ static library would. A consumer linking Slint::Slint statically gets undefined reference to Fc* at their link time, not ours. portfile.cmake forces VCPKG_LIBRARY_LINKAGE dynamic to sidestep this, matching Slint's own upstream default (BUILD_SHARED_LIBS=ON) rather than trying to enumerate every transitive system library per enabled feature.
• Testing the vendoring pipeline before publishing a release asset: you don't need a real remote URL to test vcpkg_download_distfile locally. Drop the archive into vcpkg's downloads/ directory under the exact FILENAME the portfile expects (slint-<version>-vendor.tar.zst) -- vcpkg finds it there by hash and skips the network fetch entirely, so you can validate the whole offline build against a placeholder URL before anything is actually published.

Adding a new Slint version

1. Generate and inspect the vendored-crates archive:

   ./scripts/vendor-crates.sh 1.18.0

   This clones the tag, runs cargo vendor --locked, and prints the archive's path and SHA512.

2. Publish that archive as a release asset on this repository, tagged slint-v1.18.0-assets -- not slint-v1.18.0, to avoid implying the tag itself is the Slint release; it only exists to host the vendor archive. This is the one-time network cost per version; end users installing from the registry never pay it.

3. Bump the port and regenerate the versions database:

   ./scripts/add-version.sh 1.18.0 \
       --vendor-url https://github.com/<owner>/slint-vcpkg/releases/download/slint-v1.18.0-assets/slint-1.18.0-vendor.tar.zst \
       --vendor-sha512 <printed by vendor-crates.sh>

   Requires a vcpkg binary on PATH (or VCPKG=/path/to/vcpkg) -- any vcpkg checkout works, it's used purely as a generic versioning tool here.

4. Review the diff (ports/slint/vcpkg.json, ports/slint/portfile.cmake, versions/), test locally with --overlay-ports=./ports, then commit.

Bumping corrosion follows the same shape but without any vendoring step (it never touches cargo), so vcpkg x-add-version after updating its vcpkg.json/portfile.cmake is enough.

Upstreaming

Both ports/corrosion and ports/slint are written to match microsoft/vcpkg's own port conventions, so they could plausibly be proposed there directly:

• ports/corrosion is generic infrastructure, not Slint-specific, and has no network-during-build issue at all -- it's a reasonable standalone contribution regardless of what happens with slint.
• ports/slint still has the residual risk noted above around skia-safe's own network fetching for the renderer-skia* features; the default feature set does not hit that path.