iOS

Note

When developing Slint applications for iOS, you can only use Rust as the programming language.

A Rust-based Slint application can be cross-compiled to iOS and runs on iPhones, iPads, and their respective simulators. This is implemented through the Winit backend and the Skia Renderer.

Prerequisites

• A computer running macOS.
• An up-to-date installation of Xcode ↗.
• Xcodegen ↗.
• Rust ↗
• The Rust device and simulator toolchains. Run rustup target add aarch64-apple-ios and rustup target add aarch64-apple-ios-sim to add them.

Adding iOS Support to an existing Rust Application

The following steps assume that you have a Rust application with Slint prepared. If you’re just getting started, use our Slint Rust Template ↗ to get a minimal application running.

Use XCode to building, deploy, and submit iOS applications to the App Store. Use Xcodegen ↗ to create an Xcode project from a minimal description.

1. Verify that your application compiles for iOS, by running:

cargo build --target=aarch64-apple-ios

bash

2. Create a file called project.yml with the following contents:

name: My App
options:
  bundleIdPrefix: com.company
settings:
  ENABLE_USER_SCRIPT_SANDBOXING: NO
targets:
  MyApp:
    type: application
    platform: iOS
    deploymentTarget: "12.0"
    info:
        path: Info.plist
        properties:
            UILaunchScreen:
                - ImageRespectSafeAreaInsets: false
    sources: []
    postCompileScripts:
      - script: |
          ./build_for_ios_with_cargo.bash slint-rust-template
        outputFileLists:
            $TARGET_BUILD_DIR/$EXECUTABLE_PATH

yml

Adjust the name, bundle id, and other fields as needed.

This configuration file delegates the build process to cargo through a shell script.

Note

The shell script is invoked with the name of the binary that cargo produces. Update it to match the name of your project.

2. In a new file called build_for_ios_with_cargo.bash, paste the following script code:

#!/usr/bin/env bash
# Copyright © SixtyFPS GmbH <info@slint.dev>
# SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0

set -euvx

# Fix up PATH to work around https://github.com/rust-lang/rust/issues/80817 and add cargo.
export PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:$PATH:$HOME/.cargo/bin"

# based on https://github.com/mozilla/glean/blob/main/build-scripts/xc-universal-binary.sh

if [[ "$CONFIGURATION" != "Debug" ]]; then
    CARGO_PROFILE=release
    MAYBE_RELEASE=--release
else
    CARGO_PROFILE=debug
    MAYBE_RELEASE=
fi

# Build with debug info so a dSYM can be produced below. Release builds carry no
# debug info by default, which makes the archive fail validation with a missing
# dSYM for the (cargo-built) executable.
export CARGO_PROFILE_RELEASE_DEBUG="${CARGO_PROFILE_RELEASE_DEBUG:-1}"

# Make Cargo output cache files in Xcode's directories
export CARGO_TARGET_DIR="$DERIVED_FILE_DIR/cargo"

IS_SIMULATOR=0
if [ "${LLVM_TARGET_TRIPLE_SUFFIX-}" = "-simulator" ]; then
  IS_SIMULATOR=1
fi

executables=()
for arch in $ARCHS; do
    case "$arch" in
        arm64)
            if [ $IS_SIMULATOR -eq 0 ]; then
              CARGO_TARGET=aarch64-apple-ios
            else
              CARGO_TARGET=aarch64-apple-ios-sim
            fi
            ;;
        x86_64)
            export CFLAGS_x86_64_apple_ios="-target x86_64-apple-ios"
            CARGO_TARGET=x86_64-apple-ios
            ;;
    esac

    cargo build $MAYBE_RELEASE --target $CARGO_TARGET --bin "$1" "${@:2}"

    executables+=("$DERIVED_FILE_DIR/cargo/$CARGO_TARGET/$CARGO_PROFILE/$1")
done

# Combine executables, and place them at the output path excepted by Xcode
lipo -create -output "$TARGET_BUILD_DIR/$EXECUTABLE_PATH" "${executables[@]}"

# Generate a dSYM for the executable into the folder Xcode collects dSYMs from
# for the archive. Xcode only produces dSYMs for what it compiles, not for this
# cargo-built binary, so without this the archive has no dSYM matching its UUID.
if [ -n "${DWARF_DSYM_FOLDER_PATH:-}" ] && [ -n "${DWARF_DSYM_FILE_NAME:-}" ]; then
    mkdir -p "$DWARF_DSYM_FOLDER_PATH"
    dsymutil "$TARGET_BUILD_DIR/$EXECUTABLE_PATH" -o "$DWARF_DSYM_FOLDER_PATH/$DWARF_DSYM_FILE_NAME"
fi

# Force code signing every run for device builds (non-simulator), unless code
# signing is disabled (e.g. unsigned archive builds with CODE_SIGNING_ALLOWED=NO).
if [ $IS_SIMULATOR -eq 0 ] && [ "${CODE_SIGNING_ALLOWED:-YES}" != "NO" ] && [ -n "${EXPANDED_CODE_SIGN_IDENTITY:-}" ]; then
    codesign --force --sign "${EXPANDED_CODE_SIGN_IDENTITY}" \
             --entitlements "${TARGET_TEMP_DIR}/${PRODUCT_NAME}.app.xcent" \
             "${TARGET_BUILD_DIR}/${EXECUTABLE_PATH}"
fi

bash

3. Make the script executable with chmod +x build_for_ios_with_cargo.bash.

4. Run xcodegen to create My App.xcodeproj, and open it in Xcode. Now you can build, deploy, and debug your iOS application.