A SwiftUI-like framework for creating cross-platform apps in Swift (using Gtk 4 as the backend).

This package is still quite a work-in-progress so don’t expect it to be very useful or stable yet.

NOTE: SwiftCrossUI does not attempt to replicate SwiftUI’s API because SwiftCrossUI is intended to be simpler than SwiftUI. However, many concepts from SwiftUI should still be transferrable.

Example

Here’s a simple example app demonstrate how easy it is to get started with SwiftCrossUI:

import SwiftCrossUI

class CounterState: Observable {
    @Observed var count = 0
}

@main
struct CounterApp: App {
    let identifier = "dev.stackotter.CounterApp"
    
    let state = CounterState()
    
    let windowProperties = WindowProperties(title: "CounterApp")
    
    var body: some ViewContent {
        HStack {
            Button("-") { state.count -= 1 }
            Text("Count: \(state.count)")
            Button("+") { state.count += 1 }
        }
    }
}

To run this example, run these commands:

git clone https://github.com/stackotter/swift-cross-ui
cd swift-cross-ui
swift run CounterExample

To see all of the examples, run these commands:

swift run CounterExample
swift run RandomNumberGeneratorExample
swift run WindowPropertiesExample
swift run GreetingGeneratorExample
swift run FileViewerExample
swift run NavigationExample

Documentation

Here’s the documentation site. Keep in mind that the project is still very much a work-in-progress, proper documentation and tutorials will be created once the project has matured a bit, because otherwise I have to spend too much time keeping the documentation up-to-date.

Dependencies

1. Swift 5.5 or higher
2. Gtk 4
3. clang (only required on Linux)

macOS: Installing Gtk 4

Install Gtk 4 using HomeBrew or the package manager of your choice.

brew install gtk4

Linux: Installing Gtk 4 and Clang

Install Gtk 4 and Clang using apt or the package manager of your choice. On most GNOME-based systems, Gtk should already be installed (although you should verify that it’s Gtk 3).

sudo apt install libgtk-4-dev clang

Windows (experimental): Installing Gtk 4 through vcpkg

Installing Gtk 4 using vcpkg is the supported method for setting up SwiftCrossUI on Windows.

Install vcpkg

git clone https://github.com/microsoft/vcpkg C:\vcpkg
C:\vcpkg\bootstrap-vcpkg.bat

NOTE: It’s important to install vcpkg to the root of C: or any other drive due to limitations of the Gtk build system.

Install Gtk 4 globally (recommended)

Run the following command to install Gtk 4 globally. This can take 45 minutes or longer depending on your machine. Running this command in the root of your drive will ensure that vcpkg doesn’t run in manifest mode.

C:\vcpkg\vcpkg.exe install gtk --triplet x64-windows

After installation, you must make the following changes to your environment variables:

1. Set the PKG_CONFIG_PATH environment variable to C:\vcpkg\installed\x64-windows\lib\pkgconfig. This is only required for building.
2. Add C:\vcpkg\installed\x64-windows\bin to your Path environment variable. This is only required for running.

If installing globally fails, try deleting C:\vcpkg and starting over, otherwise file an issue to the vcpkg repository and let me know at stackotter@stackotter.dev.

Install Gtk 4 with project manifest (more unreliable)

NOTE: If the absolute path to your project contains spaces, it is possible that vcpkg will break, and installing globally will be a more reliable strategy.

You can install Gtk 4 inside your package workspace, to have a package-specific dependency store. First, create a vcpkg.json at your package root. You can download the vcpkg.json file from this repo, or create it yourself;

{
    "name": "swift-cross-ui",
    "version-string": "main",
    "dependencies": ["gtk"]
}

Change directory to your package root, then run the following command to build and install dependencies.

C:\vcpkg\vcpkg.exe install --triplet x64-windows

After installation, you must make the following changes to your environment variables:

1. Set the PKG_CONFIG_PATH environment variable to PACKAGE_ROOT\vcpkg_installed\x64-windows\lib\pkgconfig to allow SwiftPM to consume the installed packages.
2. Add C:\path\to\your\project\vcpkg_installed\x64-windows\bin to your PATH environment variable.

If you run into issues (potentially related to libsass), try installing globally instead (see above).

Distribute SwiftCrossUI Apps

vcpkg_installed\<triplet>\bin contains all required DLLs for running a SwiftCrossUI application on Windows, but not all of them are necessary.

To identify which of them are required, you can use the Dependencies tool to inspect the compiled executable, and copy all vcpkg-installed DLLs along with the executable for distribution.

Usage

Just add SwiftCrossUI as a dependency in your Package.swift. See below for an example package manifest:

import PackageDescription

let package = Package(
  name: "Example",
  dependencies: [
    .package(url: "https://github.com/stackotter/swift-cross-ui", .branch("main"))
  ],
  targets: [
    .executableTarget(
      name: "Example",
      dependencies: [
        .product(name: "SwiftCrossUI", package: "swift-cross-ui")
      ]
    )
  ]
)