gir2swift

A simple GIR parser in Swift for creating Swift types for a .gir file

Getting Started

To start a project that uses Swift wrappers around low-level libraries that utilise gobject-introspection, you need to create some scripts that use gir2swift to convert the information within gobject-introspection XML (.gir) files into Swift. Here is a brief overview of the basic steps:

1. Install the prerequisites on your system (see Prerequisites below)
2. Compile gir2swift (see Building below)
3. Create a Swift Package Manager module that contains a system target for your underlying low-level library and a library target for the Swift Wrapper library that you want to build
4. Create the necessary Module files (see Module Files below)
5. Create a script that runs gir2swift (see Usage below) and then builds your project using swift build
6. If the build phase fails (more likely than not), add code that patches the generated Swift source files (e.g. using awk or sed) to correct the errors the compiler complains about

What is new?

As of version 12.2, init(raw:) is now required by the protocol and init(retainingRaw:) is required for classes, closing PR#6.

Version 12 pulls in PR#10, addressing several issues:

• Improvements to the Build experience and LSP rhx/SwiftGtk#34
• Fix issues with LLDB rhx/SwiftGtk#39
• Controversial: Implicitly marks all declarations named "priv" as if they had attribute private=1
• Prevents all "Private" records from generating unless generated in their instance record
  • -a option generates all records
• Introduces CI
• For Class metadata types no longer generates class wrappers. Ref structs now contain static method which returnes the GType of the class and instance of the Class metatype wrapped in the Ref struct.
• Adds final class GWeak where T could be any Ref struct of a type which supports ARC. This class is a property wrapper which contains weak reference to any instance of T. This is especially beneficial for capture lists.
• Adds support for weak observation.
• Constructors and factories of GObjectInitiallyUnowned classes now consume floating reference upon initialisation as advised by the GObject documentation

Partially implemented:

• Typed signal generation. Issues shown in rhx/SwiftGtk#35 hat remain to be addressed are listed here: mikolasstuchlik/gir2swift#2.

Other Notable changes

Version 11 introduces a new type system into gir2swift, to ensure it has a representation of the underlying types. This is necessary for Swift 5.3 onwards, which requires more stringent casts. As a consequence, accessors can accept and return idiomatic Swift rather than underlying types or pointers. This means that a lot of the changes will be source-breaking for code that was compiled against libraries built with earlier versions of gir2swift.

• Parameters use idiomatic Swift names (e.g. camel case instead of snake case, splitting out of "for", "from", etc.)
• Requires Swift 5.2 or later
• Uses the namespace referenced in the gir file
• Wrapper code is now @inlinable to enable the compiler to optimise away most of the wrappers
• Parameters and return types use more idiomatic Swift (e.g. Ref wrappers instead of pointers, Int instead of gint, etc.)
• Functions that take or return records now are templated instead of using the type-erased Protocol
• ErrorType has been renamed GLibError to ensure it neither clashes with Swift.Error nor the GLib.ErrorType scanner enum
• Parameters or return types for records/classes now use the corresponding, lightweight Swift Ref wrapper instead of the underlying pointer

Usage

Synopsis

gir2swift [-v][-s][-m module_boilerplate.swift]{-p file.gir}[file.gir ...]

Description

gir2swift takes the information from a gobject-introspection XML (file.gir) file and creates corresponding Swift wrappers. When reading the .gir file, gir2swift also reads a number of Module Files that you create with additional information.

The following options are available:

-m Module.swift Add Module.swift as the main (hand-crafted) Swift file for your library target.

-o directory Specify the output directory to put the generated files into.

-p pre.gir Add pre.gir as a pre-requisite .gir file to ensure the types in file.gir are known

-s Create a single .swift file per class

-v Produce verbose output.

Examples

The following command generates a Swift Wrapper in Sources/GIO from the information in /usr/share/gir-1.0/Gio-2.0.gir, copying the content from Gio-2.0.module and taking into account information in GLib-2.0.gir and GObject-2.0.gir:

	gir2swift -o Sources/GIO -m Gio-2.0.module -p /usr/share/gir-1.0/GLib-2.0.gir -p /usr/share/gir-1.0/GObject-2.0.gir /usr/share/gir-1.0/Gio-2.0.gir

The Gio-2.0.module file would need to contain the code that you would want to manually add to your Swift module, for example:

import CGLib
import GLib
import GLibObject

public struct GDatagramBased {}
public struct GUnixConnectionPrivate {}
public struct GUnixCredentialsMessagePrivate {}
public struct GUnixFDListPrivate {}
public struct GUnixFDMessagePrivate {}
public struct GUnixInputStreamPrivate {}
public struct GUnixOutputStreamPrivate {}
public struct GUnixSocketAddressPrivate {}

func g_io_module_load(_ module: UnsafeMutablePointer<GIOModule>) {
    fatalError("private g_io_module_load called")
}

func g_io_module_unload(_ module: UnsafeMutablePointer<GIOModule>) {
    fatalError("private g_io_module_unload called")
}

Also you would need a corresponding preamble file Gio-2.0.preamble that imports the necessary low-level libraries, e.g.:

import CGLib
import GLib
import GLibObject

Module Files

In addition to reading a given Module.gir file, gir2swift also reads a number of module files from the current working directory that contain additional information. These module files need to have the same name as the .gir file, but have a different file extension:

Module.preamble

This file contains the Swift code that you need to as the preamble for every generated .swift file (e.g. the import statements for all the modules you want to import).

Module.blacklist

This file contains the symbols (separated by newline) that you want to suppress in your output. Here you should include all the symbols in the .gir file that the Swift compiler cannot import from the relevant C language headers.

Module.whitelist

This file contains the symbols (separated by newline) that would otherwise be suppressed (e.g. because gir2swift thinks they are duplicates), but you would like to include in the gir2swift output.

Module.verbatim

Normally, gir2swift tries to translate constants from C to Swift, as per the definitions in the .gir files. Names of constants listed (and separated by newline) in this file will not be translated.

Prerequisites

Swift

To build, you need at least Swift 5.2 (Swift 5.3 onwards should work fine), download from https://swift.org/download/ -- if you are using macOS, make sure you have the command line tools installed as well). Test that your compiler works using swift --version, which should give you something like

$ swift --version
Apple Swift version 5.3.2 (swiftlang-1200.0.45 clang-1200.0.32.28)
Target: x86_64-apple-darwin20.3.0

on macOS, or on Linux you should get something like:

$ swift --version
Swift version 5.3.2 (swift-5.3.2-RELEASE)
Target: x86_64-unknown-linux-gnu

LibXML 2.9.4 or higher

These Swift wrappers have been tested with libxml-2.9.4 and 2.9.9. They should work with higher versions, but YMMV. Also make sure you have gobject-introspection and its .gir files installed.

macOS

On current versions of macOS, you need to install libxml2 using HomeBrew (the version that comes with the system does not include the necessary development headers -- for HomeBrew setup instructions, see http://brew.sh):

brew update
brew install libxml2 gobject-introspection

Linux

Ubuntu

On Ubuntu 16.04, 18.04 and 20.04, you can use the gtk that comes with the distribution. Just install with the apt package manager:

sudo apt update
sudo apt install libxml2-dev gobject-introspection libgirepository1.0-dev

Fedora

On Fedora 29, you can use the gtk that comes with the distribution. Just install with the dnf package manager:

sudo dnf install libxml2-devel gobject-introspection-devel

Building

Normally, you don't build this package directly, but you embed it into your own project (see 'Embedding' below). However, you can build and test this module separately to ensure that everything works. Make sure you have all the prerequisites installed (see above). After that, you can simply clone this repository and build the command line executable (be patient, this will download all the required dependencies and take a while to compile) using

git clone https://github.com/rhx/gir2swift.git
cd gir2swift
./build.sh

Xcode

On macOS, you can build the project using Xcode instead. To do this, you need to create an Xcode project first, then open the project in the Xcode IDE:

./xcodegen.sh
open gir2swift.xcodeproj

After that, use the (usual) Build and Test buttons to build/test this package.

Troubleshooting

Here are some common errors you might encounter and how to fix them.

Old Swift toolchain or Xcode

If you get an error such as

$ ./build.sh 
error: unable to invoke subcommand: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-package (No such file or directory)

this probably means that your Swift toolchain is too old. Make sure the latest toolchain is the one that is found when you run the Swift compiler (see above).

If you get an older version, make sure that the right version of the swift compiler is found first in your PATH. On macOS, use xcode-select to select and install the latest version, e.g.:

sudo xcode-select -s /Applications/Xcode.app
xcode-select --install

Known Issues

• The new build system scripts do not support directory paths with spaces (e.g. the My Drive directory used by Google Drive File Stream). As a workaround, use the old build scripts, e.g. ./build.sh instead of run-gir2swift.sh and swift build to build a package.
• BUILD_DIR is not suported in the new build system.