Safe Rust bindings for the Skia Graphics Library.

Skia Submodule Status: chrome/m138 (upstream changes, our changes).

About

This project provides up to date safe bindings that bridge idiomatic Rust with Skia’s C++ API on desktop and mobile platforms, including GPU rendering backends for Vulkan, Metal, OpenGL, and Direct3D.

Status

Documentation

Because we can’t build on docs.rs, the cargo doc output for skia-safe is manually created and uploaded to rust-skia.github.io.

We (slowly) add more documentation by converting Skia’s Doxygen comments to Rust.

Crate

A prerelease crate is available from crates.io and invoking

cargo add skia-safe

in your project’s folder should get you started. And you might want to take a look at the gl-window example if you plan to render to a window.

On Linux you may run into trouble when OpenSSL libraries are missing. On Debian and Ubuntu they can be installed with:

sudo apt-get install pkg-config libssl-dev

For other platforms, more information is available at the OpenSSL crate documentation.

Platform Support, Build Targets, and Prebuilt Binaries

Because building Skia takes a lot of time and needs tools that may be missing, the skia-bindings crate’s build.rs attempts to download prebuilt binaries from the skia-binaries repository using the curl command line tool.

Platform	Binaries
Windows	x86_64-pc-windows-msvc
Linux Ubuntu 16+ CentOS 7, 8	x86_64-unknown-linux-gnu aarch64-unknown-linux-gnu
macOS	x86_64-apple-darwin aarch64-apple-darwin
Android	aarch64-linux-android x86_64-linux-android
iOS	aarch64-apple-ios x86_64-apple-ios
WebAssembly	wasm32-unknown-emscripten

Wrappers & Codecs & Supported Features

The supported wrappers, Skia codecs, and additional Skia features are documented in the skia-safe package’s readme. Prebuilt binaries are available for most feature combinations.

Building

If the target platform or feature configuration is not available as a prebuilt binary, skia-bindings’ build.rs will try to build Skia and generate the Rust bindings.

For building Skia from source, LLVM, Python 3, and Ninja are required:

LLVM

We recommend the version that comes preinstalled with your platform, or, if not available, the latest official LLVM release. To see which version of LLVM/Clang is installed on your system, use clang --version.

Python 3

The build script probes for python --version and python3 --version and uses the first one that looks like a version 3 executable for building Skia.

Ninja

The build system for Skia. ninja is available as a binary package on all major platforms. Install ninja or ninja-build and make sure it is available PATH with ninja --version.

On macOS

• Install the Command Line Tools for Xcode with

  xcode-select --install

  or download and install the Command Line Tools for Xcode.

• As an alternative to Apple’s XCode LLVM, install LLVM via brew install llvm or brew install llvm and then set PATH, CPPFLAGS, and LDFLAGS like instructed.

  If the environment variables are not set, bindgen will most likely use the wrong libclang.dylib and cause confusing compilation errors (see #228).

On Windows

• Have the latest versions of git and Rust ready.

• Install Visual Studio 2022 Build Tools or one of the other IDE editions. If you installed the IDE, make sure that the Desktop Development with C++ workload is installed.

• Install the latest LLVM distribution.

  If the environment variable LLVM_HOME is not defined, the build script will look for LLVM installations located at C:\Program Files\LLVM\, C:\LLVM\, and %USERPROFILE%\scoop\apps\llvm\current\.

• MSYS2:

  • Install Python 3 with pacman -S python.

• Windows Shell (Cmd.exe):

  • Download and install Python 3 from python.org.

• Install and select the MSVC toolchain:

  rustup default stable-msvc

On Linux

Ubuntu 20+

• LLVM/Clang should be available already, if not, install the latest version.
• If OpenGL libraries are missing, install the drivers for you graphics card, or a mesa package like libgl1-mesa-dev.
• For X11, build with feature x11.
• For Wayland, install libwayland-dev and build with the wayland feature.

For Android

Cross compilation to Android is supported for targeting 64 bit ARM and Intel x86 architectures (aarch64 and x86_64) for API Level 26 (Oreo, Android 8):

We recommend to use cargo apk, but if that does not work for you, following are some instructions on how we build Android targets with GitHub Actions:

For example, to compile for aarch64:

1. Install the Rust target:

   rustup target install aarch64-linux-android

2. Download the r26d NDK (or newer) for your host architecture and unzip it.
3. Compile your project for the aarch64-linux-android target:

On macOS:

export ANDROID_NDK=:path-to-android-ndk-r26d
export PATH=$PATH:$ANDROID_NDK/toolchains/llvm/prebuilt/darwin-x86_64/bin
export CC_aarch64_linux_android=aarch64-linux-android26-clang
export CXX_aarch64_linux_android=aarch64-linux-android26-clang++
export AR_aarch64_linux_android=llvm-ar
export CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER=aarch64-linux-android26-clang

cargo build -vv --target aarch64-linux-android

We don’t support Apple’s Clang to build for Android on macOS, so you need to install LLVM and set the PATH like instructed.

On Linux:

export ANDROID_NDK=:path-to-android-ndk-r26d
export PATH=$PATH:$ANDROID_NDK/toolchains/llvm/prebuilt/linux-x86_64/bin
export CC_aarch64_linux_android=aarch64-linux-android26-clang
export CXX_aarch64_linux_android=aarch64-linux-android26-clang++
export AR_aarch64_linux_android=llvm-ar
export CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER=aarch64-linux-android26-clang

cargo build -vv --target aarch64-linux-android

On Windows the Android NDK Clang executable must be invoked through .cmd scripts:

export ANDROID_NDK=:path-to-android-ndk-r26d
export PATH=$PATH:$ANDROID_NDK/toolchains/llvm/prebuilt/windows-x86_64/bin
export CC_aarch64_linux_android=aarch64-linux-android26-clang.cmd
export CXX_aarch64_linux_android=aarch64-linux-android26-clang++.cmd
export AR_aarch64_linux_android=llvm-ar
export CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER=aarch64-linux-android26-clang.cmd

cargo build -vv --target aarch64-linux-android

Notes:

• At the time of this writing, the Rust compiler will automatically add a -lgcc argument to the linker, which results in a linker error, because newer NDKs do not contain libgcc.a anymore. To fix this, we created a workaround and copy libunwind.a over to libgcc.a. Cargo apk does something similar.
• The CARGO_TARGET_${TARGET}_LINKER environment variable name needs to be all uppercase.
• In some older shells (for example macOS High Sierra), environment variable replacement can not be used when the variable was defined on the same line. Therefore the ANDROID_NDK variable must be defined before it’s used in the PATH variable.
• Rebuilding skia-bindings with a different target may cause linker errors, in that case touch skia-bindings/build.rs will force a rebuild (#10).

For iOS

Compilation to iOS is supported on macOS targeting the iOS simulator (--target x86_64-apple-ios) and 64 bit ARM devices (--target aarch64-apple-ios). The ARM64e architecture is not supported yet.

For WebAssembly

Install emscripten version 3.1.57 or superior and make sure that llvm / clang 16+ is installed. In the examples below, we assume emsdk version 3.1.57 was installed with asdf.

Build with the wasm32-unknown-emscripten target (wasm32-unknown-unknown is unsupported because it is fundamentally incompatible with linking C code:

export EMSDK=~/.asdf/installs/emsdk/3.1.57
export EMCC_CFLAGS="-s ERROR_ON_UNDEFINED_SYMBOLS=0"

cargo build --target wasm32-unknown-emscripten

The EMSDK environment variable must be set to the root of your emscripten SDK.

In EMCC_CFLAGS, -s ERROR_ON_UNDEFINED_SYMBOLS is a workaround to build with emscripten > 2.0.9.

If you want to enable WebGL, you will also have to set MAX_WEBGL_VERSION=2:

export EMSDK=~/.asdf/installs/emsdk/3.1.57
export EMCC_CFLAGS="-s ERROR_ON_UNDEFINED_SYMBOLS=0 -s MAX_WEBGL_VERSION=2"

cargo build --target wasm32-unknown-emscripten --features gl

On MacOS there is a problem with the OS version of ar so you will have to install the GNU version from homebrew:

brew install binutils

Then prepend binutils path for the build. The path depends on your CPU architecture, and can be retrieved with brew info binutils. Here is an example for Apple silicon:

export EMSDK=~/.asdf/installs/emsdk/3.1.57
export EMCC_CFLAGS="-s ERROR_ON_UNDEFINED_SYMBOLS=0"
export PATH="/opt/homebrew/opt/binutils/bin:$PATH"

cargo build --target wasm32-unknown-emscripten

Skia

For situations in which Skia does not build or needs to be configured differently, we support some customization support in skia-bindings/build.rs. For more details take a look at the README of the skia-bindings package.

Please share your build experience so that we can try to automate the build and get to the point where cargo build is sufficient to build the bindings including Skia, and if that is not possible, clearly prompts to what’s missing.

Example Applications

gl-window

An example that opens an OpenGL Window and draws the rust-skia icon with skia-safe (contributed by @nornagon).

cargo run --example gl-window --features gl

On Linux the feature x11 needs to be enabled:

cargo run --example gl-window --features gl,x11

vulkan-window

An example application that opens a Window and renders a blue rectangle using Vulkano (contributed by @samizdatco in #1066)

cargo run --example vulkan-window --features "vulkan,vulkan-window"

To add Vulkan support to your system, the easiest way is to install the LunarG SDK, and enable “System Global Installation” in the installer.

icon

The icon example generates the rust-skia icon in the current directory. It computes the position of all the gear teeth etc. based on parameters such as the number of teeth and wheel radius.

If you were able to build the project, run

cargo run --example icon 512

It has a single optional parameter which is the size in pixels for the PNG file. Without parameters, it’ll produce PNG frames for the animated version.

skia-org

The other examples are taken from Skia’s website and ported to the Rust API.

cargo run -- [OUTPUT_DIR]

to generate some Skia drawn PNG images in the directory OUTPUT_DIR. To render with OpenGL, use

cargo run --features gl -- [OUTPUT_DIR] --driver gl

And to show the drivers that are supported

cargo run -- --help

Example Images

Fill, Radial Gradients, Stroke, Stroke with Gradient, Transparency:

Fill, Stroke, Text:

Sweep Gradient:

Dash Path Effect:

For more, you may take a look at the rust-skia.github.io repository.

This project needs contributions!

If you’d like to help with the bindings, take a look at the Wiki to get started and create an issue to prevent duplicate work. For smaller tasks, grep for “TODO”s in the source code. And for heroic work, check out the label help wanted. And if you like to help making the Rust API nicer to use, look out for open issues with the label api ergonomics.

More details can be found at CONTRIBUTING.md.

Notable Contributions

• Denis Kolodin (@DenisKolodin) contributed build support for Android.
• Alberto González Palomo (@AlbertoGP) designed the Rust-Skia Logo and the example program that renders it.
• Luper Rouch (@flupke, sponsored by Jitter) added build support for the wasm32-unknown-emscripten target.
• Osei Fortune (@triniwiz) and Savchenko Ivan (@Aiving) contributed rendering SVG files.

Maintainers

• LongYinan (@Brooooooklyn)
• Armin (@pragmatrix)

License

MIT