GN

GN is a new meta-build system originally designed to replace GYP in Chromium.

You can build Skia using GN in a limited number of configurations. We expect that as that limited number rises, GN will become the preferred, and then only, way to build Skia.

Supported Features

* Linux, Mac, Android, Windows
* Software, GL, Vulkan rendering
* libskia.a, libskia.so
* DM, nanobench, a few other tools
* (Pretty much everything but iOS and some complicated tools.)

Quickstart

Please check out Skia using the instructions in one of the other quick start guides. We diverge where they'd first run some command with "gyp" in it.

# After gclient sync, run fetch-gn to make sure you have GN.
gclient sync && bin/fetch-gn

# Run GN to generate your build files.
gn gen out/Static --args='is_official_build=true'
gn gen out/Shared --args='is_official_build=true is_component_build=true'

# GN allows fine-grained settings for developers and special situations.
gn gen out/Debug
gn gen out/Release  --args='is_debug=false'
gn gen out/Clang    --args='cc="clang" cxx="clang++"'
gn gen out/Cached   --args='cc_wrapper="ccache"'
gn gen out/RTTI     --args='extra_cflags_cc="-frtti"'

# To see all the current GN arguments, run
gn args out/Debug --list

# Build
ninja -C out/Static
ninja -C out/Shared
ninja -C out/Debug
ninja -C out/Release
ninja -C out/Clang
ninja -C out/Cached
ninja -C out/RTTI

From here everything is pretty much business as usual.

Android

To build Skia for Android you need an Android NDK.

If you do not have an NDK and have access to CIPD, you can use one of these commands to fetch the NDK our bots use:

python infra/bots/assets/android_ndk_linux/download.py  -t /tmp/ndk
python infra/bots/assets/android_ndk_darwin/download.py -t /tmp/ndk

When generating your GN build files, pass the path to your ndk and your desired target_cpu:

gn gen out/arm      --args='ndk="/tmp/ndk" target_cpu="arm"'
gn gen out/arm64    --args='ndk="/tmp/ndk" target_cpu="arm64"'
gn gen out/mips64el --args='ndk="/tmp/ndk" target_cpu="mips64el"'
gn gen out/mipsel   --args='ndk="/tmp/ndk" target_cpu="mipsel"'
gn gen out/x64      --args='ndk="/tmp/ndk" target_cpu="x64"'
gn gen out/x86      --args='ndk="/tmp/ndk" target_cpu="x86"'

Other arguments like is_debug and is_component_build continue to work. Tweaking ndk_api gives you access to newer Android features like Vulkan.

To test on an Android device, push the binary and resources over, and run it as normal. You may find bin/droid convenient.

ninja -C out/arm64
adb push out/arm64/dm /data/local/tmp
adb push resources /data/local/tmp
adb shell "cd /data/local/tmp; ./dm --src gm --config gpu"

Windows

Skia should build on Windows with Visual Studio 2015 Update 3. No other version, older or newer, is supported. If you use Visual Studio, you may want to pass --ide=vs to gn gen to generate all.sln.

The bots use a packaged toolchain, which you may be able to download like this:

python infra/bots/assets/win_toolchain/download.py -t C:/toolchain

If you pass that downloaded path to GN via windk, you can build using that toolchain instead of your own from Visual Studio. This toolchain is the only way we support 32-bit builds, by also setting target_cpu="x86".

CMake

We have added a GN-to-CMake translator mainly for use with IDEs that like CMake project descriptions. This is not meant for any purpose beyond development.

gn gen out/config --ide=json --json-ide-script=../../gn/gn_to_cmake.py