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.
* 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.)
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.
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"
Mac users may want to pass --ide=xcode to gn gen to generate an Xcode project.
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".
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
Skia offers several features that make use of third-party libraries, like libpng, libwebp, or libjpeg-turbo to decode images, or ICU and sftnly to subset fonts. All these third-party dependencies are optional, and can be controlled by a GN argument that looks something like skia_use_foo for appropriate foo.
Most of these third-party dependencies can also be satisfied by pre-built system libraries. If skia_use_foo is enabled, turn on skia_use_system_foo to build and link Skia against the headers and libaries found on the normal system paths. Remember, you can use extra_cflags and extra_ldflags to add include or library paths if needed.
By default Skia will attempt to build and embed its own copies of these third-party libraries. This configuration is for development and testing only. We do not recommend shipping Skia this way. Note however, this is the only configuration of Skia that receives significant testing.