SKIA EXAMPLE PROJECT

This is an example CMakeLists based that integrates Google's Skia library.

Skia is an open source 2D graphics library which provides common APIs that work across a variety of hardware and software platforms. It serves as the graphics engine for Google Chrome and ChromeOS, Android, Flutter, and many other products.

This repo has only one main.cpp file that will generate an output.png file as shown below using skia's official api usage page

Install depot_tools and Git

Follow the instructions on Installing Chromium’s depot_tools to download depot_tools (which includes gclient, git-cl, and Ninja). Below is a summary of the necessary steps.

mkdir skia_setup && cd skia_setup

git clone 'https://chromium.googlesource.com/chromium/tools/depot_tools.git'
export PATH="${PWD}/depot_tools:${PATH}"

NOTE: depot_tools will also install Git on your system, if it wasn’t installed already

Install ninja

Ninja can be supplied using gclient or with bin/fetch-ninja.

Clone the Skia repository

Skia can either be cloned using git or the fetch tool that is installed with depot_tools.

cd skia_setup
git clone https://skia.googlesource.com/skia.git
cd skia
python3 tools/git-sync-deps
bin/fetch-ninja

Add the following to the either ~/.bash_profile or ~/.bashrc to add emsdk to the path.

source "/home/bot/rds_ws/src/skia_setup/skia/third_party/externals/emsdk/emsdk_env.sh"

RECOMMENDED When running the above commands and syncing deps using commands python3 tools/git-sync-deps you might face Thread failure. So try to run the command multiple times and see if it works. In case Thread failure is still persistent then follow the below steps.

Instead of cloning, we'll use fetch tool from depot_tools to clone skia and all the dependencies. Make sure you export the depot_tools to PATH

export PATH="${PWD}/depot_tools:${PATH}"

After exporting, run the following commands:

fetch skia

Once the fetch process is complete, run the following command to install any other dependencies

cd skia
tools/install_dependencies.sh

Now we have all the necessary tools and dependencies to successfully build skia.

Generate Compilation Rules

Thanks to asperite for the next steps on generating compilation rules for skia. Basically there are two options:

Clang

Some more tools to install if using clang for builing

sudo apt-get install libc++-dev libc++abi-dev
sudo apt-get install clang

1. Generate rules for compiling skia using clang (recommended if you have clang compiler):

    gn gen out/Release-clang --args='is_debug=false is_official_build=true skia_use_system_expat=false skia_use_system_icu=false skia_use_system_libjpeg_turbo=false skia_use_system_libpng=false skia_use_system_libwebp=false skia_use_system_zlib=false skia_use_sfntly=false skia_use_freetype=true skia_use_harfbuzz=true skia_pdf_subset_harfbuzz=true skia_use_system_freetype2=false skia_use_system_harfbuzz=false cc="clang" cxx="clang++" extra_cflags_cc=["-stdlib=libc++"] extra_ldflags=["-stdlib=libc++"]'

G++

2. Generate rules for compiling skia using the default compiler (usually g++):

   gn gen out/Release-gcc --args="is_debug=false is_official_build=true skia_use_system_expat=false skia_use_system_icu=false skia_use_system_libjpeg_turbo=false skia_use_system_libpng=false skia_use_system_libwebp=false skia_use_system_zlib=false skia_use_sfntly=false skia_use_freetype=true skia_use_harfbuzz=true skia_pdf_subset_harfbuzz=true skia_use_system_freetype2=false skia_use_system_harfbuzz=false"

Final step:

# clang
ninja -C out/Release-clang skia modules

#gcc
ninja -C out/Release-gcc skia modules

Visit official skia website for more info on build process.

Build Skia_Example project

Now that we are done building skia, we can build this example repo showing how to use skia in your project.

NOTE: Assuming that both skia_setup and skia_example are on the same level in the directory. If not then make sure they are because the path for skia in CMakeLists.txt for the skia_example is set in such a way that it looks for skia on the same level as skia_example.

Also this example is built using the clang compilation rools instead of g++.

set(SKIA_DIR ${CMAKE_SOURCE_DIR}/../skia_setup/skia)

Builid skia_example

cd skia_example
mkdir build && cd build

cmake ..
make

# To run executable
./skia_example

The above commands should generate a skia_example executable inside the build directory, when run will generate the output.png file.