libreoffice-online/wasm/README.no-container.md

Collabora Online as WASM (COWASM)

Before building Collabora Online as WASM you need to build three dependencies: LibreOffice core, Poco, and zstd.

The toolchain used is Emscripten. Versions 2.0.31 and 3.1.30 are known to work. The examples below assume 3.1.30.

Below we assume that the Emscripten environment is already set up, that you have sourced the emsdk_env.sh file in your shell.

Build LibreOffice core

Use the master branch of LibreOffice core. The feature/wasm branch is not needed any longer, all commits to that branch are currently also present in the master branch.

See the static/README.wasm.md file in LibreOffice core, especially the section "Building headless LibreOffice as WASM for use in another product".

Build other Online dependencies

zstd

Build libzstd with assembly code disable, and using the Makefile (didn't try its other build systems):

tar -xzvf ~/Downloads/zstd-1.5.2.tar.gz
cd zstd-1.5.2/
emmake make CC='emcc -pthread -fexceptions -s DISABLE_EXCEPTION_CATCHING=0' CXX='em++ -pthread -fexceptions -s DISABLE_EXCEPTION_CATCHING=0' lib-mt V=1 ZSTD_NO_ASM=1 PREFIX=/opt/zstd.emsc.3.1.30
(cd lib && emmake make install-static install-includes ZSTD_NO_ASM=1 PREFIX=/opt/zstd.emsc.3.1.30)

This will install the zstd headers and libraries in /opt/zstd.emsc.3.1.30.

Poco

Poco requires two patches plus renaming one source file (which actually is from expat but Poco includes). Note that the header Poco/Platform.h maps EMSCRIPTEN to POCO_OS_LINUX. It has both Makefiles and CMake but I couldn't get CMake to work. Online requires a single include directory so "make install" must be used.

Here we assume that the online repo is cloned at $HOME/lo/online, adapt as necessary.

tar -xzvf ~/Downloads/poco-1.12.4-release.tar.gz
cd poco-poco-1.12.4-release
patch -p1 < $HOME/lo/online/wasm/poco-1.12.4-emscripten.patch
mv XML/src/xmlparse.cpp XML/src/xmlparse.c
patch -p0 < $HOME/lo/online/wasm/poco-no-special-expat-sauce.diff
emconfigure ./configure --static --no-samples --no-tests --omit=Crypto,NetSSL_OpenSSL,JWT,Data,Data/SQLite,Data/ODBC,Data/MySQL,Data/PostgreSQL,Zip,PageCompiler,PageCompiler/File2Page,MongoDB,Redis,ActiveRecord,ActiveRecord/Compiler,Prometheus
emmake make CC=emcc CXX=em++  CXXFLAGS="-DPOCO_NO_LINUX_IF_PACKET_H -DPOCO_NO_INOTIFY -pthread -s USE_PTHREADS=1 -fexceptions -s DISABLE_EXCEPTION_CATCHING=0"
make install INSTALLDIR=/opt/poco.emsc.3.1.30

This will install into /opt/poco.emsc.3.1.30.

Build Online itself

# 1. Update the directories in the command below to match your system.
# 2. Make sure that a document called sample.docx exists in the root of
#    the directory set as --with-wasm-additional-files.

./autogen.sh
emconfigure ./configure --disable-werror --with-lokit-path=/home/tml/lo/core-cool-wasm/include --with-lo-path=/home/tml/lo/core-cool-wasm/instdir --with-lo-builddir=/home/tml/lo/core-cool-wasm --with-zstd-includes=/opt/zstd.emsc.3.1.30/include --with-zstd-libs=/opt/zstd.emsc.3.1.30/lib --with-poco-includes=/opt/poco.emsc.3.1.30/include --with-poco-libs=/opt/poco.emsc.3.1.30/lib --host=wasm32-local-emscripten --with-wasm-additional-files=/home/tml/lo/online-hacking/my-sample-docs
emmake make

Running WASM Online

Once the build is done, copy the browser/dist to a safe locataion. E.g. cp -a browser/dist dist_wasm Next, re-configure Online and rebuild with normal config/settings (i.e. without WASM). Alternatively, you may have opted to build WASM in a separate directory. Either way, in the normal Online build directory, copy the wasm dist directory into the browser/dist, like this: cp -a dist_wasm browser/dist/wasm

Now point your browser to https://localhost:9980/browser/c85d8681f3/wasm.html?file_path=/some/unused/path

Notice that as of now, only the default sample.docx will be loaded. But the above steps should get one up and running.