ROOT installation with CEF

Compilation with CEF support

See details about Chromium Embedded Framework

1. Current code tested with CEF3 branch 5304, Chromium 107 (November 2022) Some older CEF versions (like 4638 or 4692) may also be supported.
2. Download binary code from https://cef-builds.spotifycdn.com/index.html and unpack it in directory without spaces and special symbols:

$ mkdir /d/cef
$ cd /d/cef/
$ wget https://cef-builds.spotifycdn.com/cef_binary_107.1.11%2Bg26c0b5e%2Bchromium-107.0.5304.110_linux64_minimal.tar.bz2
$ tar cef_binary_107.1.11+g26c0b5e+chromium-107.0.5304.110_linux64_minimal.tar.bz2

3 Install prerequisites - see comments in package CMakeLists.txt. For the linux these are: build-essential, libgtk3.0-dev

1. Compile CEF to produce libcef_dll_wrapper:

$ cd /d/cef/cef_binary_107.1.11+g26c0b5e+chromium-107.0.5304.110_linux64_minimal
$ mkdir build
$ cd build
$ cmake ..
$ make -j libcef_dll_wrapper

1. Set CEF_ROOT variable to unpacked directory:

$ export CEF_ROOT=/d/cef/cef_binary_107.1.11+g26c0b5e+chromium-107.0.5304.110_linux64_minimal

1. When configure ROOT compilation with cmake -Dwebgui=ON -Dcefweb=ON ..., CEF_ROOT shell variable should be set appropriately. During compilation library $ROOTSYS/lib/libROOTCefDisplay.so and executable $ROOTSYS/bin/cef_main should be created. Also check that several files like icudtl.dat, v8_context_snapshot_blob.bin, snapshot_blob.bin copied into ROOT library directory
2. Run ROOT with --web=cef argument to use CEF web display like:

$ root --web=cef $ROOTSYS/tutorials/rcanvas/rh2.cxx

Compile libcef_dll_wrapper on Windows

1. Download binary win32 build like https://cef-builds.spotifycdn.com/cef_binary_95.7.12%2Bg99c4ac0%2Bchromium-95.0.4638.54_windows32.tar.bz2
2. Extract in directory without spaces like C:\Soft\cef
3. Modify cmake/cef_variables.cmake to set dynamic linking, replace "/MT" by "/MD" in approx line 389
4. Start "x86 Native tools Command Prompt for VS 2019". Do:

   $ cd C:\Soft\cef
   $ mkdir build
   $ cd build
   $ cmake -G"Visual Studio 16 2019" -A Win32 -Thost=x64 ..
   $ cmake --build . --config Release --target libcef_dll_wrapper

5. Before compiling ROOT, set CEF_ROOT=C:\Soft\cef variable

Using plain CEF in ROOT batch mode on Linux

Default CEF builds, provided by https://cef-builds.spotifycdn.com/index.html, do not include support of Ozone framework, which the only support headless mode in CEF. To run ROOT in headless (or batch) made with such CEF distribution, one can use Xvfb server. Most simple way is to use xvfb-run utility like:

$ xvfb-run --server-args='-screen 0, 1024x768x16'  root.exe -l --web=cef $ROOTSYS/tutorials/rcanvas/rline.cxx -q

Or run Xvfb before starting ROOT:

$ Xvfb :99 &
$ export DISPLAY=:99
$ root.exe -l --web=cef $ROOTSYS/tutorials/rcanvas/rline.cxx -q

Compile CEF with ozone support

Since March 2019 one can compile CEF without X11, but such builds not provided. Therefore to be able to use real headless mode in CEF, one should compile it from sources. On CEF build tutorial one can find complete compilation documentation. Several Ubuntu distributions are supported by CEF, all others may require extra work. Once all depndencies are installed, CEF with ozone support can be compiled with following commands:

$ export GN_DEFINES="is_official_build=true use_sysroot=true use_allocator=none symbol_level=1 is_cfi=false use_thin_lto=false use_ozone=true"
$ python automate-git.py --download-dir=/home/user/cef --branch=4638 --minimal-distrib --client-distrib --force-clean --x64-build --build-target=cefsimple

With little luck one get prepared tarballs in /home/user/cef/chromium/src/cef/binary_distrib. Just install it in the same way as described before in this document. ROOT will automatically detect that CEF build with ozone support and will use it for both interactive and headless modes.