fontconfig v0.5.0
fontconfigjs
This is essentially a stripped-down version of FontConfig compiled to WebAssembly with a Javascript API that works in nodejs and the browser.
The FontConfig source tree is mostly intact for ease of merging with future versions.
How?
const FontConfig = await require('fontconfig');
FontConfig.addFont('/Library/Fonts/Comic Sans MS.ttf');
FontConfig.addFont('/Library/Fonts/Futura.ttc');
FontConfig.addFont('/Library/Fonts/GillSans.ttc');
FontConfig.sort({
family: "Gill Sans",
weight: FontConfig.FC_WEIGHT_LIGHT
});
// returns this:
[
{ file: '/Library/Fonts/GillSans.ttc', index: 7 },
{ file: '/Library/Fonts/GillSans.ttc', index: 6 },
{ file: '/Library/Fonts/Comic Sans MS.ttf', index: 0 },
{ file: '/Library/Fonts/Futura.ttc', index: 2 }
]
Unlike the full FontConfig library, it does not read configuration files for font lookup rules or font search directories. The FontConfig APIs for adding fonts and querying fonts are exposed instead, which the Javascript wrapper makes calls to.
Instead of using FreeType to read fonts, fontkit is used.
API
FontConfig.sort()
Returns the best possible cascade list of fonts based on a description (with later fonts suited to use when previous fonts don't have proper coverage).
The family object passed to FontConfig.sort
looks like:
family
(string) (required)weight
(number)
For more details on the individual values, continue below.
Weights
FontConfig.FC_WEIGHT_THIN
FontConfig.FC_WEIGHT_EXTRALIGHT
FontConfig.FC_WEIGHT_ULTRALIGHT
FontConfig.FC_WEIGHT_LIGHT
FontConfig.FC_WEIGHT_DEMILIGHT
FontConfig.FC_WEIGHT_SEMILIGHT
FontConfig.FC_WEIGHT_BOOK
FontConfig.FC_WEIGHT_REGULAR
FontConfig.FC_WEIGHT_NORMAL
FontConfig.FC_WEIGHT_MEDIUM
FontConfig.FC_WEIGHT_DEMIBOLD
FontConfig.FC_WEIGHT_SEMIBOLD
FontConfig.FC_WEIGHT_BOLD
FontConfig.FC_WEIGHT_EXTRABOLD
FontConfig.FC_WEIGHT_ULTRABOLD
FontConfig.FC_WEIGHT_BLACK
FontConfig.FC_WEIGHT_HEAVY
FontConfig.FC_WEIGHT_EXTRABLACK
FontConfig.FC_WEIGHT_ULTRABLACK
Enabling debugging
Thanks to WASI, you can set the environment variable FC_DEBUG
1 just like regular font config. This will print information to stdout, but only if
- You built with
-DWASI_RUNTIME
(see below) - You're using nodejs 13.3.0 or newer
- You run nodejs with
--experimental-wasi-unstable-preview1 --experimental-wasm-bigint
The WASM distributed in NPM is not built with debugging calls, though there are probably WASI runtimes available for web browsers.
1As of node 13.10 this doesn't seem to be implemented yet, so you have to manually edit src/fcdbg.c
until it's fixed.
Building the C parts
These instructions are for macOS, but they should be similar for Linux. The steps are familiar to anyone who has done cross-compilation before, but the first few are WebAssembly-specific.
LLVM_PATH=/usr/local/Cellar/llvm/9.0.0/bin
. or somewhere else appropriate. You do need a recent version of LLVM that supports WebAssembly.git clone git@github.com:chearon/wasi-libc.git
. The upstream version builds with symbols that introduce runtime dependencies.cd wasi-libc
make WASM_CC=$LLVM_PATH/clang WASM_AR=$LLVM_PATH/llvm-ar WASM_NM=$LLVM_PATH/llvm-nm
WASI_SYSROOT=$(pwd)/sysroot
- Download
wasi-sdk
builtins and copylibclang_rt.builtins-wasm32.a
to/usr/local/Cellar/llvm/9.0.0/lib/clang/9.0.0/lib/wasi/
(or wherever you installed your compiler in step 1). export LIBTOOLIZE=glibtoolize
(these next 3 steps might be macOS-specific)export GETTEXTIZE=/usr/local/opt/gettext/bin/gettextize
export AUTOPOINT=/usr/local/opt/gettext/bin/autopoint
export CC=$LLVM_PATH/clang
export CFLAGS=-target wasm32-wasi --sysroot=$WASI_SYSROOT
(for debugging, you can also add-DWASI_RUNTIME
to see FontConfig logging)export AR=$LLVM_PATH/llvm-ar
export RANLIB=$LLVM_PATH/llvm-ranlib
- Patch config.sub:
grep -q -F -- '-wasi' config.sub || sed -i -e 's/-nacl\*)/-nacl*|-wasi)/' config.sub
(thank you so much, Frank Denis) ./autogen.sh --host=wasm32-wasi
make
$LLVM_PATH/wasm-ld -L$WASI_SYSROOT/lib/wasm32-wasi --no-entry --export-all -lc --whole-archive src/.libs/libfontconfig.a -o lib.wasm