basisu_wrappers.cpp contains our JavaScript API (implemented via emscripten bindings), which is a thin layer above our encoder and transcoder‘s C++ API’s. As of Basis Universal v2.0 it supports optional WASM multithreading and WASM64.

Prebuilt versions of basis_transcoder.js and basis_transcoder.wasm are included in the build/ folder, and are sufficient for local demos. To build the transcoder yourself, first install emscripten (tutorial) and cmake (download). Then run:

cd webgl/transcoder/build/
emcmake cmake ../
make

Strict Content-Security-Policy (no unsafe-eval)

By default, the generated JavaScript glue uses new Function() to build its embind bindings at runtime. A Content-Security-Policy without 'unsafe-eval' blocks this, and module startup fails with an EvalError. To build glue that never calls eval() or new Function(), add -DNO_DYNAMIC_EXECUTION=ON:

emcmake cmake ../ -DNO_DYNAMIC_EXECUTION=ON
make

This adds -s DYNAMIC_EXECUTION=0 -s EMBIND_AOT=1 to the link flags. The .wasm file does not change. EMBIND_AOT generates the bindings at build time, so JavaScript-to-WASM calls stay as fast as in the default build. The page still needs 'wasm-unsafe-eval' in script-src to compile the WebAssembly module. Use -DEMBIND_AOT=OFF to get the smaller, generic bindings, which are slower per call.