FLTK wasm build

[danielc...@gmail.com]

Hi, 

Is there currently a standard or recommended method for compiling FLTK to WebAssembly? 

Thanks!

[Albrecht Schlosser]

On 1/16/26 05:33 danielc...@gmail.com wrote:
> Is there currently a standard or recommended method for compiling FLTK
> to WebAssembly?

There's nothing official, but if I'm not totally wrong you might want to
take a look at
https://github.com/MoAlyousef/fltk_emscripten

[danielc...@gmail.com]

Thanks. 

It would be great to see this included in FLTK 1.5 — an official, streamlined way to compile to WebAssembly would be a very welcome addition.

[Daniel G.]

How cool, I would also like to see an official WASM build (:

> Is there currently a standard or recommended method for compiling FLTK
> to WebAssembly?

Some time ago (with fltk 1.3) I managed to make it run via microwindows (FLTK -> X11 -> microwindows X11 API -> Webbrowser)
https://github.com/ghaerr/microwindows

BR,
Daniel

[danielc...@gmail.com]

It would be nice to have it compile ready in wasm , like ./vcpkg install fltklib:wasm32-emscripten

Regards

[danielc...@gmail.com]

here is a working compile .sh function for wasm:

_build_fltk_wasm() {

local repo_url="https://github.com/MoAlyousef/fltk_wasm32_emscripten.git"

local dir_name="fltk_wasm32_emscripten"

# 1. Verify that the Emscripten SDK environment is active

if ! command -v emcmake &> /dev/null; then

echo "Error: 'emcmake' not found. Please activate your Emscripten SDK first (e.g., source ./emsdk_env.sh)."

return 1

fi

# 2. Clone the repository specifically on the 'emscripten' branch

if [ ! -d "$dir_name" ]; then

echo "Cloning $repo_url (emscripten branch)..."

git clone -b emscripten "$repo_url" || return 1

else

echo "Repository already exists. Switching to emscripten branch and pulling latest..."

cd "$dir_name" || return 1

git checkout emscripten

git pull origin emscripten

cd ..

fi

# 3. Enter directory and clear old build cache

cd "$dir_name" || return 1

rm -rf build_wasm

echo "Configuring FLTK for wasm32 with CMake..."

emcmake cmake -B build_wasm \

-DCMAKE_BUILD_TYPE=Release \

-DFLTK_BUILD_TEST=OFF \

-DFLTK_BUILD_EXAMPLES=OFF \

-DFLTK_BUILD_FLUID=OFF || { cd - > /dev/null; return 1; }

# 4. Build the core FLTK wasm library

echo "Building FLTK wasm library..."

local cpu_count=$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 4)

cmake --build build_wasm --parallel "$cpu_count" || { cd - > /dev/null; return 1; }

echo "Successfully built FLTK for wasm32! Artifacts are located in: $(pwd)/build_wasm"

cd - > /dev/null

}