Compile and use FLTK in Windows Environment

Pre-Requisites

To compile the FLTK library and use it within Windows…

💡 Once WinLibs is extracted, ensure the full path to ming64/bin is in your PATH environment variable in Windows. It’s a good idea to test in a command prompt to see if gcc and cmake are found correctly.

Compiling FLTK in Windows

Navigate to the source directory for your FLTK download and run:

    $ cmake -B build
    $ cmake --build build

This will create a build folder, and in the lib folder will be *.a files (Unix-like static libraries). Even though this is in Windows, these unix-like static libraries can be linked against with the WinLibs tools to create a Windows executable (.exe).

Next move the headers (*.h files) from the FL folder in the root directory and into the build folder.

Compiling an FLTK Windows Program

Lastly, to compile your C++ program which uses FLTK, run the below - of course first changing the folder paths to suit!

    $ g++ -I C:\fltk-1.4.3 -L C:\fltk-1.4.3\lib -o myapp sample.cpp -lfltk -luser32 -lgdi32 -lole32 -lcomctl32 -mwindows -lws2_32 -luuid -lgdiplus -lwinspool

It’s a little unfortunate so many things need to be linked against, such as winspool (a component of the Windows operating system responsible for managing print jobs) which is hardly relevant in 2025.

It’s likely one could build FLTK so that you can avoid linking everything but the kitchen sink, but that’s a problem for another day.

Bonus: Linux Cross-Compile

You can compile a Windows FLTK application In linux using x86_64-w64-mingw32-g++

   $ sudo apt-get update
   $ sudo apt-get install mingw-w64

However you must first build a new copy of the FLTK library using mingw. You can’t just use the copy from your Linux distribution package manager. So find a working directory (ie. somewhere in your /home), and perform:

     $ wget https://www.fltk.org/pub/fltk/1.3.5/fltk-1.3.5-source.tar.gz
     $ tar -xzf fltk-1.3.5-source.tar.gz
     $ cd fltk-1.3.5
     $ ./configure --host=x86_64-w64-mingw32 --build=x86_64-linux-gnu
     $ make

There’s no need to run make install, we will just tell x86_64-w64-mingw32-g++ where to look.

And finally, to cross-compile your FLTK application:

$ x86_64-w64-mingw32-g++ gui.cpp -o gui.exe -I/home/foo/fltk-1.3.11 -L/home/foo/fltk-1.3.11/lib -lfltk -luser32 -lgdi32 -lole32 -lcomctl32 -mwindows -
lws2_32 -luuid -lgdiplus -lwinspool -static-libgcc -static-libstdc++

You can then run gui.exe in Wine to confirm correct behaviour.

✨ Hope this tutorial helps!