Compile and Install FLTK

1. Download latest versions of FLTK: https://www.fltk.org/
2. Extract in path, e.g. c:\opt\fltk\fltk-1.4.1
3. Download TDM-GCC: https://jmeubank.github.io/tdm-gcc/download/
4. Install in path e.g. c:\opt\TDM-GCC-64 or when Dev-C++ is installed without TDM  in the subdirectory TDM-GCC-64
5. Download and install cmake: https://cmake.org/download/
6. Extract to path e.g. c:\opt\cmake-3.31.3-windows-x86_64

Generate fltk makefiles:

Select the install path of FLTK and open a cmd window.
Run c:\opt\TDM-GCC-64\mingvars.bat
Start cmake-gui: c:\opt\cmake-3.31.3-windows-x86_64\bin\cmake-gui.exe

Set browse source code: c:/opt/fltk/fltk-1.4.1
Set build binaries : c:/opt/fltk/fltk-1.4.1-build

Click configure
Set generator for the project to MinGW Makefiles
Set C to c:\opt\TDM-GCC-64\bin\gcc
Set C++ to c:\opt\TDM-GCC-64\bin\gcc++
Set MAKE_INSTALL_PREFIX to c:\opt\fltk-1.4.1-install
Click finish, now configuration is busy….

Click configure again, all red background disappear
Check box if you want FLTK_BUILD_EXAMPLES, FLTK:SHARED_LIBS, etc….
Click configure again
Click generate, close cmake-gui
Run mingw32-make install

Takes time, that’s it.