What are some GUI development tools that include Fortran code?

Hi, how are you?

I am a student who is currently working on numerical analysis.

Generally, in the field of numerical analysis, the calculation speed is

It is known to be the fastest, so we are developing code using Fortran.

However, there are some parts that are difficult to see regarding the initial value and setting.

I'd like to organize the related part with the GUI.

The GUI is implemented using C++, and the internal numerical analysis part is implemented using Fortran.

I'd like to have the calculations carried out.

GUI doesn't insist on C++, but is looking for more.

If you want to develop a GUI program like that, what kind of tool should you use?

I'd like to get advice from the experts in the field.