main.fld

# data file for the Fltk User Interface Designer (fluid)
version 1.0107 
header_name {.h} 
code_name {.cpp}
decl {\#include <iostream>} {} 

Function {bt_callback(Fl_Widget*, void* userdata)} {open selected return_type {static void}
} {
  code {if(userdata == "test")
	std::cout << "Testing" << std::endl;
else if (userdata == "close")
	exit(0);} {}
} 

Function {} {open
} {
  Fl_Window window_main {
    label {FLTK window} open
    xywh {387 309 305 135} type Double align 80 visible
  } {
    Fl_Input input {
      label {Please enter value:}
      xywh {145 10 150 25}
    }
    Fl_Button btnTest {
      label Test
      user_data {"test"}
      callback bt_callback
      xywh {10 100 100 25}
    }
    Fl_Return_Button btnClose {
      label Close
      user_data {"close"}
      callback bt_callback
      xywh {195 100 100 25}
    }
  }
}