fltk/examples/fluid-callback.fl

# data file for the Fltk User Interface Designer (fluid)
version 1.0400
header_name {.h}
code_name {.cxx}
snap {
  ver 1
  current_suite FLTK
  current_preset 0
}
comment {README FIRST
- - - - - - -
This fluid (.fl) file demonstrates how to create a complete
FLTK program with a button with a virtual callback method
and a virtual destructor.

The code is as short as possible but demonstrates setting
virtual and static attributes on callbacks.

Note that FLTK needs static functions as callbacks assigned
to widgets like Fl_Buttons. The static callback method can
eventually call other class methods like the virtual callback
method in this example.

Use fluid interactively to open this fluid (.fl) file and
double-click on items to see how they are defined.

Hint: Open the code view (Edit/Show Source Code) and select
items to see which code each item generates. Switch tabs
'Source' and 'Header' in the code view window to see code in
the source and header file, respectively.

Use "File/Write Code" or 'fluid -c fluid-callback.fl' at
the command line to generate .cxx and .h files; compile
and build the demo program with

  fltk-config --compile fluid-callback.cxx
} {in_source not_in_header
}

decl {\#include <FL/Fl_Window.H>} {public global
}

decl {\#include <FL/Fl_Button.H>} {public global
}

decl {\#include <stdio.h>} {public global
}

class App {open : Fl_Window
} {
  Function {App(int X, int Y, const char *L) : Fl_Window(X, Y, L)} {
    comment Constructor open
  } {
    code {// Code in constructor
printf("Creating new App\\n");
Fl_Button *exit_cb = new Fl_Button(20, 20, 260, 60, "Exit: invokes virtual callback");
exit_cb->callback(Cb_Bn_static, (void *)77);
show();} {}
  }
  Function {~App()} {
    comment {Virtual destructor} open return_type virtual
  } {
    code {printf("Closing and deleting App\\n");} {}
  }
  Function {Cb_Bn_static(Fl_Widget *w, void *v)} {
    comment {Static callback method} open return_type {static void}
  } {
    code {// code in static callback
int i = (int)(fl_intptr_t)v;
printf("Executing  static callback Cb_Bn_static,  value = %d\\n", i);
Fl_Window *win = w->window();
App *app = (App *)win;
app->Cb_Bn_virtual(v);} {}
  }
  Function {Cb_Bn_virtual(void *v)} {
    comment {// Virtual callback method} open return_type {virtual void}
  } {
    code {// code in virtual callback
int i = (int)(fl_intptr_t)v;
printf("Executing virtual callback Cb_Bn_virtual, value = %d\\n", i);
// note: operator delete calls hide()
delete this;} {}
  }
}

Function {} {open return_type int
} {
  code {// Main program
App(300, 100, "Virtual Callback Test");} {selected
  }
}