Re: [fltk.general] FLTK usage in passing pointers from file to file - Forums

Regarding passing window "pointers" from one file to another, I must thank you for assisting me in this endeavour. It works well now that I understand the use of "new", begin() and end(). I do note that the text _expression_ in each instance of my declared windows only appears for the first window....or I may be missing something. Is there a way to easily have a text at the top of each window which would describe the data that will be displayed? I did look at Fl_Text_Display but it seemed rather to be an overkill.

It would be good to hear your thoughts. Take care.

On Fri, Feb 26, 2021 at 1:21 PM Bill Spitzak <spitzak@gmail.com> wrote:

The objects should work in your first example. There may be a problem with the destructor assuming other things have not been destroyed.
Generally though when using objects it works better if they are local or local static variables in functions, this defers the constructor until they are first used. Something like this is supposed to work:

main() {
Fl_Window w1(....);
some_func(w1);
}

some_func(Fl_Window& w) {
w.show();
}

On Fri, Feb 26, 2021 at 4:37 AM lifeatt...@gmail.com <lifeattickville@gmail.com> wrote:
>So when I now, as you counciled, declare all the Windows globally such as
>Fl_Window w1(5,198,600,275,"Tester");

This is why we want to see a program, not "snippets" with text. We will "guess" what you're doing and be at odds ...

I interpreted what you did differently from Greg. I think you did:

File1:

Fl_Window w1(5,198,600,275,"Tester"); // note: declared and created globally
main() {
w1.show()
}

File2:
extern Fl_Window w1;

some_func() {
w1.hide()
}

To me, the issue I think I'm seeing is you are trying to use "objects" and not pointers. I think the error you are getting at program shutdown is FLTK trying to destroy the FL_Window instances you created globally, and that can't be done. FLTK is a C library, not a C++ library, so it's best if you work with pointers.

The approach I would use is:

File1:
Fl_Window *w1;
main() {
w1 = new Fl_Window(5, 198, 600, 275, "Tester"); // note: declared globally, allocated ON THE HEAP
w1->hide(); // pointer syntax
}

File2:
extern Fl_Window *w1; // extern pointer

some_func() {
w1->hide(); // pointer syntax
}

Kevin

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