> I'm new to FLTK and I just want to change the label of Fl_Input when I
> press the button. However the label changed to a strange string instead of
> what I want.
> Any idea?
Yes - FWIW, this is a FAQ, and is described in the docs too...
> The code :
> void changelabel(Fl_Widget*ptr)
> {
> char l[15];
> Fl_Window *win = (Fl_Window *)((Fl_Button*)ptr->parent());
> Fl_Input *input = (Fl_Input*)win->child(i);
>
> sprintf_s(l,"p :=: ");
> input->label(l);
NAK: You want;
input->copy_label(l);
at this point. Check the docs:
if you simply use label(), then fltk assumes the string you are passing is
static and will refer to it directly.
However, here the string you are passing, "l", is stack-automatic and will go
out of scope as soon as your changelabel() function returns.
So, if that's what you want to do, you need to use copy_label() instead so that
fltk knows it needs to make an internal copy of the label.
You have a choice, you can either make your labels in static scope (useful if
you want to share strings between widgets, for example) or you can use
copy_label() if the strings are created in dynamic scope.
The static approach may be slightly faster, but the static memory footprint may
be higher - take your pick!
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