class Fl_Int_Input : public Fl_Input
An input field that does not accept text that cannot be passed
through strtol(). Any attempt to edit the text to something that is
not an initial substring of a legal integer is rejected
and the text is unchanged.
The text is not checked when you set it with value(), but if you
set it to something illegal then it becomes difficult to edit.
Fl_Int_Input(int x,int y,int w,int h,const char *l =
0);