How to add timeout to FLTK pop-up dialog - fltk

Question

I am using FLTK library and have used a pop-up function fl_input() from Fl_ask.h. I want a feature that if the user doesn't input and data for 3 seconds, the function should return. How can I make this function return without pressing OK or cancel. Is there anyway to get a handle to this pop-up dialog? This is the code I'm using
const char *message = "Enter name here";
Fl::lock();
char *c = (char*)fl_input(message, "");
if(c == NULL)
c = "";
Fl::unlock();

Answer 1

You can't do this easily using fl_input because there is no handle to the window. Have a look at the fl_input source in src/fl_ask.cxx. You will see it calls input_innards. If you track through to input_innards, you'll see that it calls innards. If you then follow innards, you will find a while loop which reads
while (message_form->shown()) Fl::wait();
Make a copy of fl_ask.cxx, say timed_ask.cxx. Make all the fl_ routines static. Change fl_input as follows:
const char* timed_input(double timeout, const char *fmt, const char *defstr, ...) {
if (avoidRecursion) return 0;
va_list ap;
va_start(ap, defstr);
const char* r = timed_input_innards(timeout, fmt, ap, defstr, FL_NORMAL_INPUT);
va_end(ap);
return r;
}
Make a copy of input_innards and rename the new one to timed_input_innards (this keeps the other fl_routines happy unless you want to delete them).
static const char* timed_input_innards(double timeout, const char* fmt, va_list ap,
const char* defstr, uchar type) {
...
int r = timed_innards(timeout, fmt, ap, fl_cancel, fl_ok, 0);
...
Make a copy of innards and rename the new one to timed_innards
static int timed_innards(double timeout, const char* fmt, va_list ap,
const char *b0,
const char *b1,
const char *b2)
{
...
Fl::add_timeout(timeout, hide_form, message_form);
while (message_form->shown()) Fl::wait();
...
}
Add the timeout routine
void hide_form(void* data)
{
// You could do this or use message_form directly
Fl_Window* form = reinterpret_cast<Fl_Window*>(data);
form->hide();
}
This will cause message_form->shown() to be false and exit the while loop.