Desiring bool any_key_pressed()

[Daren Scot Wilson]

Here is a very simple version of the program I'm working on.  Is 
there a way to write is_any_key_pressed() that doesn't block, 
doesn't require the Enter key, and doesn't require dragging in 
any complex libraries or dealing with low-level stuff like 
ioctl()? Is there nothing in Phobos that provides the needed 
functionality?

I won't go into the details, but I tried threading, putting the 
getchar() in a separate thread that sets a global bool 
g_keypressed variable. It was a disaster. Maybe there's a right 
way to use threading?  I am not talented at threads.

```
import core.thread;
import core.time;
import std.stdio;
import std.conv;


void light_on() {
     write("on "); stdout.flush;
}
void light_off() {
     write("off "); stdout.flush;
}

void wait()  {
     Duration dur = dur!("seconds")( to!int(1) );
     Thread.sleep(dur);
}


bool is_any_key_pressed()  {
     getchar();  // nope, requires Enter key to be pressed, and is 
blocking
     return true;
}

void main(string[] args)
{

     while (true)  {
         light_on();
         wait();
         light_off();
         wait();

         if (is_any_key_pressed())  {
             break;
         }
     }
}
```