Excuting the rest of my programme around glutMainLoop?

Question

I'm currently working on a project where an andoid app that I've written controls and object in my OpenGL window on the PC. Ive got the OpenGL window to do what I want and ive got the data from my android device to stream to a terminal. However I need the data being streamed to the terminal to be used by the OpenGL object. When I try and run them in the same script it just gets stuck in the 'glutMainLoop' and never reaches a point where connection to my device is established. I know this is a comman problem with the glutMainLoop. I'm looking for any advice. Am I going about it the wrong way? Is there a better approch? I have attached my code below:

 #include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <strings.h>
#include <vrpn_Shared.h>
#include <vrpn_Analog.h>
#include <vector>

#include <imageviewer.h>

using namespace std;

int done = 0;           // Signals that the program should exit
unsigned tracker_stride = 1;    // Every nth report will be printed


//-------------------------------------
// This section contains the data structure that holds information on
// the devices that are created.  For each named device, a remote of each
// type analog is created.

class device_info {
    public:
    char            *name;

    vrpn_Analog_Remote  *ana;

};
const unsigned MAX_DEVICES = 2;


//-------------------------------------
// This section contains the data structure that is used to determine how
// often to print a report for each sensor of each tracker.  Each element
// contains a counter that is used by the callback routine to keep track
// of how many it has skipped.  There is an element for each possible sensor.
// A new array of elements is created for each new tracker object, and a
// pointer to it is passed as the userdata pointer to the callback handlers.


class t_user_callback {
    public:
    char            t_name[vrpn_MAX_TEXT_LEN];
        vector<unsigned>    t_counts ;
};

//Callback handlers

void    VRPN_CALLBACK handle_analog (void *userdata, const vrpn_ANALOGCB a)
{
    int i;
    const char *name = (const char *)userdata;

    printf("Input from %s:\n  \n        %5.0f", name, a.channel[0]);
    for (i = 1; i < a.num_channel; i++) {
    printf(" %5.0f \n", a.channel[1]);
    }
    printf(" \n");
}


int main (int argc, char * argv [])
{

  int   print_for_tracker = 1;  // Print tracker reports?
  int   print_for_button = 1;   // Print button reports?
  int   print_for_analog = 1;   // Print analog reports?
  int   print_for_dial = 1; // Print dial reports?
  int   print_for_text = 1; // Print warning/error messages?

  device_info device_list[MAX_DEVICES];
  unsigned num_devices = 0;

  int i;

  // Parse arguments, creating objects as we go.  Arguments that
  // change the way a device is treated affect all devices that
  // follow on the command line.
  for (i = 1; i < argc; i++) {
    if (!strcmp(argv[i], "-notracker")) {
      print_for_tracker = 0;
    } else if (!strcmp(argv[i], "-nobutton")) {
      print_for_button = 0;
    } else if (!strcmp(argv[i], "-noanalog")) {
      print_for_analog = 0;
    } else if (!strcmp(argv[i], "-nodial")) {
      print_for_dial = 0;
    } else if (!strcmp(argv[i], "-notext")) {
      print_for_text = 0;
    } else if (!strcmp(argv[i], "-trackerstride")) {
      if (tracker_stride <= 0) {
      fprintf(stderr, "-trackerstride argument must be 1 or greater\n");
      return -1;
      }
    } else {    // Create a device and connect to it.
    device_info *dev;

    // Make sure we have enough room for the new device
    if (num_devices == MAX_DEVICES) {
        fprintf(stderr,"Too many devices!\n");
        exit(-1);
    }

    // Name the device and open it as everything
    dev = &device_list[num_devices];
    dev->name = argv[i];

    dev->ana = new vrpn_Analog_Remote(dev->name);

    if ( (dev->ana == NULL) ){         
        fprintf(stderr,"Error opening %s\n", dev->name);
        return -1;
    } else {
        printf("Opened %s as:", dev->name);
    }
    if (print_for_analog) {
        printf(" Analog");
        dev->ana->register_change_handler(dev->name, handle_analog);
    }
    printf(".\n");
    num_devices++;
    }

  }


 // main interactive loop

  printf("Press ^C to exit.\n");
  while ( ! done ) {
      unsigned i;

      // Let all the devices do their things
      for (i = 0; i < num_devices; i++) {

      device_list[i].ana->mainloop();

      glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
    glutInitWindowSize(400,300);
    glutInitWindowPosition(200,100);
    glutCreateWindow("ImageViewer");


    init();
    glutDisplayFunc(display);
    glutMotionFunc(drag);
    glutMouseFunc(mouse);
    glutMainLoop();


      }
  }
 return 0;
}  



// a.channel[0] =  x
// a.channel[1] =  y
// a.channel[2] =  Zoom?

Answer 1

You could stop using GLUT. GLFW gives you better control over the loop, so that it's easier to do other processing.

If you insist on using GLUT, and you're using FreeGLUT, then you can use glutMainLoopEvent. This function processes one iteration of the main loop. So you can just stick it in an infinite loop and call it repeatedly. As part of that loop, you can do other things, like pulling data from the terminal or whatever.

Answer 2

freeglut offers glutMainLoopEvent, so you can choose your running mode.