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hoss0
09-13-2011, 04:09 PM
Hi, I've been getting this error message when trying to compile an opengl program with calls to glutInitJoystick("/dev/input/js0"); and glutJoystick(joystick, 10);

singlesine.c:(.text+0x171b): undefined reference to `glutInitJoystick'

I'm using Ubuntu 10.04 (Lucid Lynx) with glut 3.7 installed.

Can anyone tell me what this error message means, and how to fix it?

Thanks in advance

marshats
09-13-2011, 07:16 PM
Interesting, I don't think glut or freeglut ever had glutInitJoystick -- it is not in my glut headers on ubuntu. A quick google search lead to a one off modified glut to include this at glutjoy (http://www.cs.unm.edu/~tkh/gfx/glutjoy.html). Maybe centOS used this rogue glut library? I am not familar with CentOS but have used Ubuntu+freeglut. A look at the header file for freeglut_std.h shows a "glutJoystickFunc" callback but note on X11 is discouraging (http://www.unix.com/man-page/All/3/glutJoystickFunc/). In other words I think GLUT is not so good for joystick controls.

As a low-level API, if you want to use the joystick in linux you could do something low level as


//
// g++ joystick.cpp
//
//http://archives.seul.org/linuxgames/Aug-1999/msg00107.html
/* this is the linux 2.2.x way of handling joysticks. It allows an arbitrary
* number of axis and buttons. It's event driven, and has full signed int
* ranges of the axis (-32768 to 32767). It also lets you pull the joysticks
* name. The only place this works of that I know of is in the linux 1.x
* joystick driver, which is included in the linux 2.2.x kernels
*/

#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/joystick.h>

#define JOY_DEV "/dev/input/js0"

int main()
{
int joy_fd, *axis=NULL, num_of_axis=0, num_of_buttons=0, x;
char *button=NULL, name_of_joystick[80];
struct js_event js;

if( ( joy_fd = open( JOY_DEV , O_RDONLY)) == -1 )
{
printf( "Couldn't open joystick\n" );
return -1;
}

ioctl( joy_fd, JSIOCGAXES, &amp;num_of_axis );
ioctl( joy_fd, JSIOCGBUTTONS, &amp;num_of_buttons );
ioctl( joy_fd, JSIOCGNAME(80), &amp;name_of_joystick );

axis = (int *) calloc( num_of_axis, sizeof( int ) );
button = (char *) calloc( num_of_buttons, sizeof( char ) );

printf("Joystick detected: %s\n\t%d axis\n\t%d buttons\n\n"
, name_of_joystick
, num_of_axis
, num_of_buttons );

fcntl( joy_fd, F_SETFL, O_NONBLOCK ); /* use non-blocking mode */

while( 1 ) /* infinite loop */
{

/* read the joystick state */
read(joy_fd, &amp;js, sizeof(struct js_event));

/* see what to do with the event */
switch (js.type & ~JS_EVENT_INIT)
{
case JS_EVENT_AXIS:
axis [ js.number ] = js.value;
break;
case JS_EVENT_BUTTON:
button [ js.number ] = js.value;
break;
}

/* print the results */
printf( "X: %6d Y: %6d ", axis[0], axis[1] );

if( num_of_axis > 2 )
printf("Z: %6d ", axis[2] );

if( num_of_axis > 3 )
printf("R: %6d ", axis[3] );

for( x=0 ; x<num_of_buttons ; ++x )
printf("B%d: %d ", x, button[x] );

printf(" \r");
fflush(stdout);
}

close( joy_fd ); /* too bad we never get here */
return 0;
}


And note that freeglut_ext.h says


/*
* Joystick functions, see freeglut_joystick.c
*/
/* USE OF THESE FUNCTIONS IS DEPRECATED !!!!! */
/* If you have a serious need for these functions in your application, please either
* contact the "freeglut" developer community at freeglut-developer@lists.sourceforge.net,
* switch to the OpenGLUT library, or else port your joystick functionality over to PLIB's
* "js" library.
*/

Stuart McDonald
09-14-2011, 02:35 AM
You also might want to consider GLFW. I prefer it to GLUT, it has joystick support and is still being updated. It's a very easy switch from GLUT to GLFW.