Question

I’m doing a program in Perl with the OpenGL bindings, i’ve got past the first roadblock when the glutReshapeFunc(\&changeSize); is called by reading the GLUT_WINDOW_HEIGHT and GLUT_WINDOW_WIDTH variables, but i have no clue how to get the value of the key passed when glutSpecialFunc(\&processSpecialKeys); is called.
Reading the API i couldn’t find a GLUT_SPECIAL_KEY variable or anything like that.

sub changeSize
{
        my $w = glutGet(GLUT_WINDOW_WIDTH);
        my $h = glutGet(GLUT_WINDOW_HEIGHT);
        if($w eq 0){
        $w = 1;
}
        my $ratio = ($w / $h);
        # Use the Projection Matrix
        glMatrixMode(GL_PROJECTION);

            #// Reset Matrix
        glLoadIdentity();

        #// Set the viewport to be the entire window
        glViewport(0, 0, $w, $h);

        #// Set the correct perspective.
        gluPerspective(45,$ratio,1,1000);

        #// Get Back to the Modelview
        glMatrixMode(GL_MODELVIEW);
        gluLookAt( $x, 1.0, $z,
            $x+$lx,1.0,$z+$lz,
            0.0,1.0,0.0);
}

sub processSpecialKeys
{

    $fraction = 0.1;
    $key = $_[0]; #my first shot was that the key value was stored at $_[0]
                      #the mouse_x was at $_[1] and $_[2] had mouse_y
        if ($key eq GLUT_KEY_LEFT)
        {
            $angle -= 0.01;
            $lx = sin($angle);
            $lz = -cos($angle);
        }
}

Answer 1

OpenGL itself doesn’t deal with user input. What you are using is GLUT, a 3rd party library.

glutReshapeFunc(\&changeSize); is called by reading the GLUT_WINDOW_HEIGHT and GLUT_WINDOW_WIDTH variables,

You normally don’t query GLUT_WINDOW_HEIGHT and GLUT_WINDOW_WIDTH from the reshape handler, since both of those values are passed as parameters to the function.

of the key passed when glutSpecialFunc(\&processSpecialKeys); is called. Reading the API i couldn’t find a GLUT_SPECIAL_KEY variable or anything like that.

Because there isn’t. The key and the position of the click are passed as parameters to the callback function.