gluUnProject iz stoopid

I have something that resembles this.

Code:

    case WM_LBUTTONDOWN:

        {
            GLdouble window_x = static_cast<double>( LOWORD(lParam) );
            GLdouble window_y = static_cast<double>( HIWORD(lParam) );

            GLdouble object_x = 0, object_y = 0, object_z = 0;

            GLdouble 
                model_view[16] = { 0 },
                projection[16] = { 0 };

            GLint viewport[4] = { 0 };

            glGetDoublev( GL_MODELVIEW_MATRIX, model_view );
            glGetDoublev( GL_PROJECTION_MATRIX, projection );
            glGetIntegerv( GL_VIEWPORT, viewport );

            if( gluUnProject( window_x, window_y, 0, model_view, projection, viewport, &object_x, &object_y, &object_z ) == GL_FALSE )
                dout << L"WTEGSDJSDKJLS!!\n";

            dout << object_x << TEXT("\t") << object_y << TEXT("\t") << object_z << TEXT("\n");

            break;
        }

There is no error, yet all the variables remain zero'ed. Do I need to do anything else? The documentation/FAQ on this function is sparse.

Dear, Abbey.

Basically I discovered that the function is actually failing. What I have in my code:

Code:

class CGame
{
    struct CViewingData
    {
        GLdouble projection[16];
        GLdouble modelview[16];
        GLint viewport[4];
    } data;

    ...
};


CGame::CGame( int width, int height )

:

m_width( width / 2.0 ), 
m_height( height / 2.0 )

...

{

...

    glGetIntegerv( GL_VIEWPORT, data.viewport );
    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();

    gluLookAt( 0, 0, m_width * 2.0, 0, 0, 0, 0, 1, 0 );
    glGetDoublev( GL_MODELVIEW_MATRIX, data.modelview );

    glMatrixMode( GL_PROJECTION );
    glGetDoublev( GL_PROJECTION_MATRIX, data.projection );

...

}


bool CGame::unProject( int x, int y, std::pair< double, double > & result )
{
    double world_x, world_y, world_z, z_depth;
    glReadPixels( x, y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &z_depth );

    if( gluUnProject( x, data.viewport[3] - y - 1, z_depth, 
        data.modelview, data.projection, data.viewport, 
        &world_x, &world_y, &world_z ) == GL_FALSE )
    {
        return false;
    }
        
    result = std::pair< double, double >( world_x, world_y );
    return true;
}

I call it like:

Code:

    case WM_LBUTTONDOWN:
        {
            std::pair< double, double > p;

            if( s_game->unProject( LOWORD(lParam), HIWORD(lParam), p ) )
            {
                dout << p.first << TEXT("\t") << p.second << TEXT("\n");
            }
            else
            {
                dout << TEXT("BLAH\n");
            }

            break;
        }

And it always is disgusted, replying "BLAH" whenever I click. How am I ever going to get my uncooperative teenage monster to behave?

Sincerely,
FLUSTERED IN MUSTARD