opengl - Preserve aspect ratio of 2D object on window resize -

i have windows (xp) application needs display two-dimensional rectangle within window. rectangle must not clipped (i.e. must lie within viewport), , must preserve aspect ratio on resize. currently, method handles layout distorts aspect ratio of rectangle match window. want rectangle scale window , centered in window (again, without clipping). method stands below. lwindist , lmaxdepth width , height of rectangle displayed (in 48ths of inch, if matters):

void crorrecview::redolayout( long lwindist, long lmaxdepth ) {     cdc* pdc = getdc() ;      if ( pdc != null )     {         m_lwindist = lwindist;         getclientrect( m_rectclient ) ;         int nclientwidth = m_rectclient.width();         int nclientheight = m_rectclient.height();         glviewport( 0, 0, nclientwidth, nclientheight );          glmatrixmode( gl_projection);         glloadidentity();          m_fwinxdist = (float) lwindist ;         m_fwinydist = lmaxdepth ;         m_faspectratio = m_fwinxdist / m_fwinydist;          glortho(0.0, m_fwinxdist, 0.0, m_fwinydist, -1, 1 ) ;          glrotatef(180.0, 0,1,0);          gltranslatef( (float)(-1 * lwindist),0,0 ); // translate across x axis          glmatrixmode( gl_modelview );         glloadidentity();          releasedc( pdc ) ;     } } 

this 1 should scale expected:

// g++ main.cpp -lglut -lgl #include <gl/glut.h>  void display() {     glclear( gl_color_buffer_bit | gl_depth_buffer_bit );      glmatrixmode( gl_projection );     glloadidentity();     double w = glutget( glut_window_width );     double h = glutget( glut_window_height );     double ar = w / h;     glortho( -2 * ar, 2 * ar, -2, 2, -1, 1);      glmatrixmode( gl_modelview );     glloadidentity();      glcolor3ub( 255, 0, 0 );     glbegin( gl_quads );     glvertex2i( -1, -1 );     glvertex2i(  1, -1 );     glvertex2i(  1,  1 );     glvertex2i( -1,  1 );     glend();      glutswapbuffers(); }  int main( int argc, char **argv ) {     glutinit( &argc, argv );     glutinitdisplaymode( glut_rgba | glut_depth | glut_double );     glutinitwindowsize( 640, 480 );     glutcreatewindow( "aspect ratio" );     glutdisplayfunc( display );     glutmainloop();     return 0; }