/* circle.c 1.1 */
/*
    Copyright 1992, 1993 O'Reilly and Associates, Inc.  Permission to
    use, copy, and modify this program is hereby granted, as long as
    this copyright notice appears in each copy of the program source
    code.
*/

#include "book_utils.h"

#define HALF_SQRT2	0.7071 /* sqrt(2)/2 */

static void
redraw( dpy, window, renderer )
    Display	*dpy;
    Window	window;
    PEXRenderer	renderer;
{
    static PEXCoord4D 	control_points[] = {
	{.5, .3, 0, 1}, {.7, .3, 0, HALF_SQRT2},
	{.7, .5, 0, 1}, {.7, .7, 0, HALF_SQRT2},
	{.5, .7, 0, 1}, {.3, .7, 0, HALF_SQRT2},
	{.3, .5, 0, 1}, {.3, .3, 0, HALF_SQRT2},
	{.5, .3, 0, 1} };
    static float	knots[] = {0,0,0,1,1,2,2,3,3,4,4,4};

    /* The same points, but without the homogeneous coordinate. */
    static PEXCoord 	pgon_points[] = {
	{.5, .3, 0}, {.7, .3, 0}, {.7, .5, 0}, {.7, .7, 0},
	{.5, .7, 0}, {.3, .7, 0}, {.3, .5, 0}, {.3, .3, 0},
	{.5, .3, 0} };

    int			order, num_knots, i;
    unsigned int	num_points;
    double		tmin, tmax;
    PEXArrayOfCoord	cpts;
    PEXColor		color;
    
    XClearWindow( dpy, window );
    PEXBeginRendering( dpy, window, renderer ); {
	SET_COLOR( 1, 1, 1, color );
	PEXSetLineColor( dpy, renderer, PEXOCRender,
			 PEXColorTypeRGB, &color );
	
	/* Set the approximation criteria. */
	PEXSetCurveApprox( dpy, renderer, PEXOCRender,
			   PEXApproxConstantBetweenKnots, (double)20 );

	/* Apply the weights to the control point coords. */
	num_points = sizeof(control_points)/sizeof(PEXCoord4D);
	for ( i = 0; i < num_points; i++ ) {
	    control_points[i].x *= control_points[i].w;
	    control_points[i].y *= control_points[i].w;
	    control_points[i].z *= control_points[i].w;
	}
	
	/* Create the curve. */
	order = 3;
	cpts.point_4d = control_points;
	num_knots = sizeof(knots)/sizeof(knots[0]);
	tmin = knots[order-1];
	tmax = knots[num_knots - order];
	PEXNURBCurve( dpy, renderer, PEXOCRender, PEXRational,
		      order, knots, num_points, cpts, tmin, tmax );
	
	/* Show the control polygon. */
	PEXSetLineType( dpy, renderer, PEXOCRender,
		        PEXLineTypeDashed );
	PEXPolyline( dpy, renderer, PEXOCRender, num_points,
		     pgon_points );
    }
    PEXEndRendering( dpy, renderer, True );
    XFlush( dpy );
}

#define WIN_GEOM	"500x500+50+50"

main( argc, argv )
    int		argc;
    char	*argv[];
{
    Display			*dpy;
    Window			window;
    XEvent			event;
    XVisualInfo			vis_info;
    XColor			bkgd_color;
    XStandardColormap		cmap_info;
    PEXColorApproxEntry		capx_info;
    PEXRenderer			renderer;
    PEXRendererAttributes	rattrs;
    PEXExtensionInfo		*pexinfo;
    int				done = 0;
    
    /* Open a display and initialize PEX. */
    dpy = ora_init_pex( argv, &pexinfo );
    if ( !dpy ) exit(1);
    
    /* Determine the best visual to use. */
    ora_find_best_visual( dpy, &vis_info );
    
    /* Get a standard colormap for the visual. */
    if ( !ora_get_standard_colormap( dpy, &vis_info, &cmap_info ) ) {
	fprintf ( stderr, "Cannot find a standard colormap\n" );
	exit(1);
    }
    ora_set_stdcmap_approx( &vis_info, &cmap_info, &capx_info );

    /* Create the window, giving it a gray background. */
    bkgd_color.red = bkgd_color.green = bkgd_color.blue = 0x5555;
    bkgd_color.flags = DoRed | DoGreen | DoBlue;
    window = ora_create_window( dpy, &vis_info, &cmap_info, WIN_GEOM,
			        &bkgd_color );
    
    if ( IMMED_MODE_SPT( pexinfo ) ) {
	renderer = ora_setup_renderer( dpy, window, &capx_info,
				       &rattrs );
    } else {
	fprintf( stderr, "No immediate mode.\n" );
	exit(1);
    }

    /* Read and respond to X events. */
    XSelectInput( dpy, window, ExposureMask | ButtonPressMask );
    while ( !done ) {
	XNextEvent( dpy, &event );
	switch ( event.type ) {
	case Expose:
	    /* Flush remaining Expose events, then redraw. */
	    while ( XCheckTypedWindowEvent( dpy, window,
					    Expose, &event ) )
		; /* empty statement */
	    redraw( dpy, window, renderer );
	    break;
	case ButtonPress:
	    done = 1;
	    break;
	}
    }

    XCloseDisplay( dpy );
    return 0;
}