---

xstarplot.C

Go to the documentation of this file.

//.............................................................................
//    version 1:  May 1989   Piet Hut            email: piet@iassns.bitnet
//                           Institute for Advanced Study, Princeton, NJ, USA
//    version 2:  Dec 1992   Piet Hut      adapted to the new C++-based Starlab
//    version 3:  Dec 1992   Steve McMillan      email: steve@zonker.drexel.edu
//                           Drexel University, Philadelphia, PA, USA
//                           Converted original ASCIIplot to X --- FIRST DRAFT!
//    version 4:  Jan 1994   Biao Lu             email: biao@eagle.drexel.edu
//                           Drexel University, Philadelphia, PA, USA
//                           Use new X interface for movie.
//            Aug/Sep 1994   Cleaned up and expanded, SMcM
//                Sep 1995   Extended to sdyn3 and nonzero radii, SMcM
//                Aug 1996   Added forward/backward step modes, SMcM
//                Aug 1996   Reworked for hdyn and nonzero radii, SMcM
//                Jul 1998   New end-of-data behavior; more robust
//                           X interface, SMcM
//.............................................................................
//  non-local functions: 
//    xstarplot
//.............................................................................
//  uses:
//    liblux.a (X interface)
//    The X graphics library
//.............................................................................

// NOTE: On some systems, it appears that overflow can occur, causing the
//       win.lnx and win.lny entries to be overwritten and leading to
//       spurious "log10" errors in draw.c (in lux_set_item, specifically).
//       This isn't fatal, but it should be fixed someday...

#include "hdyn.h"
#include "xstarplot.h"
#include "dyn_util.h"

//-------------------------------------------------------------------------


// These shouldn't really be global, but keep them this way for now...

unsigned long  win, dia, instr, colwin;
unsigned long c_energy[10], c_index[N_COLORS+1];
int      init_status = 0;

// The plotting box is determined completely by origin and lmax3d.
// Its projection onto the viewing plane is xmin, xmax, ymin, ymax

float  xmin, xmax, ymin, ymax, base_point_size, lmax3d, origin[3];

int   win_size;
int   point_scale_mode = 0;
int   kx = 1, ky = 2, kproj = 3;
int   origin_star = -1;
int   nodes = 0, links = 0, root = 0, multiples = 0, unperturbed = 0;
float theta = 0.33, costheta = cos(0.33), sintheta = sin(0.33), dtheta = 0.03;
float phi = 0.33, cosphi = cos(0.33), sinphi = sin(0.33);
real  local_offset[3];

#define MIN_DELAY  1.0
float delay_time = MIN_DELAY;

float r_factor = 1.0;

char  graph3d = 1, track = 0, cenergy = 0; // convenient to distinguish these

char   temp_buffer[255];        // convenient to share this temporary space

//-------------------------------------------------------------------------

// base_point_size defines the size of the default "dot" size on the display.
// It is used (with scaling) for stars and (without scaling) for nodes.

local void set_base_point_size(hdyn* b, float rel_point_size)
{
    base_point_size = 2 * SMALL_DOT_SIZE;       // default point size

    if (point_scale_mode == 1) {

        // Scale so the average initial mass has a reasonable size.

        real m_tot = 0;
        real n_tot = 0;
        for_all_leaves(hdyn, b, bi) {
            n_tot++;
            m_tot += bi->get_mass();
        }

        if (n_tot > 0) base_point_size /= sqrt(m_tot/n_tot);    // NB sqrt below

    } else if (point_scale_mode == 2 || point_scale_mode == 3) {

        // In the case point_scale_mode = 2, use unscaled (i.e. true)
        // radii if rel_point_size < 0.

        if (point_scale_mode == 2 && rel_point_size < 0) {

            base_point_size = 1;

        } else {

            // Scale so the average initial radius has a reasonable size.

            real r_tot = 0;
            real n_tot = 0;
            for_all_leaves(hdyn, b, bi) {
                n_tot++;
                r_tot += bi->get_radius();
            }

            if (n_tot > 0) {
                if (point_scale_mode == 2)
                    base_point_size /= r_tot/n_tot;
                else
                    base_point_size /= sqrt(r_tot/n_tot);
            }
        }
    }

    // Optional additional scaling:

    if (rel_point_size > 0.0)  base_point_size *= rel_point_size;
}

local float get_point_size(hdyn* bi)
{
    // Scaling by mass is too extreme.  Use sqrt(mass).
    // Also, impose a lower limit on the point size.

    if (point_scale_mode == 1)
        return max(SMALL_DOT_SIZE, base_point_size * sqrt(bi->get_mass()));
    else if (point_scale_mode == 2)
        return max(SMALL_DOT_SIZE, base_point_size * bi->get_radius());
    else if (point_scale_mode == 3)
        return max(SMALL_DOT_SIZE, base_point_size * sqrt(bi->get_radius()));
    else
        return base_point_size;
}

local void draw_star_point(unsigned long win, float r, float s,
                           float actual_point_size, bool f_flag)

// Plot a point of size actual_point_size at (r,s), filled or unfilled
// according to the value of f_flag.

{
    if (f_flag)
        lux_fill_arcf(win, r - actual_point_size/2, s - actual_point_size/2,
                      actual_point_size, actual_point_size, 0.0, 360.0);
    else
        lux_draw_arcf(win, r - actual_point_size/2, s - actual_point_size/2, 
                      actual_point_size, actual_point_size, 0.0, 360.0);
}

local void draw_links_2d(hdyn* b, float r, float s)
{
    for_all_daughters(hdyn, b, bb) {

        float rr = bb->get_pos()[kx]-local_offset[kx];
        float ss = bb->get_pos()[ky]-local_offset[ky];
        float stemp;

        // Deal with the 9 possible locations of (rr,ss) with respect
        // to the box defined by xmin, xmax, ymin, and ymax.

        if (rr < xmin) {

            if (ss < ymin) {
                float stemp = interp_to_x(r, s, rr, ss, xmin);
                if (stemp >= ymin)
                    rr = xmin, ss = stemp;
                else
                    rr = interp_to_y(r, s, rr, ss, ymin), ss = ymin;
            } else if (ss > ymax) {
                if ((stemp = interp_to_x(r, s, rr, ss, xmin)) <= ymax)
                    rr = xmin, ss = stemp;
                else
                    rr = interp_to_y(r, s, rr, ss, ymax), ss = ymax;
            } else
                ss = interp_to_x(r, s, rr, ss, xmin), rr = xmin;

        } else if (rr > xmax) {

            if (ss < ymin) {
                if ((stemp = interp_to_x(r, s, rr, ss, xmax)) >= ymin)
                    rr = xmax, ss = stemp;
                else
                    rr = interp_to_y(r, s, rr, ss, ymin), ss = ymin;
            } else if (ss > ymax) {
                if ((stemp = interp_to_x(r, s, rr, ss, xmax)) <= ymax)
                    rr = xmax, ss = stemp;
                else
                    rr = interp_to_y(r, s, rr, ss, ymax), ss = ymax;
            } else
                ss = interp_to_x(r, s, rr, ss, xmax), rr = xmax;

        } else {

            if (ss < ymin)
                rr = interp_to_y(r, s, rr, ss, ymin), ss = ymin;
            else if (ss > ymax)
                rr = interp_to_y(r, s, rr, ss, ymax), ss = ymax;

        }
        lux_draw_linef(win, r, s, rr, ss);
    }
}                                          

local void draw_links_3d(hdyn* b, float r, float s)
{
    for_all_daughters(hdyn, b, bb) {

        float X = (float)bb->get_pos()[0] - local_offset[0] - origin[0];
        float Y = (float)bb->get_pos()[1] - local_offset[1] - origin[1];
        float Z = (float)bb->get_pos()[2] - local_offset[2] - origin[2];

        // Don't attempt to deal with the 27 possible locations
        // of (X, Y, Z) with respect to the box!

        float rr, ss;
        project3d(X, Y, Z, rr, ss, costheta, sintheta, cosphi, sinphi);
        lux_draw_linef(win, r, s, rr, ss);
    }
}                                          

local int clean_index(hdyn* b)
{
    int clean_name = 0;

    if (b->get_index() > 0) 
        clean_name = b->get_index();
    else if (b->get_name()) {
        int i = 0;
        if (sscanf(b->get_name(), "%d", &i)) clean_name = i;
    }

    return clean_name;
}

local void plot_star(hdyn *bi, float r, float s,
                     float actual_point_size, int f_flag)
{
    // Plot a point at (r, s) representing star bi.

    // Determine the color to use.

    bool temp_flag = f_flag;
    if (bi->get_oldest_daughter()) {

        lux_set_color(win, lux_lookup_color(win, "grey"));
        temp_flag =  1 - f_flag;

    } else {

        if (cenergy) {

            char c;

            compute_energies(bi->get_root(), bi, c);
            lux_set_color(win, c_energy[c]);

        } else if (clean_index(bi) > 0) {

            // Wrap the color map.

            int ii = clean_index(bi);
            while (ii > N_COLORS) ii -= N_COLORS;

            lux_set_color(win,c_index[ii]);
        }
    }

    if (track)

        lux_draw_pointf(win, r, s);

    else {

        real scale = 1.0;
        real reset_grey = false;

        // Deal with possible highlighted systems.

        if (multiples
            && bi->is_top_level_node()
            && bi->get_oldest_daughter()
            && bi->n_leaves() > 2) {

            scale = 4.0;
            if (bi->n_leaves() == 3)
                lux_set_color(win, lux_lookup_color(win, "yellow"));
            else if (bi->n_leaves() == 4)
                lux_set_color(win, lux_lookup_color(win, "orange"));
            else
                lux_set_color(win, lux_lookup_color(win, "red"));

            reset_grey = true;

        } else if (unperturbed
                   && bi->get_oldest_daughter()
                   && bi->get_oldest_daughter()
                   ->get_fully_unperturbed()) {

            scale = 2.0;
            lux_set_color(win, lux_lookup_color(win, "blue"));

            reset_grey = true;

        }

        draw_star_point(win, r, s,
                        scale*actual_point_size, temp_flag);
        if (links && reset_grey)
            lux_set_color(win, lux_lookup_color(win, "grey"));
    }
}

local int plot_stars(hdyn* b, int f_flag)
{
    int  n_stars = b->n_leaves();
    if (b->get_oldest_daughter() == NULL) n_stars = 0;

    int  n_nodes = count_nodes(b);
    float r, s;

    if (graph3d) {

        for_all_nodes(hdyn, b, bi) if (root || bi->get_parent()) {
            if (nodes
                || (multiples && bi->is_top_level_node())
                || (unperturbed && bi->get_oldest_daughter())
                || (bi->get_oldest_daughter() == NULL)) {
                
                float X = (float)bi->get_pos()[0] - local_offset[0] - origin[0];
                float Y = (float)bi->get_pos()[1] - local_offset[1] - origin[1];
                float Z = (float)bi->get_pos()[2] - local_offset[2] - origin[2];

                float actual_point_size = get_point_size(bi);

                if (   (X > (-lmax3d + actual_point_size))
                    && (X < ( lmax3d - actual_point_size)) 
                    && (Y > (-lmax3d + actual_point_size))
                    && (Y < ( lmax3d - actual_point_size)) 
                    && (Z > (-lmax3d + actual_point_size))
                    && (Z < ( lmax3d - actual_point_size))) {

                    // Should really sort by depth here...

                    project3d(X, Y, Z, r, s,
                              costheta, sintheta,
                              cosphi, sinphi);

                    plot_star(bi, r, s, actual_point_size, f_flag);

                    if (links && bi->get_oldest_daughter())
                        draw_links_3d(bi, r, s);
                }
            }
        }

    } else {

        // Make a list of all nodes, *including* the root node if root = 1.
        // Root will be at the start of the list if it is being displayed.

        hdynptr* p = new hdynptr[n_nodes+root];

        int ip = 0;
        for_all_nodes(hdyn, b, bi) if (root || bi != b) p[ip++] = bi;
        if (ip != n_nodes+root) {
            cerr << "plot_stars: n_nodes = " << n_nodes+root
                << " counted " << ip << endl;
            exit(1);
        }

        // Sort by kproj (note that kproj = 1, 2, or 3 for x, y, or z):

        for (ip = 0; ip < n_nodes+root; ip++)
            for (int jp = ip+1; jp < n_nodes+root; jp++)
                if (p[jp]->get_pos()[kproj-1] < p[ip]->get_pos()[kproj-1]) {
                    hdynptr bb = p[jp];
                    p[jp] = p[ip];
                    p[ip] = bb;
                }

        // Plot ordered by depth.

        for (ip = 0; ip < n_nodes+root; ip++) {
            hdyn * bi = p[ip];
            if ( (root || bi != b)
                && (nodes
                    || (multiples && bi->is_top_level_node())
                    || (unperturbed && bi->get_oldest_daughter())
                    || (bi->get_oldest_daughter() == NULL))) {

                r = (float)bi->get_pos()[kx] - local_offset[kx];
                s = (float)bi->get_pos()[ky] - local_offset[ky];

                float actual_point_size = get_point_size(bi);

                if (   (r > (xmin + actual_point_size))
                    && (r < (xmax - actual_point_size)) 
                    && (s > (ymin + actual_point_size))
                    && (s < (ymax - actual_point_size)) ) {

                    plot_star(bi, r, s, actual_point_size, f_flag);

                    if (links && bi->get_oldest_daughter())
                        draw_links_2d(bi, r, s);
                }
            }
        }
        delete p;
    }
    return n_stars;
}

local int type(int which)
{
    if (which == tracking || which == graph3dim || which == colorenergy)
        return BUTTON_WINDOW;
    else
        return INPUT_WINDOW;
}

local int subtype(int which)
{
    if (which == tracking || which == graph3dim || which == colorenergy)
        return CHECK_BUTTON;
    else
        return NO_TYPE;
}

local void set_temp_buffer(int which)
{
    // Translate ID into a string representing the value.

    char c = -1;
    int i = -1;
    float f = 1.e30;    // Don't use VERY_LARGE_NUMBER here (DEC may object!)

    switch (which) {
        case colorenergy:       c = cenergy; break;
        case tracking:          c = track;   break;
        case graph3dim:         c = graph3d; break;
        case xminimum:          f = xmin; break;
        case xmaximum:          f = xmax; break;
        case yminimum:          f = ymin; break;
        case ymaximum:          f = ymax; break;
        case basepointsize:     f = base_point_size; break;
        case pointscalemode:    i = point_scale_mode; break;
        case lmax3D:            f = 2*lmax3d; break;
        case theta3D:           f = theta; break;
        case phi3D:             f = phi; break;
        case DelayTime:         f = delay_time; break;
        case dtheta3D:          f = dtheta; break;
        case Xorigin:           f = origin[0]; break;
        case Yorigin:           f = origin[0]; break;
        case Zorigin:           f = origin[0]; break;
        case view2D:            i = kproj; break;
        case originstar:        i = origin_star; break;
        default:                cerr << "xstarplot: diag error...\n";
    }

    if (f < 1.e30)
        sprintf(temp_buffer, "%f", f);
    else if (c == -1)
        sprintf(temp_buffer, " %d ", i);
    else
        temp_buffer[0] = c;
}

local void set_diag_item(int which, char* id, int label_on_left,
                         int x1, int x2, int y)
{
    set_temp_buffer(which);

    if (label_on_left) {        // label to left of (real) input box

        lux_set_item(dia, which, TEXT_WINDOW, NO_TYPE,
                     _R_(x1), _R_(y), strlen(id), id);
        lux_set_item(dia, which, INPUT_WINDOW, NO_TYPE,
                     _R_(x2), _R_(y), 10, temp_buffer);

    } else {                    // label to right of (integer) input box/button

        if (type(which) == INPUT_WINDOW) {

            lux_set_item(dia, which, INPUT_WINDOW, NO_TYPE,
                         _R_(x1), _R_(y), 3, temp_buffer);
            lux_set_item(dia, which, TEXT_WINDOW, NO_TYPE,
                         _R_(x2), _R_(y), strlen(id), id);

        } else {

            lux_set_item(dia, which, BUTTON_WINDOW, CHECK_BUTTON,
                         _R_(x1), _R_(y), 1, temp_buffer);
            lux_set_item(dia, which, TEXT_WINDOW, CHECK_BUTTON,
                         _R_(x2), _R_(y), strlen(id), id);
        }
    }
}

local void initialize_dialog(int xorigin, int yorigin)
{
    // Initialize dialog box material (note: y is measured up from bottom!)

    float save = r_factor;
    if (r_factor > 1) r_factor = 1;

    int xsize = 550;
    int ysize = 550;
    if (r_factor <= 0.6) xsize = (int) (xsize / (r_factor/0.6));
    dia = lux_open_dialog(xorigin, yorigin, _R_(xsize), _R_(ysize));

    // ---------- 3-D origin info across top of box (special case): ----------

     lux_set_item(dia, Origin, TEXT_WINDOW, NO_TYPE,
                 _R_(70), _R_(500), 6, "origin");

    sprintf(temp_buffer, "%f", origin[0]);
    lux_set_item(dia, Xorigin, INPUT_WINDOW, NO_TYPE,
                 _R_(160), _R_(500), 10, temp_buffer);

    sprintf(temp_buffer, "%f", origin[1]);
    lux_set_item(dia, Yorigin, INPUT_WINDOW, NO_TYPE,
                 _R_(280), _R_(500), 10, temp_buffer);

    sprintf(temp_buffer, "%f", origin[2]);
    lux_set_item(dia, Zorigin, INPUT_WINDOW, NO_TYPE,
                 _R_(400), _R_(500), 10, temp_buffer);


    // ---------- Left-hand column of dialog box: ----------

    //          xmin
    //          xmax
    //          ymin
    //          ymax
    //          3-D cube size
    //          projection theta
    //          projection phi
    //          projection dtheta
    //          point scale
    //          delay time

    // Minima and maxima of 2-D display:

    set_diag_item(xminimum, "xmin", 1, 70, 160, 460);
    set_diag_item(xmaximum, "xmax", 1, 70, 160, 420);
    set_diag_item(yminimum, "ymin", 1, 70, 160, 380);
    set_diag_item(ymaximum, "ymax", 1, 70, 160, 340);

    // 3-D cube size:

    set_diag_item(lmax3D, "cube size", 1, 70, 180, 300);

    // 3-D projection direction:

    set_diag_item(theta3D,  "theta",  1, 70, 180, 260);
    set_diag_item(phi3D,    "phi",    1, 70, 180, 220);
    set_diag_item(dtheta3D, "dtheta", 1, 70, 180, 180);

    // Point size:

    set_diag_item(basepointsize, "point scale", 1, 70, 180, 140);

    // Delay time:

    set_diag_item(DelayTime, "delay time", 1, 70, 180, 100);


    // ---------- Right-hand column of dialog box: ----------

    //          origin star
    //          2-D view axis
    //          3-D plot?

    //          point display mode
    //          color by energy?
    //          track particles?

    // Origin star:

    set_diag_item(originstar, "Origin Star", 0, 320, 360, 460);

    // 2-D view axis:

    set_diag_item(view2D, "2-D view axis", 0, 320, 360, 420);

    // 3D graphics:

    set_diag_item(graph3dim, "3-D graph", 0, 320, 350, 380);

    // Point display mode

    set_diag_item(pointscalemode, "point display mode", 0, 320, 360, 300);

    // Color by energy:

    set_diag_item(colorenergy, "color by energy", 0, 320, 350, 260);

    // Track particles:

    set_diag_item(tracking, "track particles", 0, 320, 350, 220);

    // lux_draw_palette(dia);

    // OK/cancel:

    lux_set_item(dia, ok, BUTTON_WINDOW, OK_BUTTON,
                 _R_(100), _R_(25), 9, "OK, CLEAR");
    lux_set_item(dia, ok_keep, BUTTON_WINDOW, OK_KEEP_BUTTON,
                 _R_(250), _R_(25), 8, "OK, KEEP");
    lux_set_item(dia, cancel, BUTTON_WINDOW, CANCEL_BUTTON,
                 _R_(400), _R_(25), 6, "CANCEL");

    r_factor = save;
}

local void make_relative_to_root(hdyn* b)
{
    vector root_pos = b->get_pos();
    vector root_vel = b->get_vel();
    for_all_nodes(hdyn, b, bi) {
        bi->inc_pos(-root_pos);
        bi->inc_vel(-root_vel);
    }
}

local void update_diag_item(int which)
{
    set_temp_buffer(which);
    lux_update_itemvalue(dia, which, type(which), subtype(which),
                         temp_buffer);
}

local void get_diag_string(int which) {
}

// Overloaded function:

local void read_diag_item(int which, float& f)
{
    lux_get_itemvalue(dia, which, type(which), subtype(which),
                      temp_buffer);
    sscanf(temp_buffer, "%f", &f);
}

local void read_diag_item(int which, int& i)
{
    lux_get_itemvalue(dia, which, type(which), subtype(which),
                      temp_buffer);
    sscanf(temp_buffer, "%d", &i);
}

local void read_diag_item(int which, char& c)
{
    lux_get_itemvalue(dia, which, type(which), subtype(which),
                      temp_buffer);
    c = temp_buffer[0];
}

local void update_from_dialog(bool r_flag)
{
    // Read all data from the dialog box.  Note that it is
    // important that the box be maintained correctly.
    // Any errors in the data displayed in the box will be
    // propogated to the "real" data by this procedure.

    read_diag_item(view2D, kproj);
    if (kproj == 1)
        kx = 1, ky = 2;
    else if (kproj == 2)
        kx = 2, ky = 0;
    else
        kx = 0, ky = 1;

    read_diag_item(originstar, origin_star);

    read_diag_item(Xorigin, origin[0]);
    read_diag_item(Yorigin, origin[1]);
    read_diag_item(Zorigin, origin[2]);

    read_diag_item(lmax3D, lmax3d);
    lmax3d /= 2;                        // display twice lmax3d

    // ------------------------------------------------------

    // NOTE: xmin, xmax, ymin, ymax are IRRELEVANT, since they
    // will be forced to be consistent with origin and lmax3d.

    read_diag_item(xminimum, xmin);
    read_diag_item(xmaximum, xmax);
    read_diag_item(yminimum, ymin);
    read_diag_item(ymaximum, ymax);

    set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);

    // Make sure entries in the dialog box are consistent:

    update_diag_item(xminimum);
    update_diag_item(xmaximum);
    update_diag_item(yminimum);
    update_diag_item(ymaximum);

    // ------------------------------------------------------

    read_diag_item(basepointsize,base_point_size);

    read_diag_item(theta3D, theta);
    costheta = cos(theta);
    sintheta = sin(theta);

    read_diag_item(phi3D, phi);
    cosphi = cos(phi);
    sinphi = sin(phi);

    read_diag_item(dtheta3D, dtheta);

    read_diag_item(DelayTime, delay_time);
    if (delay_time < MIN_DELAY) delay_time = MIN_DELAY;

    read_diag_item(colorenergy, cenergy);
    show_color_scheme(colwin, c_energy, c_index,
                      r_factor, cenergy, r_flag, 1);

    read_diag_item(tracking, track);
    read_diag_item(graph3dim, graph3d);

    lux_clear_window(win);

    if (graph3d) {
        lux_setup_axis(win, -FAC3D*lmax3d, FAC3D*lmax3d, 
                            -FAC3D*lmax3d, FAC3D*lmax3d);
        draw3d_axis(win, lmax3d, costheta, sintheta,
                    cosphi, sinphi);
    } else {
        lux_setup_axis(win, xmin, xmax, ymin, ymax);
        draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);
    }

    read_diag_item(pointscalemode, point_scale_mode);
}

local void show_static_rotation(hdyn* b, bool f_flag)
{
    // Handle static rotation using lux_check_keypress:

    show_instructions(instr, r_factor,
                      "Pause...\n  r: rotate, (p,c): continue                ",
                      1);

    char rotate = 0;
    do {
        if (lux_check_keypress(win,'r')) {
            show_instructions(instr, r_factor,
                      "Rotate... p: pause, c: continue, c: exit rotation     ",
                              0);
            rotate = 1;

            do {
                theta += dtheta;
                if (theta < 0.0)
                    theta += 2*PI;
                else if (theta > PI*2)
                    theta -= 2*PI;
                costheta = cos(theta);
                sintheta = sin(theta);
                update_diag_item(theta3D);

                lux_clear_current_region(win);
                draw3d_axis(win, lmax3d, costheta, sintheta,
                            cosphi, sinphi);

                for_all_leaves(hdyn, b, bi) {

                    float X = (float)bi->get_pos()[0] - origin[0];
                    float Y = (float)bi->get_pos()[1] - origin[1];
                    float Z = (float)bi->get_pos()[2] - origin[2];

                    float actual_point_size = get_point_size(bi);

                    if (   (X > (-lmax3d + actual_point_size))
                        && (X < ( lmax3d - actual_point_size)) 
                        && (Y > (-lmax3d + actual_point_size))
                        && (Y < ( lmax3d - actual_point_size)) 
                        && (Z > (-lmax3d + actual_point_size))
                        && (Z < ( lmax3d - actual_point_size))){

                        float r, s;
                        project3d(X, Y, Z, r, s,
                                  costheta, sintheta,
                                  cosphi, sinphi);

                        if (cenergy) {
                            char c;
                            compute_energies(b, bi, c);
                            lux_set_color(win,c_energy[c]);
                        } else if (clean_index(bi)>0) {
                            if (clean_index(bi) <= N_COLORS)
                                lux_set_color(win,
                                              c_index[clean_index(bi)]);
                            else
                                lux_set_color(win,c_index[1]);
                        }

                        if (track) 
                            lux_draw_pointf(win,r,s);
                        else
                            if (f_flag)
                                lux_fill_arcf(win,
                                              r - actual_point_size/2,
                                              s - actual_point_size/2, 
                                              actual_point_size,
                                              actual_point_size,
                                              0.0, 360.0);
                            else
                                lux_draw_arcf(win,
                                              r - actual_point_size/2,
                                              s - actual_point_size/2, 
                                              actual_point_size,
                                              actual_point_size,
                                              0.0, 360.0);
                    }
                }
                update_with_delay(win, max(MIN_DELAY, delay_time));

                if (lux_check_keypress(win,'p')) 
                    while(!lux_check_keypress(win,'c'));

            } while(!lux_check_keypress(win,'c'));

            // Flush "c"s from input stream:

            while(lux_check_keypress(win,'c'));
        }

    } while(!lux_check_keypress(win,'p')
            && !lux_check_keypress(win,'c') && !rotate);

    rotate = 0;
    lux_set_color(win,c_energy[default_color]);
}

local char check_for_input(unsigned long win, hdyn* b,
                           bool r_flag, bool f_flag, bool eod)
{
    // Check for (and immediately act upon) interactive input.
    // Loop through the input buffer until no more events remain.

    // lux_next_keypress gets and discards the next key in the input stream.

    char key, string[20], shift, control;
    bool key_pressed = false;

    while (lux_next_keypress(win, &key, string, &shift, &control)) {

        // A "defined" key has been pressed.  See if it is one we want.

        key_pressed = true;

        if (key == 0                    // key = 0 for non-ASCII character
                                        // e.g. Up, Down, Home, etc.--see win.c
            || key == 'h'
            || key == 'a') {

            // "Shift" functions:

            int change = 0;

            if (key == 'h')             // keyboard lookalikes for
                change = 4;             // function keys
            else if (key == 'a')
                change = 5;

            else if (strcmp(string, "Up") == 0) {
                change = ky + 1;
                origin[ky] += lmax3d/2;
            } else if (strcmp(string, "Down") == 0) {
                change = ky + 1;
                origin[ky] -= lmax3d/2;
            } else if (strcmp(string, "Right") == 0) {
                change = kx + 1;
                origin[kx] += lmax3d/2;
            } else if (strcmp(string, "Left") == 0) {
                change = kx + 1;
                origin[kx] -= lmax3d/2;
            } else if (strcmp(string, "PgUp") == 0) {
                change = kproj;
                origin[kproj-1] += lmax3d/2;
            } else if (strcmp(string, "PgDn") == 0) {
                change = kproj;
                origin[kproj-1] -= lmax3d/2;
            } else if (strcmp(string, "Home") == 0)
                change = 4;
            else if (strcmp(string, "R11") == 0)
                change = 5;

            if (change) {

                if (change == 4) {
                    origin[kx] = origin[ky] = origin[kproj-1] = 0;
                } else if (change == 5) {

                    real save = lmax3d;
                    lmax3d = 0;

                    // Use all dimensions in redetermining the scale!

                    for_all_leaves(hdyn, b, bi)
                        for (int kk = 0; kk < 3; kk++)
                            lmax3d = max(lmax3d, abs(bi->get_pos()[kk]
                                                     - local_offset[kk]));
                
                    // Round lmax3d up to something reasonable:
                
                    lmax3d *= 1.2;
                    if (lmax3d <= 0) lmax3d = 1;
                
                    real m_log = log10(lmax3d);
                    int i_log = (int) m_log;
                    if (m_log - i_log > 0.699) i_log++;
                    real scale = pow(10.0, i_log);
                    lmax3d = ((int) (lmax3d/scale) + 1) * scale;

                    origin[kx] = origin[ky] = origin[kproj-1] = 0;              
                    base_point_size *= lmax3d/save;
                }

                set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);

                // Update all entries in the dialog box, as needed:

                update_diag_item(xminimum);
                update_diag_item(xmaximum);
                update_diag_item(yminimum);
                update_diag_item(ymaximum);

                if (change == 1 || change >= 4) update_diag_item(Xorigin);
                if (change == 2 || change >= 4) update_diag_item(Yorigin);
                if (change == 3 || change >= 4) update_diag_item(Zorigin);

                if (change == 5) {
                    update_diag_item(basepointsize);
                    update_diag_item(lmax3D);
                }

                // No redrawing of axes is needed for 3D graphs for change != 5.
                
                if (!graph3d) {
                    lux_clear_window(win);
                    lux_setup_axis(win, xmin, xmax, ymin, ymax);
                    draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);
                } else if (change == 5) {
                    lux_clear_window(win);
                    lux_setup_axis(win, -FAC3D*lmax3d, FAC3D*lmax3d, 
                                   -FAC3D*lmax3d, FAC3D*lmax3d);
                    draw3d_axis(win, lmax3d, costheta, sintheta,
                                cosphi, sinphi);
                }
            }

        } else {                        // key is the ASCII code

            // Check for "quit" first.

            if (key == 'q') {
                show_instructions(instr, r_factor,
                    "\n   Quitting...                                        ",
                                  1);
                lux_exit();             // note that this is now quick_exit
            }

            //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

            if (graph3d && !track) {
                int button;

                // 3-D operations:

                if (key== 'R') {

                    show_static_rotation(b, f_flag);

                } else {

                    button = lux_check_buttonpress(win);

                    if (key == '^') {
                        phi = phi - dtheta;
                        if (phi < -PI) phi = phi + 2.0*PI;
                        cosphi = cos(phi);
                        sinphi = sin(phi);
                        update_diag_item(phi3D);
                    } else if (key == 'V') {
                        phi = phi + dtheta;
                        if (phi > PI) phi = phi - 2.0*PI;
                        cosphi = cos(phi);
                        sinphi = sin(phi);
                        update_diag_item(phi3D);
                    } else if (key == '<') {
                        theta = theta + dtheta;
                        if (theta > 2*PI) theta -= 2*PI;
                        costheta = cos(theta);
                        sintheta = sin(theta);
                        update_diag_item(theta3D);
                    } else if (key == '>') {
                        theta = theta - dtheta;
                        if (theta < 0.0) theta += 2*PI;
                        costheta = cos(theta);
                        sintheta = sin(theta);
                        update_diag_item(theta3D);
                    }
                }
            }

            //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

            if (key == 'p' || key == 'P') {     // modify base point size

                if (key == 'p') {
                    if (base_point_size > 4*lmax3d/win_size)
                        base_point_size /= PFAC;
                } else
                    base_point_size *= PFAC;

                update_diag_item(basepointsize);

            } else if (key == 'm') {            // toggle multiple display

                multiples = 1 - multiples;
                if (multiples == 1) nodes = 1;

            } else if (key == 'n') {            // toggle tree display

                nodes = 1 - nodes;
                if (nodes == 0) links = 0;

            } else if (key == 'l') {            // toggle links/nodes

                links = 1 - links;
                if (links == 1) nodes = 1;

            } else if (key == 'r') {            // show root node

                root = 1 - root;

            } else if (key == 't') {            // toggle tracking

                track = 1 - track;
                update_diag_item(tracking);

            } else if (key == 'u') {            // toggle unperturbed display

                unperturbed = 1 - unperturbed;

            } else if (key == '3' && !graph3d) {    // enter 3D mode

                graph3d = 1;
                update_diag_item(graph3dim);
                lux_clear_window(win);
                lux_setup_axis(win, -FAC3D*lmax3d, FAC3D*lmax3d, 
                               -FAC3D*lmax3d, FAC3D*lmax3d);
                draw3d_axis(win, lmax3d, costheta, sintheta, cosphi, sinphi);

                // Refresh the color window.

//              show_color_scheme(colwin, c_energy, c_index,
//                                r_factor, cenergy, r_flag, 1);

            } else if (graph3d &&
                       (key == '2' || key == 'x'
                          || key == 'y' || key == 'k')) {   // enter 2D mode

                graph3d = 0;
                update_diag_item(graph3dim);
                lux_clear_window(win);
                lux_setup_axis(win, xmin, xmax, ymin, ymax);
                draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);

                // Refresh the color window.

//              show_color_scheme(colwin, c_energy, c_index,
//                                r_factor, cenergy, r_flag, 1);

            } else if (key == 'e') {            // color by energy

                cenergy = !cenergy;
                update_diag_item(colorenergy);
                show_color_scheme(colwin, c_energy, c_index,
                                  r_factor, cenergy, r_flag, 1);

            } else if (key == '+' || key == '=') {    // increase delay time

                delay_time *= 2;
                update_diag_item(DelayTime);

            } else if (key == '-') {            // decrease delay time

                delay_time /= 2;
                if (delay_time < MIN_DELAY) delay_time = MIN_DELAY;
                update_diag_item(DelayTime);

            } else if (key == '0') {            // set delay time = "0"

                delay_time = MIN_DELAY;
                update_diag_item(DelayTime);

                // Flush the queue:

                while(lux_check_keypress(win,'+')
                      || lux_check_keypress(win,'-'));

            } else if (key == 'R') {            // color by energy

                show_color_scheme(colwin, c_energy, c_index,
                                  r_factor, cenergy, r_flag, 1);

            } else if (key == 'z') {            // zoom in
                                                // (fixed axes and origin)

                lmax3d /= ZOOM;
                set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);
                base_point_size /= ZOOM;

                if (graph3d) {
                    lux_clear_window(win);
                    lux_setup_axis(win,-FAC3D*lmax3d,FAC3D*lmax3d, 
                                   -FAC3D*lmax3d, FAC3D*lmax3d);
                    draw3d_axis(win, lmax3d, costheta, sintheta,
                                cosphi, sinphi);
                } else {
                    lux_clear_window(win);
                    lux_setup_axis(win, xmin, xmax, ymin, ymax);
                    draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);
                }

                update_diag_item(basepointsize);
                update_diag_item(lmax3D);
                update_diag_item(xminimum);
                update_diag_item(xmaximum);
                update_diag_item(yminimum);
                update_diag_item(ymaximum);

            } else if (key == 'Z') {            // zoom out

                lmax3d *= ZOOM;
                set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);
                base_point_size *= ZOOM;

                if (graph3d) {
                    lux_clear_window(win);
                    lux_setup_axis(win, -FAC3D*lmax3d, FAC3D*lmax3d, 
                                   -FAC3D*lmax3d, FAC3D*lmax3d);
                    draw3d_axis(win, lmax3d, costheta, sintheta,
                                cosphi, sinphi);
                } else {
                    lux_clear_window(win);
                    lux_setup_axis(win, xmin, xmax, ymin, ymax);
                    draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);
                }

                update_diag_item(basepointsize);
                update_diag_item(lmax3D);
                update_diag_item(xminimum);
                update_diag_item(xmaximum);
                update_diag_item(yminimum);
                update_diag_item(ymaximum);

            } else if (key == 'k') {            // change projection axis to z
                                                // (fixed origin, scale)
                if (graph3d) {

                    theta = -PI/2;
                    phi = PI/2.0;
                    costheta = cos(theta);
                    sintheta = sin(theta);
                    cosphi = cos(phi);
                    sinphi = sin(phi);

                    update_diag_item(theta3D);
                    update_diag_item(phi3D);

                    while (lux_check_keypress(win,'<')
                           || lux_check_keypress(win,'>')
                           || lux_check_keypress(win,'^')
                           || lux_check_keypress(win,'V') );

                } else {

                    kproj = 3;
                    kx = 0;
                    ky = 1;
                    set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);
                    lux_clear_window(win);
                    lux_setup_axis(win, xmin, xmax, ymin, ymax);
                    draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);

                    update_diag_item(view2D);

                }

            } else if (key == 'y') {            // change projection axis to y

                if (graph3d) {

                    theta = -PI/2.0;
                    phi = 0.0;
                    costheta = cos(theta);
                    sintheta = sin(theta);
                    cosphi = cos(phi);
                    sinphi = sin(phi);

                    while (lux_check_keypress(win,'<')
                           || lux_check_keypress(win,'>')
                           || lux_check_keypress(win,'^')
                           || lux_check_keypress(win,'V') );

                    update_diag_item(theta3D);
                    update_diag_item(phi3D);

                } else {

                    kproj = 2;
                    kx = 2;
                    ky = 0;
                    set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);
                    lux_clear_window(win);
                    lux_setup_axis(win, xmin, xmax, ymin, ymax);
                    draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);

                    update_diag_item(view2D);

                }

            } else if (key == 'x') {            // change projection axis to x

                if (graph3d) {
                    theta = 0.0;
                    phi = 0.0;
                    costheta = cos(theta);
                    sintheta = sin(theta);
                    cosphi = cos(phi);
                    sinphi = sin(phi);

                    while (lux_check_keypress(win,'<')
                           || lux_check_keypress(win,'>')
                           || lux_check_keypress(win,'^')
                           || lux_check_keypress(win,'V') );

                    update_diag_item(theta3D);
                    update_diag_item(phi3D);

                } else {

                    kproj = 1;
                    kx = 1;
                    ky = 2;
                    set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);
                    lux_clear_window(win);
                    lux_setup_axis(win, xmin, xmax, ymin, ymax);
                    draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);

                    update_diag_item(view2D);

                }
            }

            // Select new origin: 'o' ==> point in space, 'O' ==> star

            if (key == 'o' && !graph3d) {

                show_instructions(instr, r_factor,
                " Use mouse-right to select new origin...\n",1);
                float r, s;
                get_mouse_position(win, &r, &s);

                // Looks like r and s come back in the correct units!

                origin[kx] = r;
                origin[ky] = s;
                set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);

                lux_clear_window(win);
                lux_setup_axis(win, xmin, xmax, ymin, ymax);
                draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);

                origin_star = -1;

                update_diag_item(Xorigin);
                update_diag_item(Yorigin);
                update_diag_item(Zorigin);
                update_diag_item(xminimum);
                update_diag_item(xmaximum);
                update_diag_item(yminimum);
                update_diag_item(ymaximum);
                update_diag_item(originstar);

            } else if (!graph3d && key == 'O') {

                show_instructions(instr, r_factor,
                " Use mouse-right to select new origin star...\n",1);
                float r, s;
                get_mouse_position(win, &r, &s);

                // Looks like r and s come back in the correct units!

                // Find the star closest to the (2-D) mouse position.

                origin_star = nearest_index(b, r, s, kx, ky);

                if (origin_star > 0) {
                    for (int kk = 0; kk < 3; kk++) origin[kk] = 0;
                    set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);
                }

                lux_clear_window(win);
                lux_setup_axis(win, xmin, xmax, ymin, ymax);
                draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);

                update_diag_item(Xorigin);
                update_diag_item(Yorigin);
                update_diag_item(Zorigin);
                update_diag_item(xminimum);
                update_diag_item(xmaximum);
                update_diag_item(yminimum);
                update_diag_item(ymaximum);
                update_diag_item(originstar);

            } else if (key == 'b' || key == 'B') {

                return 'b';

            } else if (key == 'c' || key == 'C') {

                return 'c';

            } else if (key == 'f' || key == 'F' || key == 's' || key == 'S') {

                return 'f';

            }

            // -------------------------------------------------------------

            while(lux_check_keypress(win,'r'));  // clean up any replay garbage

            // Idle mode and dialog box input:

            int return_value = 0;

            if (key == 'i') {

                show_instructions(instr, r_factor,
                  " Idle...\n  d: dialog, r: replay, c: continue, q: quit",1);
                return_value = lux_getevent();

            } else if (key == 'd') {

                show_instructions(instr, r_factor,
"Dialog mode keyboard options\n\n\
  Dialog window:\n\
    o   OK, keep dialog window\n\
    O   OK, close dialog window\n\
    c   CANCEL, keep dialog window\n\
    C   CANCEL, close dialog window\n\n\
  Other windows:\n\
    r   replay\n\
    c   continue (keep dialog window,\n\
                  ignore dialog changes)\n\
    q   quit\n\
",1);
                lux_show_dialog(dia);
                return_value = lux_getevent();
            }
            
            // Update all values if OK button was clicked (clicking
            // OK forces a return value of 3).
            
            if (return_value == 3) update_from_dialog(r_flag);

        }
    }

    if (key_pressed) {

        // Hitting any key will cause the instruction and color
        // windows to be updated immediately.

        show_main_instructions(instr, r_factor, graph3d, 1, eod,
                               nodes, links, multiples, unperturbed, root);
        show_color_scheme(colwin, c_energy, c_index,
                          r_factor, cenergy, r_flag, 1);

        return ' ';
    }

    return 0;
}

/*-----------------------------------------------------------------------------
 *  xstarplot.C  --  project the positions of all particles onto the screen
 *                   input:   pn: a pointer to a nbody system,
 *                              k: the number of the coordinate axis along which
 *                                 the projection is directed, with {k,x,y}
 *                                 having a right-handed orientation,
 *                           xmax: displayed x-axis spans [-xmax, xmax]
 *                           ymax: displayed y-axis spans [-ymax, ymax]
 *-----------------------------------------------------------------------------
 */

#define INSTR_FREQ_MAX 32
#define INSTR_FREQ_FAC 64
static int instr_freq = INSTR_FREQ_MAX;
static int count_instr = 0;

void xstarplot(hdyn* b, float scale, int k, int d, float lmax,
               int point_mode, float rel_point_size,
               float D, int ce,
               bool r_flag, bool f_flag, bool t_flag,
               int init_flag, int& step_mode, bool eod)
{
    r_factor = scale;

    if (!eod && init_flag == 0) {

        int xorigin, yorigin;

        if (t_flag) nodes = links = 1;

        // Open windows for plotting and instructions, set up color
        // schemes, etc.

        if (init_status == 0) initialize_graphics(r_factor, r_flag,
                                                  win, instr, colwin,
                                                  c_index, c_energy,
                                                  win_size, xorigin, yorigin);
        lux_clear_window(win);
        lux_update_fg(win);
        lux_clear_window(colwin);
        lux_update_fg(colwin);
        lux_clear_window(instr);
        lux_update_fg(instr);

        // Determine which axes to plot:

        kproj = k;
        switch (kproj) {
            case 1:     kx = 1; ky = 2; graph3d = 0; break;
            case 2:     kx = 2; ky = 0; graph3d = 0; break;
            case 3:     kx = 0; ky = 1; graph3d = 0; break;
            default:    cerr << "xstarplot: k = " << k
                             << ": illegal value; choose from {1, 2, 3}"
                             << endl;
                        exit(0);
        }

        switch(d) {
            case 2:     graph3d = 0;  break;
            case 3:     graph3d = 1;  break;
            default:    cerr << "xstarplot: d = " << d
                             << " illegal value; choose from {2, 3)"
                             << endl;
                        exit(0);
        }

        point_scale_mode = point_mode;

        cenergy = ce?1:0;
        show_color_scheme(colwin, c_energy, c_index,
                          r_factor, cenergy, r_flag, 1);

        delay_time = D;

        if (lmax > 0.0)

            lmax3d = lmax;

        else {

            lmax3d = 0;

            // Use all dimensions in determining the initial scale!

            for_all_leaves(hdyn, b, bi)
                for (int kk = 0; kk < 3; kk++)
                    lmax3d = max(lmax3d, abs(bi->get_pos()[kk]));

            // Round lmax3d up to something reasonable:

            lmax3d *= 1.2;
            if (lmax3d <= 0) lmax3d = 1;

            real m_log = log10(lmax3d);
            int i_log = (int) m_log;
            if (m_log - i_log > 0.699) i_log++;
            real scale = pow(10.0, i_log);
            lmax3d = ((int) (lmax3d/scale) + 1) * scale;
        }

        for (int ko = 0; ko < 3; ko++)
            origin[ko] = 0;

        set_limits(origin, lmax3d, kx, xmin, xmax, ky, ymin, ymax);
        set_base_point_size(b, rel_point_size);
        
        if (graph3d) {
            lux_setup_axis(win, -FAC3D*lmax3d, FAC3D*lmax3d, 
                           -FAC3D*lmax3d, FAC3D*lmax3d);      
            draw3d_axis(win, lmax3d, costheta, sintheta, cosphi, sinphi);
        } else {
            lux_setup_axis(win, xmin, xmax, ymin, ymax);
            draw2d_axis(win, xmin, xmax, ymin, ymax, kproj);
        }

        // Complete the initialization with the dialog box.

        if (init_status == 0)
            initialize_dialog(xorigin, yorigin);

        init_status = 1;
            
    }

    //------------------------------------------------------------------------

    // End of initialization or start of next plot.
    // Delete current points, and possibly redraw axes and instructions.

    if (track == 0) {
        lux_clear_current_region(win);
        if (graph3d) draw3d_axis(win, lmax3d, costheta, sintheta,
                                 cosphi, sinphi);
    }

    if (!eod) {

        // Showing these instructions too frequently causes malloc problems
        // in lux_draw_image_string (for unknown reasons; possibly this is
        // a timing problem of some sort with the X display).
        //
        // Work around the problem by reducing the display frequency.
        // See also gfx_util for further limitations.

        instr_freq = INSTR_FREQ_FAC / b->n_leaves();
        if (instr_freq > INSTR_FREQ_MAX) instr_freq = INSTR_FREQ_MAX;
        if (instr_freq < 1) instr_freq = 1;

        if (count_instr++%instr_freq == 0)
            show_main_instructions(instr, r_factor, graph3d, 1, eod,
                                   nodes, links, multiples, unperturbed, root);
    }

    //------------------------------------------------------------------------

    // Always express all positions and velocities relative to the root node.
    // (There is no requirement that the root node be at rest at the origin...)

    make_relative_to_root(b);

    // Determine local offset, if any.

    if (origin_star > 0) {
        for_all_leaves(hdyn, b, bi)
            if (clean_index(bi) == origin_star) {
                for (int kk = 0; kk < 3; kk++)
                    local_offset[kk] = bi->get_pos()[kk];
                break;
            }
    } else
        for (int kk = 0; kk < 3; kk++)
            local_offset[kk] = 0;

    // Plot the data points (sorted by kproj-component in the 2D case):

    int n_stars = plot_stars(b, f_flag);

    // Update headers.

    lux_set_color(win, c_energy[default_color]);

    if (graph3d) {

        //sprintf(temp_buffer, "   N = %d (snapshot #%5d) max=%5.3f   ",
        //      n_stars, init_flag + 1, lmax3d);
        sprintf(temp_buffer, "   N = %d (t = %.3f) max=%5.3f   ",
                n_stars, b->get_real_system_time(), lmax3d);
        lux_draw_image_string(win, 0.0, lmax3d*FAC3D, 0.5, temp_buffer, 0);

    } else {

        //sprintf(temp_buffer, "   N = %d  (snapshot #%5d)   ",
        //      n_stars, init_flag + 1);
        sprintf(temp_buffer, "   N = %d  (frame %d, t = %.3f)   ",
                n_stars, init_flag + 1, b->get_real_system_time());
        lux_draw_image_string(win, (xmin+xmax)/2.0, ymax, 0.5, temp_buffer, 0);

    }

    // Update the display.

    update_with_delay(win, max(MIN_DELAY, delay_time));

    // Deal with user input.  In step mode, wait for
    // 'b', 'c', or 's' before continuing.

    while (true) {

        char c = check_for_input(win, b, r_flag, f_flag, eod);

        // Special treatment required for forward/backward step modes.

        if (c == 'b' || c == 'f') {             // Enter/continue step mode

            step_mode = (c == 'b' ? -1 : 1);
            return;

        } else if (c == 'c') {                  // Cancel step mode

            if (eod)
                step_mode = 1;
            else
                step_mode = 0;

            return;
        }

        // In eod mode, hitting 'b' or 'f' will go to a new frame.
        // Hitting any other key will cause the current frame to be
        // redisplayed (with any specified changes made).

        if (eod && c != 0) {
            step_mode = 0;
            return;
        }
        if (!eod && step_mode == 0) return;

        // Wait for 10 milliseconds before retrying.

        lux_pause(10000);
    }

}

/*-----------------------------------------------------------------------------
 *  main  --  driver to use  xstarplot()  as a tool. 
 *               The argument -a is interpreted as the axis along which to
 *            view the N-body system: the number of the coordinate axis along
 *            which the projection is directed, with {k,x,y} having a
 *            right-handend orientation.
 *               If an argument -l is provided, it defines the maximum
 *            lengths along the remaining axes.
 *-----------------------------------------------------------------------------
 */

main(int argc, char** argv)
{
    // Establish some defaults:

    int   k = 3;                // Note x = 1, y = 2, z = 3 here!
    int   d = 2;
    float D = 16*MIN_DELAY;
    int   cenergy = 0;
    float lmax = -1.0;
    int   point_mode = 0;
    float rel_point_size = 0.0;
    float scale = 1.0;

    bool  f_flag = TRUE;        // if TRUE, the star is solid
    bool  o_flag = FALSE;       // if TRUE, output stdin to stdout
    bool  r_flag = TRUE;        // if TRUE, the background is black
    bool  t_flag = FALSE;       // if TRUE, show tree structure

    bool verbose = false;

    // Store snapshots in a short circular list to allow backward steps.
    // Note: "short" is relative.  Currently, 128 copies of a 1000-body
    // is too much to keep in memory!

#define MAX_SNAP 64

    hdynptr b[MAX_SNAP];        // Array of snapshots
    int max_snap = 1;

    check_help();

    extern char *poptarg;
    char* params = "a:bd:D:efl:L:mop:P:rs:tuv";
    int   c;

    while ((c = pgetopt(argc, argv, params)) != -1)
        switch(c) {

            case 'a': k = atoi(poptarg);        // projection axis [z]
                      break;
            case 'b': max_snap = MAX_SNAP;      // allow backward steps [no]
                      break;
            case 'd': d = atoi(poptarg);        // number of dimensions [2]
                      break;
            case 'D': D = atof(poptarg);        // delay between frames [0]
                      break;
            case 'e': cenergy = 1;              // color by energy [no]
                      break;
            case 'f': f_flag = FALSE;           // fill star points [yes]
                      break;
            case 'L':
            case 'l': lmax = atof(poptarg);     // axes +/- lmax [use data]
                      break;
            case 'm': multiples = 1 - multiples;
                      break;
            case 'o': o_flag = TRUE;            // output stdin to stdout [no]
                      break;
            case 'p': point_mode = atoi(poptarg);       // point scale mode [0]
                      break;
            case 'P': rel_point_size = atof(poptarg);   // point scale factor
                      if (rel_point_size < 0.5)
                          rel_point_size = 0.5;
                      break;
            case 'r': r_flag = FALSE;           // black background [yes]
                      break;
            case 's': scale = atof(poptarg);    // rescale display [1.0]
                      break;
            case 't': t_flag = TRUE;            // show tree links [no]
                      break;
            case 'u': unperturbed = 1 - unperturbed;
                      break;
            case 'v': verbose = true;           // verbose mode [no]
                      break;
            case '?': params_to_usage(cerr, argv[0], params);
                      get_help();
                      exit(0);
        }            

    int * frame_id = new int[max_snap]; // Global ids of snapshots
    frame_id[max_snap-1] = -1;

    int snap_counter = -1;      // Index of frame in snapshot array.
    int first_snap = 0;         // The usable list runs from first_snap to
    bool wrapped = false;       // snap_counter, wrapping if necessary.
    int step_mode = 0;
    int snap_display = -1;      // Index of frame currently being displayed.
    int isnap = 0;

    bool eod = false;

    while (true) {

        // Get index of next location to be filled, and update bookeeping.
        // Definition of "next" depends on step_mode.

        if (step_mode >= 0) {

            // Obtain the next snapshot to display.

            if (!eod && snap_display == snap_counter) {

                // Read in a new snapshot from stdin.

                hdyn* bbb;
                bbb = get_hdyn(cin);

                if (bbb == NULL) {

                    // End of input data.

                    cerr << "End of input data reached;"
                         << " entering step mode."
                         << endl << flush;
                    step_mode = 1;
                    eod = true;

                    if (o_flag) cout << "End of data\n" << flush;

                } else {

                    // Place the new snapshot on the list.

                    if (++snap_counter >= max_snap) {
                        snap_counter = 0;
                        wrapped = true;
                    }

                    if (wrapped) {

                        // Clean up the contents of the element we are
                        // about to overwrite.

                        rmtree(b[snap_counter]);
                        first_snap = snap_counter + 1;
                        if (first_snap >= max_snap) first_snap = 0;
                    }

                    b[snap_counter] = bbb;
                    if (verbose)
                        cerr << "Snap " << isnap++
                             << ":  t = " << bbb->get_system_time()
                             << ",  N = " << bbb->n_leaves() << endl;

                    // Convert all coordinates to absolute values.

                    convert_relative_to_absolute(b[snap_counter]);

                    int prev_snap = snap_counter - 1;
                    if (prev_snap < 0) prev_snap = max_snap -1;
                    frame_id[snap_counter] = frame_id[prev_snap] + 1;

                    snap_display = snap_counter;
                    if (o_flag) put_node(cout, *b[snap_display]);
                }

            } else {

                // Use an existing snapshot.

                if (!eod || step_mode > 0) snap_display++;

                if (snap_display >= max_snap) snap_display = 0;
                if (!wrapped && snap_display > snap_counter)
                    snap_display = 0;

            }

        } else {

            // Use an existing snapshot.

            if (--snap_display < 0) {
                if (!wrapped)
                    snap_display = snap_counter;
                else
                    snap_display = max_snap - 1;
            }

        }

        // We have a legal snapshot.  Transform and display it.

        xstarplot(b[snap_display], scale, k, d, lmax,
                  point_mode, rel_point_size, D, cenergy,
                  r_flag, f_flag, t_flag, frame_id[snap_display],
                  step_mode, eod);

    }
}

---