The R Project SVN R

/*
 *  R : A Computer Language for Statistical Data Analysis
 *  Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka
 *  Copyright (C) 1997--1999  Robert Gentleman, Ross Ihaka and the
 *                            R Development Core Team
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef HAVE_CONFIG_H
#include <Rconfig.h>
#endif

#include "Defn.h"
#include "Mathlib.h"
#include "Graphics.h"
#include "Print.h"

void NewFrameConfirm()
{
    char buf[16];
    R_ReadConsole("Hit <Return> to see next plot: ", buf, 16, 0);
}

    /* Remember: +1 and/or -1 because C arrays are */
    /* zero-based and R-vectors are one-based. */

#define checkArity_length                   \
    checkArity(op, args);                   \
    if(!LENGTH(CAR(args)))                  \
    errorcall(call, "argument must have positive length")


SEXP do_devcontrol(SEXP call, SEXP op, SEXP args, SEXP env)
{
    checkArity(op, args);
    inhibitDisplayList(CurrentDevice());
    return R_NilValue;
}

SEXP do_devcopy(SEXP call, SEXP op, SEXP args, SEXP env)
{
    checkArity_length;
    copyDisplayList(INTEGER(CAR(args))[0] - 1);
    return R_NilValue;
}

SEXP do_devcur(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP cd = allocVector(INTSXP, 1);
    checkArity(op, args);
    INTEGER(cd)[0] = curDevice() + 1;
    return cd;
}

SEXP do_devnext(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP nd = allocVector(INTSXP, 1);
    checkArity_length;
    INTEGER(nd)[0] = nextDevice(INTEGER(CAR(args))[0] - 1) + 1;
    return nd;
}

SEXP do_devprev(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP pd = allocVector(INTSXP, 1);
    checkArity_length;
    INTEGER(pd)[0] = prevDevice(INTEGER(CAR(args))[0] - 1) + 1;
    return pd;
}

SEXP do_devset(SEXP call, SEXP op, SEXP args, SEXP env)
{
    int devNum = INTEGER(CAR(args))[0] - 1;
    SEXP sd = allocVector(INTSXP, 1);
    checkArity(op, args);
    INTEGER(sd)[0] = selectDevice(devNum) + 1;
    return sd;
}

SEXP do_devoff(SEXP call, SEXP op, SEXP args, SEXP env)
{
    checkArity_length;
    killDevice(INTEGER(CAR(args))[0] - 1);
    return R_NilValue;
}


/*  P A R A M E T E R    U T I L I T I E S  */


/* ProcessInLinePars handles inline par specifications in graphics functions.
 * It does this by calling Specify2() from ./par.c */

void ProcessInlinePars(SEXP s, DevDesc *dd)
{
    if (isList(s)) {
    while (s != R_NilValue) {
        if (isList(CAR(s)))
        ProcessInlinePars(CAR(s), dd);
        else if (TAG(s) != R_NilValue)
        Specify2(CHAR(PRINTNAME(TAG(s))), CAR(s), dd);
        s = CDR(s);
    }
    }
}

/* GetPar is intended for looking through a list  -- typically that bound
 *  to ... --  for a particular parameter value.  This is easier than
 *  trying to match every graphics parameter in argument lists explicitly.
 * FIXME: This needs to be destructive, so that "ProcessInlinePars"
 *  can be safely called afterwards.
 */
SEXP GetPar(char *which, SEXP parlist)
{
    SEXP w, p;
    w = install(which);
    for (p = parlist; p != R_NilValue; p = CDR(p)) {
    if (TAG(p) == w)
        return CAR(p);
    }
    return R_NilValue;
}

SEXP FixupPch(SEXP pch, int dflt)
{
    int i, n;
    SEXP ans = R_NilValue;/* -Wall*/

    n = length(pch);
    if (n == 0) {
    ans = allocVector(INTSXP, 1);
    INTEGER(ans)[0] = dflt;
    }
    else if (isList(pch)) {
    ans = allocVector(INTSXP, n);
    for (i = 0; pch != R_NilValue;  pch = CDR(pch))
        INTEGER(ans)[i++] = asInteger(CAR(pch));
    }
    else if (isInteger(pch)) {
    ans = allocVector(INTSXP, n);
    for (i = 0; i < n; i++)
        INTEGER(ans)[i] = INTEGER(pch)[i];
    }
    else if (isReal(pch)) {
    ans = allocVector(INTSXP, n);
    for (i = 0; i < n; i++)
        INTEGER(ans)[i] = R_FINITE(REAL(pch)[i]) ?
        REAL(pch)[i] : NA_INTEGER;
    }
    else if (isString(pch)) {
    ans = allocVector(INTSXP, n);
    for (i = 0; i < n; i++)
        INTEGER(ans)[i] = CHAR(STRING(pch)[i])[0];
    }
    else error("invalid plotting symbol");
    for (i = 0; i < n; i++) {
    if (INTEGER(ans)[i] < 0)
        INTEGER(ans)[i] = dflt;
    }
    return ans;
}

SEXP FixupLty(SEXP lty, int dflt)
{
    int i, n;
    SEXP ans;
    n = length(lty);
    if (n == 0) {
    ans = allocVector(INTSXP, 1);
    INTEGER(ans)[0] = dflt;
    }
    else {
    ans = allocVector(INTSXP, n);
    for (i = 0; i < n; i++)
        INTEGER(ans)[i] = LTYpar(lty, i);
    }
    return ans;
}

SEXP FixupLwd(SEXP lwd, double dflt)
{
    int i, n;
    double w;
    SEXP ans = NULL;

    n = length(lwd);
    if (n == 0) {
        ans = allocVector(REALSXP, 1);
        REAL(ans)[0] = dflt;
    }
    else {
    PROTECT(lwd = coerceVector(lwd, REALSXP));
    n = length(lwd);
        ans = allocVector(REALSXP, n);
        for (i = 0; i < n; i++) {
            w = REAL(lwd)[i];
        if (w < 0) w = NA_REAL;
            REAL(ans)[i] = w;

    }
    UNPROTECT(1);
    }
    return ans;
}

SEXP FixupFont(SEXP font, int dflt)
{
    int i, k, n;
    SEXP ans = R_NilValue;/* -Wall*/
    n = length(font);
    if (n == 0) {
    ans = allocVector(INTSXP, 1);
    INTEGER(ans)[0] = dflt;
    }
    else if (isInteger(font) || isLogical(font)) {
    ans = allocVector(INTSXP, n);
    for (i = 0; i < n; i++) {
        k = INTEGER(font)[i];
        if (k < 1 || k > 4) k = NA_INTEGER;
        INTEGER(ans)[i] = k;
    }
    }
    else if (isReal(font)) {
    ans = allocVector(INTSXP, n);
    for (i = 0; i < n; i++) {
        k = REAL(font)[i];
        if (k < 1 || k > 4) k = NA_INTEGER;
        INTEGER(ans)[i] = k;
    }
    }
    else error("invalid font specification");
    return ans;
}

SEXP FixupCol(SEXP col, unsigned int dflt)
{
    int i, n;
    SEXP ans;
    n = length(col);
    if (length(col) == 0) {
    ans = allocVector(INTSXP, 1);
    INTEGER(ans)[0] = dflt;
    }
    else if (isList(col)) {
    ans = allocVector(INTSXP, n);
    for (i = 0; i < n; i++) {
        INTEGER(ans)[i] = RGBpar(CAR(col), 0);
        col = CDR(col);
    }
    }
    else {
    ans = allocVector(INTSXP, n);
    for (i = 0; i < n; i++)
        INTEGER(ans)[i] = RGBpar(col, i);
    }
    return ans;
}

SEXP FixupCex(SEXP cex, double dflt)
{
    SEXP ans = R_NilValue;/* -Wall*/
    int i, n;
    double c;
    n = length(cex);
    if (length(cex) == 0) {
    ans = allocVector(REALSXP, 1);
    if (R_FINITE(dflt) && dflt > 0)
        REAL(ans)[0] = dflt;
    else
        REAL(ans)[0] = NA_REAL;
    }
    else if (isReal(cex)) {
    ans = allocVector(REALSXP, n);
    for (i = 0; i < n; i++) {
        c = REAL(cex)[i];
        if (R_FINITE(c) && c > 0)
        REAL(ans)[i] = c;
        else
        REAL(ans)[i] = NA_REAL;
    }
    }
    else if (isInteger(cex) || isLogical(cex)) {
    ans = allocVector(REALSXP, n);
    for (i = 0; i < n; i++) {
        c = INTEGER(cex)[i];
        if (c == NA_INTEGER || c <= 0)
        c = NA_REAL;
        REAL(ans)[i] = c;
    }
    }
    return ans;
}


    /* GRAPHICS FUNCTION ENTRY POINTS */


SEXP do_plot_new(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /* plot.new(ask) - create a new plot "frame" */
    int ask, asksave;
    DevDesc *dd;

    checkArity(op, args);

    ask = asLogical(CAR(args));
    dd = GNewPlot(call != R_NilValue, ask);

    ask = asLogical(CAR(args));
    if (ask == NA_LOGICAL)
    ask = dd->dp.ask;
    asksave = dd->gp.ask;
    dd->gp.ask = ask;


    dd->dp.xlog = dd->gp.xlog = 0;
    dd->dp.ylog = dd->gp.ylog = 0;

    GScale(0.0, 1.0, 1, dd);
    GScale(0.0, 1.0, 2, dd);
    GMapWin2Fig(dd);
    GSetState(1, dd);

    dd->gp.ask = asksave;
    /* NOTE: during replays, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, args, dd);
    return R_NilValue;
}


/*
 *  SYNOPSIS
 *
 *  plot.window(xlim, ylim, log="", asp=NA)
 *
 *  DESCRIPTION
 *
 *  This function sets up the world coordinates for a graphics
 *  window.  Note that if asp is a finite positive value then
 *  the window is set up so that one data unit in the y direction
 *  is equal in length to one data unit in the x direction divided
 *  by asp.
 *
 *  The special case asp == 1 produces plots where distances
 *  between points are represented accurately on screen.
 *
 *  NOTE
 *
 *  The use of asp can have weird effects when axis is an
 *  interpreted function.  It has to be internal so that the
 *  full computation is captured in the display list.
 */

SEXP do_plot_window(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP xlim, ylim, log;
    double asp, xmin, xmax, ymin, ymax;
    int logscale;
    char *p;
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    if (length(args) < 3)
    errorcall(call, "at least 3 arguments required");

    xlim = CAR(args);
    if (!isNumeric(xlim) || LENGTH(xlim) != 2)
    errorcall(call, "invalid xlim");
    args = CDR(args);

    ylim = CAR(args);
    if (!isNumeric(ylim) || LENGTH(ylim) != 2)
    errorcall(call, "invalid ylim");
    args = CDR(args);

    logscale = 0;
    log = CAR(args);
    if (!isString(log))
    errorcall(call, "\"log=\" specification must be character");
    p = CHAR(STRING(log)[0]);
    while (*p) {
    switch (*p) {
    case 'x':
        dd->dp.xlog = dd->gp.xlog = 1;
        logscale = 1;
        break;
    case 'y':
        dd->dp.ylog = dd->gp.ylog = 1;
        logscale = 1;
        break;
    default:
        errorcall(call,"invalid \"log=%s\" specification",p);
    }
    p++;
    }
    args = CDR(args);

    asp = asReal(CAR(args));
    if (logscale) asp = NA_REAL;
    args = CDR(args);

    GSavePars(dd);
    ProcessInlinePars(args, dd);

    if (isInteger(xlim)) {
    if (INTEGER(xlim)[0] == NA_INTEGER || INTEGER(xlim)[1] == NA_INTEGER)
        errorcall(call, "NAs not allowed in xlim");
    xmin = INTEGER(xlim)[0];
    xmax = INTEGER(xlim)[1];
    }
    else {
    if (!R_FINITE(REAL(xlim)[0]) || !R_FINITE(REAL(xlim)[1]))
        errorcall(call, "need finite xlim values");
    xmin = REAL(xlim)[0];
    xmax = REAL(xlim)[1];
    }
    if (isInteger(ylim)) {
    if (INTEGER(ylim)[0] == NA_INTEGER || INTEGER(ylim)[1] == NA_INTEGER)
        errorcall(call, "NAs not allowed in ylim");
    ymin = INTEGER(ylim)[0];
    ymax = INTEGER(ylim)[1];
    }
    else {
    if (!R_FINITE(REAL(ylim)[0]) || !R_FINITE(REAL(ylim)[1]))
        errorcall(call, "need finite ylim values");
    ymin = REAL(ylim)[0];
    ymax = REAL(ylim)[1];
    }
    if ((dd->dp.xlog && (xmin < 0 || xmax < 0)) ||
       (dd->dp.ylog && (ymin < 0 || ymax < 0)))
        errorcall(call, "Logarithmic axis must have positive limits");

    if (R_FINITE(asp) && asp > 0) {
    double pin1, pin2, scale, xdelta, ydelta, xscale, yscale, xadd, yadd;
    pin1 = GConvertXUnits(1.0, NPC, INCHES, dd);
    pin2 = GConvertYUnits(1.0, NPC, INCHES, dd);
    xdelta = fabs(xmax - xmin) / asp;
    ydelta = fabs(ymax - ymin);
    xscale = pin1 / xdelta;
    yscale = pin2 / ydelta;
    scale = (xscale < yscale) ? xscale : yscale;
    xadd = .5 * (pin1 / scale - xdelta) * asp;
    yadd = .5 * (pin2 / scale - ydelta);
    GScale(xmin - xadd, xmax + xadd, 1, dd);
    GScale(ymin - yadd, ymax + yadd, 2, dd);
    }
    else {
    GScale(xmin, xmax, 1, dd);
    GScale(ymin, ymax, 2, dd);
    }
    GMapWin2Fig(dd);
    GRestorePars(dd);
    /* NOTE: the operation is only recorded if there was no "error" */
    /* NOTE: if we're replaying then call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}

static void GetAxisLimits(double left, double right, double *low, double *high)
{
/*  Called from do_axis()   such as
 *  GetAxisLimits(dd->gp.usr[0], dd->gp.usr[1], &low, &high)
 *
 *  Computes  *low < left, right < *high  (even if left=right)
 */
    double eps;
    if (left > right) {/* swap */
    eps = left; left = right; right = eps;
    }
    eps = right - left;
    if (eps == 0.)
    eps = 0.5 * FLT_EPSILON;
    else
    eps *= FLT_EPSILON;
    *low = left - eps;
    *high = right + eps;
}


/* axis(side, at, labels, ...) */

static SEXP labelformat(SEXP labels)
{
    SEXP ans = R_NilValue;/* -Wall*/
    int save_digits, i, n, w, d, e, wi, di, ei;
    char *strp;
    n = length(labels);
    save_digits = R_print.digits;
    R_print.digits = 7;
    switch(TYPEOF(labels)) {
    case LGLSXP:
    PROTECT(ans = allocVector(STRSXP, n));
    for (i = 0; i < n; i++) {
        strp = EncodeLogical(LOGICAL(labels)[i], 0);
        STRING(ans)[i] = mkChar(strp);
    }
    UNPROTECT(1);
    break;
    case INTSXP:
    PROTECT(ans = allocVector(STRSXP, n));
    for (i = 0; i < n; i++) {
        strp = EncodeInteger(INTEGER(labels)[i], 0);
        STRING(ans)[i] = mkChar(strp);
    }
    UNPROTECT(1);
    break;
    case REALSXP:
    formatReal(REAL(labels), n, &w, &d, &e);
    PROTECT(ans = allocVector(STRSXP, n));
    for (i = 0; i < n; i++) {
        strp = EncodeReal(REAL(labels)[i], 0, d, e);
        STRING(ans)[i] = mkChar(strp);
    }
    UNPROTECT(1);
    break;
    case CPLXSXP:
    formatComplex(COMPLEX(labels), n, &w, &d, &e, &wi, &di, &ei);
    PROTECT(ans = allocVector(STRSXP, n));
    for (i = 0; i < n; i++) {
        strp = EncodeComplex(COMPLEX(labels)[i], 0, d, e, 0, di, ei);
        STRING(ans)[i] = mkChar(strp);
    }
    UNPROTECT(1);
    break;
    case STRSXP:
    formatString(STRING(labels), n, &w, 0);
    PROTECT(ans = allocVector(STRSXP, n));
    for (i = 0; i < n; i++) {
#ifdef OLD
        strp = EncodeString(CHAR(STRING(labels)[i]), 0, 0, adj_left);
        STRING(ans)[i] = mkChar(strp);
#else
        STRING(ans)[i] = STRING(labels)[i];
#endif
    }
    UNPROTECT(1);
    break;
    default:
    error("invalid type for axis labels");
    }
    return ans;
}

static SEXP CreateAtVector(double *axp, double *usr, int nint, int log)
{
/*  Create an  'at = ...' vector for  axis(.) / do_axis,
 *  i.e., the vector of tick mark locations,
 *  when none has been specified (= default).
 *
 *  axp[0:2] = (x1, x2, nint), where x1..x2 are the extreme tick marks
 *
 *  The resulting REAL vector must have length >= 1, ideally >= 2
 */
    SEXP at = R_NilValue;/* -Wall*/
    double umin, umax, dn, rng, small;
    int i, n, ne;
    if (!log || axp[2] < 0) { /* ---- linear axis ---- Only use axp[]  arg. */
    n = fabs(axp[2]) + 0.25;/* >= 0 */
    dn = n;
    rng = axp[1] - axp[0];
    small = fabs(rng)/(100.*dn);
    at = allocVector(REALSXP, n + 1);
    for (i = 0; i <= n; i++) {
        REAL(at)[i] = axp[0] + (i / dn) * rng;
        if (fabs(REAL(at)[i]) < small)
        REAL(at)[i] = 0;
    }
    }
    else { /* ------ log axis ----- */
    n = (axp[2] + 0.5);
    /* {xy}axp[2] for 'log': GLpretty() [../graphics.c] sets
       n < 0: very small scale ==> linear axis, above, or
       n = 1,2,3.  see switch() below */
    umin = usr[0];
    umax = usr[1];
    /* Debugging: When does the following happen... ? */
    if (umin > umax)
        warning("CreateAtVector \"log\"(from axis()): "
            "usr[0] = %g > %g = usr[1] !", umin, umax);
    dn = axp[0];
    if (dn < 1e-300)
        warning("CreateAtVector \"log\"(from axis()): axp[0] = %g !", dn);

    /* You get the 3 cases below by
     *  for (y in 1e-5*c(1,2,8))  plot(y, log = "y")
     */
    switch(n) {
    case 1: /* large range: 1    * 10^k */
        i = floor(log10(axp[1])) - ceil(log10(axp[0])) + 0.25;
        ne = i / nint + 1;
        if (ne < 1)
        error("log - axis(), 'at' creation, _LARGE_ range: "
              "ne = %d <= 0 !!\n"
              "\t axp[0:1]=(%g,%g) ==> i = %d;  nint = %d",
              ne, axp[0],axp[1], i, nint);
        rng = pow(10., (double)ne);/* >= 10 */
        n = 0;
        while (dn < umax) {
        n++;
        dn *= rng;
        }
        if (!n)
        error("log - axis(), 'at' creation, _LARGE_ range: "
              "illegal {xy}axp or par; nint=%d\n"
              "  axp[0:1]=(%g,%g), usr[0:1]=(%g,%g); i=%d, ni=%d",
              nint, axp[0],axp[1], umin,umax, i,ne);
        at = allocVector(REALSXP, n);
        dn = axp[0];
        n = 0;
        while (dn < umax) {
        REAL(at)[n++] = dn;
        dn *= rng;
        }
        break;

    case 2: /* medium range:  1, 5    * 10^k */
        n = 0;
        if (0.5 * dn >= umin) n++;
        for (;;) {
        if (dn > umax) break;       n++;
        if (5 * dn > umax) break;   n++;
        dn *= 10;
        }
        if (!n)
        error("log - axis(), 'at' creation, _MEDIUM_ range: "
              "illegal {xy}axp or par;\n"
              "  axp[0]= %g, usr[0:1]=(%g,%g)",
              axp[0], umin,umax);

        at = allocVector(REALSXP, n);
        dn = axp[0];
        n = 0;
        if (0.5 * dn >= umin) REAL(at)[n++] = 0.5 * dn;
        for (;;) {
        if (dn > umax) break;       REAL(at)[n++] = dn;
        if (5 * dn > umax) break;   REAL(at)[n++] = 5 * dn;
        dn *= 10;
        }
        break;

    case 3: /* small range:  1,2,5,10 * 10^k */
        n = 0;
        if (0.2 * dn >= umin) n++;
        if (0.5 * dn >= umin) n++;
        for (;;) {
        if (dn > umax) break;       n++;
        if (2 * dn > umax) break;   n++;
        if (5 * dn > umax) break;   n++;
        dn *= 10;
        }
        if (!n)
        error("log - axis(), 'at' creation, _SMALL_ range: "
              "illegal {xy}axp or par;\n"
              "  axp[0]= %g, usr[0:1]=(%g,%g)",
              axp[0], umin,umax);
        at = allocVector(REALSXP, n);
        dn = axp[0];
        n = 0;
        if (0.2 * dn >= umin) REAL(at)[n++] = 0.2 * dn;
        if (0.5 * dn >= umin) REAL(at)[n++] = 0.5 * dn;
        for (;;) {
        if (dn > umax) break;       REAL(at)[n++] = dn;
        if (2 * dn > umax) break;   REAL(at)[n++] = 2 * dn;
        if (5 * dn > umax) break;   REAL(at)[n++] = 5 * dn;
        dn *= 10;
        }
        break;
    default:
        error("log - axis(), 'at' creation: ILLEGAL {xy}axp[3] = %g",
          axp[2]);
    }
    }
    return at;
}

SEXP do_axis(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /* axis(side, at, labels, ...) - draw an axis */
    SEXP at, lab;
    int dolabels, logflag=0;
    int col, fg;
    int i, n, nint=0;
    int side, xtckCoords, ytckCoords, *ind;
    double x, y, tempx, tempy, tnew, tlast;
    double tck;
    double axp[3], usr[2];
    double gap, labw, low, high;

    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    /* initial checks */

    if (length(args) < 3) errorcall(call, "too few arguments");
    GCheckState(dd);

    /* required argument "side" */

    side = asInteger(CAR(args));
    if (side < 1 || side > 4)
    errorcall(call, "invalid axis number");
    args = CDR(args);

    /* tick-label locations;  these are coerced lower down */

    at = CAR(args); args = CDR(args);

    /* labels */

    dolabels = 1;
    if (isLogical(CAR(args)) && length(CAR(args)) > 0) {
    i = asLogical(CAR(args));
    if (i == 0 || i == NA_LOGICAL)
        dolabels = 0;
    PROTECT(lab = R_NilValue);
    } else if (isExpression(CAR(args))) {
    PROTECT(lab = CAR(args));
    } else {
    PROTECT(lab = coerceVector(CAR(args), STRSXP));
    }
    args = CDR(args);

    /* Retrieve relevant "par" values. */

    switch(side) {
    case 1:
    case 3:
    axp[0] = dd->dp.xaxp[0];
    axp[1] = dd->dp.xaxp[1];
    axp[2] = dd->dp.xaxp[2];
    usr[0] = dd->dp.usr[0];
    usr[1] = dd->dp.usr[1];
    logflag = dd->dp.xlog;
    nint = dd->dp.lab[0];
    break;
    case 2:
    case 4:
    axp[0] = dd->dp.yaxp[0];
    axp[1] = dd->dp.yaxp[1];
    axp[2] = dd->dp.yaxp[2];
    usr[0] = dd->dp.usr[2];
    usr[1] = dd->dp.usr[3];
    logflag = dd->dp.ylog;
    nint = dd->dp.lab[1];
    break;
    }

    /* Determine the tick mark positions.  Note that these may fall */
    /* outside the plot window. We will clip them in the code below. */

    if (length(at) == 0) {
    PROTECT(at = CreateAtVector(axp, usr, nint, logflag));
    n = length(at);
    }
    else {
    if (isReal(at)) PROTECT(at = duplicate(at));
    else PROTECT(at = coerceVector(at, REALSXP));
    n = length(at);
    }

    if (dolabels) {
    if (length(lab) == 0)
        lab = labelformat(at);
    else if (!isExpression(lab))
        lab = labelformat(lab);
    if (length(at) != length(lab))
        errorcall(call, "location and label lengths differ");
    }
    UNPROTECT(2);
    ind = (int *) R_alloc(n, sizeof(int));
    for(i = 0; i < n; i++) ind[i] = i;
    rsort_with_index(REAL(at), ind, n);
    R_Visible = 0;
    GSavePars(dd);
    ProcessInlinePars(args, dd);

    /* override par("xpd") and force clipping to figure region */
    /* NOTE: don't override to _reduce_ clipping region */
#ifdef OLD
    if (dd->gp.xpd < 1)
    dd->gp.xpd = 1;
#else
    dd->gp.xpd = 2;
#endif

    dd->gp.adj = 0.5;
    dd->gp.font = dd->gp.fontaxis;
    dd->gp.cex = dd->gp.cexbase * dd->gp.cexaxis;
    col = dd->gp.col;
    fg = dd->gp.fg;

    /* Check the axis type parameter, if it is 'n', */
    /* there is nothing to do */

    if (side == 1 || side == 3) {
    if (dd->gp.xaxt == 'n') {
        GRestorePars(dd);       return R_NilValue;
    }
    } else if (side == 2 || side == 4) {
    if (dd->gp.yaxt == 'n') {
        GRestorePars(dd);       return R_NilValue;
    }
    }
    else errorcall(call, "invalid \"side\" value");

    x = dd->gp.usr[0];
    y = dd->gp.usr[2];
    xtckCoords = MAR1;
    ytckCoords = MAR2;

    /* Draw the axis */
    GMode(1, dd);
    switch (side) {
    case 1: /*--- x-axis -- horizontal --- */
    case 3:
    GetAxisLimits(dd->gp.usr[0], dd->gp.usr[1], &low, &high);
    if (side == 3) {
        y = dd->gp.usr[3];
        xtckCoords = MAR3;
    }
    dd->gp.col = fg;
    GLine(REAL(at)[0], y, REAL(at)[n - 1], y, USER, dd);
    if (R_FINITE(dd->gp.tck)) {
        /* The S way of doing ticks */
        double y0, y1;
        if (dd->gp.tck > 0.5) {
        if (side == 1) {
            y0 = dd->gp.usr[2];
            y1 = dd->gp.usr[2] + dd->gp.tck *
            (dd->gp.usr[3] - dd->gp.usr[2]);
        }
        else {
            y0 = dd->gp.usr[3];
            y1 = dd->gp.usr[3] + dd->gp.tck *
            (dd->gp.usr[2] - dd->gp.usr[3]);
        }
        }
        else {
        tck = dd->gp.tck * ((dd->gp.fin[0] < dd->gp.fin[1]) ?
                    dd->gp.fin[0] : dd->gp.fin[1]);
        if (side == 1) {
            y0 = dd->gp.usr[2];
            y1 = dd->gp.usr[2] + (tck / dd->gp.fin[1]) *
            (dd->gp.usr[3] - dd->gp.usr[2]);
        }
        else {
            y0 = dd->gp.usr[3];
            y1 = dd->gp.usr[3] + (tck / dd->gp.fin[1]) *
            (dd->gp.usr[2] - dd->gp.usr[3]);
        }
        }
        for (i = 0; i < n; i++) {
        x = REAL(at)[i];
        if (low <= x && x <= high) {
            GLine(x, y0, x, y1, USER, dd);
        }
        }
    }
    else {
        /* The R(ight) way of doing ticks (using "tcl", not "tck") */
        for (i = 0; i < n; i++) {
        x = REAL(at)[i];
        if (low <= x && x <= high) {
            GLine(x, 0, x, -dd->gp.tcl, xtckCoords, dd);
        }
        }
    }
    dd->gp.col = dd->gp.colaxis;
    /* labels */
    tlast = -1.0;
    if (dd->gp.las == 2 || dd->gp.las == 3) {
        if (side == 1) dd->gp.adj = 1;
        else dd->gp.adj = 0;
    }
    else dd->gp.adj = 0.5;

    gap = GStrWidth("m", NFC, dd);  /* FIXUP x/y distance */
    for (i = 0; i < n; i++) {
        x = REAL(at)[i];
        tempx = x; tempy = y;
        GConvert(&tempx, &tempy, USER, NFC, dd);
        if (dolabels) {
        if (isExpression(lab)) {
            GMMathText(VECTOR(lab)[ind[i]], side,
                   dd->gp.mgp[1], 0, x, dd->gp.las, dd);
        }
        else {
            labw = GStrWidth(CHAR(STRING(lab)[ind[i]]), NFC, dd);
            tnew = tempx - 0.5 * labw;
            /* Check that there is space */
            /* for  perpendicular labels. */
            if (dd->gp.las == 2 || dd->gp.las == 3 ||
            tnew - tlast >= gap) {
            GMtext(CHAR(STRING(lab)[ind[i]]), side,
                   dd->gp.mgp[1], 0, x,
                   dd->gp.las, dd);
            tlast = tempx + 0.5 *labw;
            }
        }
        }
    }
    break;

    case 2: /*--- y-axis -- vertical --- */
    case 4:
    GetAxisLimits(dd->gp.usr[2], dd->gp.usr[3], &low, &high);
    if (side == 4) {
        x = dd->gp.usr[1];
        ytckCoords = MAR4;
    }
    dd->gp.col = fg;
    GLine(x, REAL(at)[0], x, REAL(at)[n - 1], USER, dd);
    if (R_FINITE(dd->gp.tck)) {
        /* The S way of doing ticks */
        double x0, x1;
        if (dd->gp.tck > 0.5) {
        if (side == 2) {
            x0 = dd->gp.usr[0];
            x1 = dd->gp.usr[0] + dd->gp.tck *
            (dd->gp.usr[1] - dd->gp.usr[0]);
        }
        else {
            x0 = dd->gp.usr[1];
            x1 = dd->gp.usr[1] + dd->gp.tck *
            (dd->gp.usr[0] - dd->gp.usr[1]);
        }
        }
        else {
        tck = dd->gp.tck * ((dd->gp.fin[0] < dd->gp.fin[1]) ?
                    dd->gp.fin[0] : dd->gp.fin[1]);
        if (side == 2) {
            x0 = dd->gp.usr[0];
            x1 = dd->gp.usr[0] + (tck / dd->gp.fin[0]) *
            (dd->gp.usr[1] - dd->gp.usr[0]);
        }
        else {
            x0 = dd->gp.usr[1];
            x1 = dd->gp.usr[1] + (tck / dd->gp.fin[0]) *
            (dd->gp.usr[0] - dd->gp.usr[1]);
        }
        }
        for (i = 0; i < n; i++) {
        y = REAL(at)[i];
        if (low <= y && y <= high) {
            GLine(x0, y, x1, y, USER, dd);
        }
        }
    }
    else {
        for (i = 0; i < n; i++) {
        y = REAL(at)[i];
        if (low <= y && y <= high) {
            GLine(y, 0, y, -dd->gp.tcl, ytckCoords, dd);
        }
        }
    }
    dd->gp.col = dd->gp.colaxis;
    gap = GStrWidth("m", INCHES, dd);
    gap = GConvertYUnits(gap, INCHES, NFC, dd);
    tlast = -1.0;
    if (dd->gp.las == 1 || dd->gp.las == 2) {
        if (side == 2) dd->gp.adj = 1;
        else dd->gp.adj = 0;
    }
    else dd->gp.adj = 0.5;
    for (i = 0; i < n; i++) {
        y = REAL(at)[i];
        tempx = x; tempy = y;
        GConvert(&tempx, &tempy, USER, NFC, dd);
        if (dolabels) {
        if (isExpression(lab)) {
            GMMathText(VECTOR(lab)[ind[i]], side,
                   dd->gp.mgp[1], 0, y, dd->gp.las, dd);
        }
        else {
            labw = GStrWidth(CHAR(STRING(lab)[ind[i]]), INCHES, dd);
            labw = GConvertYUnits(labw, INCHES, NFC, dd);
            tnew = tempy - 0.5 * labw;
            /* Check room for  perpendicular labels: */
            if (dd->gp.las == 1 || dd->gp.las == 2 ||
            tnew - tlast >= gap) {
            GMtext(CHAR(STRING(lab)[ind[i]]), side,
                   dd->gp.mgp[1], 0, y,
                   dd->gp.las, dd);
            tlast = tempy + 0.5 *labw;
            }
        }
        }
    }
    break;
    }

    GMode(0, dd);
    GRestorePars(dd);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: during replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}


SEXP do_plot_xy(SEXP call, SEXP op, SEXP args, SEXP env)
{
/*  plot.xy(xy, type, pch, lty, col, cex, ...)

 *  plot points or lines of various types
 */
    SEXP sxy, sx, sy, pch, cex, col, bg, lty;
    double *x, *y, xold, yold, xx, yy;
    int i, n, npch, ncex, ncol, nbg, nlty, type=0, start=0;
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    /* Basic Checks */
    GCheckState(dd);
    if (length(args) < 6)
    errorcall(call, "too few arguments");

    sx = R_NilValue;            /* -Wall */
    sy = R_NilValue;            /* -Wall */

    /* Required Arguments */
    sxy = CAR(args);
    if (isNewList(sxy) && length(sxy) >= 2) {
    internalTypeCheck(call, sx = VECTOR(sxy)[0], REALSXP);
    internalTypeCheck(call, sy = VECTOR(sxy)[1], REALSXP);
    }
    else if (isList(sxy) && length(sxy) >= 2) {
    internalTypeCheck(call, sx = CAR(sxy), REALSXP);
    internalTypeCheck(call, sy = CADR(sxy), REALSXP);
    }
    else
    errorcall(call, "invalid plotting structure");
    if (LENGTH(sx) != LENGTH(sy))
    error("x and y lengths differ for plot");
    n = LENGTH(sx);
    args = CDR(args);

    if (isNull(CAR(args))) type = 'p';
    else {
    if (isString(CAR(args)) && LENGTH(CAR(args)) == 1)
        type = CHAR(STRING(CAR(args))[0])[0];
    else errorcall(call, "invalid plot type");
    }
    args = CDR(args);

    PROTECT(pch = FixupPch(CAR(args), dd->gp.pch)); args = CDR(args);
    npch = length(pch);

    PROTECT(lty = FixupLty(CAR(args), dd->gp.lty)); args = CDR(args);
    nlty = length(lty);

    PROTECT(col = FixupCol(CAR(args), NA_INTEGER)); args = CDR(args);
    ncol = LENGTH(col);

    PROTECT(bg = FixupCol(CAR(args), NA_INTEGER));  args = CDR(args);
    nbg = LENGTH(bg);

    PROTECT(cex = FixupCex(CAR(args), 1.0));    args = CDR(args);
    ncex = LENGTH(cex);

    /* Miscellaneous Graphical Parameters -- e.g., lwd */
    GSavePars(dd);
    ProcessInlinePars(args, dd);

    x = REAL(sx);
    y = REAL(sy);

    if (nlty && INTEGER(lty)[0] != NA_INTEGER)
    dd->gp.lty = INTEGER(lty)[0];

    if (ncex && R_FINITE(REAL(cex)[0]))
    dd->gp.cex = dd->gp.cexbase * REAL(cex)[0];
    else
    dd->gp.cex = dd->gp.cexbase;

    GMode(1, dd);
    /* removed by paul 26/5/99 because all clipping now happens in graphics.c
     * GClip(dd);
     */

    if (type == 'l' || type == 'o') {
    /* lines and overplotted lines and points */
    dd->gp.col = INTEGER(col)[0];
    xold = NA_REAL;
    yold = NA_REAL;
    for (i = 0; i < n; i++) {
        xx = x[i];
        yy = y[i];
        /* do the conversion now to check for non-finite */
        GConvert(&xx, &yy, USER, DEVICE, dd);
        if ((R_FINITE(xx) && R_FINITE(yy)) &&
        !(R_FINITE(xold) && R_FINITE(yold)))
        start = i;
        else if ((R_FINITE(xold) && R_FINITE(yold)) &&
             !(R_FINITE(xx) && R_FINITE(yy))) {
        if (i-start > 1)
            GPolyline(i-start, x+start, y+start,
                  USER, dd);
        }
        else if ((R_FINITE(xold) && R_FINITE(yold)) &&
             (i == n-1))
        GPolyline(n-start, x+start, y+start, USER, dd);
        xold = xx;
        yold = yy;
    }
    }
    else if (type == 'b' || type == 'c') {
    /* points connected with broken lines */
    double d, f;
    d = GConvertYUnits(0.5, CHARS, INCHES, dd);
    dd->gp.col = INTEGER(col)[0];
    xold = NA_REAL;
    yold = NA_REAL;
    for (i = 0; i < n; i++) {
        xx = x[i];
        yy = y[i];
        GConvert(&xx, &yy, USER, INCHES, dd);
        if (R_FINITE(xold) && R_FINITE(yold) &&
        R_FINITE(xx) && R_FINITE(yy)) {
        if ((f = d/hypot(xx-xold, yy-yold)) < 0.5) {
            GLine(xold + f * (xx - xold),
              yold + f * (yy - yold),
              xx + f * (xold - xx),
              yy + f * (yold - yy),
              INCHES, dd);
        }
        }
        xold = xx;
        yold = yy;
    }
    }
    else if (type == 's') { /* step function  I */
    double xtemp[3], ytemp[3];
    dd->gp.col = INTEGER(col)[0];
    xold = x[0];
    yold = y[0];
    GConvert(&xold, &yold, USER, DEVICE, dd);
    for (i = 1; i < n; i++) {
        xx = x[i];
        yy = y[i];
        GConvert(&xx, &yy, USER, DEVICE, dd);
        if (R_FINITE(xold) && R_FINITE(yold) &&
        R_FINITE(xx) && R_FINITE(yy)) {
        xtemp[0] = xold; ytemp[0] = yold;
        xtemp[1] = xx;  ytemp[1] = yold;
        xtemp[2] = xx;  ytemp[2] = yy;
        GPolyline(3, xtemp, ytemp, DEVICE, dd);
        }
        xold = xx;
        yold = yy;
    }
    }
    else if (type == 'S') { /* step function  II */
    double xtemp[3], ytemp[3];
    dd->gp.col = INTEGER(col)[0];
    xold = x[0];
    yold = y[0];
    GConvert(&xold, &yold, USER, DEVICE, dd);
    for (i = 1; i < n; i++) {
        xx = x[i];
        yy = y[i];
        GConvert(&xx, &yy, USER, DEVICE, dd);
        if (R_FINITE(xold) && R_FINITE(yold) &&
        R_FINITE(xx) && R_FINITE(yy)) {
        xtemp[0] = xold; ytemp[0] = yold;
        xtemp[1] = xold; ytemp[1] = yy;
        xtemp[2] = xx; ytemp[2] = yy;
        GPolyline(3, xtemp, ytemp, DEVICE, dd);
        }
        xold = xx;
        yold = yy;
    }
    }
    else if (type == 'h') { /* h[istogram] (bar plot) */
    dd->gp.col = INTEGER(col)[0];
    if (dd->gp.ylog)
        yold = dd->gp.usr[2];/* DBL_MIN fails.. why ???? */
    else
        yold = 0.0;
    yold = GConvertY(yold, USER, DEVICE, dd);
    for (i = 0; i < n; i++) {
        xx = x[i];
        yy = y[i];
        GConvert(&xx, &yy, USER, DEVICE, dd);
        if (R_FINITE(xx) && R_FINITE(yy)) {
        GLine(xx, yold, xx, yy, DEVICE, dd);
        }
    }
    }
    if (type == 'p' || type == 'b' || type == 'o') {
    for (i = 0; i < n; i++) {
        xx = x[i];
        yy = y[i];
        GConvert(&xx, &yy, USER, DEVICE, dd);
        if (R_FINITE(xx) && R_FINITE(yy)) {
        if (ncex > 1) 
            dd->gp.cex = dd->gp.cexbase * REAL(cex)[i % ncex];
        dd->gp.col = INTEGER(col)[i % ncol];
        dd->gp.bg = INTEGER(bg)[i % nbg];
        GSymbol(xx, yy, DEVICE,
            INTEGER(pch)[i % npch], dd);
        }
    }
    }
    GMode(0, dd);
    GRestorePars(dd);
    UNPROTECT(5);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: during replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}

/* Checks for ... , x0, y0, x1, y1 ... */

static void xypoints(SEXP call, SEXP args, int *n)
{
    int k=0;/* -Wall */

    if (!isNumeric(CAR(args)) || (k = LENGTH(CAR(args))) <= 0)
    errorcall(call, "first argument invalid");
    CAR(args) = coerceVector(CAR(args), REALSXP);
    *n = k;
    args = CDR(args);

    if (!isNumeric(CAR(args)) || (k = LENGTH(CAR(args))) <= 0)
    errorcall(call, "second argument invalid");
    CAR(args) = coerceVector(CAR(args), REALSXP);
    if (k > *n) *n = k;
    args = CDR(args);

    if (!isNumeric(CAR(args)) || (k = LENGTH(CAR(args))) <= 0)
    errorcall(call, "third argument invalid");
    CAR(args) = coerceVector(CAR(args), REALSXP);
    if (k > *n) *n = k;
    args = CDR(args);

    if (!isNumeric(CAR(args)) || (k = LENGTH(CAR(args))) <= 0)
    errorcall(call, "fourth argument invalid");
    CAR(args) = coerceVector(CAR(args), REALSXP);
    if (k > *n) *n = k;
    args = CDR(args);
}


SEXP do_segments(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /* segments(x0, y0, x1, y1, col, lty, lwd, xpd) */
    SEXP sx0, sx1, sy0, sy1, col, lty, lwd;
    double *x0, *x1, *y0, *y1;
    double xx[2], yy[2];
    int nx0, nx1, ny0, ny1, i, n, ncol, nlty, nlwd;
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    if (length(args) < 4) errorcall(call, "too few arguments");
    GCheckState(dd);

    xypoints(call, args, &n);

    sx0 = CAR(args); nx0 = length(sx0); args = CDR(args);
    sy0 = CAR(args); ny0 = length(sy0); args = CDR(args);
    sx1 = CAR(args); nx1 = length(sx1); args = CDR(args);
    sy1 = CAR(args); ny1 = length(sy1); args = CDR(args);

    PROTECT(col = FixupCol(CAR(args), NA_INTEGER));
    ncol = LENGTH(col); args = CDR(args);

    PROTECT(lty = FixupLty(CAR(args), dd->gp.lty));
    nlty = length(lty); args = CDR(args);

    PROTECT(lwd = FixupLwd(CAR(args), dd->gp.lwd));
    nlwd = length(lwd); args = CDR(args);

    GSavePars(dd);
    ProcessInlinePars(args, dd);

    x0 = REAL(sx0);
    y0 = REAL(sy0);
    x1 = REAL(sx1);
    y1 = REAL(sy1);

    GMode(1, dd);
    for (i = 0; i < n; i++) {
    xx[0] = x0[i%nx0];
    yy[0] = y0[i%ny0];
    xx[1] = x1[i%nx1];
    yy[1] = y1[i%ny1];
    GConvert(xx, yy, USER, DEVICE, dd);
    GConvert(xx+1, yy+1, USER, DEVICE, dd);
    if (R_FINITE(xx[0]) && R_FINITE(yy[0]) &&
        R_FINITE(xx[1]) && R_FINITE(yy[1]))
    {
        dd->gp.col = INTEGER(col)[i % ncol];
        if (dd->gp.col == NA_INTEGER)
        dd->gp.col = dd->dp.col;
        dd->gp.lty = INTEGER(lty)[i % nlty];
        dd->gp.lwd = REAL(lwd)[i % nlwd];
        GLine(xx[0], yy[0], xx[1], yy[1], DEVICE, dd);
    }
    }
    GMode(0, dd);
    GRestorePars(dd);

    UNPROTECT(3);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}


SEXP do_rect(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /* rect(xl, yb, xr, yt, col, border, lty, xpd) */
    SEXP sxl, sxr, syb, syt, col, lty, border;
    double *xl, *xr, *yb, *yt, x0, y0, x1, y1;
    int i, n, nxl, nxr, nyb, nyt;
    int ncol, nlty, nborder, xpd;
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    if (length(args) < 4) errorcall(call, "too few arguments");
    GCheckState(dd);

    xypoints(call, args, &n);
    sxl = CAR(args); nxl = length(sxl); args = CDR(args);
    syb = CAR(args); nyb = length(syb); args = CDR(args);
    sxr = CAR(args); nxr = length(sxr); args = CDR(args);
    syt = CAR(args); nyt = length(syt); args = CDR(args);

    PROTECT(col = FixupCol(GetPar("col", args), NA_INTEGER));
    ncol = LENGTH(col);

    PROTECT(border =  FixupCol(GetPar("border", args), NA_INTEGER));
    nborder = LENGTH(border);

    PROTECT(lty = FixupLty(GetPar("lty", args), dd->gp.lty));
    nlty = length(lty);

    xpd = asInteger(GetPar("xpd", args));

    GSavePars(dd);

    if (xpd == NA_INTEGER)
    dd->gp.xpd = 2;
    else
    dd->gp.xpd = xpd;

    xl = REAL(sxl);
    xr = REAL(sxr);
    yb = REAL(syb);
    yt = REAL(syt);

    GMode(1, dd);
    for (i = 0; i < n; i++) {
    if (nlty && INTEGER(lty)[i % nlty] != NA_INTEGER)
      dd->gp.lty = INTEGER(lty)[i % nlty];
    else
      dd->gp.lty = dd->dp.lty;
    x0 = xl[i%nxl];
    y0 = yb[i%nyb];
    x1 = xr[i%nxr];
    y1 = yt[i%nyt];
    GConvert(&x0, &y0, USER, DEVICE, dd);
    GConvert(&x1, &y1, USER, DEVICE, dd);
    if (R_FINITE(x0) && R_FINITE(y0) && R_FINITE(x1) && R_FINITE(y1))
        GRect(x0, y0, x1, y1, DEVICE, INTEGER(col)[i % ncol],
          INTEGER(border)[i % nborder], dd);
    }
    GMode(0, dd);

    GRestorePars(dd);
    UNPROTECT(3);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}


SEXP do_arrows(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /* arrows(x0, y0, x1, y1, length, angle, code, col, lty, lwd, xpd) */
    SEXP sx0, sx1, sy0, sy1, col, lty, lwd;
    double *x0, *x1, *y0, *y1;
    double xx0, yy0, xx1, yy1;
    double hlength, angle;
    int code;
    int nx0, nx1, ny0, ny1, i, n, ncol, nlty, nlwd, xpd;
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    if (length(args) < 4) errorcall(call, "too few arguments");
    GCheckState(dd);

    xypoints(call, args, &n);

    sx0 = CAR(args); nx0 = length(sx0); args = CDR(args);
    sy0 = CAR(args); ny0 = length(sy0); args = CDR(args);
    sx1 = CAR(args); nx1 = length(sx1); args = CDR(args);
    sy1 = CAR(args); ny1 = length(sy1); args = CDR(args);

    hlength = asReal(GetPar("length", args));
    if (!R_FINITE(hlength) || hlength <= 0)
    errorcall(call, "invalid head length");

    angle = asReal(GetPar("angle", args));
    if (!R_FINITE(angle))
    errorcall(call, "invalid head angle");

    code = asInteger(GetPar("code", args));
    if (code == NA_INTEGER || code < 0 || code > 3)
    errorcall(call, "invalid arrow head specification");

    PROTECT(col = FixupCol(GetPar("col", args), NA_INTEGER));
    ncol = LENGTH(col);

    PROTECT(lty = FixupLty(GetPar("lty", args), dd->gp.lty));
    nlty = length(lty);

    PROTECT(lwd = GetPar("lwd", args));/*need  FixupLwd ?*/
    nlwd = length(lwd);
    if (nlwd == 0)
    errorcall(call, "'lwd' must be numeric of length >=1");

    xpd = asInteger(GetPar("xpd", args));

    GSavePars(dd);

    if (xpd == NA_INTEGER)
    dd->gp.xpd = 2;
    else
    dd->gp.xpd = xpd;

    x0 = REAL(sx0);
    y0 = REAL(sy0);
    x1 = REAL(sx1);
    y1 = REAL(sy1);

    GMode(1, dd);
    for (i = 0; i < n; i++) {
    xx0 = x0[i%nx0];
    yy0 = y0[i%ny0];
    xx1 = x1[i%nx1];
    yy1 = y1[i%ny1];
    GConvert(&xx0, &yy0, USER, DEVICE, dd);
    GConvert(&xx1, &yy1, USER, DEVICE, dd);
    if (R_FINITE(xx0) && R_FINITE(yy0) && R_FINITE(xx1) && R_FINITE(yy1)) {
      dd->gp.col = INTEGER(col)[i % ncol];
        if (dd->gp.col == NA_INTEGER)
        dd->gp.col = dd->dp.col;
        if (nlty == 0 || INTEGER(lty)[i % nlty] == NA_INTEGER)
        dd->gp.lty = dd->dp.lty;
        else
        dd->gp.lty = INTEGER(lty)[i % nlty];
        dd->gp.lwd = REAL(lwd)[i % nlwd];
        GArrow(xx0, yy0, xx1, yy1, DEVICE,
           hlength, angle, code, dd);
    }
    }
    GMode(0, dd);
    GRestorePars(dd);

    UNPROTECT(3);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}


SEXP do_polygon(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /* polygon(x, y, col, border) */
    SEXP sx, sy, col, border, lty, sxpd;
    int nx=1, ny=1, ncol, nborder, nlty, xpd, i, start=0;
    int num = 0;
    double *x, *y, xx, yy, xold, yold;

    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    GCheckState(dd);

    if (length(args) < 2) errorcall(call, "too few arguments");

    if (!isNumeric(CAR(args)) || (nx = LENGTH(CAR(args))) <= 0)
    errorcall(call, "first argument invalid");
    sx = CAR(args) = coerceVector(CAR(args), REALSXP);
    args = CDR(args);

    if (!isNumeric(CAR(args)) || (ny = LENGTH(CAR(args))) <= 0)
    errorcall(call, "second argument invalid");
    sy = CAR(args) = coerceVector(CAR(args), REALSXP);
    args = CDR(args);

    if (ny != nx)
    errorcall(call, "x and y lengths differ in polygon");

    PROTECT(col = FixupCol(GetPar("col", args), NA_INTEGER));
    ncol = LENGTH(col);

    PROTECT(border = FixupCol(GetPar("border", args), NA_INTEGER));
    nborder = LENGTH(border);

    PROTECT(lty = FixupLty(GetPar("lty", args), dd->gp.lty));
    nlty = length(lty);

    /*
     * Have to use GetPar("xpd"...) here rather than ProcessInLinePars
     * because ProcessInLinePars will choke on "border" (until GetPar
     * is fixed - see GetPar)
     * GetPar returning R_NilValue means xpd wasn't specified (so just
     * use current setting of par(xpd))
     * Need separate check for this because otherwise unspecified xpd
     * is the same as xpd=NA (because asInteger(R_NilValue)==NA_INTEGER)
     */
    sxpd = GetPar("xpd", args);
    if (sxpd != R_NilValue)
    xpd = asInteger(sxpd);
    else
    xpd = dd->gp.xpd;

    GSavePars(dd);

    if (xpd == NA_INTEGER)
    dd->gp.xpd = 2;
    else
    dd->gp.xpd = xpd;

    GMode(1, dd);

    if (INTEGER(lty)[0] == NA_INTEGER)
    dd->gp.lty = dd->dp.lty;
    else
    dd->gp.lty = INTEGER(lty)[0];

    x = REAL(sx);
    y = REAL(sy);
    xold = NA_REAL;
    yold = NA_REAL;
    for (i = 0; i < nx; i++) {
    xx = x[i];
    yy = y[i];
    GConvert(&xx, &yy, USER, DEVICE, dd);
    if ((R_FINITE(xx) && R_FINITE(yy)) &&
        !(R_FINITE(xold) && R_FINITE(yold)))
        start = i; /* first point of current segment */
    else if ((R_FINITE(xold) && R_FINITE(yold)) &&
         !(R_FINITE(xx) && R_FINITE(yy))) {
        if (i-start > 1) {
        GPolygon(i-start, x+start, y+start, USER,
             INTEGER(col)[num%ncol], INTEGER(border)[0], dd);
        num++;
        }
    }
    else if ((R_FINITE(xold) && R_FINITE(yold)) && (i == nx-1)) { /* last */
        GPolygon(nx-start, x+start, y+start, USER,
             INTEGER(col)[num%ncol], INTEGER(border)[0], dd);
        num++;
    }
    xold = xx;
    yold = yy;
    }

    GMode(0, dd);

    GRestorePars(dd);
    UNPROTECT(3);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}


SEXP do_text(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP sx, sy, sxy, txt, adj, pos, cex, col, font;
    int i, n, ncex, ncol, nfont, ntxt, xpd;
    double adjx = 0, adjy = 0, offset = 0.5;
    double *x, *y;
    double xx, yy;
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    GCheckState(dd);

    if (length(args) < 3) errorcall(call, "too few arguments");

    sx = R_NilValue;            /* -Wall */
    sy = R_NilValue;            /* -Wall */

    sxy = CAR(args);
    if (isNewList(sxy) && length(sxy) >= 2) {
        internalTypeCheck(call, sx = VECTOR(sxy)[0], REALSXP);
        internalTypeCheck(call, sy = VECTOR(sxy)[1], REALSXP);
    }
    else if (isList(sxy) && length(sxy) >= 2) {
        internalTypeCheck(call, sx = CAR(sxy), REALSXP);
        internalTypeCheck(call, sy = CADR(sxy), REALSXP);
    }
    else
    errorcall(call, "invalid plotting structure");
    if (LENGTH(sx) != LENGTH(sy))
    error("x and y lengths differ for plot");
    n = LENGTH(sx);
    args = CDR(args);

    txt = CAR(args);
    if (isNull(txt) || LENGTH(txt) <= 0)
    errorcall(call, "zero length \"text\" specified");
    args = CDR(args);

    PROTECT(adj = CAR(args));
    if (isNull(adj) || (isNumeric(adj) && length(adj) == 0)) {
    adjx = dd->gp.adj;
    adjy = NA_REAL;
    }
    else if (isReal(adj)) {
    if (LENGTH(adj) == 1) {
        adjx = REAL(adj)[0];
        adjy = NA_REAL;
    }
    else {
        adjx = REAL(adj)[0];
        adjy = REAL(adj)[1];
    }
    }
    else errorcall(call, "invalid adj value");
    args = CDR(args);

    PROTECT(pos = coerceVector(CAR(args), INTSXP));
    for (i = 0; i < length(pos); i++)
        if (INTEGER(pos)[i] < 1 || INTEGER(pos)[i] > 4)
        errorcall(call, "invalid pos value");
    args = CDR(args);

    offset = GConvertXUnits(asReal(CAR(args)), CHARS, INCHES, dd);
    args = CDR(args);

    PROTECT(cex = FixupCex(GetPar("cex", args), 1.0));
    ncex = LENGTH(cex);

    PROTECT(col = FixupCol(GetPar("col", args), NA_INTEGER));
    ncol = LENGTH(col);

    PROTECT(font = FixupFont(GetPar("font", args), NA_INTEGER));
    nfont = LENGTH(font);

    xpd = asLogical(GetPar("xpd", args));
    if (xpd == NA_LOGICAL)
    xpd = dd->gp.xpd; /* was 0 */

    x = REAL(sx);
    y = REAL(sy);
    n = LENGTH(sx);
    ntxt = LENGTH(txt);

    GSavePars(dd);
    ProcessInlinePars(args, dd);

    GMode(1, dd);
    for (i = 0; i < n; i++) {
    xx = x[i % n];
    yy = y[i % n];
    GConvert(&xx, &yy, USER, INCHES, dd);
    if (R_FINITE(xx) && R_FINITE(yy)) {
        if (ncol && INTEGER(col)[i % ncol] != NA_INTEGER)
        dd->gp.col = INTEGER(col)[i % ncol];
        else
        dd->gp.col = dd->dp.col;
        if (ncex && R_FINITE(REAL(cex)[i%ncex]))
        dd->gp.cex = dd->gp.cexbase * REAL(cex)[i % ncex];
        else
        dd->gp.cex = dd->gp.cexbase;
        if (nfont && INTEGER(font)[i % nfont] != NA_INTEGER)
        dd->gp.font = INTEGER(font)[i % nfont];
        else
        dd->gp.font = dd->dp.font;
        if (length(pos) > 0) {
        switch(INTEGER(pos)[i%length(pos)]) {
        case 1:
            yy = yy - offset;
            adjx = 0.5;
            adjy = 1 - (0.5 - dd->gp.yCharOffset);
            break;
        case 2:
            xx = xx - offset;
            adjx = 1;
            adjy = dd->gp.yCharOffset;
            break;
        case 3:
            yy = yy + offset;
            adjx = 0.5;
            adjy = 0;
            break;
        case 4:
            xx = xx + offset;
            adjx = 0;
            adjy = dd->gp.yCharOffset;
            break;
        }
        }
        if (isExpression(txt))
        GMathText(xx, yy, INCHES,
              VECTOR(txt)[i % ntxt],
              adjx, adjy, dd->gp.srt, dd);
        else
        GText(xx, yy, INCHES,
              CHAR(STRING(txt)[i % ntxt]),
              adjx, adjy, dd->gp.srt, dd);
    }
    }
    GMode(0, dd);

    GRestorePars(dd);
    UNPROTECT(5);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}

static double ComputeAdjValue(double adj, int side, int las)
{
    if (!R_FINITE(adj)) {
    switch(las) {
    case 0:/* parallel to axis */
        adj = 0.5; break;
    case 1:/* horizontal */
        switch(side) {
        case 1:
        case 3: adj = 0.5; break;
        case 2: adj = 1.0; break;
        case 4: adj = 0.0; break;
        }
    case 2:/* perpendicular to axis */
        switch(side) {
        case 1:
        case 2: adj = 1.0; break;
        case 3:
        case 4: adj = 0.0; break;
        }
    case 3:/* vertical */
        switch(side) {
        case 1: adj = 1.0; break;
        case 3: adj = 0.0; break;
        case 2:
        case 4: adj = 0.5; break;
        }
    }
    }
    return adj;
}

static double ComputeAtValue(double at, double adj, int side, int outer,
                 DevDesc *dd)
{
    if (!R_FINITE(at)) {
    switch(side % 2) {
    case 0:
        at  = outer ? adj : yNPCtoUsr(adj, dd);
        break;
    case 1:
        at = outer ? adj : xNPCtoUsr(adj, dd);
        break;
    }
    }
    return at;
}

/* mtext(text,
         side = 3,
         line = 0,
     outer = TRUE,
         at = NA,
         adj = NA,
         cex = NA,
         col = NA,
         font = NA,
         ...) */

SEXP do_mtext(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP text, side, line, outer, at, adj, cex, col, font;
    int ntext, nside, nline, nouter, nat, nadj, ncex, ncol, nfont;
    int dirtyplot = 0, gpnewsave = 0, dpnewsave = 0;
    int i, n, fontsave, colsave;
    double cexsave;
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    GCheckState(dd);

    if (length(args) < 9)
    errorcall(call, "too few arguments");

    /* Arg1 : text= */
    /* This has been coerced with char.or.expr() */
    text = CAR(args);
    n = ntext = length(text);
    if (ntext <= 0)
    errorcall(call, "zero length \"text\" specified");
    args = CDR(args);

    /* Arg2 : side= */
    PROTECT(side = coerceVector(CAR(args), INTSXP));
    nside = length(side);
    if (nside <= 0) errorcall(call, "zero length \"side\" specified");
    if (n < nside) n = nside;
    args = CDR(args);

    /* Arg3 : line= */
    PROTECT(line = coerceVector(CAR(args), REALSXP));
    nline = length(line);
    if (nline <= 0) errorcall(call, "zero length \"line\" specified");
    if (n < nline) n = nline;
    args = CDR(args);

    /* Arg4 : outer= */
    /* outer == NA => outer <- 0 */
    PROTECT(outer = coerceVector(CAR(args), INTSXP));
    nouter = length(outer);
    if (nouter <= 0) errorcall(call, "zero length \"outer\" specified");
    if (n < nouter) n = nouter;
    args = CDR(args);

    /* Arg5 : at= */
    PROTECT(at = coerceVector(CAR(args), REALSXP));
    nat = length(at);
    if (nat <= 0) errorcall(call, "zero length \"at\" specified");
    if (n < nat) n = nat;
    args = CDR(args);

    /* Arg6 : adj= */
    PROTECT(adj = coerceVector(CAR(args), REALSXP));
    nadj = length(adj);
    if (nadj <= 0) errorcall(call, "zero length \"adj\" specified");
    if (n < nadj) n = nadj;
    args = CDR(args);

    /* Arg7 : cex */
    PROTECT(cex = FixupCex(CAR(args), 1.0));
    ncex = length(cex);
    if (ncex <= 0) errorcall(call, "zero length \"cex\" specified");
    if (n < ncex) n = ncex;
    args = CDR(args);

    /* Arg8 : col */
    PROTECT(col = FixupCol(CAR(args), NA_INTEGER));
    ncol = length(col);
    if (ncol <= 0) errorcall(call, "zero length \"col\" specified");
    if (n < ncol) n = ncol;
    args = CDR(args);

    /* Arg9 : font */
    PROTECT(font = FixupFont(CAR(args), NA_INTEGER));
    nfont = length(font);
    if (nfont <= 0) errorcall(call, "zero length \"font\" specified");
    if (n < nfont) n = nfont;
    args = CDR(args);

    GSavePars(dd);
    ProcessInlinePars(args, dd);

    /* If we only scribble in the outer margins, */
    /* we don't want to mark the plot as dirty. */

    dirtyplot = 0;
    gpnewsave = dd->gp.new;
    dpnewsave = dd->dp.new;
    cexsave = dd->gp.cex;
    fontsave = dd->gp.font;
    colsave = dd->gp.col;

    /* override par("xpd") and force clipping to figure region */
    /* NOTE: don't override to _reduce_ clipping region */
    if (dd->gp.xpd < 1)
    dd->gp.xpd = 1;

    if (outer) {
    gpnewsave = dd->gp.new;
    dpnewsave = dd->dp.new;
    /* override par("xpd") and force clipping to device region */
    dd->gp.xpd = 2;
    }
    GMode(1, dd);

    for (i = 0; i < n; i++) {
    double atval = REAL(at)[i%nat];
    double adjval = REAL(adj)[i%nadj];
    double cexval = REAL(cex)[i%ncex];
    double lineval = REAL(line)[i%nline];
    int outerval = INTEGER(outer)[i%nouter];
    int sideval = INTEGER(side)[i%nside];
    int fontval = INTEGER(font)[i%nfont];
    int colval = INTEGER(col)[i%ncol];

    if (outerval == NA_INTEGER) outerval = 0;
    /* Note : we ignore any shrinking produced */
    /* by mfrow / mfcol specs here.  I.e. don't */
    /* dd->gp.cexbase. */
    if (R_FINITE(cexval)) dd->gp.cex = cexval;
    else cexval = cexsave;
    dd->gp.font = (fontval == NA_INTEGER) ? fontsave : fontval;
    dd->gp.col = (colval == NA_INTEGER) ? colsave : colval;
    dd->gp.adj = ComputeAdjValue(adjval, sideval, dd->gp.las);
    atval = ComputeAtValue(atval, dd->gp.adj, sideval, outerval, dd);
    if (isExpression(text))
        GMMathText(VECTOR(text)[i%ntext],
               sideval, lineval, outerval, atval, dd->gp.las, dd);
    else
        GMtext(CHAR(STRING(text)[i%ntext]),
           sideval, lineval, outerval, atval, dd->gp.las, dd);
        if (outerval == 0) dirtyplot = 1;
}
    GMode(0, dd);

    GRestorePars(dd);
    if (!dirtyplot) {
    dd->gp.new = gpnewsave;
    dd->dp.new = dpnewsave;
    }
    UNPROTECT(8);

    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}

SEXP do_title(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /* title(main=NULL, sub=NULL, xlab=NULL, ylab=NULL, ...) */
    SEXP Main, xlab, ylab, sub;
    double adj, offset;
    int i, n;
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    GCheckState(dd);

    if (length(args) < 4) errorcall(call, "too few arguments");

    Main = sub = xlab = ylab = R_NilValue;

    if (CAR(args) != R_NilValue && LENGTH(CAR(args)) > 0)
    Main = CAR(args);
    args = CDR(args);

    if (CAR(args) != R_NilValue && LENGTH(CAR(args)) > 0)
    sub = CAR(args);
    args = CDR(args);

    if (CAR(args) != R_NilValue && LENGTH(CAR(args)) > 0)
    xlab = CAR(args);
    args = CDR(args);

    if (CAR(args) != R_NilValue && LENGTH(CAR(args)) > 0)
    ylab = CAR(args);
    args = CDR(args);

    GSavePars(dd);
    ProcessInlinePars(args, dd);

    /* override par("xpd") and force clipping to figure region */
    /* NOTE: don't override to _reduce_ clipping region */
    if (dd->gp.xpd < 1)
    dd->gp.xpd = 1;

    adj = dd->gp.adj;

    GMode(1, dd);
    if (Main != R_NilValue) {
    dd->gp.cex = dd->gp.cexbase * dd->gp.cexmain;
    dd->gp.col = dd->gp.colmain;
    dd->gp.font = dd->gp.fontmain;
    if (isExpression(Main)) {
        GMathText(xNPCtoUsr(adj, dd), 0.5*dd->gp.mar[2], MAR3,
              VECTOR(Main)[0], adj, 0.5, 0.0, dd);
    }
    else {
      n = length(Main);
      offset = 0.5 * (n - 1) + 0.5 * dd->gp.mar[2];
      for (i = 0; i < n; i++)
        GText(xNPCtoUsr(adj, dd), offset - i, MAR3,
          CHAR(STRING(Main)[i]), adj, 0.5, 0.0, dd);
    }
    }
    if (sub != R_NilValue) {
    dd->gp.cex = dd->gp.cexbase * dd->gp.cexsub;
    dd->gp.col = dd->gp.colsub;
    dd->gp.font = dd->gp.fontsub;
    if (isExpression(sub))
        GMMathText(VECTOR(sub)[0], 1, dd->gp.mgp[0] + 1.0, 0,
               xNPCtoUsr(adj, dd), 0, dd);
    else {
        n = length(sub);
        for (i = 0; i < n; i++)
        GMtext(CHAR(STRING(sub)[i]), 1, dd->gp.mgp[0] + 1.0, 0,
           xNPCtoUsr(adj, dd), 0, dd);
    }
    }
    if (xlab != R_NilValue) {
    dd->gp.cex = dd->gp.cexbase * dd->gp.cexlab;
    dd->gp.col = dd->gp.collab;
    dd->gp.font = dd->gp.fontlab;
    if (isExpression(xlab))
        GMMathText(VECTOR(xlab)[0], 1, dd->gp.mgp[0], 0,
               xNPCtoUsr(adj, dd), 0, dd);
    else {
        n = length(xlab);
        for (i = 0; i < n; i++)
        GMtext(CHAR(STRING(xlab)[i]), 1, dd->gp.mgp[0] + i, 0,
           xNPCtoUsr(adj, dd), 0, dd);
    }
    }
    if (ylab != R_NilValue) {
    dd->gp.cex = dd->gp.cexbase * dd->gp.cexlab;
    dd->gp.col = dd->gp.collab;
    dd->gp.font = dd->gp.fontlab;
    if (isExpression(ylab))
        GMMathText(VECTOR(ylab)[0], 2, dd->gp.mgp[0], 0,
               yNPCtoUsr(adj, dd), 0, dd);
    else {
        n = length(ylab);
        for (i = 0; i < n; i++)
        GMtext(CHAR(STRING(ylab)[i]), 2, dd->gp.mgp[0] - i, 0,
           yNPCtoUsr(adj, dd), 0, dd);
    }
    }
    GMode(0, dd);
    GRestorePars(dd);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}


/*  abline(a, b, h, v, col, lty, lwd, ...)
    draw lines in intercept/slope form.  */

SEXP do_abline(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP a, b, h, v, untf, col, lty, lwd;
    int i, ncol, nlines, nlty, nlwd;
    double aa, bb, x[2], y[2];
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    GCheckState(dd);

    if (length(args) < 5) errorcall(call, "too few arguments");

    if ((a = CAR(args)) != R_NilValue)
    CAR(args) = a = coerceVector(a, REALSXP);
    args = CDR(args);

    if ((b = CAR(args)) != R_NilValue)
    CAR(args) = b = coerceVector(b, REALSXP);
    args = CDR(args);

    if ((h = CAR(args)) != R_NilValue)
    CAR(args) = h = coerceVector(h, REALSXP);
    args = CDR(args);

    if ((v = CAR(args)) != R_NilValue)
    CAR(args) = v = coerceVector(v, REALSXP);
    args = CDR(args);
    
    if ((untf = CAR(args)) != R_NilValue)
    CAR(args) = untf = coerceVector(untf, LGLSXP);
    args = CDR(args);


    PROTECT(col = FixupCol(CAR(args), NA_INTEGER)); args = CDR(args);
    ncol = LENGTH(col);

    PROTECT(lty = FixupLty(CAR(args), dd->gp.lty)); args = CDR(args);
    nlty = length(lty);

    PROTECT(lwd = FixupLwd(CAR(args), dd->gp.lwd));     args = CDR(args);
    nlwd = length(lwd);

    GSavePars(dd);

    nlines = 0;

    if (a != R_NilValue) {
    if (b == R_NilValue) {
        if (LENGTH(a) != 2)
        errorcall(call, "invalid a=, b= specification");
        aa = REAL(a)[0];
        bb = REAL(a)[1];
    }
    else {
        aa = asReal(a);
        bb = asReal(b);
    }
    if (!R_FINITE(aa) || !R_FINITE(bb))
        errorcall(call, "\"a\" and \"b\" must be finite");
    dd->gp.col = INTEGER(col)[0];
    dd->gp.lwd = REAL(lwd)[0];
    if (nlty && INTEGER(lty)[0] != NA_INTEGER)
        dd->gp.lty = INTEGER(lty)[0];
    else
        dd->gp.lty = dd->dp.lty;
    GMode(1, dd);
    x[0] = dd->gp.usr[0];
    x[1] = dd->gp.usr[1];
    if (R_FINITE(dd->gp.lwd)) {
        if (LOGICAL(untf)[0] == 1 && (dd->gp.xlog || dd->gp.ylog)) {
        double xx[101], yy[101];
        int i;
        double xstep = (x[1] - x[0])/100;
        for (i = 0; i < 100; i++) {
            xx[i] = x[0] + i*xstep;
            yy[i] = aa + xx[i] * bb;
        }
        xx[100] = x[1];
        yy[100] = aa + x[1] * bb;
        GPolyline(101, xx, yy, USER, dd);
        }
        else {
        double x0, x1;

        x0 = ( dd->gp.xlog ) ?  log10(x[0]) : x[0];
        x1 = ( dd->gp.xlog ) ?  log10(x[1]) : x[1];


        y[0] = aa + x0 * bb;
        y[1] = aa + x1 * bb;

        if ( dd->gp.ylog ){
            y[0] = pow(10.,y[0]);
            y[1] = pow(10.,y[1]);
        }

        GLine(x[0], y[0], x[1], y[1], USER, dd);
        }
    }
    GMode(0, dd);
    nlines++;
    }
    if (h != R_NilValue) {
    GMode(1, dd);
    for (i = 0; i < LENGTH(h); i++) {
        dd->gp.col = INTEGER(col)[nlines % ncol];
        if (nlty && INTEGER(lty)[nlines % nlty] != NA_INTEGER)
        dd->gp.lty = INTEGER(lty)[nlines % nlty];
        else
        dd->gp.lty = dd->dp.lty;
        dd->gp.lwd = REAL(lwd)[nlines % nlwd];
        aa = REAL(h)[i];
        if (R_FINITE(aa) && R_FINITE(dd->gp.lwd)) {
        x[0] = dd->gp.usr[0];
        x[1] = dd->gp.usr[1];
        y[0] = aa;
        y[1] = aa;
        GLine(x[0], y[0], x[1], y[1], USER, dd);
        }
        nlines++;
    }
    GMode(0, dd);
    }
    if (v != R_NilValue) {
    GMode(1, dd);
    for (i = 0; i < LENGTH(v); i++) {
        dd->gp.col = INTEGER(col)[nlines % ncol];
        if (nlty && INTEGER(lty)[nlines % nlty] != NA_INTEGER)
        dd->gp.lty = INTEGER(lty)[nlines % nlty];
        else
        dd->gp.lty = dd->dp.lty;
        dd->gp.lwd = REAL(lwd)[nlines % nlwd];
        aa = REAL(v)[i];
        if (R_FINITE(aa) && R_FINITE(dd->gp.lwd)) {
        y[0] = dd->gp.usr[2];
        y[1] = dd->gp.usr[3];
        x[0] = aa;
        x[1] = aa;
        GLine(x[0], y[0], x[1], y[1], USER, dd);
        }
        nlines++;
    }
    GMode(0, dd);
    }
    UNPROTECT(3);
    GRestorePars(dd);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}

SEXP do_box(SEXP call, SEXP op, SEXP args, SEXP env)
{
/*     box(which="plot", lty="solid", ...)
       --- which is coded, 1 = plot, 2 = figure, 3 = inner, 4 = outer.
*/
    int which, col, fg;
    SEXP originalArgs = args;
    DevDesc *dd = CurrentDevice();

    GCheckState(dd);
    GSavePars(dd);
    which = asInteger(CAR(args)); args = CDR(args);
    if (which < 1 || which > 4)
    errorcall(call, "invalid \"which\" specification");
    col= dd->gp.col;    dd->gp.col= NA_INTEGER;
    fg = dd->gp.col;    dd->gp.fg = NA_INTEGER;
    ProcessInlinePars(args, dd);
    if (dd->gp.col == NA_INTEGER) {
    if (dd->gp.fg == NA_INTEGER)
        dd->gp.col = col;
    else
        dd->gp.col = dd->gp.fg;
    }
    /* override par("xpd") and force clipping to device region */
    dd->gp.xpd = 2;
    GMode(1, dd);
    GBox(which, dd);
    GMode(0, dd);
    GRestorePars(dd);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;
}

SEXP do_locator(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP x, y, nobs, ans;
    int i, n, type='p';
    double xp, yp, xold=0, yold=0;
    DevDesc *dd = CurrentDevice();

    GCheckState(dd);

    checkArity(op, args);
    n = asInteger(CAR(args));
    if (n <= 0 || n == NA_INTEGER)
    error("invalid number of points in locator");
    args = CDR(args);
    if (isString(CAR(args)) && LENGTH(CAR(args)) == 1)
    type = CHAR(STRING(CAR(args))[0])[0];
    else errorcall(call, "invalid plot type");
    PROTECT(x = allocVector(REALSXP, n));
    PROTECT(y = allocVector(REALSXP, n));
    PROTECT(nobs=allocVector(INTSXP,1));
    i = 0;

    GMode(2, dd);
    while (i < n) {
    if (!GLocator(&(REAL(x)[i]), &(REAL(y)[i]), USER, dd))
        break;
    if (type != 'n') {
        GMode(1, dd);
        xp = REAL(x)[i];
        yp = REAL(y)[i];
        GConvert(&xp, &yp, USER, DEVICE, dd);
        if (type == 'p' || type == 'o')
        GSymbol(xp, yp, DEVICE, dd->gp.pch, dd);
        if ((type == 'l' || type == 'o') && (i > 0))
        GLine(xold, yold, xp, yp, DEVICE, dd);
        GMode(2, dd);
        xold = xp; yold = yp;
    }
    i += 1;
    }
    GMode(0, dd);
    INTEGER(nobs)[0] = i;
    while (i < n) {
    REAL(x)[i] = NA_REAL;
    REAL(y)[i] = NA_REAL;
    i += 1;
    }
    ans = allocList(3);
    UNPROTECT(3);
    CAR(ans) = x;
    CADR(ans) = y;
    CADDR(ans) = nobs;
    return ans;
}


#ifdef Macintosh
double hypot(double x, double y)
{
    return sqrt(x*x+y*y);
}
#endif

#define THRESHOLD   0.25

SEXP do_identify(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP ans, x, y, l, ind, pos, Offset;
    double xi, yi, xp, yp, d, dmin, offset;
    int i, imin, k, n, npts, plot;
    DevDesc *dd = CurrentDevice();

    GCheckState(dd);

    checkArity(op, args);
    x = CAR(args);
    args = CDR(args); y = CAR(args);
    args = CDR(args); l = CAR(args);
    args = CDR(args); npts = asInteger(CAR(args));
    args = CDR(args); plot = asLogical(CAR(args));
    args = CDR(args); Offset = CAR(args);
    if (npts <= 0 || npts == NA_INTEGER)
    error("invalid number of points in identify");
    if (!isReal(x) || !isReal(y) || !isString(l) || !isReal(Offset))
    errorcall(call, "incorrect argument type");
    if (LENGTH(x) != LENGTH(y) || LENGTH(x) != LENGTH(l))
    errorcall(call, "different argument lengths");
    n = LENGTH(x);
    if (n <= 0) {
    R_Visible = 0;
    return NULL;
    }

    offset = GConvertXUnits(asReal(Offset), CHARS, INCHES, dd);
    PROTECT(ind = allocVector(LGLSXP, n));
    PROTECT(pos = allocVector(INTSXP, n));
    for (i = 0; i < n; i++)
    LOGICAL(ind)[i] = 0;

    k = 0;
    GMode(2, dd);
    while (k < npts) {
    if (!GLocator(&xp, &yp, INCHES, dd)) break;
    dmin = DBL_MAX;
    imin = -1;
    for (i = 0; i < n; i++) {
        xi = REAL(x)[i];
        yi = REAL(y)[i];
        GConvert(&xi, &yi, USER, INCHES, dd);
        if (!R_FINITE(xi) || !R_FINITE(yi)) continue;
        d = hypot(xp-xi, yp-yi);
        if (d < dmin) {
        imin = i;
        dmin = d;
        }
    }
    if (dmin > THRESHOLD)
        REprintf("warning: no point with %.2f inches\n", THRESHOLD);
    else if (LOGICAL(ind)[imin])
        REprintf("warning: nearest point already identified\n");
    else {
        k++;
        LOGICAL(ind)[imin] = 1;
        xi = REAL(x)[imin];
        yi = REAL(y)[imin];
        GConvert(&xi, &yi, USER, INCHES, dd);
        if (fabs(xp-xi) >= fabs(yp-yi)) {
        if (xp >= xi) {
            INTEGER(pos)[imin] = 4;
            xi = xi+offset;
            if (plot) GText(xi, yi, INCHES,
              CHAR(STRING(l)[imin]), 0.0,
              dd->gp.yCharOffset, 0.0, dd);
        }
        else {
            INTEGER(pos)[imin] = 2;
            xi = xi-offset;
            if (plot) GText(xi, yi, INCHES,
              CHAR(STRING(l)[imin]), 1.0,
              dd->gp.yCharOffset, 0.0, dd);
        }
        }
        else {
        if (yp >= yi) {
            INTEGER(pos)[imin] = 3;
            yi = yi+offset;
            if (plot) GText(xi, yi, INCHES,
              CHAR(STRING(l)[imin]), 0.5,
              0.0, 0.0, dd);
        }
        else {
            INTEGER(pos)[imin] = 1;
            yi = yi-offset;
            if (plot) GText(xi, yi, INCHES,
              CHAR(STRING(l)[imin]), 0.5,
              1-(0.5-dd->gp.yCharOffset),
              0.0, dd);
        }
        }
    }
    }
    GMode(0, dd);
    ans = allocList(2);
    CAR(ans) = ind;
    CADR(ans) = pos;
    UNPROTECT(2);
    return ans;
}

SEXP do_dotplot(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP x, labs, offset, saveargs;
    double adj, xpd, wd, ht, lw, gw, xi, xmin, xmax;
#ifdef OLD
    SEXP colors, ltypes;
    double save_mar[4];
#endif
    int save_mUnits, save_defaultPlot;
    int i, n;
    DevDesc *dd;

    /* checkArity(op, args); */

    saveargs = args;
    x = CAR(args); args = CDR(args);        /* real */
    labs = CAR(args); args = CDR(args);     /* character */
    offset = CAR(args); args = CDR(args);   /* logical */
#ifdef NEW
    colors = CAR(args); args = CDR(args);   /* integer */
    ltypes = CAR(args); args = CDR(args);   /* integer */
#endif

    /* checks on lengths/types here */

    n = length(labs);

    /* compute the plot layout */

    dd = GNewPlot(call != R_NilValue, NA_LOGICAL);
    lw = 0;
    gw = 0;
    ht = GStrHeight("M", INCHES, dd);
    xmin = DBL_MAX;
    xmax = DBL_MIN;
    for (i = 0; i < n; i++) {
    wd = GStrWidth(CHAR(STRING(labs)[i]), INCHES, dd) / ht;
    if (wd > 0) {
        if (INTEGER(offset)[i] == 1) {
        if (wd > gw) gw = wd;
        }
        else {
        if (wd > lw) lw = wd;
        }
    }
    xi = REAL(x)[i];
    if (R_FINITE(xi)) {
        if (xi < xmin) xmin = xi;
        if (xi > xmax) xmax = xi;
    }
    }
    if (gw > 0) {
    if (gw < lw + 1)
        gw = lw + 1;
    lw = lw + 1;
    gw = gw + 1;
    }
    else {
    lw = lw + 1;
    gw = lw;
    }
    save_mUnits = dd->gp.mUnits;
    save_defaultPlot = dd->dp.defaultPlot;
    dd->gp.mar[1] = dd->gp.mar[3] + gw;
    dd->dp.mUnits = dd->gp.mUnits = LINES;
    dd->dp.defaultPlot = dd->gp.defaultPlot = 1;
    GReset(dd);

    /* Set up the plotting window */

    dd->gp.yaxs = 'i';
    GScale(xmin, xmax, 1, dd);
    GScale((double)0.5, (double)(n + 0.5), 2, dd);
    GMapWin2Fig(dd);
    GSetState(1, dd);

    /* Axis labelling must be done here. */
    /* The offsets must be recomputed */
    /* each time the plot is redrawn. */

    adj = dd->gp.adj;
    xpd = dd->gp.xpd;
    dd->gp.adj = 0;
    /* override par("xpd") and force clipping to figure region */
    /* NOTE: don't override to _reduce_ clipping region */
    if (dd->gp.xpd < 1)
    xpd = 1;

    for (i = 0; i < n; i++) {
    if (strlen(CHAR(STRING(labs)[i])) > 0) {
        if (LOGICAL(offset)[i])
        GMtext(CHAR(STRING(labs)[i]), 2, gw, 0, (double)(i+1), 2, dd);
        else
        GMtext(CHAR(STRING(labs)[i]), 2, lw, 0, (double)(i+1), 2, dd);
    }
    }
    dd->gp.adj = adj;
    dd->gp.xpd = xpd;

    /* Plotting could be done here */
    /* or later in interpreted code. */

    if (call != R_NilValue)
    recordGraphicOperation(op, saveargs, dd);
    return R_NilValue;
}


SEXP do_strheight(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /* strheight(str, units) */
    SEXP ans, str;
    int i, n, units;
    double cex, cexsave;
    DevDesc *dd = CurrentDevice();

    checkArity(op,args);
    str = CAR(args);
    if ((TYPEOF(str) != STRSXP) && (TYPEOF(str) != EXPRSXP))
    errorcall(call, "character or expression first argument expected");
    args = CDR(args);

    if ((units = asInteger(CAR(args))) == NA_INTEGER || units < 0)
    errorcall(call, "invalid units");
    args = CDR(args);

    if (isNull(CAR(args)))
    cex = dd->gp.cex;
    else if (!R_FINITE(cex = asReal(CAR(args))) || cex <= 0.0)
    errorcall(call, "invalid cex value");

    n = LENGTH(str);
    PROTECT(ans = allocVector(REALSXP, n));
    cexsave = dd->gp.cex;
    dd->gp.cex = cex * dd->gp.cexbase;
    for (i = 0; i < n; i++)
    if (isExpression(str))
        REAL(ans)[i] = GExpressionHeight(VECTOR(str)[i],
                         GMapUnits(units), dd);
    else
        REAL(ans)[i] = GStrHeight(CHAR(STRING(str)[i]),
                      GMapUnits(units), dd);
    dd->gp.cex = cexsave;
    UNPROTECT(1);
    return ans;
}


SEXP do_strwidth(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /* strwidth(str, units) */
    SEXP ans, str;
    int i, n, units;
    double cex, cexsave;
    DevDesc *dd = CurrentDevice();

    checkArity(op, args);
    GCheckState(dd);

    str = CAR(args);
    if ((TYPEOF(str) != STRSXP) && (TYPEOF(str) != EXPRSXP))
    errorcall(call, "character or expression first argument expected");
    args = CDR(args);

    if ((units = asInteger(CAR(args))) == NA_INTEGER || units < 0)
    errorcall(call, "invalid units");
    args = CDR(args);

    if (isNull(CAR(args)))
    cex = dd->gp.cex;
    else if (!R_FINITE(cex = asReal(CAR(args))) || cex <= 0.0)
    errorcall(call, "invalid cex value");

    n = LENGTH(str);
    PROTECT(ans = allocVector(REALSXP, n));
    cexsave = dd->gp.cex;
    dd->gp.cex = cex * dd->gp.cexbase;
    for (i = 0; i < n; i++)
    if (isExpression(str))
        REAL(ans)[i] = GExpressionWidth(VECTOR(str)[i],
                        GMapUnits(units), dd);
    else
        REAL(ans)[i] = GStrWidth(CHAR(STRING(str)[i]),
                     GMapUnits(units), dd);
    dd->gp.cex = cexsave;
    UNPROTECT(1);
    return ans;
}

static int dnd_n;
static int *dnd_lptr;
static int *dnd_rptr;
static double *dnd_hght;
static double *dnd_xpos;
static double dnd_hang;
static double dnd_offset;
static SEXP *dnd_llabels;


static void drawdend(int node, double *x, double *y, DevDesc *dd)
{
    double xl, xr, yl, yr;
    double xx[4], yy[4];
    int k;
    *y = dnd_hght[node-1];
    k = dnd_lptr[node-1];
    if (k > 0) drawdend(k, &xl, &yl, dd);
    else {
    xl = dnd_xpos[-k-1];
    if (dnd_hang >= 0) yl = *y - dnd_hang;
    else yl = 0;
    GText(xl, yl-dnd_offset, USER, CHAR(dnd_llabels[-k-1]),
          1.0, 0.3, 90.0, dd);
    }
    k = dnd_rptr[node-1];
    if (k > 0) drawdend(k, &xr, &yr, dd);
    else {
    xr = dnd_xpos[-k-1];
    if (dnd_hang >= 0) yr = *y - dnd_hang;
    else yr = 0;
    GText(xr, yr-dnd_offset, USER, CHAR(dnd_llabels[-k-1]),
          1.0, 0.3, 90.0, dd);
    }
    xx[0] = xl; yy[0] = yl;
    xx[1] = xl; yy[1] = *y;
    xx[2] = xr; yy[2] = *y;
    xx[3] = xr; yy[3] = yr;
    GPolyline(4, xx, yy, USER, dd);
    *x = 0.5 * (xl + xr);
}


SEXP do_dend(SEXP call, SEXP op, SEXP args, SEXP env)
{
    double x, y;
    SEXP originalArgs;
    DevDesc *dd;

    dd = CurrentDevice();
    GCheckState(dd);

    originalArgs = args;
    if (length(args) < 6)
    errorcall(call, "too few arguments");

    dnd_n = asInteger(CAR(args));
    if (dnd_n == NA_INTEGER || dnd_n < 2)
    goto badargs;
    args = CDR(args);

    if (TYPEOF(CAR(args)) != INTSXP || length(CAR(args)) != 2*dnd_n)
    goto badargs;
    dnd_lptr = &(INTEGER(CAR(args))[0]);
    dnd_rptr = &(INTEGER(CAR(args))[dnd_n]);
    args = CDR(args);

    if (TYPEOF(CAR(args)) != REALSXP || length(CAR(args)) != dnd_n)
    goto badargs;
    dnd_hght = REAL(CAR(args));
    args = CDR(args);

    if (TYPEOF(CAR(args)) != REALSXP || length(CAR(args)) != dnd_n+1)
    goto badargs;
    dnd_xpos = REAL(CAR(args));
    args = CDR(args);

    dnd_hang = asReal(CAR(args));
    if (!R_FINITE(dnd_hang))
    goto badargs;
    dnd_hang = dnd_hang * (dnd_hght[dnd_n-1] - dnd_hght[0]);
    args = CDR(args);

    if (TYPEOF(CAR(args)) != STRSXP || length(CAR(args)) != dnd_n+1)
    goto badargs;
    dnd_llabels = STRING(CAR(args));
    args = CDR(args);

    GSavePars(dd);
    ProcessInlinePars(args, dd);
    dd->gp.cex = dd->gp.cexbase * dd->gp.cex;
    dnd_offset = GConvertYUnits(GStrWidth("m", INCHES, dd), INCHES, USER, dd);

    /* override par("xpd") and force clipping to figure region */
    /* NOTE: don't override to _reduce_ clipping region */
    if (dd->gp.xpd < 1)
    dd->gp.xpd = 1;

    GMode(1, dd);
    drawdend(dnd_n, &x, &y, dd);
    GMode(0, dd);
    GRestorePars(dd);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    return R_NilValue;

  badargs:
    error("invalid dendrogram input");
    return R_NilValue;/* never used; to keep -Wall happy */
}

SEXP do_dendwindow(SEXP call, SEXP op, SEXP args, SEXP env)
{
    int i, imax, n;
    double pin, *ll, tmp, yval, *y, ymin, ymax, yrange;
    SEXP originalArgs, merge, height, llabels;
    char *vmax;
    DevDesc *dd;
    dd = CurrentDevice();
    GCheckState(dd);
    originalArgs = args;
    if (length(args) < 6)
    errorcall(call, "too few arguments");
    n = asInteger(CAR(args));
    if (n == NA_INTEGER || n < 2)
    goto badargs;
    args = CDR(args);
    if (TYPEOF(CAR(args)) != INTSXP || length(CAR(args)) != 2 * n)
    goto badargs;
    merge = CAR(args);
    args = CDR(args);
    if (TYPEOF(CAR(args)) != REALSXP || length(CAR(args)) != n)
    goto badargs;
    height = CAR(args);
    args = CDR(args);
    if (TYPEOF(CAR(args)) != REALSXP || length(CAR(args)) != n + 1)
    goto badargs;
    dnd_xpos = REAL(CAR(args));
    args = CDR(args);
    dnd_hang = asReal(CAR(args));
    if (!R_FINITE(dnd_hang))
    goto badargs;
    args = CDR(args);
    if (TYPEOF(CAR(args)) != STRSXP || length(CAR(args)) != n + 1)
    goto badargs;

    llabels = CAR(args);
    args = CDR(args);
    GSavePars(dd);
    ProcessInlinePars(args, dd);
    dd->gp.cex = dd->gp.cexbase * dd->gp.cex;
    dnd_offset = GStrWidth("m", INCHES, dd);
    vmax = vmaxget();
    y =  (double*)R_alloc(n, sizeof(double));
    ll =  (double*)R_alloc(n, sizeof(double));
    dnd_lptr = &(INTEGER(merge)[0]);
    dnd_rptr = &(INTEGER(merge)[n]);
    ymin = REAL(height)[0];
    ymax = REAL(height)[n - 1];
    pin = dd->gp.pin[1];
    for (i = 0; i < n; i++)
    ll[i] = GStrWidth(CHAR(STRING(llabels)[i]), INCHES, dd)
        + dnd_offset;
    if (dnd_hang >= 0) {
    ymin = ymax - (1 + dnd_hang) * (ymax - ymin);
    yrange = ymax - ymin;
    /* determine leaf heights */
    for (i = 0; i < n; i++) {
        if (dnd_lptr[i] < 0)
        y[-dnd_lptr[i] - 1] = REAL(height)[i];
        if (dnd_rptr[i] < 0)
        y[-dnd_rptr[i] - 1] = REAL(height)[i];
    }
    /* determine the most extreme label depth */
    /* assuming that we are using the full plot */
    /* window for the tree itself */
    imax = -1;
    yval = -DBL_MAX;
    for (i = 0; i < n; i++) {
        tmp = ((ymax - y[i]) / yrange) * pin + ll[i];
        if (tmp > yval) {
        yval = tmp;
        imax = i;
        }
    }
    }
    else {
    ymin = 0;
    yrange = ymax;
    imax = -1;
    yval = -DBL_MAX;
    for (i = 0; i < n; i++) {
        tmp = pin + ll[i];
        if (tmp > yval) {
        yval = tmp;
        imax = i;
        }
    }
    }
    /* now determine how much to scale */
    ymin = ymax - (pin/(pin - ll[imax])) * (ymax - ymin);
    GScale(1.0, n+1.0, 1, dd);
    GScale(ymin, ymax, 2, dd);
    GMapWin2Fig(dd);
    GRestorePars(dd);
    /* NOTE: only record operation if no "error"  */
    /* NOTE: on replay, call == R_NilValue */
    if (call != R_NilValue)
    recordGraphicOperation(op, originalArgs, dd);
    vmaxset(vmax);
    return R_NilValue;
  badargs:
    error("invalid dendrogram input");
    return R_NilValue;/* never used; to keep -Wall happy */
}


SEXP do_erase(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP col;
    int ncol;
    DevDesc *dd = CurrentDevice();
    checkArity(op, args);
    PROTECT(col = FixupCol(CAR(args), NA_INTEGER));
    ncol = LENGTH(col);
    GSavePars(dd);
    GMode(1, dd);
    GRect(0.0, 0.0, 1.0, 1.0, NDC, INTEGER(col)[0], NA_INTEGER, dd);
    GMode(0, dd);
    GRestorePars(dd);
    UNPROTECT(1);
    return R_NilValue;
}


SEXP do_replay(SEXP call, SEXP op, SEXP args, SEXP env)
{
    DevDesc *dd = CurrentDevice();
    checkArity(op, args);
    dd->dp.resize();
    playDisplayList(dd);
    return R_NilValue;
}