show mini-map when hovering over the empty mini-map frame

[micropolis] / src / tk / tkcvline.c

/* 
 * tkCanvLine.c --
 *
 *      This file implements line items for canvas widgets.
 *
 * Copyright 1991-1992 Regents of the University of California.
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  The University of California
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */

#ifndef lint
static char rcsid[] = "$Header: /user6/ouster/wish/RCS/tkCanvLine.c,v 1.7 92/07/28 15:40:08 ouster Exp $ SPRITE (Berkeley)";
#endif

#include <stdio.h>
#include <math.h>
#include "tkint.h"
#include "tkcanvas.h"
#include "tkconfig.h"

/*
 * The structure below defines the record for each line item.
 */

typedef struct LineItem  {
    Tk_Item header;             /* Generic stuff that's the same for all
                                 * types.  MUST BE FIRST IN STRUCTURE. */
    Tk_Canvas *canvasPtr;       /* Canvas containing item.  Needed for
                                 * parsing arrow shapes. */
    int numPoints;              /* Number of points in line (always >= 2). */
    double *coordPtr;           /* Pointer to malloc-ed array containing
                                 * x- and y-coords of all points in line.
                                 * X-coords are even-valued indices, y-coords
                                 * are corresponding odd-valued indices. */
    int width;                  /* Width of line. */
    XColor *fg;                 /* Foreground color for line. */
    Pixmap fillStipple;         /* Stipple bitmap for filling line. */
    int capStyle;               /* Cap style for line. */
    int joinStyle;              /* Join style for line. */
    GC gc;                      /* Graphics context for filling line. */
    Tk_Uid arrow;               /* Indicates whether or not to draw arrowheads:
                                 * "none", "first", "last", or "both". */
    float arrowShapeA;          /* Distance from tip of arrowhead to center. */
    float arrowShapeB;          /* Distance from tip of arrowhead to trailing
                                 * point, measured along shaft. */
    float arrowShapeC;          /* Distance of trailing points from outside
                                 * edge of shaft. */
    double *firstArrowPtr;      /* Points to array of 5 points describing
                                 * polygon for arrowhead at first point in
                                 * line.  First point of arrowhead is tip.
                                 * Malloc'ed.  NULL means no arrowhead at
                                 * first point. */
    double *lastArrowPtr;       /* Points to polygon for arrowhead at last
                                 * point in line (5 points, first of which
                                 * is tip).  Malloc'ed.  NULL means no
                                 * arrowhead at last point. */
    int smooth;                 /* Non-zero means draw line smoothed (i.e.
                                 * with Bezier splines). */
    int splineSteps;            /* Number of steps in each spline segment. */
} LineItem;

/*
 * Number of points in an arrowHead:
 */

#define PTS_IN_ARROW 6

/*
 * Prototypes for procedures defined in this file:
 */

static void             ComputeLineBbox _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            LineItem *linePtr));
static int              ConfigureLine _ANSI_ARGS_((
                            Tk_Canvas *canvasPtr, Tk_Item *itemPtr, int argc,
                            char **argv, int flags));
static int              ConfigureArrows _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            LineItem *linePtr));
static int              CreateLine _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            struct Tk_Item *itemPtr, int argc, char **argv));
static void             DeleteLine _ANSI_ARGS_((Tk_Item *itemPtr));
static void             DisplayLine _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, Drawable dst));
static int              LineCoords _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, int argc, char **argv));
static int              LineToArea _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double *rectPtr));
static double           LineToPoint _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double *coordPtr));
static int              ParseArrowShape _ANSI_ARGS_((ClientData clientData,
                            Tcl_Interp *interp, Tk_Window tkwin, char *value,
                            char *recordPtr, int offset));
static char *           PrintArrowShape _ANSI_ARGS_((ClientData clientData,
                            Tk_Window tkwin, char *recordPtr, int offset,
                            Tcl_FreeProc **freeProcPtr));
static void             ScaleLine _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double originX, double originY,
                            double scaleX, double scaleY));
static void             TranslateLine _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double deltaX, double deltaY));

/*
 * Information used for parsing configuration specs.  If you change any
 * of the default strings, be sure to change the corresponding default
 * values in CreateLine.
 */

static Tk_CustomOption arrowShapeOption = {ParseArrowShape,
        PrintArrowShape, (ClientData) NULL};

static Tk_ConfigSpec configSpecs[] = {
    {TK_CONFIG_UID, "-arrow", (char *) NULL, (char *) NULL,
        "none", Tk_Offset(LineItem, arrow), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_CUSTOM, "-arrowshape", (char *) NULL, (char *) NULL,
        "8 10 3", Tk_Offset(LineItem, arrowShapeA),
        TK_CONFIG_DONT_SET_DEFAULT, &arrowShapeOption},
    {TK_CONFIG_CAP_STYLE, "-capstyle", (char *) NULL, (char *) NULL,
        "butt", Tk_Offset(LineItem, capStyle), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_COLOR, "-fill", (char *) NULL, (char *) NULL,
        "black", Tk_Offset(LineItem, fg), 0},
    {TK_CONFIG_JOIN_STYLE, "-joinstyle", (char *) NULL, (char *) NULL,
        "round", Tk_Offset(LineItem, joinStyle), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_BOOLEAN, "-smooth", (char *) NULL, (char *) NULL,
        "no", Tk_Offset(LineItem, smooth), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_INT, "-splinesteps", (char *) NULL, (char *) NULL,
        "12", Tk_Offset(LineItem, splineSteps), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_BITMAP, "-stipple", (char *) NULL, (char *) NULL,
        (char *) NULL, Tk_Offset(LineItem, fillStipple), TK_CONFIG_NULL_OK},
    {TK_CONFIG_CUSTOM, "-tags", (char *) NULL, (char *) NULL,
        (char *) NULL, 0, TK_CONFIG_NULL_OK, &tkCanvasTagsOption},
    {TK_CONFIG_PIXELS, "-width", (char *) NULL, (char *) NULL,
        "1", Tk_Offset(LineItem, width), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_END, (char *) NULL, (char *) NULL, (char *) NULL,
        (char *) NULL, 0, 0}
};

/*
 * The structures below defines the line item type by means
 * of procedures that can be invoked by generic item code.
 */

Tk_ItemType TkLineType = {
    "line",                             /* name */
    sizeof(LineItem),                   /* itemSize */
    CreateLine,                         /* createProc */
    configSpecs,                        /* configSpecs */
    ConfigureLine,                      /* configureProc */
    LineCoords,                         /* coordProc */
    DeleteLine,                         /* deleteProc */
    DisplayLine,                        /* displayProc */
    0,                                  /* alwaysRedraw */
    LineToPoint,                        /* pointProc */
    LineToArea,                         /* areaProc */
    (Tk_ItemPostscriptProc *) NULL,     /* postscriptProc */
    ScaleLine,                          /* scaleProc */
    TranslateLine,                      /* translateProc */
    (Tk_ItemIndexProc *) NULL,          /* indexProc */
    (Tk_ItemCursorProc *) NULL,         /* cursorProc */
    (Tk_ItemSelectionProc *) NULL,      /* selectionProc */
    (Tk_ItemInsertProc *) NULL,         /* insertProc */
    (Tk_ItemDCharsProc *) NULL,         /* dTextProc */
    (Tk_ItemType *) NULL                /* nextPtr */
};

/*
 * The Tk_Uid's below refer to uids for the various arrow types:
 */

static Tk_Uid noneUid = NULL;
static Tk_Uid firstUid = NULL;
static Tk_Uid lastUid = NULL;
static Tk_Uid bothUid = NULL;

/*
 * The definition below determines how large are static arrays
 * used to hold spline points (splines larger than this have to
 * have their arrays malloc-ed).
 */

#define MAX_STATIC_POINTS 200
\f
/*
 *--------------------------------------------------------------
 *
 * CreateLine --
 *
 *      This procedure is invoked to create a new line item in
 *      a canvas.
 *
 * Results:
 *      A standard Tcl return value.  If an error occurred in
 *      creating the item, then an error message is left in
 *      canvasPtr->interp->result;  in this case itemPtr is
 *      left uninitialized, so it can be safely freed by the
 *      caller.
 *
 * Side effects:
 *      A new line item is created.
 *
 *--------------------------------------------------------------
 */

static int
CreateLine(canvasPtr, itemPtr, argc, argv)
    register Tk_Canvas *canvasPtr;      /* Canvas to hold new item. */
    Tk_Item *itemPtr;                   /* Record to hold new item;  header
                                         * has been initialized by caller. */
    int argc;                           /* Number of arguments in argv. */
    char **argv;                        /* Arguments describing line. */
{
    register LineItem *linePtr = (LineItem *) itemPtr;
    int i;

    if (argc < 4) {
        Tcl_AppendResult(canvasPtr->interp, "wrong # args:  should be \"",
                Tk_PathName(canvasPtr->tkwin),
                "\" create x1 y1 x2 y2 ?x3 y3 ...? ?options?",
                (char *) NULL);
        return TCL_ERROR;
    }

    /*
     * Carry out initialization that is needed to set defaults and to
     * allow proper cleanup after errors during the the remainder of
     * this procedure.
     */

    linePtr->canvasPtr = canvasPtr;
    linePtr->numPoints = 0;
    linePtr->coordPtr = NULL;
    linePtr->width = 1;
    linePtr->fg = None;
    linePtr->fillStipple = None;
    linePtr->capStyle = CapButt;
    linePtr->joinStyle = JoinRound;
    linePtr->gc = None;
    if (noneUid == NULL) {
        noneUid = Tk_GetUid("none");
        firstUid = Tk_GetUid("first");
        lastUid = Tk_GetUid("last");
        bothUid = Tk_GetUid("both");
    }
    linePtr->arrow = noneUid;
    linePtr->arrowShapeA = 8.0;
    linePtr->arrowShapeB = 10.0;
    linePtr->arrowShapeC = 3.0;
    linePtr->firstArrowPtr = NULL;
    linePtr->lastArrowPtr = NULL;
    linePtr->smooth = 0;
    linePtr->splineSteps = 12;

    /*
     * Count the number of points and then parse them into a point
     * array.  Leading arguments are assumed to be points if they
     * start with a digit or a minus sign followed by a digit.
     */

    for (i = 4; i < (argc-1); i+=2) {
        if ((!isdigit(argv[i][0])) &&
                ((argv[i][0] != '-') || (!isdigit(argv[i][1])))) {
            break;
        }
    }
    if (LineCoords(canvasPtr, itemPtr, i, argv) != TCL_OK) {
        goto error;
    }
    if (ConfigureLine(canvasPtr, itemPtr, argc-i, argv+i, 0) == TCL_OK) {
        return TCL_OK;
    }

    error:
    DeleteLine(itemPtr);
    return TCL_ERROR;
}
\f
/*
 *--------------------------------------------------------------
 *
 * LineCoords --
 *
 *      This procedure is invoked to process the "coords" widget
 *      command on lines.  See the user documentation for details
 *      on what it does.
 *
 * Results:
 *      Returns TCL_OK or TCL_ERROR, and sets canvasPtr->interp->result.
 *
 * Side effects:
 *      The coordinates for the given item may be changed.
 *
 *--------------------------------------------------------------
 */

static int
LineCoords(canvasPtr, itemPtr, argc, argv)
    register Tk_Canvas *canvasPtr;      /* Canvas containing item. */
    Tk_Item *itemPtr;                   /* Item whose coordinates are to be
                                         * read or modified. */
    int argc;                           /* Number of coordinates supplied in
                                         * argv. */
    char **argv;                        /* Array of coordinates: x1, y1,
                                         * x2, y2, ... */
{
    register LineItem *linePtr = (LineItem *) itemPtr;
    char buffer[300];
    int i, numPoints;

    if (argc == 0) {
        for (i = 0; i < 2*linePtr->numPoints; i++) {
            sprintf(buffer, "%g", linePtr->coordPtr[i]);
            Tcl_AppendElement(canvasPtr->interp, buffer, 0);
        }
    } else if (argc < 4) {
        Tcl_AppendResult(canvasPtr->interp,
                "too few coordinates for line:  must have at least 4",
                (char *) NULL);
        return TCL_ERROR;
    } else if (argc & 1) {
        Tcl_AppendResult(canvasPtr->interp,
                "odd number of coordinates specified for line",
                (char *) NULL);
        return TCL_ERROR;
    } else {
        numPoints = argc/2;
        if (linePtr->numPoints != numPoints) {
            if (linePtr->coordPtr != NULL) {
                ckfree((char *) linePtr->coordPtr);
            }
            linePtr->coordPtr = (double *) ckalloc((unsigned)
                    (sizeof(double) * argc));
            linePtr->numPoints = numPoints;
        }
        for (i = argc-1; i >= 0; i--) {
            if (TkGetCanvasCoord(canvasPtr, argv[i], &linePtr->coordPtr[i])
                    != TCL_OK) {
                return TCL_ERROR;
            }
        }
        ComputeLineBbox(canvasPtr, linePtr);
    }
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * ConfigureLine --
 *
 *      This procedure is invoked to configure various aspects
 *      of a line item such as its background color.
 *
 * Results:
 *      A standard Tcl result code.  If an error occurs, then
 *      an error message is left in canvasPtr->interp->result.
 *
 * Side effects:
 *      Configuration information, such as colors and stipple
 *      patterns, may be set for itemPtr.
 *
 *--------------------------------------------------------------
 */

static int
ConfigureLine(canvasPtr, itemPtr, argc, argv, flags)
    Tk_Canvas *canvasPtr;       /* Canvas containing itemPtr. */
    Tk_Item *itemPtr;           /* Line item to reconfigure. */
    int argc;                   /* Number of elements in argv.  */
    char **argv;                /* Arguments describing things to configure. */
    int flags;                  /* Flags to pass to Tk_ConfigureWidget. */
{
    register LineItem *linePtr = (LineItem *) itemPtr;
    XGCValues gcValues;
    GC newGC;
    unsigned long mask;

    if (Tk_ConfigureWidget(canvasPtr->interp, canvasPtr->tkwin,
            configSpecs, argc, argv, (char *) linePtr, flags) != TCL_OK) {
        return TCL_ERROR;
    }

    /*
     * A few of the options require additional processing, such as
     * graphics contexts.
     */

    if (linePtr->fg == NULL) {
        newGC = None;
    } else {
        gcValues.foreground = linePtr->fg->pixel;
        gcValues.join_style = linePtr->joinStyle;
        if (linePtr->width < 0) {
            linePtr->width = 1;
        }
        gcValues.line_width = linePtr->width;
        mask = GCForeground|GCJoinStyle|GCLineWidth;
        if (linePtr->fillStipple != None) {
            gcValues.stipple = linePtr->fillStipple;
            gcValues.fill_style = FillStippled;
            mask |= GCStipple|GCFillStyle;
        }
        if (linePtr->arrow == noneUid) {
            gcValues.cap_style = linePtr->capStyle;
            mask |= GCCapStyle;
        }
        newGC = Tk_GetGC(canvasPtr->tkwin, mask, &gcValues);
    }
    if (linePtr->gc != None) {
        Tk_FreeGC(linePtr->gc);
    }
    linePtr->gc = newGC;

    /*
     * Keep spline parameters within reasonable limits.
     */

    if (linePtr->splineSteps < 1) {
        linePtr->splineSteps = 1;
    } else if (linePtr->splineSteps > 100) {
        linePtr->splineSteps = 100;
    }

    /*
     * Setup arrowheads, if needed.  If arrowheads are turned off,
     * restore the line's endpoints (they were shortened when the
     * arrowheads were added).
     */

    if ((linePtr->firstArrowPtr != NULL) && (linePtr->arrow != firstUid)
            && (linePtr->arrow != bothUid)) {
        linePtr->coordPtr[0] = linePtr->firstArrowPtr[0];
        linePtr->coordPtr[1] = linePtr->firstArrowPtr[1];
        ckfree((char *) linePtr->firstArrowPtr);
        linePtr->firstArrowPtr = NULL;
    }
    if ((linePtr->lastArrowPtr != NULL) && (linePtr->arrow != lastUid)
            && (linePtr->arrow != bothUid)) {
        int index;

        index = 2*(linePtr->numPoints-1);
        linePtr->coordPtr[index] = linePtr->lastArrowPtr[0];
        linePtr->coordPtr[index+1] = linePtr->lastArrowPtr[1];
        ckfree((char *) linePtr->lastArrowPtr);
        linePtr->lastArrowPtr = NULL;
    }
    if (linePtr->arrow != noneUid) {
        if ((linePtr->arrow != firstUid) && (linePtr->arrow != lastUid)
                && (linePtr->arrow != bothUid)) {
            Tcl_AppendResult(canvasPtr->interp, "bad arrow spec \"",
                    linePtr->arrow, "\": must be none, first, last, or both",
                    (char *) NULL);
            linePtr->arrow = noneUid;
            return TCL_ERROR;
        }
        ConfigureArrows(canvasPtr, linePtr);
    }

    /*
     * Recompute bounding box for line.
     */

    ComputeLineBbox(canvasPtr, linePtr);

    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * DeleteLine --
 *
 *      This procedure is called to clean up the data structure
 *      associated with a line item.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Resources associated with itemPtr are released.
 *
 *--------------------------------------------------------------
 */

static void
DeleteLine(itemPtr)
    Tk_Item *itemPtr;                   /* Item that is being deleted. */
{
    register LineItem *linePtr = (LineItem *) itemPtr;

    if (linePtr->coordPtr != NULL) {
        ckfree((char *) linePtr->coordPtr);
    }
    if (linePtr->fg != NULL) {
        Tk_FreeColor(linePtr->fg);
    }
    if (linePtr->fillStipple != None) {
        Tk_FreeBitmap(linePtr->fillStipple);
    }
    if (linePtr->gc != None) {
        Tk_FreeGC(linePtr->gc);
    }
    if (linePtr->firstArrowPtr != NULL) {
        ckfree((char *) linePtr->firstArrowPtr);
    }
    if (linePtr->lastArrowPtr != NULL) {
        ckfree((char *) linePtr->lastArrowPtr);
    }
}
\f
/*
 *--------------------------------------------------------------
 *
 * ComputeLineBbox --
 *
 *      This procedure is invoked to compute the bounding box of
 *      all the pixels that may be drawn as part of a line.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The fields x1, y1, x2, and y2 are updated in the header
 *      for itemPtr.
 *
 *--------------------------------------------------------------
 */

static void
ComputeLineBbox(canvasPtr, linePtr)
    register Tk_Canvas *canvasPtr;      /* Canvas that contains item. */
    LineItem *linePtr;                  /* Item whose bbos is to be
                                         * recomputed. */
{
    register double *coordPtr;
    int i;

    coordPtr = linePtr->coordPtr;
    linePtr->header.x1 = linePtr->header.x2 = *coordPtr;
    linePtr->header.y1 = linePtr->header.y2 = coordPtr[1];

    /*
     * Compute the bounding box of all the points in the line,
     * then expand in all directions by the line's width to take
     * care of butting or rounded corners and projecting or
     * rounded caps.  This expansion is an overestimate (worst-case
     * is square root of two over two) but it's simple.  Don't do
     * anything special for curves.  This causes an additional
     * overestimate in the bounding box, but is faster.
     */

    for (i = 1, coordPtr = linePtr->coordPtr+2; i < linePtr->numPoints;
            i++, coordPtr += 2) {
        TkIncludePoint(canvasPtr, (Tk_Item *) linePtr, coordPtr);
    }
    linePtr->header.x1 -= linePtr->width;
    linePtr->header.x2 += linePtr->width;
    linePtr->header.y1 -= linePtr->width;
    linePtr->header.y2 += linePtr->width;

    /*
     * For mitered lines, make a second pass through all the points.
     * Compute the locations of the two miter vertex points and add
     * those into the bounding box.
     */

    if (linePtr->joinStyle == JoinMiter) {
        for (i = linePtr->numPoints, coordPtr = linePtr->coordPtr; i >= 3;
                i--, coordPtr += 2) {
            double miter[4];
            int j;
    
            if (TkGetMiterPoints(coordPtr, coordPtr+2, coordPtr+4,
                    (double) linePtr->width, miter, miter+2)) {
                for (j = 0; j < 4; j += 2) {
                    TkIncludePoint(canvasPtr, (Tk_Item *) linePtr, miter+j);
                }
            }
        }
    }

    /*
     * Add in the sizes of arrowheads, if any.
     */

    if (linePtr->arrow != noneUid) {
        if (linePtr->arrow != lastUid) {
            for (i = 0, coordPtr = linePtr->firstArrowPtr; i < PTS_IN_ARROW;
                    i++, coordPtr += 2) {
                TkIncludePoint(canvasPtr, (Tk_Item *) linePtr, coordPtr);
            }
        }
        if (linePtr->arrow != firstUid) {
            for (i = 0, coordPtr = linePtr->lastArrowPtr; i < PTS_IN_ARROW;
                    i++, coordPtr += 2) {
                TkIncludePoint(canvasPtr, (Tk_Item *) linePtr, coordPtr);
            }
        }
    }

    /*
     * Add one more pixel of fudge factor just to be safe (e.g.
     * X may round differently than we do).
     */

    linePtr->header.x1 -= 1;
    linePtr->header.x2 += 1;
    linePtr->header.y1 -= 1;
    linePtr->header.y2 += 1;
}
\f
/*
 *--------------------------------------------------------------
 *
 * DisplayLine --
 *
 *      This procedure is invoked to draw a line item in a given
 *      drawable.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      ItemPtr is drawn in drawable using the transformation
 *      information in canvasPtr.
 *
 *--------------------------------------------------------------
 */

static void
DisplayLine(canvasPtr, itemPtr, drawable)
    register Tk_Canvas *canvasPtr;      /* Canvas that contains item. */
    Tk_Item *itemPtr;                   /* Item to be displayed. */
    Drawable drawable;                  /* Pixmap or window in which to draw
                                         * item. */
{
    register LineItem *linePtr = (LineItem *) itemPtr;
    XPoint staticPoints[MAX_STATIC_POINTS];
    XPoint *pointPtr;
    register XPoint *pPtr;
    register double *coordPtr;
    int i, numPoints;

    if (linePtr->gc == None) {
        return;
    }

    /*
     * Build up an array of points in screen coordinates.  Use a
     * static array unless the line has an enormous number of points;
     * in this case, dynamically allocate an array.  For smoothed lines,
     * generate the curve points on each redisplay.
     */

    if ((linePtr->smooth) && (linePtr->numPoints > 2)) {
        numPoints = 1 + linePtr->numPoints*linePtr->splineSteps;
    } else {
        numPoints = linePtr->numPoints;
    }

    if (numPoints <= MAX_STATIC_POINTS) {
        pointPtr = staticPoints;
    } else {
        pointPtr = (XPoint *) ckalloc((unsigned) (numPoints * sizeof(XPoint)));
    }

    if (linePtr->smooth) {
        numPoints = TkMakeBezierCurve(canvasPtr, linePtr->coordPtr,
                linePtr->numPoints, linePtr->splineSteps, pointPtr,
                (double *) NULL);
    } else {
        for (i = 0, coordPtr = linePtr->coordPtr, pPtr = pointPtr;
                i < linePtr->numPoints;  i += 1, coordPtr += 2, pPtr++) {
            pPtr->x = SCREEN_X(canvasPtr, *coordPtr);
            pPtr->y = SCREEN_Y(canvasPtr, coordPtr[1]);
        }
    }

    /*
     * Display line, the free up line storage if it was dynamically
     * allocated.
     */

    XDrawLines(Tk_Display(canvasPtr->tkwin), drawable, linePtr->gc,
            pointPtr, numPoints, CoordModeOrigin);
    if (pointPtr != staticPoints) {
        ckfree((char *) pointPtr);
    }

    /*
     * Display arrowheads, if they are wanted.
     */

    if (linePtr->arrow != noneUid) {
        if (linePtr->arrow != lastUid) {
            TkFillPolygon(canvasPtr, linePtr->firstArrowPtr, PTS_IN_ARROW,
                    drawable, linePtr->gc);
        }
        if (linePtr->arrow != firstUid) {
            TkFillPolygon(canvasPtr, linePtr->lastArrowPtr, PTS_IN_ARROW,
                    drawable, linePtr->gc);
        }
    }
}
\f
/*
 *--------------------------------------------------------------
 *
 * LineToPoint --
 *
 *      Computes the distance from a given point to a given
 *      line, in canvas units.
 *
 * Results:
 *      The return value is 0 if the point whose x and y coordinates
 *      are pointPtr[0] and pointPtr[1] is inside the line.  If the
 *      point isn't inside the line then the return value is the
 *      distance from the point to the line.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static double
LineToPoint(canvasPtr, itemPtr, pointPtr)
    Tk_Canvas *canvasPtr;       /* Canvas containing item. */
    Tk_Item *itemPtr;           /* Item to check against point. */
    double *pointPtr;           /* Pointer to x and y coordinates. */
{
    register LineItem *linePtr = (LineItem *) itemPtr;
    register double *coordPtr, *linePoints;
    double staticSpace[2*MAX_STATIC_POINTS];
    double poly[10];
    double bestDist, dist;
    int numPoints, count;
    int changedMiterToBevel;    /* Non-zero means that a mitered corner
                                 * had to be treated as beveled after all
                                 * because the angle was < 11 degrees. */

    bestDist = 1.0e40;

    /*
     * Handle smoothed lines by generating an expanded set of points
     * against which to do the check.
     */

    if ((linePtr->smooth) && (linePtr->numPoints > 2)) {
        numPoints = 1 + linePtr->numPoints*linePtr->splineSteps;
        if (numPoints <= MAX_STATIC_POINTS) {
            linePoints = staticSpace;
        } else {
            linePoints = (double *) ckalloc((unsigned)
                    (2*numPoints*sizeof(double)));
        }
        numPoints = TkMakeBezierCurve(canvasPtr, linePtr->coordPtr,
                linePtr->numPoints, linePtr->splineSteps, (XPoint *) NULL,
                linePoints);
    } else {
        numPoints = linePtr->numPoints;
        linePoints = linePtr->coordPtr;
    }

    /*
     * The overall idea is to iterate through all of the edges of
     * the line, computing a polygon for each edge and testing the
     * point against that polygon.  In addition, there are additional
     * tests to deal with rounded joints and caps.
     */

    changedMiterToBevel = 0;
    for (count = numPoints, coordPtr = linePoints; count >= 2;
            count--, coordPtr += 2) {

        /*
         * If rounding is done around the first point then compute
         * the distance between the point and the point.
         */

        if (((linePtr->capStyle == CapRound) && (count == numPoints))
                || ((linePtr->joinStyle == JoinRound)
                        && (count != numPoints))) {
            dist = hypot(coordPtr[0] - pointPtr[0], coordPtr[1] - pointPtr[1])
                    - linePtr->width/2.0;
            if (dist <= 0.0) {
                bestDist = 0.0;
                goto done;
            } else if (dist < bestDist) {
                bestDist = dist;
            }
        }

        /*
         * Compute the polygonal shape corresponding to this edge,
         * consisting of two points for the first point of the edge
         * and two points for the last point of the edge.
         */

        if (count == numPoints) {
            TkGetButtPoints(coordPtr+2, coordPtr, (double) linePtr->width,
                    linePtr->capStyle == CapProjecting, poly, poly+2);
        } else if ((linePtr->joinStyle == JoinMiter) && !changedMiterToBevel) {
            poly[0] = poly[6];
            poly[1] = poly[7];
            poly[2] = poly[4];
            poly[3] = poly[5];
        } else {
            TkGetButtPoints(coordPtr+2, coordPtr, (double) linePtr->width, 0,
                    poly, poly+2);

            /*
             * If this line uses beveled joints, then check the distance
             * to a polygon comprising the last two points of the previous
             * polygon and the first two from this polygon;  this checks
             * the wedges that fill the mitered joint.
             */

            if ((linePtr->joinStyle == JoinBevel) || changedMiterToBevel) {
                poly[8] = poly[0];
                poly[9] = poly[1];
                dist = TkPolygonToPoint(poly, 5, pointPtr);
                if (dist <= 0.0) {
                    bestDist = 0.0;
                    goto done;
                } else if (dist < bestDist) {
                    bestDist = dist;
                }
                changedMiterToBevel = 0;
            }
        }
        if (count == 2) {
            TkGetButtPoints(coordPtr, coordPtr+2, (double) linePtr->width,
                    linePtr->capStyle == CapProjecting, poly+4, poly+6);
        } else if (linePtr->joinStyle == JoinMiter) {
            if (TkGetMiterPoints(coordPtr, coordPtr+2, coordPtr+4,
                    (double) linePtr->width, poly+4, poly+6) == 0) {
                changedMiterToBevel = 1;
                TkGetButtPoints(coordPtr, coordPtr+2, (double) linePtr->width,
                        0, poly+4, poly+6);
            }
        } else {
            TkGetButtPoints(coordPtr, coordPtr+2, (double) linePtr->width, 0,
                    poly+4, poly+6);
        }
        poly[8] = poly[0];
        poly[9] = poly[1];
        dist = TkPolygonToPoint(poly, 5, pointPtr);
        if (dist <= 0.0) {
            bestDist = 0.0;
            goto done;
        } else if (dist < bestDist) {
            bestDist = dist;
        }
    }

    /*
     * If caps are rounded, check the distance to the cap around the
     * final end point of the line.
     */

    if (linePtr->capStyle == CapRound) {
        dist = hypot(coordPtr[0] - pointPtr[0], coordPtr[1] - pointPtr[1])
                - linePtr->width/2.0;
        if (dist <= 0.0) {
            bestDist = 0.0;
            goto done;
        } else if (dist < bestDist) {
            bestDist = dist;
        }
    }

    /*
     * If there are arrowheads, check the distance to the arrowheads.
     */

    if (linePtr->arrow != noneUid) {
        if (linePtr->arrow != lastUid) {
            dist = TkPolygonToPoint(linePtr->firstArrowPtr, PTS_IN_ARROW,
                    pointPtr);
            if (dist <= 0.0) {
                bestDist = 0.0;
                goto done;
            } else if (dist < bestDist) {
                bestDist = dist;
            }
        }
        if (linePtr->arrow != firstUid) {
            dist = TkPolygonToPoint(linePtr->lastArrowPtr, PTS_IN_ARROW,
                    pointPtr);
            if (dist <= 0.0) {
                bestDist = 0.0;
                goto done;
            } else if (dist < bestDist) {
                bestDist = dist;
            }
        }
    }

    done:
    if ((linePoints != staticSpace) && (linePoints != linePtr->coordPtr)) {
        ckfree((char *) linePoints);
    }
    return bestDist;
}
\f
/*
 *--------------------------------------------------------------
 *
 * LineToArea --
 *
 *      This procedure is called to determine whether an item
 *      lies entirely inside, entirely outside, or overlapping
 *      a given rectangular area.
 *
 * Results:
 *      -1 is returned if the item is entirely outside the
 *      area, 0 if it overlaps, and 1 if it is entirely
 *      inside the given area.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static int
LineToArea(canvasPtr, itemPtr, rectPtr)
    Tk_Canvas *canvasPtr;       /* Canvas containing item. */
    Tk_Item *itemPtr;           /* Item to check against line. */
    double *rectPtr;
{
    register LineItem *linePtr = (LineItem *) itemPtr;
    register double *coordPtr;
    double staticSpace[2*MAX_STATIC_POINTS];
    double *linePoints, poly[10];
    double radius;
    int numPoints, count;
    int changedMiterToBevel;    /* Non-zero means that a mitered corner
                                 * had to be treated as beveled after all
                                 * because the angle was < 11 degrees. */
    int inside;                 /* Tentative guess about what to return,
                                 * based on all points seen so far:  one
                                 * means everything seen so far was
                                 * inside the area;  -1 means everything
                                 * was outside the area.  0 means overlap
                                 * has been found. */ 

    radius = linePtr->width/2.0;
    inside = -1;

    /*
     * Handle smoothed lines by generating an expanded set of points
     * against which to do the check.
     */

    if ((linePtr->smooth) && (linePtr->numPoints > 2)) {
        numPoints = 1 + linePtr->numPoints*linePtr->splineSteps;
        if (numPoints <= MAX_STATIC_POINTS) {
            linePoints = staticSpace;
        } else {
            linePoints = (double *) ckalloc((unsigned)
                    (2*numPoints*sizeof(double)));
        }
        numPoints = TkMakeBezierCurve(canvasPtr, linePtr->coordPtr,
                linePtr->numPoints, linePtr->splineSteps, (XPoint *) NULL,
                linePoints);
    } else {
        numPoints = linePtr->numPoints;
        linePoints = linePtr->coordPtr;
    }

    coordPtr = linePoints;
    if ((coordPtr[0] >= rectPtr[0]) && (coordPtr[0] <= rectPtr[2])
            && (coordPtr[1] >= rectPtr[1]) && (coordPtr[1] <= rectPtr[3])) {
        inside = 1;
    }

    /*
     * Iterate through all of the edges of the line, computing a polygon
     * for each edge and testing the area against that polygon.  In
     * addition, there are additional tests to deal with rounded joints
     * and caps.
     */

    changedMiterToBevel = 0;
    for (count = numPoints; count >= 2; count--, coordPtr += 2) {

        /*
         * If rounding is done around the first point of the edge
         * then test a circular region around the point with the
         * area.
         */

        if (((linePtr->capStyle == CapRound) && (count == numPoints))
                || ((linePtr->joinStyle == JoinRound)
                && (count != numPoints))) {
            poly[0] = coordPtr[0] - radius;
            poly[1] = coordPtr[1] - radius;
            poly[2] = coordPtr[0] + radius;
            poly[3] = coordPtr[1] + radius;
            if (TkOvalToArea(poly, rectPtr) != inside) {
                inside = 0;
                goto done;
            }
        }

        /*
         * Compute the polygonal shape corresponding to this edge,
         * consisting of two points for the first point of the edge
         * and two points for the last point of the edge.
         */

        if (count == numPoints) {
            TkGetButtPoints(coordPtr+2, coordPtr, (double) linePtr->width,
                    linePtr->capStyle == CapProjecting, poly, poly+2);
        } else if ((linePtr->joinStyle == JoinMiter) && !changedMiterToBevel) {
            poly[0] = poly[6];
            poly[1] = poly[7];
            poly[2] = poly[4];
            poly[3] = poly[5];
        } else {
            TkGetButtPoints(coordPtr+2, coordPtr, (double) linePtr->width, 0,
                    poly, poly+2);

            /*
             * If the last joint was beveled, then also check a
             * polygon comprising the last two points of the previous
             * polygon and the first two from this polygon;  this checks
             * the wedges that fill the beveled joint.
             */

            if ((linePtr->joinStyle == JoinBevel) || changedMiterToBevel) {
                poly[8] = poly[0];
                poly[9] = poly[1];
                if (TkPolygonToArea(poly, 5, rectPtr) != inside) {
                    inside = 0;
                    goto done;
                }
                changedMiterToBevel = 0;
            }
        }
        if (count == 2) {
            TkGetButtPoints(coordPtr, coordPtr+2, (double) linePtr->width,
                    linePtr->capStyle == CapProjecting, poly+4, poly+6);
        } else if (linePtr->joinStyle == JoinMiter) {
            if (TkGetMiterPoints(coordPtr, coordPtr+2, coordPtr+4,
                    (double) linePtr->width, poly+4, poly+6) == 0) {
                changedMiterToBevel = 1;
                TkGetButtPoints(coordPtr, coordPtr+2, (double) linePtr->width,
                        0, poly+4, poly+6);
            }
        } else {
            TkGetButtPoints(coordPtr, coordPtr+2, (double) linePtr->width, 0,
                    poly+4, poly+6);
        }
        poly[8] = poly[0];
        poly[9] = poly[1];
        if (TkPolygonToArea(poly, 5, rectPtr) != inside) {
            inside = 0;
            goto done;
        }
    }

    /*
     * If caps are rounded, check the cap around the final point
     * of the line.
     */

    if (linePtr->capStyle == CapRound) {
        poly[0] = coordPtr[0] - radius;
        poly[1] = coordPtr[1] - radius;
        poly[2] = coordPtr[0] + radius;
        poly[3] = coordPtr[1] + radius;
        if (TkOvalToArea(poly, rectPtr) != inside) {
            inside = 0;
            goto done;
        }
    }

    /*
     * Check arrowheads, if any.
     */

    if (linePtr->arrow != noneUid) {
        if (linePtr->arrow != lastUid) {
            if (TkPolygonToArea(linePtr->firstArrowPtr, PTS_IN_ARROW,
                    rectPtr) != inside) {
                inside = 0;
                goto done;
            }
        }
        if (linePtr->arrow != firstUid) {
            if (TkPolygonToArea(linePtr->lastArrowPtr, PTS_IN_ARROW,
                    rectPtr) != inside) {
                inside = 0;
                goto done;
            }
        }
    }

    done:
    if ((linePoints != staticSpace) && (linePoints != linePtr->coordPtr)) {
        ckfree((char *) linePoints);
    }
    return inside;
}
\f
/*
 *--------------------------------------------------------------
 *
 * ScaleLine --
 *
 *      This procedure is invoked to rescale a line item.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The line referred to by itemPtr is rescaled so that the
 *      following transformation is applied to all point
 *      coordinates:
 *              x' = originX + scaleX*(x-originX)
 *              y' = originY + scaleY*(y-originY)
 *
 *--------------------------------------------------------------
 */

static void
ScaleLine(canvasPtr, itemPtr, originX, originY, scaleX, scaleY)
    Tk_Canvas *canvasPtr;               /* Canvas containing line. */
    Tk_Item *itemPtr;                   /* Line to be scaled. */
    double originX, originY;            /* Origin about which to scale rect. */
    double scaleX;                      /* Amount to scale in X direction. */
    double scaleY;                      /* Amount to scale in Y direction. */
{
    LineItem *linePtr = (LineItem *) itemPtr;
    register double *coordPtr;
    int i;

    for (i = 0, coordPtr = linePtr->coordPtr; i < linePtr->numPoints;
            i++, coordPtr += 2) {
        coordPtr[0] = originX + scaleX*(*coordPtr - originX);
        coordPtr[1] = originY + scaleY*(coordPtr[1] - originY);
    }
    if (linePtr->firstArrowPtr != NULL) {
        for (i = 0, coordPtr = linePtr->firstArrowPtr; i < PTS_IN_ARROW;
                i++, coordPtr += 2) {
            coordPtr[0] = originX + scaleX*(coordPtr[0] - originX);
            coordPtr[1] = originY + scaleY*(coordPtr[1] - originY);
        }
    }
    if (linePtr->lastArrowPtr != NULL) {
        for (i = 0, coordPtr = linePtr->lastArrowPtr; i < PTS_IN_ARROW;
                i++, coordPtr += 2) {
            coordPtr[0] = originX + scaleX*(coordPtr[0] - originX);
            coordPtr[1] = originY + scaleY*(coordPtr[1] - originY);
        }
    }
    ComputeLineBbox(canvasPtr, linePtr);
}
\f
/*
 *--------------------------------------------------------------
 *
 * TranslateLine --
 *
 *      This procedure is called to move a line by a given amount.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The position of the line is offset by (xDelta, yDelta), and
 *      the bounding box is updated in the generic part of the item
 *      structure.
 *
 *--------------------------------------------------------------
 */

static void
TranslateLine(canvasPtr, itemPtr, deltaX, deltaY)
    Tk_Canvas *canvasPtr;               /* Canvas containing item. */
    Tk_Item *itemPtr;                   /* Item that is being moved. */
    double deltaX, deltaY;              /* Amount by which item is to be
                                         * moved. */
{
    LineItem *linePtr = (LineItem *) itemPtr;
    register double *coordPtr;
    int i;

    for (i = 0, coordPtr = linePtr->coordPtr; i < linePtr->numPoints;
            i++, coordPtr += 2) {
        coordPtr[0] += deltaX;
        coordPtr[1] += deltaY;
    }
    if (linePtr->firstArrowPtr != NULL) {
        for (i = 0, coordPtr = linePtr->firstArrowPtr; i < PTS_IN_ARROW;
                i++, coordPtr += 2) {
            coordPtr[0] += deltaX;
            coordPtr[1] += deltaY;
        }
    }
    if (linePtr->lastArrowPtr != NULL) {
        for (i = 0, coordPtr = linePtr->lastArrowPtr; i < PTS_IN_ARROW;
                i++, coordPtr += 2) {
            coordPtr[0] += deltaX;
            coordPtr[1] += deltaY;
        }
    }
    ComputeLineBbox(canvasPtr, linePtr);
}
\f
/*
 *--------------------------------------------------------------
 *
 * ParseArrowShape --
 *
 *      This procedure is called back during option parsing to
 *      parse arrow shape information.
 *
 * Results:
 *      The return value is a standard Tcl result:  TCL_OK means
 *      that the arrow shape information was parsed ok, and
 *      TCL_ERROR means it couldn't be parsed.
 *
 * Side effects:
 *      Arrow information in recordPtr is updated.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static int
ParseArrowShape(clientData, interp, tkwin, value, recordPtr, offset)
    ClientData clientData;      /* Not used. */
    Tcl_Interp *interp;         /* Used for error reporting. */
    Tk_Window tkwin;            /* Not used. */
    char *value;                /* Textual specification of arrow shape. */
    char *recordPtr;            /* Pointer to item record in which to
                                 * store arrow information. */
    int offset;                 /* Offset of shape information in widget
                                 * record. */
{
    LineItem *linePtr = (LineItem *) recordPtr;
    double a, b, c;
    int argc;
    char **argv = NULL;

    if (offset != Tk_Offset(LineItem, arrowShapeA)) {
        panic("ParseArrowShape received bogus offset");
    }

    if (Tcl_SplitList(interp, value, &argc, &argv) != TCL_OK) {
        syntaxError:
        Tcl_ResetResult(interp);
        Tcl_AppendResult(interp, "bad arrow shape \"", value,
                "\": must be list with three numbers", (char *) NULL);
        if (argv != NULL) {
            ckfree((char *) argv);
        }
        return TCL_ERROR;
    }
    if (argc != 3) {
        goto syntaxError;
    }
    if ((TkGetCanvasCoord(linePtr->canvasPtr, argv[0], &a) != TCL_OK)
            || (TkGetCanvasCoord(linePtr->canvasPtr, argv[1], &b) != TCL_OK)
            || (TkGetCanvasCoord(linePtr->canvasPtr, argv[2], &c) != TCL_OK)) {
        goto syntaxError;
    }
    linePtr->arrowShapeA = a;
    linePtr->arrowShapeB = b;
    linePtr->arrowShapeC = c;
    ckfree((char *) argv);
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * PrintArrowShape --
 *
 *      This procedure is a callback invoked by the configuration
 *      code to return a printable value describing an arrow shape.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

    /* ARGSUSED */
static char *
PrintArrowShape(clientData, tkwin, recordPtr, offset, freeProcPtr)
    ClientData clientData;      /* Not used. */
    Tk_Window tkwin;            /* Window associated with linePtr's widget. */
    char *recordPtr;            /* Pointer to item record containing current
                                 * shape information. */
    int offset;                 /* Offset of arrow information in record. */
    Tcl_FreeProc **freeProcPtr; /* Store address of procedure to call to
                                 * free string here. */
{
    LineItem *linePtr = (LineItem *) recordPtr;
    char *buffer;

    buffer = ckalloc(120);
    sprintf(buffer, "%.5g %.5g %.5g", linePtr->arrowShapeA,
            linePtr->arrowShapeB, linePtr->arrowShapeC);
    *freeProcPtr = (Tcl_FreeProc *) free;
    return buffer;
}
\f
/*
 *--------------------------------------------------------------
 *
 * ConfigureArrows --
 *
 *      If arrowheads have been requested for a line, this
 *      procedure makes arrangements for the arrowheads.
 *
 * Results:
 *      A standard Tcl return value.  If an error occurs, then
 *      an error message is left in canvasPtr->interp->result.
 *
 * Side effects:
 *      Information in linePtr is set up for one or two arrowheads.
 *      the firstArrowPtr and lastArrowPtr polygons are allocated
 *      and initialized, if need be, and the end points of the line
 *      are adjusted so that a thick line doesn't stick out past
 *      the arrowheads.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static int
ConfigureArrows(canvasPtr, linePtr)
    Tk_Canvas *canvasPtr;               /* Canvas in which arrows will be
                                         * displayed (interp and tkwin
                                         * fields are needed). */
    register LineItem *linePtr;         /* Item to configure for arrows. */
{
    double *poly, *coordPtr;
    double dx, dy, length, sinTheta, cosTheta, temp, shapeC;
    double fracHeight;                  /* Line width as fraction of
                                         * arrowhead width. */
    double backup;                      /* Distance to backup end points
                                         * so the line ends in the middle
                                         * of the arrowhead. */
    double vertX, vertY;                /* Position of arrowhead vertex. */

    /*
     * If there's an arrowhead on the first point of the line, compute
     * its polygon and adjust the first point of the line so that the
     * line doesn't stick out past the leading edge of the arrowhead.
     */

    shapeC = linePtr->arrowShapeC + linePtr->width/2.0;
    fracHeight = (linePtr->width/2.0)/shapeC;
    backup = fracHeight*linePtr->arrowShapeB
            + linePtr->arrowShapeA*(1.0 - fracHeight)/2.0;
    if (linePtr->arrow != lastUid) {
        poly = linePtr->firstArrowPtr;
        if (poly == NULL) {
            poly = (double *) ckalloc((unsigned)
                    (2*PTS_IN_ARROW*sizeof(double)));
            poly[0] = poly[10] = linePtr->coordPtr[0];
            poly[1] = poly[11] = linePtr->coordPtr[1];
            linePtr->firstArrowPtr = poly;
        }
        dx = poly[0] - linePtr->coordPtr[2];
        dy = poly[1] - linePtr->coordPtr[3];
        length = hypot(dx, dy);
        if (length == 0) {
            sinTheta = cosTheta = 0.0;
        } else {
            sinTheta = dy/length;
            cosTheta = dx/length;
        }
        vertX = poly[0] - linePtr->arrowShapeA*cosTheta;
        vertY = poly[1] - linePtr->arrowShapeA*sinTheta;
        temp = shapeC*sinTheta;
        poly[2] = poly[0] - linePtr->arrowShapeB*cosTheta + temp;
        poly[8] = poly[2] - 2*temp;
        temp = shapeC*cosTheta;
        poly[3] = poly[1] - linePtr->arrowShapeB*sinTheta - temp;
        poly[9] = poly[3] + 2*temp;
        poly[4] = poly[2]*fracHeight + vertX*(1.0-fracHeight);
        poly[5] = poly[3]*fracHeight + vertY*(1.0-fracHeight);
        poly[6] = poly[8]*fracHeight + vertX*(1.0-fracHeight);
        poly[7] = poly[9]*fracHeight + vertY*(1.0-fracHeight);

        /*
         * Polygon done.  Now move the first point towards the second so
         * that the corners at the end of the line are inside the
         * arrowhead.
         */

        linePtr->coordPtr[0] = poly[0] - backup*cosTheta;
        linePtr->coordPtr[1] = poly[1] - backup*sinTheta;
    }

    /*
     * Similar arrowhead calculation for the last point of the line.
     */

    if (linePtr->arrow != firstUid) {
        coordPtr = linePtr->coordPtr + 2*(linePtr->numPoints-2);
        poly = linePtr->lastArrowPtr;
        if (poly == NULL) {
            poly = (double *) ckalloc((unsigned)
                    (2*PTS_IN_ARROW*sizeof(double)));
            poly[0] = poly[10] = coordPtr[2];
            poly[1] = poly[11] = coordPtr[3];
            linePtr->lastArrowPtr = poly;
        }
        dx = poly[0] - coordPtr[0];
        dy = poly[1] - coordPtr[1];
        length = hypot(dx, dy);
        if (length == 0) {
            sinTheta = cosTheta = 0.0;
        } else {
            sinTheta = dy/length;
            cosTheta = dx/length;
        }
        vertX = poly[0] - linePtr->arrowShapeA*cosTheta;
        vertY = poly[1] - linePtr->arrowShapeA*sinTheta;
        temp = shapeC*sinTheta;
        poly[2] = poly[0] - linePtr->arrowShapeB*cosTheta + temp;
        poly[8] = poly[2] - 2*temp;
        temp = shapeC*cosTheta;
        poly[3] = poly[1] - linePtr->arrowShapeB*sinTheta - temp;
        poly[9] = poly[3] + 2*temp;
        poly[4] = poly[2]*fracHeight + vertX*(1.0-fracHeight);
        poly[5] = poly[3]*fracHeight + vertY*(1.0-fracHeight);
        poly[6] = poly[8]*fracHeight + vertX*(1.0-fracHeight);
        poly[7] = poly[9]*fracHeight + vertY*(1.0-fracHeight);
        coordPtr[2] = poly[0] - backup*cosTheta;
        coordPtr[3] = poly[1] - backup*sinTheta;
    }

    return TCL_OK;
}