Import Micropolis from http://www.donhopkins.com/home/micropolis/

[micropolis] / src / tk / tkcvarc.c

/* 
 * tkCanvArc.c --
 *
 *      This file implements arc items for canvas widgets.
 *
 * Copyright 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/tkCanvArc.c,v 1.5 92/08/16 15:42:20 ouster Exp $ SPRITE (Berkeley)";
#endif

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

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

typedef struct ArcItem  {
    Tk_Item header;             /* Generic stuff that's the same for all
                                 * types.  MUST BE FIRST IN STRUCTURE. */
    double bbox[4];             /* Coordinates (x1, y1, x2, y2) of bounding
                                 * box for oval of which arc is a piece. */
    double start;               /* Angle at which arc begins, in degrees
                                 * between 0 and 360. */
    double extent;              /* Extent of arc (angular distance from
                                 * start to end of arc) in degrees between
                                 * -360 and 360. */
    double *outlinePtr;         /* Points to (x,y) coordinates for points
                                 * that define one or two closed polygons
                                 * representing the portion of the outline
                                 * that isn't part of the arc (the V-shape
                                 * for a pie slice or a line-like segment
                                 * for a chord).  Malloc'ed. */
    int numOutlinePoints;       /* Number of points at outlinePtr.  Zero
                                 * means no space allocated. */
    int width;                  /* Width of outline (in pixels). */
    XColor *outlineColor;       /* Color for outline.  NULL means don't
                                 * draw outline. */
    XColor *fillColor;          /* Color for filling arc (used for drawing
                                 * outline too when style is "arc").  NULL
                                 * means don't fill arc. */
    Pixmap fillStipple;         /* Stipple bitmap for filling item. */
    Tk_Uid style;               /* How to draw arc: arc, chord, or pieslice. */
    GC outlineGC;               /* Graphics context for outline. */
    GC fillGC;                  /* Graphics context for filling item. */
    double center1[2];          /* Coordinates of center of arc outline at
                                 * start (see ComputeArcOutline). */
    double center2[2];          /* Coordinates of center of arc outline at
                                 * start+extent (see ComputeArcOutline). */
} ArcItem;

/*
 * The definitions below define the sizes of the polygons used to
 * display outline information for various styles of arcs:
 */

#define CHORD_OUTLINE_PTS       7
#define PIE_OUTLINE1_PTS        6
#define PIE_OUTLINE2_PTS        7

/*
 * Information used for parsing configuration specs:
 */

static Tk_ConfigSpec configSpecs[] = {
    {TK_CONFIG_DOUBLE, "-extent", (char *) NULL, (char *) NULL,
        "90", Tk_Offset(ArcItem, extent), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_COLOR, "-fill", (char *) NULL, (char *) NULL,
        (char *) NULL, Tk_Offset(ArcItem, fillColor), TK_CONFIG_NULL_OK},
    {TK_CONFIG_COLOR, "-outline", (char *) NULL, (char *) NULL,
        "black", Tk_Offset(ArcItem, outlineColor), TK_CONFIG_NULL_OK},
    {TK_CONFIG_DOUBLE, "-start", (char *) NULL, (char *) NULL,
        "0", Tk_Offset(ArcItem, start), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_BITMAP, "-stipple", (char *) NULL, (char *) NULL,
        (char *) NULL, Tk_Offset(ArcItem, fillStipple), TK_CONFIG_NULL_OK},
    {TK_CONFIG_UID, "-style", (char *) NULL, (char *) NULL,
        "pieslice", Tk_Offset(ArcItem, style), TK_CONFIG_DONT_SET_DEFAULT},
    {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(ArcItem, width), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_END, (char *) NULL, (char *) NULL, (char *) NULL,
        (char *) NULL, 0, 0}
};

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

static int              ArcCoords _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, int argc, char **argv));
static int              AngleInRange _ANSI_ARGS_((double x, double y,
                            double start, double extent));
static int              ArcToArea _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double *rectPtr));
static double           ArcToPoint _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double *coordPtr));
static void             ComputeArcBbox _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            ArcItem *arcPtr));
static void             ComputeArcOutline _ANSI_ARGS_((ArcItem *arcPtr));
static int              ConfigureArc _ANSI_ARGS_((
                            Tk_Canvas *canvasPtr, Tk_Item *itemPtr, int argc,
                            char **argv, int flags));
static int              CreateArc _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            struct Tk_Item *itemPtr, int argc, char **argv));
static void             DeleteArc _ANSI_ARGS_((Tk_Item *itemPtr));
static void             DisplayArc _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, Drawable dst));
static int              HorizLineToArc _ANSI_ARGS_((double x1, double x2,
                            double y, double rx, double ry,
                            double start, double extent));
static void             ScaleArc _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double originX, double originY,
                            double scaleX, double scaleY));
static void             TranslateArc _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double deltaX, double deltaY));
static int              VertLineToArc _ANSI_ARGS_((double x, double y1,
                            double y2, double rx, double ry,
                            double start, double extent));

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

Tk_ItemType TkArcType = {
    "arc",                              /* name */
    sizeof(ArcItem),                    /* itemSize */
    CreateArc,                          /* createProc */
    configSpecs,                        /* configSpecs */
    ConfigureArc,                       /* configureProc */
    ArcCoords,                          /* coordProc */
    DeleteArc,                          /* deleteProc */
    DisplayArc,                         /* displayProc */
    0,                                  /* alwaysRedraw */
    ArcToPoint,                         /* pointProc */
    ArcToArea,                          /* areaProc */
    (Tk_ItemPostscriptProc *) NULL,     /* postscriptProc */
    ScaleArc,                           /* scaleProc */
    TranslateArc,                       /* 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 */
};

#define PI 3.14159265358979323846

/*
 * The uid's below comprise the legal values for the "-style"
 * option for arcs.
 */

static Tk_Uid arcUid =  NULL;
static Tk_Uid chordUid =  NULL;
static Tk_Uid pieSliceUid = NULL;
\f
/*
 *--------------------------------------------------------------
 *
 * CreateArc --
 *
 *      This procedure is invoked to create a new arc 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 arc item is created.
 *
 *--------------------------------------------------------------
 */

static int
CreateArc(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 arc. */
{
    register ArcItem *arcPtr = (ArcItem *) itemPtr;

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

    /*
     * Carry out once-only initialization.
     */

    if (arcUid == NULL) {
        arcUid = Tk_GetUid("arc");
        chordUid = Tk_GetUid("chord");
        pieSliceUid = Tk_GetUid("pieslice");
    }

    /*
     * Carry out initialization that is needed in order to clean
     * up after errors during the the remainder of this procedure.
     */

    arcPtr->start = 0;
    arcPtr->extent = 90;
    arcPtr->outlinePtr = NULL;
    arcPtr->numOutlinePoints = 0;
    arcPtr->width = 1;
    arcPtr->outlineColor = NULL;
    arcPtr->fillColor = NULL;
    arcPtr->fillStipple = None;
    arcPtr->style = pieSliceUid;
    arcPtr->outlineGC = None;
    arcPtr->fillGC = None;

    /*
     * Process the arguments to fill in the item record.
     */

    if ((TkGetCanvasCoord(canvasPtr, argv[0], &arcPtr->bbox[0]) != TCL_OK)
            || (TkGetCanvasCoord(canvasPtr, argv[1],
                &arcPtr->bbox[1]) != TCL_OK)
            || (TkGetCanvasCoord(canvasPtr, argv[2],
                    &arcPtr->bbox[2]) != TCL_OK)
            || (TkGetCanvasCoord(canvasPtr, argv[3],
                    &arcPtr->bbox[3]) != TCL_OK)) {
        return TCL_ERROR;
    }

    if (ConfigureArc(canvasPtr, itemPtr, argc-4, argv+4, 0) != TCL_OK) {
        DeleteArc(itemPtr);
        return TCL_ERROR;
    }
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * ArcCoords --
 *
 *      This procedure is invoked to process the "coords" widget
 *      command on arcs.  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
ArcCoords(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 ArcItem *arcPtr = (ArcItem *) itemPtr;
    char buffer[500];

    if (argc == 0) {
        sprintf(buffer, "%g %g %g %g", arcPtr->bbox[0],
                arcPtr->bbox[1], arcPtr->bbox[2],
                arcPtr->bbox[3]);
        Tcl_SetResult(canvasPtr->interp, buffer, TCL_VOLATILE);
    } else if (argc == 4) {
        if ((TkGetCanvasCoord(canvasPtr, argv[0],
                    &arcPtr->bbox[0]) != TCL_OK)
                || (TkGetCanvasCoord(canvasPtr, argv[1],
                    &arcPtr->bbox[1]) != TCL_OK)
                || (TkGetCanvasCoord(canvasPtr, argv[2],
                        &arcPtr->bbox[2]) != TCL_OK)
                || (TkGetCanvasCoord(canvasPtr, argv[3],
                        &arcPtr->bbox[3]) != TCL_OK)) {
            return TCL_ERROR;
        }
        ComputeArcBbox(canvasPtr, arcPtr);
    } else {
        sprintf(canvasPtr->interp->result,
                "wrong # coordinates:  expected 0 or 4, got %d",
                argc);
        return TCL_ERROR;
    }
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * ConfigureArc --
 *
 *      This procedure is invoked to configure various aspects
 *      of a arc item, such as its outline and fill colors.
 *
 * 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
ConfigureArc(canvasPtr, itemPtr, argc, argv, flags)
    Tk_Canvas *canvasPtr;       /* Canvas containing itemPtr. */
    Tk_Item *itemPtr;           /* Arc 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 ArcItem *arcPtr = (ArcItem *) itemPtr;
    XGCValues gcValues;
    GC newGC;
    unsigned long mask;
    int i;

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

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

    i = arcPtr->start/360.0;
    arcPtr->start -= i*360.0;
    if (arcPtr->start < 0) {
        arcPtr->start += 360.0;
    }
    i = arcPtr->extent/360.0;
    arcPtr->extent -= i*360.0;

    if ((arcPtr->style != arcUid) && (arcPtr->style != chordUid)
            && (arcPtr->style != pieSliceUid)) {
        Tcl_AppendResult(canvasPtr->interp, "bad -style option \"",
                arcPtr->style, "\": must be arc, chord, or pieslice",
                (char *) NULL);
        arcPtr->style = pieSliceUid;
        return TCL_ERROR;
    }

    if (arcPtr->width < 0) {
        arcPtr->width = 1;
    }
    if (arcPtr->style == arcUid) {
        if (arcPtr->fillColor == NULL) {
            newGC = None;
        } else {
            gcValues.foreground = arcPtr->fillColor->pixel;
            gcValues.cap_style = CapButt;
            gcValues.line_width = arcPtr->width;
            mask = GCForeground|GCCapStyle|GCLineWidth;
            if (arcPtr->fillStipple != None) {
                gcValues.stipple = arcPtr->fillStipple;
                gcValues.fill_style = FillStippled;
                mask |= GCStipple|GCFillStyle;
            }
            newGC = Tk_GetGC(canvasPtr->tkwin, mask, &gcValues);
        }
    } else if (arcPtr->outlineColor == NULL) {
        newGC = None;
    } else {
        gcValues.foreground = arcPtr->outlineColor->pixel;
        gcValues.cap_style = CapButt;
        gcValues.line_width = arcPtr->width;
        mask = GCForeground|GCCapStyle|GCLineWidth;
        newGC = Tk_GetGC(canvasPtr->tkwin, mask, &gcValues);
    }
    if (arcPtr->outlineGC != None) {
        Tk_FreeGC(arcPtr->outlineGC);
    }
    arcPtr->outlineGC = newGC;

    if ((arcPtr->fillColor == NULL) || (arcPtr->style == arcUid)) {
        newGC = None;
    } else {
        gcValues.foreground = arcPtr->fillColor->pixel;
        if (arcPtr->style == chordUid) {
            gcValues.arc_mode = ArcChord;
        } else {
            gcValues.arc_mode = ArcPieSlice;
        }
        mask = GCForeground|GCArcMode;
        if (arcPtr->fillStipple != None) {
            gcValues.stipple = arcPtr->fillStipple;
            gcValues.fill_style = FillStippled;
            mask |= GCStipple|GCFillStyle;
        }
        newGC = Tk_GetGC(canvasPtr->tkwin, mask, &gcValues);
    }
    if (arcPtr->fillGC != None) {
        Tk_FreeGC(arcPtr->fillGC);
    }
    arcPtr->fillGC = newGC;

    ComputeArcBbox(canvasPtr, arcPtr);
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * DeleteArc --
 *
 *      This procedure is called to clean up the data structure
 *      associated with a arc item.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Resources associated with itemPtr are released.
 *
 *--------------------------------------------------------------
 */

static void
DeleteArc(itemPtr)
    Tk_Item *itemPtr;                   /* Item that is being deleted. */
{
    register ArcItem *arcPtr = (ArcItem *) itemPtr;

    if (arcPtr->numOutlinePoints != 0) {
        ckfree((char *) arcPtr->outlinePtr);
    }
    if (arcPtr->outlineColor != NULL) {
        Tk_FreeColor(arcPtr->outlineColor);
    }
    if (arcPtr->fillColor != NULL) {
        Tk_FreeColor(arcPtr->fillColor);
    }
    if (arcPtr->fillStipple != None) {
        Tk_FreeBitmap(arcPtr->fillStipple);
    }
    if (arcPtr->outlineGC != None) {
        Tk_FreeGC(arcPtr->outlineGC);
    }
    if (arcPtr->fillGC != None) {
        Tk_FreeGC(arcPtr->fillGC);
    }
}
\f
/*
 *--------------------------------------------------------------
 *
 * ComputeArcBbox --
 *
 *      This procedure is invoked to compute the bounding box of
 *      all the pixels that may be drawn as part of an arc.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The fields x1, y1, x2, and y2 are updated in the header
 *      for itemPtr.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static void
ComputeArcBbox(canvasPtr, arcPtr)
    register Tk_Canvas *canvasPtr;      /* Canvas that contains item. */
    register ArcItem *arcPtr;           /* Item whose bbox is to be
                                         * recomputed. */
{
    double tmp, center[2], point[2];

    /*
     * Make sure that the first coordinates are the lowest ones.
     */

    if (arcPtr->bbox[1] > arcPtr->bbox[3]) {
        double tmp;
        tmp = arcPtr->bbox[3];
        arcPtr->bbox[3] = arcPtr->bbox[1];
        arcPtr->bbox[1] = tmp;
    }
    if (arcPtr->bbox[0] > arcPtr->bbox[2]) {
        double tmp;
        tmp = arcPtr->bbox[2];
        arcPtr->bbox[2] = arcPtr->bbox[0];
        arcPtr->bbox[0] = tmp;
    }

    ComputeArcOutline(arcPtr);

    /*
     * To compute the bounding box, start with the the bbox formed
     * by the two endpoints of the arc.  Then add in the center of
     * the arc's oval (if relevant) and the 3-o'clock, 6-o'clock,
     * 9-o'clock, and 12-o'clock positions, if they are relevant.
     */

    arcPtr->header.x1 = arcPtr->header.x2 = arcPtr->center1[0];
    arcPtr->header.y1 = arcPtr->header.y2 = arcPtr->center1[1];
    TkIncludePoint(canvasPtr, (Tk_Item *) arcPtr, arcPtr->center2);
    center[0] = (arcPtr->bbox[0] + arcPtr->bbox[2])/2;
    center[1] = (arcPtr->bbox[1] + arcPtr->bbox[3])/2;
    if (arcPtr->style != arcUid) {
        TkIncludePoint(canvasPtr, (Tk_Item *) arcPtr, center);
    }

    tmp = -arcPtr->start;
    if (tmp < 0) {
        tmp += 360.0;
    }
    if ((tmp < arcPtr->extent) || ((tmp-360) > arcPtr->extent)) {
        point[0] = arcPtr->bbox[2];
        point[1] = center[1];
        TkIncludePoint(canvasPtr, (Tk_Item *) arcPtr, point);
    }
    tmp = 90.0 - arcPtr->start;
    if (tmp < 0) {
        tmp += 360.0;
    }
    if ((tmp < arcPtr->extent) || ((tmp-360) > arcPtr->extent)) {
        point[0] = center[0];
        point[1] = arcPtr->bbox[1];
        TkIncludePoint(canvasPtr, (Tk_Item *) arcPtr, point);
    }
    tmp = 180.0 - arcPtr->start;
    if (tmp < 0) {
        tmp += 360.0;
    }
    if ((tmp < arcPtr->extent) || ((tmp-360) > arcPtr->extent)) {
        point[0] = arcPtr->bbox[0];
        point[1] = center[1];
        TkIncludePoint(canvasPtr, (Tk_Item *) arcPtr, point);
    }
    tmp = 270.0 - arcPtr->start;
    if (tmp < 0) {
        tmp += 360.0;
    }
    if ((tmp < arcPtr->extent) || ((tmp-360) > arcPtr->extent)) {
        point[0] = center[0];
        point[1] = arcPtr->bbox[3];
        TkIncludePoint(canvasPtr, (Tk_Item *) arcPtr, point);
    }

    /*
     * Lastly, expand by the width of the arc (if the arc's outline is
     * being drawn) and add one extra pixel just for safety.
     */

    if (arcPtr->outlineColor == NULL) {
        tmp = 1;
    } else {
        tmp = (arcPtr->width + 1)/2 + 1;
    }
    arcPtr->header.x1 -= tmp;
    arcPtr->header.y1 -= tmp;
    arcPtr->header.x2 += tmp;
    arcPtr->header.y2 += tmp;
}
\f
/*
 *--------------------------------------------------------------
 *
 * DisplayArc --
 *
 *      This procedure is invoked to draw an arc item in a given
 *      drawable.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      ItemPtr is drawn in drawable using the transformation
 *      information in canvasPtr.
 *
 *--------------------------------------------------------------
 */

static void
DisplayArc(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 ArcItem *arcPtr = (ArcItem *) itemPtr;
    Display *display = Tk_Display(canvasPtr->tkwin);
    int x1, y1, x2, y2, start, extent;

    /*
     * Compute the screen coordinates of the bounding box for the item,
     * plus integer values for the angles.
     */

    x1 = SCREEN_X(canvasPtr, arcPtr->bbox[0]);
    y1 = SCREEN_Y(canvasPtr, arcPtr->bbox[1]);
    x2 = SCREEN_X(canvasPtr, arcPtr->bbox[2]);
    y2 = SCREEN_Y(canvasPtr, arcPtr->bbox[3]);
    if (x2 <= x1) {
        x2 = x1+1;
    }
    if (y2 <= y1) {
        y2 = y1+1;
    }
    start = (64*arcPtr->start) + 0.5;
    extent = (64*arcPtr->extent) + 0.5;

    /*
     * Display filled arc first (if wanted), then outline.
     */

    if (arcPtr->fillGC != None) {
        XFillArc(display, drawable, arcPtr->fillGC, x1, y1, (x2-x1),
                (y2-y1), start, extent);
    }
    if (arcPtr->outlineGC != None) {
        XDrawArc(display, drawable, arcPtr->outlineGC, x1, y1, (x2-x1),
                (y2-y1), start, extent);

        /*
         * If the outline width is very thin, don't use polygons to draw
         * the linear parts of the outline (this often results in nothing
         * being displayed); just draw lines instead.
         */

        if (arcPtr->width <= 2) {
            x1 = SCREEN_X(canvasPtr, arcPtr->center1[0]);
            y1 = SCREEN_Y(canvasPtr, arcPtr->center1[1]);
            x2 = SCREEN_X(canvasPtr, arcPtr->center2[0]);
            y2 = SCREEN_Y(canvasPtr, arcPtr->center2[1]);

            if (arcPtr->style == chordUid) {
                XDrawLine(display, drawable, arcPtr->outlineGC,
                        x1, y1, x2, y2);
            } else if (arcPtr->style == pieSliceUid) {
                int cx, cy;
    
                cx = SCREEN_X(canvasPtr, (arcPtr->bbox[0] + arcPtr->bbox[2])/2.0);
                cy = SCREEN_Y(canvasPtr, (arcPtr->bbox[1] + arcPtr->bbox[3])/2.0);
                XDrawLine(display, drawable, arcPtr->outlineGC,
                        cx, cy, x1, y1);
                XDrawLine(display, drawable, arcPtr->outlineGC,
                        cx, cy, x2, y2);
            }
        } else {
            if (arcPtr->style == chordUid) {
                TkFillPolygon(canvasPtr, arcPtr->outlinePtr,
                        CHORD_OUTLINE_PTS, drawable, arcPtr->outlineGC);
            } else if (arcPtr->style == pieSliceUid) {
                TkFillPolygon(canvasPtr, arcPtr->outlinePtr,
                        PIE_OUTLINE1_PTS, drawable, arcPtr->outlineGC);
                TkFillPolygon(canvasPtr,
                        arcPtr->outlinePtr + 2*PIE_OUTLINE1_PTS,
                        PIE_OUTLINE2_PTS, drawable, arcPtr->outlineGC);
            }
        }
    }
}
\f
/*
 *--------------------------------------------------------------
 *
 * ArcToPoint --
 *
 *      Computes the distance from a given point to a given
 *      arc, in canvas units.
 *
 * Results:
 *      The return value is 0 if the point whose x and y coordinates
 *      are coordPtr[0] and coordPtr[1] is inside the arc.  If the
 *      point isn't inside the arc then the return value is the
 *      distance from the point to the arc.  If itemPtr is filled,
 *      then anywhere in the interior is considered "inside"; if
 *      itemPtr isn't filled, then "inside" means only the area
 *      occupied by the outline.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static double
ArcToPoint(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 ArcItem *arcPtr = (ArcItem *) itemPtr;
    double vertex[2], pointAngle, diff, dist, newDist;
    double poly[8], polyDist, width;
    int filled, angleInRange;

    if ((arcPtr->fillGC != None) || (arcPtr->outlineGC == None)) {
        filled = 1;
    } else {
        filled = 0;
    }

    /*
     * See if the point is within the angular range of the arc.
     * Remember, X angles are backwards from the way we'd normally
     * think of them.  Also, compensate for any eccentricity of
     * the oval.
     */

    vertex[0] = (arcPtr->bbox[0] + arcPtr->bbox[2])/2.0;
    vertex[1] = (arcPtr->bbox[1] + arcPtr->bbox[3])/2.0;
    pointAngle = -atan2((pointPtr[1] - vertex[1])
            /(arcPtr->bbox[3] - arcPtr->bbox[1]),
            (pointPtr[0] - vertex[0])/(arcPtr->bbox[2] - arcPtr->bbox[0]));
    pointAngle *= 180/PI;
    diff = pointAngle - arcPtr->start;
    diff -= ((int) (diff/360.0) * 360.0);
    if (diff < 0) {
        diff += 360.0;
    }
    angleInRange = (diff <= arcPtr->extent) ||
            ((arcPtr->extent < 0) && ((diff - 360.0) >= arcPtr->extent));

    /*
     * Now perform different tests depending on what kind of arc
     * we're dealing with.
     */

    if (arcPtr->style == arcUid) {
        if (angleInRange) {
            return TkOvalToPoint(arcPtr->bbox, (double) arcPtr->width,
                    0, pointPtr);
        }
        dist = hypot(pointPtr[0] - arcPtr->center1[0],
                pointPtr[1] - arcPtr->center1[1]);
        newDist = hypot(pointPtr[0] - arcPtr->center2[0],
                pointPtr[1] - arcPtr->center2[1]);
        if (newDist < dist) {
            return newDist;
        }
        return dist;
    }

    if ((arcPtr->fillGC != None) || (arcPtr->outlineGC == None)) {
        filled = 1;
    } else {
        filled = 0;
    }
    if (arcPtr->outlineGC == None) {
        width = 0.0;
    } else {
        width = arcPtr->width;
    }

    if (arcPtr->style == pieSliceUid) {
        if (width > 1.0) {
            dist = TkPolygonToPoint(arcPtr->outlinePtr, PIE_OUTLINE1_PTS,
                    pointPtr);
            newDist = TkPolygonToPoint(arcPtr->outlinePtr + 2*PIE_OUTLINE1_PTS,
                        PIE_OUTLINE2_PTS, pointPtr);
        } else {
            dist = TkLineToPoint(vertex, arcPtr->center1, pointPtr);
            newDist = TkLineToPoint(vertex, arcPtr->center2, pointPtr);
        }
        if (newDist < dist) {
            dist = newDist;
        }
        if (angleInRange) {
            newDist = TkOvalToPoint(arcPtr->bbox, width, filled, pointPtr);
            if (newDist < dist) {
                dist = newDist;
            }
        }
        return dist;
    }

    /*
     * This is a chord-style arc.  We have to deal specially with the
     * triangular piece that represents the difference between a
     * chord-style arc and a pie-slice arc (for small angles this piece
     * is excluded here where it would be included for pie slices;
     * for large angles the piece is included here but would be
     * excluded for pie slices).
     */

    if (width > 1.0) {
        dist = TkPolygonToPoint(arcPtr->outlinePtr, CHORD_OUTLINE_PTS,
                    pointPtr);
    } else {
        dist = TkLineToPoint(arcPtr->center1, arcPtr->center2, pointPtr);
    }
    poly[0] = poly[6] = vertex[0];
    poly[1] = poly[7] = vertex[1];
    poly[2] = arcPtr->center1[0];
    poly[3] = arcPtr->center1[1];
    poly[4] = arcPtr->center2[0];
    poly[5] = arcPtr->center2[1];
    polyDist = TkPolygonToPoint(poly, 4, pointPtr);
    if (angleInRange) {
        if ((arcPtr->extent < -180.0) || (arcPtr->extent > 180.0)
                || (polyDist > 0.0)) {
            newDist = TkOvalToPoint(arcPtr->bbox, width, filled, pointPtr);
            if (newDist < dist) {
                dist = newDist;
            }
        }
    } else {
        if ((arcPtr->extent < -180.0) || (arcPtr->extent > 180.0)) {
            if (filled && (polyDist < dist)) {
                dist = polyDist;
            }
        }
    }
    return dist;
}
\f
/*
 *--------------------------------------------------------------
 *
 * ArcToArea --
 *
 *      This procedure is called to determine whether an item
 *      lies entirely inside, entirely outside, or overlapping
 *      a given area.
 *
 * Results:
 *      -1 is returned if the item is entirely outside the area
 *      given by rectPtr, 0 if it overlaps, and 1 if it is entirely
 *      inside the given area.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static int
ArcToArea(canvasPtr, itemPtr, rectPtr)
    Tk_Canvas *canvasPtr;       /* Canvas containing item. */
    Tk_Item *itemPtr;           /* Item to check against arc. */
    double *rectPtr;            /* Pointer to array of four coordinates
                                 * (x1, y1, x2, y2) describing rectangular
                                 * area.  */
{
    register ArcItem *arcPtr = (ArcItem *) itemPtr;
    double rx, ry;              /* Radii for transformed oval:  these define
                                 * an oval centered at the origin. */
    double tRect[4];            /* Transformed version of x1, y1, x2, y2,
                                 * for coord. system where arc is centered
                                 * on the origin. */
    double center[2], width, angle, tmp;
    double points[20], *pointPtr;
    int numPoints, filled;
    int inside;                 /* Non-zero means every test so far suggests
                                 * that arc is inside rectangle.  0 means
                                 * every test so far shows arc to be outside
                                 * of rectangle. */
    int newInside;

    if ((arcPtr->fillGC != None) || (arcPtr->outlineGC == None)) {
        filled = 1;
    } else {
        filled = 0;
    }
    if (arcPtr->outlineGC == None) {
        width = 0.0;
    } else {
        width = arcPtr->width;
    }

    /*
     * Transform both the arc and the rectangle so that the arc's oval
     * is centered on the origin.
     */

    center[0] = (arcPtr->bbox[0] + arcPtr->bbox[2])/2.0;
    center[1] = (arcPtr->bbox[1] + arcPtr->bbox[3])/2.0;
    tRect[0] = rectPtr[0] - center[0];
    tRect[1] = rectPtr[1] - center[1];
    tRect[2] = rectPtr[2] - center[0];
    tRect[3] = rectPtr[3] - center[1];
    rx = arcPtr->bbox[2] - center[0] + width/2.0;
    ry = arcPtr->bbox[3] - center[1] + width/2.0;

    /*
     * Find the extreme points of the arc and see whether these are all
     * inside the rectangle (in which case we're done), partly in and
     * partly out (in which case we're done), or all outside (in which
     * case we have more work to do).  The extreme points include the
     * following, which are checked in order:
     *
     * 1. The outside points of the arc, corresponding to start and
     *    extent.
     * 2. The center of the arc (but only in pie-slice mode).
     * 3. The 12, 3, 6, and 9-o'clock positions (but only if the arc
     *    includes those angles).
     */

    pointPtr = points;
    numPoints = 0;
    angle = -arcPtr->start*(PI/180.0);
    pointPtr[0] = rx*cos(angle);
    pointPtr[1] = ry*sin(angle);
    angle += -arcPtr->extent*(PI/180.0);
    pointPtr[2] = rx*cos(angle);
    pointPtr[3] = ry*sin(angle);
    numPoints = 2;
    pointPtr += 4;

    if ((arcPtr->style == pieSliceUid) && (arcPtr->extent < 180.0)) {
        pointPtr[0] = 0.0;
        pointPtr[1] = 0.0;
        numPoints++;
        pointPtr += 2;
    }

    tmp = -arcPtr->start;
    if (tmp < 0) {
        tmp += 360.0;
    }
    if ((tmp < arcPtr->extent) || ((tmp-360) > arcPtr->extent)) {
        pointPtr[0] = rx;
        pointPtr[1] = 0.0;
        numPoints++;
        pointPtr += 2;
    }
    tmp = 90.0 - arcPtr->start;
    if (tmp < 0) {
        tmp += 360.0;
    }
    if ((tmp < arcPtr->extent) || ((tmp-360) > arcPtr->extent)) {
        pointPtr[0] = 0.0;
        pointPtr[1] = -ry;
        numPoints++;
        pointPtr += 2;
    }
    tmp = 180.0 - arcPtr->start;
    if (tmp < 0) {
        tmp += 360.0;
    }
    if ((tmp < arcPtr->extent) || ((tmp-360) > arcPtr->extent)) {
        pointPtr[0] = -rx;
        pointPtr[1] = 0.0;
        numPoints++;
        pointPtr += 2;
    }
    tmp = 270.0 - arcPtr->start;
    if (tmp < 0) {
        tmp += 360.0;
    }
    if ((tmp < arcPtr->extent) || ((tmp-360) > arcPtr->extent)) {
        pointPtr[0] = 0.0;
        pointPtr[1] = ry;
        numPoints++;
        pointPtr += 2;
    }

    /*
     * Now that we've located the extreme points, loop through them all
     * to see which are inside the rectangle.
     */

    inside = (points[0] > tRect[0]) && (points[0] < tRect[2])
            && (points[1] > tRect[1]) && (points[1] < tRect[3]);
    for (pointPtr = points+2; numPoints > 1; pointPtr += 2, numPoints--) {
        newInside = (pointPtr[0] > tRect[0]) && (pointPtr[0] < tRect[2])
                && (pointPtr[1] > tRect[1]) && (pointPtr[1] < tRect[3]);
        if (newInside != inside) {
            return 0;
        }
    }

    if (inside) {
        return 1;
    }

    /*
     * So far, oval appears to be outside rectangle, but can't yet tell
     * for sure.  Next, test each of the four sides of the rectangle
     * against the bounding region for the arc.  If any intersections
     * are found, then return "overlapping".  First, test against the
     * polygon(s) forming the sides of a chord or pie-slice.
     */

    if (arcPtr->style == pieSliceUid) {
        if (width >= 1.0) {
            if (TkPolygonToArea(arcPtr->outlinePtr, PIE_OUTLINE1_PTS,
                    rectPtr) != -1)  {
                return 0;
            }
            if (TkPolygonToArea(arcPtr->outlinePtr + 2*PIE_OUTLINE1_PTS,
                    PIE_OUTLINE2_PTS, rectPtr) != -1) {
                return 0;
            }
        } else {
            if ((TkLineToArea(center, arcPtr->center1, rectPtr) != -1) ||
                    (TkLineToArea(center, arcPtr->center2, rectPtr) != -1)) {
                return 0;
            }
        }
    } else if (arcPtr->style == chordUid) {
        if (width >= 1.0) {
            if (TkPolygonToArea(arcPtr->outlinePtr, CHORD_OUTLINE_PTS,
                    rectPtr) != -1) {
                return 0;
            }
        } else {
            if (TkLineToArea(arcPtr->center1, arcPtr->center2,
                    rectPtr) != -1) {
                return 0;
            }
        }
    }

    /*
     * Next check for overlap between each of the four sides and the
     * outer perimiter of the arc.  If the arc isn't filled, then also
     * check the inner perimeter of the arc.
     */

    if (HorizLineToArc(tRect[0], tRect[2], tRect[1], rx, ry, arcPtr->start,
                arcPtr->extent)
            || HorizLineToArc(tRect[0], tRect[2], tRect[3], rx, ry,
                arcPtr->start, arcPtr->extent)
            || VertLineToArc(tRect[0], tRect[1], tRect[3], rx, ry,
                arcPtr->start, arcPtr->extent)
            || VertLineToArc(tRect[2], tRect[1], tRect[3], rx, ry,
                arcPtr->start, arcPtr->extent)) {
        return 0;
    }
    if ((width > 1.0) && !filled) {
        rx -= width;
        ry -= width;
        if (HorizLineToArc(tRect[0], tRect[2], tRect[1], rx, ry, arcPtr->start,
                    arcPtr->extent)
                || HorizLineToArc(tRect[0], tRect[2], tRect[3], rx, ry,
                    arcPtr->start, arcPtr->extent)
                || VertLineToArc(tRect[0], tRect[1], tRect[3], rx, ry,
                    arcPtr->start, arcPtr->extent)
                || VertLineToArc(tRect[2], tRect[1], tRect[3], rx, ry,
                    arcPtr->start, arcPtr->extent)) {
            return 0;
        }
    }

    /*
     * The arc still appears to be totally disjoint from the rectangle,
     * but it's also possible that the rectangle is totally inside the arc.
     * Do one last check, which is to check one point of the rectangle
     * to see if it's inside the arc.  If it is, we've got overlap.  If
     * it isn't, the arc's really outside the rectangle.
     */

    if (ArcToPoint(canvasPtr, itemPtr, rectPtr) == 0.0) {
        return 0;
    }
    return -1;
}
\f
/*
 *--------------------------------------------------------------
 *
 * ScaleArc --
 *
 *      This procedure is invoked to rescale an arc item.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The arc 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
ScaleArc(canvasPtr, itemPtr, originX, originY, scaleX, scaleY)
    Tk_Canvas *canvasPtr;               /* Canvas containing arc. */
    Tk_Item *itemPtr;                   /* Arc 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. */
{
    register ArcItem *arcPtr = (ArcItem *) itemPtr;

    arcPtr->bbox[0] = originX + scaleX*(arcPtr->bbox[0] - originX);
    arcPtr->bbox[1] = originY + scaleY*(arcPtr->bbox[1] - originY);
    arcPtr->bbox[2] = originX + scaleX*(arcPtr->bbox[2] - originX);
    arcPtr->bbox[3] = originY + scaleY*(arcPtr->bbox[3] - originY);
    ComputeArcBbox(canvasPtr, arcPtr);
}
\f
/*
 *--------------------------------------------------------------
 *
 * TranslateArc --
 *
 *      This procedure is called to move an arc by a given amount.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The position of the arc is offset by (xDelta, yDelta), and
 *      the bounding box is updated in the generic part of the item
 *      structure.
 *
 *--------------------------------------------------------------
 */

static void
TranslateArc(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. */
{
    register ArcItem *arcPtr = (ArcItem *) itemPtr;

    arcPtr->bbox[0] += deltaX;
    arcPtr->bbox[1] += deltaY;
    arcPtr->bbox[2] += deltaX;
    arcPtr->bbox[3] += deltaY;
    ComputeArcBbox(canvasPtr, arcPtr);
}
\f
/*
 *--------------------------------------------------------------
 *
 * ComputeArcOutline --
 *
 *      This procedure creates a polygon describing everything in
 *      the outline for an arc except what's in the curved part.
 *      For a "pie slice" arc this is a V-shaped chunk, and for
 *      a "chord" arc this is a linear chunk (with cutaway corners).
 *      For "arc" arcs, this stuff isn't relevant.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The information at arcPtr->outlinePtr gets modified, and
 *      storage for arcPtr->outlinePtr may be allocated or freed.
 *
 *--------------------------------------------------------------
 */

static void
ComputeArcOutline(arcPtr)
    register ArcItem *arcPtr;
{
    double sin1, cos1, sin2, cos2, angle, halfWidth;
    double boxWidth, boxHeight;
    double vertex[2], corner1[2], corner2[2];
    double *outlinePtr;

    /*
     * Make sure that the outlinePtr array is large enough to hold
     * either a chord or pie-slice outline.
     */

    if (arcPtr->numOutlinePoints == 0) {
        arcPtr->outlinePtr = (double *) ckalloc((unsigned)
                (26 * sizeof(double)));
        arcPtr->numOutlinePoints = 22;
    }
    outlinePtr = arcPtr->outlinePtr;

    /*
     * First compute the two points that lie at the centers of
     * the ends of the curved arc segment, which are marked with
     * X's in the figure below:
     *
     *
     *                            * * *
     *                        *          *
     *                     *      * *      *
     *                   *    *         *    *
     *                  *   *             *   *
     *                   X *               * X
     *
     * The code is tricky because the arc can be ovular in shape.
     * It computes the position for a unit circle, and then
     * scales to fit the shape of the arc's bounding box.
     *
     * Also, watch out because angles go counter-clockwise like you
     * might expect, but the y-coordinate system is inverted.  To
     * handle this, just negate the angles in all the computations.
     */

    boxWidth = arcPtr->bbox[2] - arcPtr->bbox[0];
    boxHeight = arcPtr->bbox[3] - arcPtr->bbox[1];
    angle = -arcPtr->start*PI/180.0;
    sin1 = sin(angle);
    cos1 = cos(angle);
    angle -= arcPtr->extent*PI/180.0;
    sin2 = sin(angle);
    cos2 = cos(angle);
    vertex[0] = (arcPtr->bbox[0] + arcPtr->bbox[2])/2.0;
    vertex[1] = (arcPtr->bbox[1] + arcPtr->bbox[3])/2.0;
    arcPtr->center1[0] = vertex[0] + cos1*boxWidth/2.0;
    arcPtr->center1[1] = vertex[1] + sin1*boxHeight/2.0;
    arcPtr->center2[0] = vertex[0] + cos2*boxWidth/2.0;
    arcPtr->center2[1] = vertex[1] + sin2*boxHeight/2.0;

    /*
     * Next compute the "outermost corners" of the arc, which are
     * marked with X's in the figure below:
     *
     *                            * * *
     *                        *          *
     *                     *      * *      *
     *                   *    *         *    *
     *                  X   *             *   X
     *                     *               *
     *
     * The code below is tricky because it has to handle eccentricity
     * in the shape of the oval.  The key in the code below is to
     * realize that the slope of the line from arcPtr->center1 to corner1
     * is (boxWidth*sin1)/(boxHeight*cos1), and similarly for arcPtr->center2
     * and corner2.  These formulas can be computed from the formula for
     * the oval.
     */

    halfWidth = arcPtr->width/2.0;
    angle = atan2(boxWidth*sin1, boxHeight*cos1);
    corner1[0] = arcPtr->center1[0] + cos(angle)*halfWidth;
    corner1[1] = arcPtr->center1[1] + sin(angle)*halfWidth;
    angle = atan2(boxWidth*sin2, boxHeight*cos2);
    corner2[0] = arcPtr->center2[0] + cos(angle)*halfWidth;
    corner2[1] = arcPtr->center2[1] + sin(angle)*halfWidth;

    /*
     * For a chord outline, generate a six-sided polygon with three
     * points for each end of the chord.  The first and third points
     * for each end are butt points generated on either side of the
     * center point.  The second point is the corner point.
     */

    if (arcPtr->style == chordUid) {
        outlinePtr[0] = outlinePtr[12] = corner1[0];
        outlinePtr[1] = outlinePtr[13] = corner1[1];
        TkGetButtPoints(arcPtr->center2, arcPtr->center1,
                (double) arcPtr->width, 0, outlinePtr+10, outlinePtr+2);
        outlinePtr[4] = arcPtr->center2[0] + outlinePtr[2]
                - arcPtr->center1[0];
        outlinePtr[5] = arcPtr->center2[1] + outlinePtr[3]
                - arcPtr->center1[1];
        outlinePtr[6] = corner2[0];
        outlinePtr[7] = corner2[1];
        outlinePtr[8] = arcPtr->center2[0] + outlinePtr[10]
                - arcPtr->center1[0];
        outlinePtr[9] = arcPtr->center2[1] + outlinePtr[11]
                - arcPtr->center1[1];
    } else if (arcPtr->style == pieSliceUid) {
        /*
         * For pie slices, generate two polygons, one for each side
         * of the pie slice.  The first arm has a shape like this,
         * where the center of the oval is X, arcPtr->center1 is at Y, and
         * corner1 is at Z:
         *
         *       _____________________
         *      |                     \
         *      |                      \
         *      X                    Y  Z
         *      |                      /
         *      |_____________________/
         *
         */

        TkGetButtPoints(arcPtr->center1, vertex, (double) arcPtr->width, 0,
                outlinePtr, outlinePtr+2);
        outlinePtr[4] = arcPtr->center1[0] + outlinePtr[2] - vertex[0];
        outlinePtr[5] = arcPtr->center1[1] + outlinePtr[3] - vertex[1];
        outlinePtr[6] = corner1[0];
        outlinePtr[7] = corner1[1];
        outlinePtr[8] = arcPtr->center1[0] + outlinePtr[0] - vertex[0];
        outlinePtr[9] = arcPtr->center1[1] + outlinePtr[1] - vertex[1];
        outlinePtr[10] = outlinePtr[0];
        outlinePtr[11] = outlinePtr[1];

        /*
         * The second arm has a shape like this:
         *
         *
         *         ______________________
         *        /                       \
         *       /                         \
         *      Z  Y                    X  /
         *       \                        /
         *        \______________________/
         *
         * Similar to above X is the center of the oval/circle, Y is
         * arcPtr->center2, and Z is corner2.  The extra jog out to the left
         * of X is needed in or to produce a butted joint with the
         * first arm;  the corner to the right of X is one of the
         * first two points of the first arm, depending on extent.
         */

        TkGetButtPoints(arcPtr->center2, vertex, (double) arcPtr->width, 0,
                outlinePtr+12, outlinePtr+16);
        if ((arcPtr->extent > 180) ||
                ((arcPtr->extent < 0) && (arcPtr->extent > -180))) {
            outlinePtr[14] = outlinePtr[0];
            outlinePtr[15] = outlinePtr[1];
        } else {
            outlinePtr[14] = outlinePtr[2];
            outlinePtr[15] = outlinePtr[3];
        }
        outlinePtr[18] = arcPtr->center2[0] + outlinePtr[16] - vertex[0];
        outlinePtr[19] = arcPtr->center2[1] + outlinePtr[17] - vertex[1];
        outlinePtr[20] = corner2[0];
        outlinePtr[21] = corner2[1];
        outlinePtr[22] = arcPtr->center2[0] + outlinePtr[12] - vertex[0];
        outlinePtr[23] = arcPtr->center2[1] + outlinePtr[13] - vertex[1];
        outlinePtr[24] = outlinePtr[12];
        outlinePtr[25] = outlinePtr[13];
    }
}
\f
/*
 *--------------------------------------------------------------
 *
 * HorizLineToArc --
 *
 *      Determines whether a horizontal line segment intersects
 *      a given arc.
 *
 * Results:
 *      The return value is 1 if the given line intersects the
 *      infinitely-thin arc section defined by rx, ry, start,
 *      and extent, and 0 otherwise.  Only the perimeter of the
 *      arc is checked: interior areas (e.g. pie-slice or chord)
 *      are not checked.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

static int
HorizLineToArc(x1, x2, y, rx, ry, start, extent)
    double x1, x2;              /* X-coords of endpoints of line segment. 
                                 * X1 must be <= x2. */
    double y;                   /* Y-coordinate of line segment. */
    double rx, ry;              /* These x- and y-radii define an oval
                                 * centered at the origin. */
    double start, extent;       /* Angles that define extent of arc, in
                                 * the standard fashion for this module. */
{
    double tmp;
    double tx, ty;              /* Coordinates of intersection point in
                                 * transformed coordinate system. */
    double x;

    /*
     * Compute the x-coordinate of one possible intersection point
     * between the arc and the line.  Use a transformed coordinate
     * system where the oval is a unit circle centered at the origin.
     * Then scale back to get actual x-coordinate.
     */

    ty = y/ry;
    tmp = 1 - ty*ty;
    if (tmp < 0) {
        return 0;
    }
    tx = sqrt(tmp);
    x = tx*rx;

    /*
     * Test both intersection points.
     */

    if ((x >= x1) && (x <= x2) && AngleInRange(tx, ty, start, extent)) {
        return 1;
    }
    if ((-x >= x1) && (-x <= x2) && AngleInRange(-tx, ty, start, extent)) {
        return 1;
    }
    return 0;
}
\f
/*
 *--------------------------------------------------------------
 *
 * VertLineToArc --
 *
 *      Determines whether a vertical line segment intersects
 *      a given arc.
 *
 * Results:
 *      The return value is 1 if the given line intersects the
 *      infinitely-thin arc section defined by rx, ry, start,
 *      and extent, and 0 otherwise.  Only the perimeter of the
 *      arc is checked: interior areas (e.g. pie-slice or chord)
 *      are not checked.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

static int
VertLineToArc(x, y1, y2, rx, ry, start, extent)
    double x;                   /* X-coordinate of line segment. */
    double y1, y2;              /* Y-coords of endpoints of line segment. 
                                 * Y1 must be <= y2. */
    double rx, ry;              /* These x- and y-radii define an oval
                                 * centered at the origin. */
    double start, extent;       /* Angles that define extent of arc, in
                                 * the standard fashion for this module. */
{
    double tmp;
    double tx, ty;              /* Coordinates of intersection point in
                                 * transformed coordinate system. */
    double y;

    /*
     * Compute the y-coordinate of one possible intersection point
     * between the arc and the line.  Use a transformed coordinate
     * system where the oval is a unit circle centered at the origin.
     * Then scale back to get actual y-coordinate.
     */

    tx = x/rx;
    tmp = 1 - tx*tx;
    if (tmp < 0) {
        return 0;
    }
    ty = sqrt(tmp);
    y = ty*ry;

    /*
     * Test both intersection points.
     */

    if ((y > y1) && (y < y2) && AngleInRange(tx, ty, start, extent)) {
        return 1;
    }
    if ((-y > y1) && (-y < y2) && AngleInRange(tx, -ty, start, extent)) {
        return 1;
    }
    return 0;
}
\f
/*
 *--------------------------------------------------------------
 *
 * AngleInRange --
 *
 *      Determine whether the angle from the origin to a given
 *      point is within a given range.
 *
 * Results:
 *      The return value is 1 if the angle from (0,0) to (x,y)
 *      is in the range given by start and extent, where angles
 *      are interpreted in the standard way for ovals (meaning
 *      backwards from normal interpretation).  Otherwise the
 *      return value is 0.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

static int
AngleInRange(x, y, start, extent)
    double x, y;                /* Coordinate of point;  angle measured
                                 * from origin to here, relative to x-axis. */
    double start;               /* First angle, degrees, >=0, <=360. */
    double extent;              /* Size of arc in degrees >=-360, <=360. */
{
    double diff;

    diff = -atan2(y, x);
    diff = diff*(180.0/PI) - start;
    while (diff > 360.0) {
        diff -= 360.0;
    }
    while (diff < 0.0) {
        diff += 360.0;
    }
    if (extent >= 0) {
        return diff <= extent;
    }
    return (diff-360.0) >= extent;
}