text: /*
   * tkCanvArc.c --
   *
   *	This file implements arc items for canvas widgets.
   *
   * Copyright (c) 1992-1994 The Regents of the University of California.
   * Copyright (c) 1994-1997 Sun Microsystems, Inc.
   *
   * See the file "license.terms" for information on usage and redistribution of
   * this file, and for a DISCLAIMER OF ALL WARRANTIES.
   */
  
  #include "tkInt.h"
  #include "tkCanvas.h"
  
  #include "float.h"
  
  /*
   * The structure below defines the record for each arc item.
   */
  
  typedef enum {
      PIESLICE_STYLE, CHORD_STYLE, ARC_STYLE
  } Style;
  
  typedef struct ArcItem {
      Tk_Item header;		/* Generic stuff that's the same for all
  				 * types. MUST BE FIRST IN STRUCTURE. */
      Tk_Outline outline;		/* Outline 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. */
      Tk_TSOffset tsoffset;
      XColor *fillColor;		/* Color for filling arc (used for drawing
  				 * outline too when style is "arc"). NULL
  				 * means don't fill arc. */
      XColor *activeFillColor;	/* Color for filling arc (used for drawing
  				 * outline too when style is "arc" and state
  				 * is "active"). NULL means use fillColor. */
      XColor *disabledFillColor;	/* Color for filling arc (used for drawing
  				 * outline too when style is "arc" and state
  				 * is "disabled". NULL means use fillColor */
      Pixmap fillStipple;		/* Stipple bitmap for filling item. */
      Pixmap activeFillStipple;	/* Stipple bitmap for filling item if state is
  				 * active. */
      Pixmap disabledFillStipple;	/* Stipple bitmap for filling item if state is
  				 * disabled. */
      Style style;		/* How to draw arc: arc, chord, or
  				 * pieslice. */
      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). */
      double height;              /* Distance from the arc's chord to its
  				 * mid-point. */
      double startPoint[2];       /* Start point of arc used when specifying
  				 * height. */
      double endPoint[2];         /* End point of arc used when specifying
  				 * height. */
  } 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 int	StyleParseProc(ClientData clientData, Tcl_Interp *interp,
  		    Tk_Window tkwin, const char *value,
  		    char *widgRec, int offset);
  static const char * StylePrintProc(ClientData clientData, Tk_Window tkwin,
  		    char *widgRec, int offset, Tcl_FreeProc **freeProcPtr);
  
  static const Tk_CustomOption stateOption = {
      TkStateParseProc, TkStatePrintProc, INT2PTR(2)
  };
  static const Tk_CustomOption styleOption = {
      StyleParseProc, StylePrintProc, NULL
  };
  static const Tk_CustomOption tagsOption = {
      Tk_CanvasTagsParseProc, Tk_CanvasTagsPrintProc, NULL
  };
  static const Tk_CustomOption dashOption = {
      TkCanvasDashParseProc, TkCanvasDashPrintProc, NULL
  };
  static const Tk_CustomOption offsetOption = {
      TkOffsetParseProc, TkOffsetPrintProc, INT2PTR(TK_OFFSET_RELATIVE)
  };
  static const Tk_CustomOption pixelOption = {
      TkPixelParseProc, TkPixelPrintProc, NULL
  };
  
  static const Tk_ConfigSpec configSpecs[] = {
      {TK_CONFIG_CUSTOM, "-activedash", NULL, NULL,
  	NULL, offsetof(ArcItem, outline.activeDash),
  	TK_CONFIG_NULL_OK, &dashOption},
      {TK_CONFIG_COLOR, "-activefill", NULL, NULL,
  	NULL, offsetof(ArcItem, activeFillColor), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_COLOR, "-activeoutline", NULL, NULL,
  	NULL, offsetof(ArcItem, outline.activeColor), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_BITMAP, "-activeoutlinestipple", NULL, NULL,
  	NULL, offsetof(ArcItem, outline.activeStipple), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_BITMAP, "-activestipple", NULL, NULL,
  	NULL, offsetof(ArcItem, activeFillStipple), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_CUSTOM, "-activewidth", NULL, NULL,
  	"0.0", offsetof(ArcItem, outline.activeWidth),
  	TK_CONFIG_DONT_SET_DEFAULT, &pixelOption},
      {TK_CONFIG_CUSTOM, "-dash", NULL, NULL,
  	NULL, offsetof(ArcItem, outline.dash),
  	TK_CONFIG_NULL_OK, &dashOption},
      {TK_CONFIG_PIXELS, "-dashoffset", NULL, NULL,
  	"0", offsetof(ArcItem, outline.offset), TK_CONFIG_DONT_SET_DEFAULT, NULL},
      {TK_CONFIG_CUSTOM, "-disableddash", NULL, NULL,
  	NULL, offsetof(ArcItem, outline.disabledDash),
  	TK_CONFIG_NULL_OK, &dashOption},
      {TK_CONFIG_COLOR, "-disabledfill", NULL, NULL,
  	NULL, offsetof(ArcItem, disabledFillColor), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_COLOR, "-disabledoutline", NULL, NULL,
  	NULL, offsetof(ArcItem, outline.disabledColor), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_BITMAP, "-disabledoutlinestipple", NULL, NULL,
  	NULL, offsetof(ArcItem, outline.disabledStipple), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_BITMAP, "-disabledstipple", NULL, NULL,
  	NULL, offsetof(ArcItem, disabledFillStipple), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_CUSTOM, "-disabledwidth", NULL, NULL,
  	"0.0", offsetof(ArcItem, outline.disabledWidth),
  	TK_CONFIG_DONT_SET_DEFAULT, &pixelOption},
      {TK_CONFIG_DOUBLE, "-extent", NULL, NULL,
  	"90", offsetof(ArcItem, extent), TK_CONFIG_DONT_SET_DEFAULT, NULL},
      {TK_CONFIG_COLOR, "-fill", NULL, NULL,
  	NULL, offsetof(ArcItem, fillColor), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_DOUBLE, "-height", NULL, NULL,
  	0, offsetof(ArcItem, height), TK_CONFIG_DONT_SET_DEFAULT, NULL},
      {TK_CONFIG_CUSTOM, "-offset", NULL, NULL,
  	"0,0", offsetof(ArcItem, tsoffset),
  	TK_CONFIG_DONT_SET_DEFAULT, &offsetOption},
      {TK_CONFIG_COLOR, "-outline", NULL, NULL,
  	"black", offsetof(ArcItem, outline.color), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_CUSTOM, "-outlineoffset", NULL, NULL,
  	"0,0", offsetof(ArcItem, outline.tsoffset),
  	TK_CONFIG_DONT_SET_DEFAULT, &offsetOption},
      {TK_CONFIG_BITMAP, "-outlinestipple", NULL, NULL,
  	NULL, offsetof(ArcItem, outline.stipple), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_DOUBLE, "-start", NULL, NULL,
  	"0", offsetof(ArcItem, start), TK_CONFIG_DONT_SET_DEFAULT, NULL},
      {TK_CONFIG_CUSTOM, "-state", NULL, NULL,
  	NULL, offsetof(Tk_Item, state), TK_CONFIG_NULL_OK, &stateOption},
      {TK_CONFIG_BITMAP, "-stipple", NULL, NULL,
  	NULL, offsetof(ArcItem, fillStipple), TK_CONFIG_NULL_OK, NULL},
      {TK_CONFIG_CUSTOM, "-style", NULL, NULL,
  	NULL, offsetof(ArcItem, style), TK_CONFIG_DONT_SET_DEFAULT,
  	&styleOption},
      {TK_CONFIG_CUSTOM, "-tags", NULL, NULL,
  	NULL, 0, TK_CONFIG_NULL_OK, &tagsOption},
      {TK_CONFIG_CUSTOM, "-width", NULL, NULL,
  	"1.0", offsetof(ArcItem, outline.width), TK_CONFIG_DONT_SET_DEFAULT,
  	&pixelOption},
      {TK_CONFIG_END, NULL, NULL, NULL, NULL, 0, 0, NULL}
  };
  
  /*
   * Prototypes for functions defined in this file:
   */
  
  static void		ComputeArcBbox(Tk_Canvas canvas, ArcItem *arcPtr);
  static int		ConfigureArc(Tcl_Interp *interp,
  			    Tk_Canvas canvas, Tk_Item *itemPtr, int objc,
  			    Tcl_Obj *const objv[], int flags);
  static void		ComputeArcParametersFromHeight(ArcItem *arcPtr);
  static int		CreateArc(Tcl_Interp *interp,
  			    Tk_Canvas canvas, struct Tk_Item *itemPtr,
  			    int objc, Tcl_Obj *const objv[]);
  static void		DeleteArc(Tk_Canvas canvas,
  			    Tk_Item *itemPtr, Display *display);
  static void		DisplayArc(Tk_Canvas canvas,
  			    Tk_Item *itemPtr, Display *display, Drawable dst,
  			    int x, int y, int width, int height);
  static int		ArcCoords(Tcl_Interp *interp, Tk_Canvas canvas,
  			    Tk_Item *itemPtr, int objc, Tcl_Obj *const objv[]);
  static int		ArcToArea(Tk_Canvas canvas,
  			    Tk_Item *itemPtr, double *rectPtr);
  static double		ArcToPoint(Tk_Canvas canvas,
  			    Tk_Item *itemPtr, double *coordPtr);
  static int		ArcToPostscript(Tcl_Interp *interp,
  			    Tk_Canvas canvas, Tk_Item *itemPtr, int prepass);
  static void		ScaleArc(Tk_Canvas canvas,
  			    Tk_Item *itemPtr, double originX, double originY,
  			    double scaleX, double scaleY);
  static void		TranslateArc(Tk_Canvas canvas,
  			    Tk_Item *itemPtr, double deltaX, double deltaY);
  static int		AngleInRange(double x, double y,
  			    double start, double extent);
  static void		ComputeArcOutline(Tk_Canvas canvas, ArcItem *arcPtr);
  static int		HorizLineToArc(double x1, double x2,
  			    double y, double rx, double ry,
  			    double start, double extent);
  static int		VertLineToArc(double x, double y1,
  			    double y2, double rx, double ry,
  			    double start, double extent);
  static void		RotateArc(Tk_Canvas canvas, Tk_Item *itemPtr,
  			    double originX, double originY, double angleRad);
  
  /*
   * The structures below defines the arc item types by means of functions 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 */
      TK_CONFIG_OBJS,		/* flags */
      ArcToPoint,			/* pointProc */
      ArcToArea,			/* areaProc */
      ArcToPostscript,		/* postscriptProc */
      ScaleArc,			/* scaleProc */
      TranslateArc,		/* translateProc */
      NULL,			/* indexProc */
      NULL,			/* icursorProc */
      NULL,			/* selectionProc */
      NULL,			/* insertProc */
      NULL,			/* dTextProc */
      NULL,			/* nextPtr */
      RotateArc,			/* rotateProc */
      0, NULL, NULL
  };
  
  /*
   *--------------------------------------------------------------
   *
   * CreateArc --
   *
   *	This function 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 the interp's 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(
      Tcl_Interp *interp,		/* Interpreter for error reporting. */
      Tk_Canvas canvas,		/* Canvas to hold new item. */
      Tk_Item *itemPtr,		/* Record to hold new item; header has been
  				 * initialized by caller. */
      int objc,			/* Number of arguments in objv. */
      Tcl_Obj *const objv[])	/* Arguments describing arc. */
  {
      ArcItem *arcPtr = (ArcItem *) itemPtr;
      int i;
  
      if (objc == 0) {
  	Tcl_Panic("canvas did not pass any coords");
      }
  
      /*
       * Carry out initialization that is needed in order to clean up after
       * errors during the the remainder of this function.
       */
  
      Tk_CreateOutline(&(arcPtr->outline));
      arcPtr->start = 0;
      arcPtr->extent = 90;
      arcPtr->outlinePtr = NULL;
      arcPtr->numOutlinePoints = 0;
      arcPtr->tsoffset.flags = 0;
      arcPtr->tsoffset.xoffset = 0;
      arcPtr->tsoffset.yoffset = 0;
      arcPtr->fillColor = NULL;
      arcPtr->activeFillColor = NULL;
      arcPtr->disabledFillColor = NULL;
      arcPtr->fillStipple = None;
      arcPtr->activeFillStipple = None;
      arcPtr->disabledFillStipple = None;
      arcPtr->style = PIESLICE_STYLE;
      arcPtr->fillGC = NULL;
      arcPtr->height = 0;
  
      /*
       * Process the arguments to fill in the item record.
       */
  
      for (i = 1; i < objc; i++) {
  	const char *arg = Tcl_GetString(objv[i]);
  
  	if ((arg[0] == '-') && (arg[1] >= 'a') && (arg[1] <= 'z')) {
  	    break;
  	}
      }
      if (ArcCoords(interp, canvas, itemPtr, i, objv) != TCL_OK) {
  	goto error;
      }
      if (ConfigureArc(interp, canvas, itemPtr, objc-i, objv+i, 0) == TCL_OK) {
  	return TCL_OK;
      }
  
    error:
      DeleteArc(canvas, itemPtr, Tk_Display(Tk_CanvasTkwin(canvas)));
      return TCL_ERROR;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * ArcCoords --
   *
   *	This function 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 the interp's result.
   *
   * Side effects:
   *	The coordinates for the given item may be changed.
   *
   *--------------------------------------------------------------
   */
  
  static int
  ArcCoords(
      Tcl_Interp *interp,		/* Used for error reporting. */
      Tk_Canvas canvas,		/* Canvas containing item. */
      Tk_Item *itemPtr,		/* Item whose coordinates are to be read or
  				 * modified. */
      int objc,			/* Number of coordinates supplied in objv. */
      Tcl_Obj *const objv[])	/* Array of coordinates: x1, y1, x2, y2, ... */
  {
      ArcItem *arcPtr = (ArcItem *) itemPtr;
  
      if (objc == 0) {
  	Tcl_Obj *objs[4];
  
  	objs[0] = Tcl_NewDoubleObj(arcPtr->bbox[0]);
  	objs[1] = Tcl_NewDoubleObj(arcPtr->bbox[1]);
  	objs[2] = Tcl_NewDoubleObj(arcPtr->bbox[2]);
  	objs[3] = Tcl_NewDoubleObj(arcPtr->bbox[3]);
  	Tcl_SetObjResult(interp, Tcl_NewListObj(4, objs));
      } else if ((objc == 1) || (objc == 4)) {
  	if (objc == 1) {
  	    if (Tcl_ListObjGetElements(interp, objv[0], &objc,
  		    (Tcl_Obj ***) &objv) != TCL_OK) {
  		return TCL_ERROR;
  	    } else if (objc != 4) {
  		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
  			"wrong # coordinates: expected 4, got %d", objc));
  		Tcl_SetErrorCode(interp, "TK", "CANVAS", "COORDS", "ARC",
  			NULL);
  		return TCL_ERROR;
  	    }
  	}
  	if ((Tk_CanvasGetCoordFromObj(interp, canvas, objv[0],
   		    &arcPtr->bbox[0]) != TCL_OK)
  		|| (Tk_CanvasGetCoordFromObj(interp, canvas, objv[1],
  		    &arcPtr->bbox[1]) != TCL_OK)
  		|| (Tk_CanvasGetCoordFromObj(interp, canvas, objv[2],
  			&arcPtr->bbox[2]) != TCL_OK)
  		|| (Tk_CanvasGetCoordFromObj(interp, canvas, objv[3],
  			&arcPtr->bbox[3]) != TCL_OK)) {
  	    return TCL_ERROR;
  	}
  
  	/*
  	 * Store bbox as start and end points so they can be used if either
  	 * radius or height is specified.
  	 */
  
  	arcPtr->startPoint[0] = arcPtr->bbox[0];
  	arcPtr->startPoint[1] = arcPtr->bbox[1];
  	arcPtr->endPoint[0] = arcPtr->bbox[2];
  	arcPtr->endPoint[1] = arcPtr->bbox[3];
  
  	ComputeArcBbox(canvas, arcPtr);
      } else {
  	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
  		"wrong # coordinates: expected 0 or 4, got %d", objc));
  	Tcl_SetErrorCode(interp, "TK", "CANVAS", "COORDS", "ARC", NULL);
  	return TCL_ERROR;
      }
      return TCL_OK;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * ConfigureArc --
   *
   *	This function 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 the interp's result.
   *
   * Side effects:
   *	Configuration information, such as colors and stipple patterns, may be
   *	set for itemPtr.
   *
   *--------------------------------------------------------------
   */
  
  static int
  ConfigureArc(
      Tcl_Interp *interp,		/* Used for error reporting. */
      Tk_Canvas canvas,		/* Canvas containing itemPtr. */
      Tk_Item *itemPtr,		/* Arc item to reconfigure. */
      int objc,			/* Number of elements in objv. */
      Tcl_Obj *const objv[],	/* Arguments describing things to configure. */
      int flags)			/* Flags to pass to Tk_ConfigureWidget. */
  {
      ArcItem *arcPtr = (ArcItem *) itemPtr;
      XGCValues gcValues;
      GC newGC;
      unsigned long mask;
      int i;
      Tk_Window tkwin;
      Tk_TSOffset *tsoffset;
      XColor *color;
      Pixmap stipple;
      Tk_State state;
  
      tkwin = Tk_CanvasTkwin(canvas);
      if (TCL_OK != Tk_ConfigureWidget(interp, tkwin, configSpecs, objc,
  	    (const char **) objv, (char *) arcPtr, flags|TK_CONFIG_OBJS)) {
  	return TCL_ERROR;
      }
  
      state = itemPtr->state;
  
      /*
       * A few of the options require additional processing, such as style and
       * graphics contexts.
       */
  
      if (arcPtr->outline.activeWidth > arcPtr->outline.width ||
  	    arcPtr->outline.activeDash.number != 0 ||
  	    arcPtr->outline.activeColor != NULL ||
  	    arcPtr->outline.activeStipple != None ||
  	    arcPtr->activeFillColor != NULL ||
  	    arcPtr->activeFillStipple != None) {
  	itemPtr->redraw_flags |= TK_ITEM_STATE_DEPENDANT;
      } else {
  	itemPtr->redraw_flags &= ~TK_ITEM_STATE_DEPENDANT;
      }
  
      /*
       * Override the start and extent if the height is given.
       */
  
      ComputeArcParametersFromHeight(arcPtr);
  
      ComputeArcBbox(canvas, arcPtr);
  
      i = (int) (arcPtr->start/360.0);
      arcPtr->start -= i*360.0;
      if (arcPtr->start < 0) {
  	arcPtr->start += 360.0;
      }
      i = (int) (arcPtr->extent/360.0);
      arcPtr->extent -= i*360.0;
  
      tsoffset = &arcPtr->outline.tsoffset;
      flags = tsoffset->flags;
      if (flags & TK_OFFSET_LEFT) {
  	tsoffset->xoffset = (int) (arcPtr->bbox[0] + 0.5);
      } else if (flags & TK_OFFSET_CENTER) {
  	tsoffset->xoffset = (int) ((arcPtr->bbox[0]+arcPtr->bbox[2]+1)/2);
      } else if (flags & TK_OFFSET_RIGHT) {
  	tsoffset->xoffset = (int) (arcPtr->bbox[2] + 0.5);
      }
      if (flags & TK_OFFSET_TOP) {
  	tsoffset->yoffset = (int) (arcPtr->bbox[1] + 0.5);
      } else if (flags & TK_OFFSET_MIDDLE) {
  	tsoffset->yoffset = (int) ((arcPtr->bbox[1]+arcPtr->bbox[3]+1)/2);
      } else if (flags & TK_OFFSET_BOTTOM) {
  	tsoffset->yoffset = (int) (arcPtr->bbox[2] + 0.5);
      }
  
      mask = Tk_ConfigOutlineGC(&gcValues, canvas, itemPtr, &(arcPtr->outline));
      if (mask) {
  	gcValues.cap_style = CapButt;
  	mask |= GCCapStyle;
  	newGC = Tk_GetGC(tkwin, mask, &gcValues);
      } else {
  	newGC = NULL;
      }
      if (arcPtr->outline.gc != NULL) {
  	Tk_FreeGC(Tk_Display(tkwin), arcPtr->outline.gc);
      }
      arcPtr->outline.gc = newGC;
  
      if(state == TK_STATE_NULL) {
  	state = Canvas(canvas)->canvas_state;
      }
      if (state==TK_STATE_HIDDEN) {
  	ComputeArcBbox(canvas, arcPtr);
  	return TCL_OK;
      }
  
      color = arcPtr->fillColor;
      stipple = arcPtr->fillStipple;
      if (Canvas(canvas)->currentItemPtr == itemPtr) {
  	if (arcPtr->activeFillColor!=NULL) {
  	    color = arcPtr->activeFillColor;
  	}
  	if (arcPtr->activeFillStipple!=None) {
  	    stipple = arcPtr->activeFillStipple;
  	}
      } else if (state==TK_STATE_DISABLED) {
  	if (arcPtr->disabledFillColor!=NULL) {
  	    color = arcPtr->disabledFillColor;
  	}
  	if (arcPtr->disabledFillStipple!=None) {
  	    stipple = arcPtr->disabledFillStipple;
  	}
      }
  
      if (arcPtr->style == ARC_STYLE) {
  	newGC = NULL;
      } else if (color == NULL) {
  	newGC = NULL;
      } else {
  	gcValues.foreground = color->pixel;
  	if (arcPtr->style == CHORD_STYLE) {
  	    gcValues.arc_mode = ArcChord;
  	} else {
  	    gcValues.arc_mode = ArcPieSlice;
  	}
  	mask = GCForeground|GCArcMode;
  	if (stipple != None) {
  	    gcValues.stipple = stipple;
  	    gcValues.fill_style = FillStippled;
  	    mask |= GCStipple|GCFillStyle;
  	}
  	newGC = Tk_GetGC(tkwin, mask, &gcValues);
      }
      if (arcPtr->fillGC != NULL) {
  	Tk_FreeGC(Tk_Display(tkwin), arcPtr->fillGC);
      }
      arcPtr->fillGC = newGC;
  
      tsoffset = &arcPtr->tsoffset;
      flags = tsoffset->flags;
      if (flags & TK_OFFSET_LEFT) {
  	tsoffset->xoffset = (int) (arcPtr->bbox[0] + 0.5);
      } else if (flags & TK_OFFSET_CENTER) {
  	tsoffset->xoffset = (int) ((arcPtr->bbox[0]+arcPtr->bbox[2]+1)/2);
      } else if (flags & TK_OFFSET_RIGHT) {
  	tsoffset->xoffset = (int) (arcPtr->bbox[2] + 0.5);
      }
      if (flags & TK_OFFSET_TOP) {
  	tsoffset->yoffset = (int) (arcPtr->bbox[1] + 0.5);
      } else if (flags & TK_OFFSET_MIDDLE) {
  	tsoffset->yoffset = (int) ((arcPtr->bbox[1]+arcPtr->bbox[3]+1)/2);
      } else if (flags & TK_OFFSET_BOTTOM) {
  	tsoffset->yoffset = (int) (arcPtr->bbox[3] + 0.5);
      }
  
      ComputeArcBbox(canvas, arcPtr);
      return TCL_OK;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * ComputeArcParametersFromHeight --
   *
   *	This function calculates the arc parameters given start-point,
   *	end-point and height (!= 0).
   *
   * Results:
   *	None.
   *
   * Side effects:
   *	The height parameter is set to 0 on exit.
   *
   *--------------------------------------------------------------
   */
  
  static void
  ComputeArcParametersFromHeight(
      ArcItem* arcPtr)
  {
      double chordLen, chordDir[2], chordCen[2], arcCen[2], d, radToDeg, radius;
  
      /*
       * Do nothing if no height has been specified.
       */
  
      if (arcPtr->height == 0)
          return;
  
      /*
       * Calculate the chord length, return early if it is too small.
       */
  
      chordLen = hypot(arcPtr->endPoint[1] - arcPtr->startPoint[1],
  	    arcPtr->startPoint[0] - arcPtr->endPoint[0]);
  
      if (chordLen < DBL_EPSILON) {
          arcPtr->start = arcPtr->extent = arcPtr->height = 0;
          return;
      }
  
      chordDir[0] = (arcPtr->endPoint[0] - arcPtr->startPoint[0]) / chordLen;
      chordDir[1] = (arcPtr->endPoint[1] - arcPtr->startPoint[1]) / chordLen;
      chordCen[0] = (arcPtr->startPoint[0] + arcPtr->endPoint[0]) / 2;
      chordCen[1] = (arcPtr->startPoint[1] + arcPtr->endPoint[1]) / 2;
  
      /*
       * Calculate the radius (assumes height != 0).
       */
  
      radius = (4*pow(arcPtr->height, 2) + pow(chordLen, 2))
  	    / (8 * arcPtr->height);
  
      /*
       * The arc centre.
       */
  
      d = radius - arcPtr->height;
      arcCen[0] = chordCen[0] - d * chordDir[1];
      arcCen[1] = chordCen[1] + d * chordDir[0];
  
      /*
       * The arc start and span. Angles are negated because the coordinate
       * system is left-handed.
       */
  
      radToDeg = 45 / atan(1);
      arcPtr->start = atan2(arcCen[1] - arcPtr->startPoint[1],
  	    arcPtr->startPoint[0] - arcCen[0]) * radToDeg;
      arcPtr->extent = -2 * asin(chordLen / (2 * radius)) * radToDeg;
  
      /*
       * Handle spans > 180.
       */
  
      if (fabs(2 * arcPtr->height) > chordLen) {
  	arcPtr->extent = arcPtr->extent > 0 ? (360 - arcPtr->extent)
  		: -(360 + arcPtr->extent);
      }
  
      /*
       * Create the bounding box.
       */
  
      arcPtr->bbox[0] = arcCen[0] - radius;
      arcPtr->bbox[1] = arcCen[1] - radius;
      arcPtr->bbox[2] = arcCen[0] + radius;
      arcPtr->bbox[3] = arcCen[1] + radius;
  
      /*
       * Set the height to 0 so that itemcget -height returns 0.
       */
  
      arcPtr->height = 0;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * DeleteArc --
   *
   *	This function is called to clean up the data structure associated with
   *	an arc item.
   *
   * Results:
   *	None.
   *
   * Side effects:
   *	Resources associated with itemPtr are released.
   *
   *--------------------------------------------------------------
   */
  
  static void
  DeleteArc(
      Tk_Canvas canvas,		/* Info about overall canvas. */
      Tk_Item *itemPtr,		/* Item that is being deleted. */
      Display *display)		/* Display containing window for canvas. */
  {
      ArcItem *arcPtr = (ArcItem *) itemPtr;
  
      Tk_DeleteOutline(display, &(arcPtr->outline));
      if (arcPtr->numOutlinePoints != 0) {
  	ckfree(arcPtr->outlinePtr);
      }
      if (arcPtr->fillColor != NULL) {
  	Tk_FreeColor(arcPtr->fillColor);
      }
      if (arcPtr->activeFillColor != NULL) {
  	Tk_FreeColor(arcPtr->activeFillColor);
      }
      if (arcPtr->disabledFillColor != NULL) {
  	Tk_FreeColor(arcPtr->disabledFillColor);
      }
      if (arcPtr->fillStipple != None) {
  	Tk_FreeBitmap(display, arcPtr->fillStipple);
      }
      if (arcPtr->activeFillStipple != None) {
  	Tk_FreeBitmap(display, arcPtr->activeFillStipple);
      }
      if (arcPtr->disabledFillStipple != None) {
  	Tk_FreeBitmap(display, arcPtr->disabledFillStipple);
      }
      if (arcPtr->fillGC != NULL) {
  	Tk_FreeGC(display, arcPtr->fillGC);
      }
  }
  
  /*
   *--------------------------------------------------------------
   *
   * ComputeArcBbox --
   *
   *	This function 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(
      Tk_Canvas canvas,		/* Canvas that contains item. */
      ArcItem *arcPtr)		/* Item whose bbox is to be recomputed. */
  {
      double tmp, center[2], point[2];
      double width;
      Tk_State state = arcPtr->header.state;
  
      if (state == TK_STATE_NULL) {
  	state = Canvas(canvas)->canvas_state;
      }
  
      width = arcPtr->outline.width;
      if (width < 1.0) {
  	width = 1.0;
      }
      if (state==TK_STATE_HIDDEN) {
  	arcPtr->header.x1 = arcPtr->header.x2 =
  	arcPtr->header.y1 = arcPtr->header.y2 = -1;
  	return;
      } else if (Canvas(canvas)->currentItemPtr == (Tk_Item *) arcPtr) {
  	if (arcPtr->outline.activeWidth>width) {
  	    width = arcPtr->outline.activeWidth;
  	}
      } else if (state==TK_STATE_DISABLED) {
  	if (arcPtr->outline.disabledWidth>0) {
  	    width = arcPtr->outline.disabledWidth;
  	}
      }
  
      /*
       * Make sure that the first coordinates are the lowest ones.
       */
  
      if (arcPtr->bbox[1] > arcPtr->bbox[3]) {
  	double tmp = arcPtr->bbox[3];
  
  	arcPtr->bbox[3] = arcPtr->bbox[1];
  	arcPtr->bbox[1] = tmp;
      }
      if (arcPtr->bbox[0] > arcPtr->bbox[2]) {
  	double tmp = arcPtr->bbox[2];
  
  	arcPtr->bbox[2] = arcPtr->bbox[0];
  	arcPtr->bbox[0] = tmp;
      }
  
      ComputeArcOutline(canvas,arcPtr);
  
      /*
       * To compute the bounding box, start with 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 = (int) arcPtr->center1[0];
      arcPtr->header.y1 = arcPtr->header.y2 = (int) arcPtr->center1[1];
      TkIncludePoint((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 == PIESLICE_STYLE) {
  	TkIncludePoint((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((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((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((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((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->outline.gc == NULL) {
  	tmp = 1;
      } else {
  	tmp = (int) ((width + 1.0)/2.0 + 1);
      }
      arcPtr->header.x1 -= (int) tmp;
      arcPtr->header.y1 -= (int) tmp;
      arcPtr->header.x2 += (int) tmp;
      arcPtr->header.y2 += (int) tmp;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * DisplayArc --
   *
   *	This function 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
   *	canvas.
   *
   *--------------------------------------------------------------
   */
  
  static void
  DisplayArc(
      Tk_Canvas canvas,		/* Canvas that contains item. */
      Tk_Item *itemPtr,		/* Item to be displayed. */
      Display *display,		/* Display on which to draw item. */
      Drawable drawable,		/* Pixmap or window in which to draw item. */
      int x, int y,		/* Describes region of canvas that must be */
      int width, int height)	/* redisplayed (not used). */
  {
      ArcItem *arcPtr = (ArcItem *) itemPtr;
      short x1, y1, x2, y2;
      int start, extent, dashnumber;
      double lineWidth;
      Tk_State state = itemPtr->state;
      Pixmap stipple;
  
      if (state == TK_STATE_NULL) {
  	state = Canvas(canvas)->canvas_state;
      }
      lineWidth = arcPtr->outline.width;
      if (lineWidth < 1.0) {
  	lineWidth = 1.0;
      }
      dashnumber = arcPtr->outline.dash.number;
      stipple = arcPtr->fillStipple;
      if (Canvas(canvas)->currentItemPtr == itemPtr) {
  	if (arcPtr->outline.activeWidth>lineWidth) {
  	    lineWidth = arcPtr->outline.activeWidth;
  	}
  	if (arcPtr->outline.activeDash.number != 0) {
  	    dashnumber = arcPtr->outline.activeDash.number;
  	}
  	if (arcPtr->activeFillStipple != None) {
  	    stipple = arcPtr->activeFillStipple;
  	}
      } else if (state == TK_STATE_DISABLED) {
  	if (arcPtr->outline.disabledWidth > 0) {
  	    lineWidth = arcPtr->outline.disabledWidth;
  	}
  	if (arcPtr->outline.disabledDash.number != 0) {
  	    dashnumber = arcPtr->outline.disabledDash.number;
  	}
  	if (arcPtr->disabledFillStipple != None) {
  	    stipple = arcPtr->disabledFillStipple;
  	}
      }
  
      /*
       * Compute the screen coordinates of the bounding box for the item, plus
       * integer values for the angles.
       */
  
      Tk_CanvasDrawableCoords(canvas, arcPtr->bbox[0], arcPtr->bbox[1],
  	    &x1, &y1);
      Tk_CanvasDrawableCoords(canvas, arcPtr->bbox[2], arcPtr->bbox[3],
  	    &x2, &y2);
      if (x2 <= x1) {
  	x2 = x1+1;
      }
      if (y2 <= y1) {
  	y2 = y1+1;
      }
      start = (int) ((64*arcPtr->start) + 0.5);
      extent = (int) ((64*arcPtr->extent) + 0.5);
  
      /*
       * Display filled arc first (if wanted), then outline. If the extent is
       * zero then don't invoke XFillArc or XDrawArc, since this causes some
       * window servers to crash and should be a no-op anyway.
       */
  
      if ((arcPtr->fillGC != NULL) && (extent != 0)) {
  	if (stipple != None) {
  	    int w = 0;
  	    int h = 0;
  	    Tk_TSOffset *tsoffset = &arcPtr->tsoffset;
  	    int flags = tsoffset->flags;
  
  	    if (flags & (TK_OFFSET_CENTER|TK_OFFSET_MIDDLE)) {
  		Tk_SizeOfBitmap(display, stipple, &w, &h);
  		if (flags & TK_OFFSET_CENTER) {
  		    w /= 2;
  		} else {
  		    w = 0;
  		}
  		if (flags & TK_OFFSET_MIDDLE) {
  		    h /= 2;
  		} else {
  		    h = 0;
  		}
  	    }
  	    tsoffset->xoffset -= w;
  	    tsoffset->yoffset -= h;
  	    Tk_CanvasSetOffset(canvas, arcPtr->fillGC, tsoffset);
  	    if (tsoffset) {
  		tsoffset->xoffset += w;
  		tsoffset->yoffset += h;
  	    }
  	}
  	XFillArc(display, drawable, arcPtr->fillGC, x1, y1, (unsigned) (x2-x1),
  		(unsigned) (y2-y1), start, extent);
  	if (stipple != None) {
  	    XSetTSOrigin(display, arcPtr->fillGC, 0, 0);
  	}
      }
      if (arcPtr->outline.gc != NULL) {
  	Tk_ChangeOutlineGC(canvas, itemPtr, &(arcPtr->outline));
  
  	if (extent != 0) {
  	    XDrawArc(display, drawable, arcPtr->outline.gc, x1, y1,
  		    (unsigned) (x2-x1), (unsigned) (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. The same is done if the
  	 * outline is dashed, because then polygons don't work.
  	 */
  
  	if (lineWidth < 1.5 || dashnumber != 0) {
  	    Tk_CanvasDrawableCoords(canvas, arcPtr->center1[0],
  		    arcPtr->center1[1], &x1, &y1);
  	    Tk_CanvasDrawableCoords(canvas, arcPtr->center2[0],
  		    arcPtr->center2[1], &x2, &y2);
  
  	    if (arcPtr->style == CHORD_STYLE) {
  		XDrawLine(display, drawable, arcPtr->outline.gc,
  			x1, y1, x2, y2);
  	    } else if (arcPtr->style == PIESLICE_STYLE) {
  		short cx, cy;
  
  		Tk_CanvasDrawableCoords(canvas,
  			(arcPtr->bbox[0] + arcPtr->bbox[2])/2.0,
  			(arcPtr->bbox[1] + arcPtr->bbox[3])/2.0, &cx, &cy);
  		XDrawLine(display, drawable, arcPtr->outline.gc,
  			cx, cy, x1, y1);
  		XDrawLine(display, drawable, arcPtr->outline.gc,
  			cx, cy, x2, y2);
  	    }
  	} else {
  	    if (arcPtr->style == CHORD_STYLE) {
  		TkFillPolygon(canvas, arcPtr->outlinePtr, CHORD_OUTLINE_PTS,
  			display, drawable, arcPtr->outline.gc, NULL);
  	    } else if (arcPtr->style == PIESLICE_STYLE) {
  		TkFillPolygon(canvas, arcPtr->outlinePtr, PIE_OUTLINE1_PTS,
  			display, drawable, arcPtr->outline.gc, NULL);
  		TkFillPolygon(canvas, arcPtr->outlinePtr + 2*PIE_OUTLINE1_PTS,
  			PIE_OUTLINE2_PTS, display, drawable,
  			arcPtr->outline.gc, NULL);
  	    }
  	}
  
  	Tk_ResetOutlineGC(canvas, itemPtr, &(arcPtr->outline));
      }
  }
  
  /*
   *--------------------------------------------------------------
   *
   * 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(
      Tk_Canvas canvas,		/* Canvas containing item. */
      Tk_Item *itemPtr,		/* Item to check against point. */
      double *pointPtr)		/* Pointer to x and y coordinates. */
  {
      ArcItem *arcPtr = (ArcItem *) itemPtr;
      double vertex[2], pointAngle, diff, dist, newDist;
      double poly[8], polyDist, width, t1, t2;
      int filled, angleInRange;
      Tk_State state = itemPtr->state;
  
      if (state == TK_STATE_NULL) {
  	state = Canvas(canvas)->canvas_state;
      }
  
      width = (double) arcPtr->outline.width;
      if (Canvas(canvas)->currentItemPtr == itemPtr) {
  	if (arcPtr->outline.activeWidth>width) {
  	    width = (double) arcPtr->outline.activeWidth;
  	}
      } else if (state == TK_STATE_DISABLED) {
  	if (arcPtr->outline.disabledWidth>0) {
  	    width = (double) arcPtr->outline.disabledWidth;
  	}
      }
  
      /*
       * 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;
      t1 = arcPtr->bbox[3] - arcPtr->bbox[1];
      if (t1 != 0.0) {
  	t1 = (pointPtr[1] - vertex[1]) / t1;
      }
      t2 = arcPtr->bbox[2] - arcPtr->bbox[0];
      if (t2 != 0.0) {
  	t2 = (pointPtr[0] - vertex[0]) / t2;
      }
      if ((t1 == 0.0) && (t2 == 0.0)) {
  	pointAngle = 0;
      } else {
  	pointAngle = -atan2(t1, t2)*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 == ARC_STYLE) {
  	if (angleInRange) {
  	    return TkOvalToPoint(arcPtr->bbox, 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 != NULL) || (arcPtr->outline.gc == NULL)) {
  	filled = 1;
      } else {
  	filled = 0;
      }
      if (arcPtr->outline.gc == NULL) {
  	width = 0.0;
      }
  
      if (arcPtr->style == PIESLICE_STYLE) {
  	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;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * ArcToArea --
   *
   *	This function 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(
      Tk_Canvas canvas,		/* 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. */
  {
      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;
      Tk_State state = itemPtr->state;
  
      if(state == TK_STATE_NULL) {
  	state = Canvas(canvas)->canvas_state;
      }
      width = (double) arcPtr->outline.width;
      if (Canvas(canvas)->currentItemPtr == itemPtr) {
  	if (arcPtr->outline.activeWidth>width) {
  	    width = (double) arcPtr->outline.activeWidth;
  	}
      } else if (state == TK_STATE_DISABLED) {
  	if (arcPtr->outline.disabledWidth>0) {
  	    width = (double) arcPtr->outline.disabledWidth;
  	}
      }
  
      if ((arcPtr->fillGC != NULL) || (arcPtr->outline.gc == NULL)) {
  	filled = 1;
      } else {
  	filled = 0;
      }
      if (arcPtr->outline.gc == NULL) {
  	width = 0.0;
      }
  
      /*
       * 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;
      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 == PIESLICE_STYLE) && (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++;
      }
  
      /*
       * 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 == PIESLICE_STYLE) {
  	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 == CHORD_STYLE) {
  	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(canvas, itemPtr, rectPtr) == 0.0) {
  	return 0;
      }
      return -1;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * ScaleArc --
   *
   *	This function 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(
      Tk_Canvas canvas,		/* Canvas containing arc. */
      Tk_Item *itemPtr,		/* Arc to be scaled. */
      double originX,		/* Origin about which to scale rect. */
      double originY,
      double scaleX,		/* Amount to scale in X direction. */
      double scaleY)		/* Amount to scale in Y direction. */
  {
      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(canvas, arcPtr);
  }
  
  /*
   *--------------------------------------------------------------
   *
   * RotateArc --
   *
   *	This function is called to rotate an arc by a given amount.
   *
   * Results:
   *	None.
   *
   * Side effects:
   *	The position of the arc is rotated by angleRad radians about (originX,
   *	originY), and the bounding box is updated in the generic part of the
   *	item structure.
   *
   *--------------------------------------------------------------
   */
  
  static void
  RotateArc(
      Tk_Canvas canvas,
      Tk_Item *itemPtr,
      double originX,
      double originY,
      double angleRad)
  {
      ArcItem *arcPtr = (ArcItem *) itemPtr;
      double newX, newY, oldX, oldY;
  
      /*
       * Compute the centre of the box, then rotate that about the origin.
       */
  
      newX = oldX = (arcPtr->bbox[0] + arcPtr->bbox[2]) / 2.0;
      newY = oldY = (arcPtr->bbox[1] + arcPtr->bbox[3]) / 2.0;
      TkRotatePoint(originX, originY, sin(angleRad), cos(angleRad),
  	    &newX, &newY);
  
      /*
       * Apply the translation to the box.
       */
  
      arcPtr->bbox[0] += newX - oldX;
      arcPtr->bbox[1] += newY - oldY;
      arcPtr->bbox[2] += newX - oldX;
      arcPtr->bbox[3] += newY - oldY;
  
      /*
       * TODO: update the arc endpoints?
       */
  
      ComputeArcBbox(canvas, arcPtr);
  }
  
  /*
   *--------------------------------------------------------------
   *
   * TranslateArc --
   *
   *	This function 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(
      Tk_Canvas canvas,		/* Canvas containing item. */
      Tk_Item *itemPtr,		/* Item that is being moved. */
      double deltaX,		/* Amount by which item is to be moved. */
      double deltaY)
  {
      ArcItem *arcPtr = (ArcItem *) itemPtr;
  
      arcPtr->bbox[0] += deltaX;
      arcPtr->bbox[1] += deltaY;
      arcPtr->bbox[2] += deltaX;
      arcPtr->bbox[3] += deltaY;
      ComputeArcBbox(canvas, arcPtr);
  }
  
  /*
   *--------------------------------------------------------------
   *
   * ComputeArcOutline --
   *
   *	This function 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(
      Tk_Canvas canvas,		/* Information about overall canvas. */
      ArcItem *arcPtr)		/* Information about arc. */
  {
      double sin1, cos1, sin2, cos2, angle, width, halfWidth;
      double boxWidth, boxHeight;
      double vertex[2], corner1[2], corner2[2];
      double *outlinePtr;
      Tk_State state = arcPtr->header.state;
  
      /*
       * Make sure that the outlinePtr array is large enough to hold either a
       * chord or pie-slice outline.
       */
  
      if (arcPtr->numOutlinePoints == 0) {
  	arcPtr->outlinePtr = ckalloc(26 * sizeof(double));
  	arcPtr->numOutlinePoints = 22;
      }
      outlinePtr = arcPtr->outlinePtr;
  
      if (state == TK_STATE_NULL) {
  	state = Canvas(canvas)->canvas_state;
      }
  
      /*
       * 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)
       * divided by (boxHeight*cos1), and similarly for arcPtr->center2 and
       * corner2. These formulas can be computed from the formula for the oval.
       */
  
      width = arcPtr->outline.width;
      if (Canvas(canvas)->currentItemPtr == (Tk_Item *) arcPtr) {
  	if (arcPtr->outline.activeWidth>arcPtr->outline.width) {
  	    width = arcPtr->outline.activeWidth;
  	}
      } else if (state == TK_STATE_DISABLED) {
  	if (arcPtr->outline.disabledWidth>arcPtr->outline.width) {
  	    width = arcPtr->outline.disabledWidth;
  	}
      }
      halfWidth = width/2.0;
  
      if (((boxWidth*sin1) == 0.0) && ((boxHeight*cos1) == 0.0)) {
  	angle = 0.0;
      } else {
  	angle = atan2(boxWidth*sin1, boxHeight*cos1);
      }
      corner1[0] = arcPtr->center1[0] + cos(angle)*halfWidth;
      corner1[1] = arcPtr->center1[1] + sin(angle)*halfWidth;
      if (((boxWidth*sin2) == 0.0) && ((boxHeight*cos2) == 0.0)) {
  	angle = 0.0;
      } else {
  	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 == CHORD_STYLE) {
  	outlinePtr[0] = outlinePtr[12] = corner1[0];
  	outlinePtr[1] = outlinePtr[13] = corner1[1];
  	TkGetButtPoints(arcPtr->center2, arcPtr->center1,
  		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 == PIESLICE_STYLE) {
  	/*
  	 * 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, 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, 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];
      }
  }
  
  /*
   *--------------------------------------------------------------
   *
   * 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. chord
   *	or pie-slice) are not checked.
   *
   * Side effects:
   *	None.
   *
   *--------------------------------------------------------------
   */
  
  static int
  HorizLineToArc(
      double x1, double x2,	/* X-coords of endpoints of line segment. X1
  				 * must be <= x2. */
      double y,			/* Y-coordinate of line segment. */
      double rx, double ry,	/* These x- and y-radii define an oval
  				 * centered at the origin. */
      double start, double extent)/* Angles that define extent of arc, in the
  				 * standard fashion for this module. */
  {
      double tmp, x;
      double tx, ty;		/* Coordinates of intersection point in
  				 * transformed coordinate system. */
  
      /*
       * 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;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * 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. chord
   *	or pie-slice) are not checked.
   *
   * Side effects:
   *	None.
   *
   *--------------------------------------------------------------
   */
  
  static int
  VertLineToArc(
      double x,			/* X-coordinate of line segment. */
      double y1, double y2,	/* Y-coords of endpoints of line segment. Y1
  				 * must be <= y2. */
      double rx, double ry,	/* These x- and y-radii define an oval
  				 * centered at the origin. */
      double start, double extent)/* Angles that define extent of arc, in the
  				 * standard fashion for this module. */
  {
      double tmp, y;
      double tx, ty;		/* Coordinates of intersection point in
  				 * transformed coordinate system. */
  
      /*
       * 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;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * 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(
      double x, double 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;
  
      if ((x == 0.0) && (y == 0.0)) {
  	return 1;
      }
      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;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * ArcToPostscript --
   *
   *	This function is called to generate Postscript for arc items.
   *
   * Results:
   *	The return value is a standard Tcl result. If an error occurs in
   *	generating Postscript then an error message is left in the interp's
   *	result, replacing whatever used to be there. If no error occurs, then
   *	Postscript for the item is appended to the result.
   *
   * Side effects:
   *	None.
   *
   *--------------------------------------------------------------
   */
  
  static int
  ArcToPostscript(
      Tcl_Interp *interp,		/* Leave Postscript or error message here. */
      Tk_Canvas canvas,		/* Information about overall canvas. */
      Tk_Item *itemPtr,		/* Item for which Postscript is wanted. */
      int prepass)		/* 1 means this is a prepass to collect font
  				 * information; 0 means final Postscript is
  				 * being created. */
  {
      ArcItem *arcPtr = (ArcItem *) itemPtr;
      double y1, y2, ang1, ang2;
      XColor *color;
      Pixmap stipple;
      XColor *fillColor;
      Pixmap fillStipple;
      Tk_State state = itemPtr->state;
      Tcl_Obj *psObj;
      Tcl_InterpState interpState;
  
      y1 = Tk_CanvasPsY(canvas, arcPtr->bbox[1]);
      y2 = Tk_CanvasPsY(canvas, arcPtr->bbox[3]);
      ang1 = arcPtr->start;
      ang2 = ang1 + arcPtr->extent;
      if (ang2 < ang1) {
  	ang1 = ang2;
  	ang2 = arcPtr->start;
      }
  
      if (state == TK_STATE_NULL) {
  	state = Canvas(canvas)->canvas_state;
      }
      color = arcPtr->outline.color;
      stipple = arcPtr->outline.stipple;
      fillColor = arcPtr->fillColor;
      fillStipple = arcPtr->fillStipple;
      if (Canvas(canvas)->currentItemPtr == itemPtr) {
  	if (arcPtr->outline.activeColor!=NULL) {
  	    color = arcPtr->outline.activeColor;
  	}
  	if (arcPtr->outline.activeStipple!=None) {
  	    stipple = arcPtr->outline.activeStipple;
  	}
  	if (arcPtr->activeFillColor!=NULL) {
  	    fillColor = arcPtr->activeFillColor;
  	}
  	if (arcPtr->activeFillStipple!=None) {
  	    fillStipple = arcPtr->activeFillStipple;
  	}
      } else if (state == TK_STATE_DISABLED) {
  	if (arcPtr->outline.disabledColor!=NULL) {
  	    color = arcPtr->outline.disabledColor;
  	}
  	if (arcPtr->outline.disabledStipple!=None) {
  	    stipple = arcPtr->outline.disabledStipple;
  	}
  	if (arcPtr->disabledFillColor!=NULL) {
  	    fillColor = arcPtr->disabledFillColor;
  	}
  	if (arcPtr->disabledFillStipple!=None) {
  	    fillStipple = arcPtr->disabledFillStipple;
  	}
      }
  
      /*
       * Make our working space.
       */
  
      psObj = Tcl_NewObj();
      interpState = Tcl_SaveInterpState(interp, TCL_OK);
  
      /*
       * If the arc is filled, output Postscript for the interior region of the
       * arc.
       */
  
      if (arcPtr->fillGC != NULL) {
  	Tcl_AppendPrintfToObj(psObj,
  		"matrix currentmatrix\n"
  		"%.15g %.15g translate %.15g %.15g scale\n",
  		(arcPtr->bbox[0] + arcPtr->bbox[2])/2, (y1 + y2)/2,
  		(arcPtr->bbox[2] - arcPtr->bbox[0])/2, (y1 - y2)/2);
  
  	if (arcPtr->style != CHORD_STYLE) {
  	    Tcl_AppendToObj(psObj, "0 0 moveto ", -1);
  	}
  	Tcl_AppendPrintfToObj(psObj,
  		"0 0 1 %.15g %.15g arc closepath\nsetmatrix\n",
  		ang1, ang2);
  
  	Tcl_ResetResult(interp);
  	if (Tk_CanvasPsColor(interp, canvas, fillColor) != TCL_OK) {
  	    goto error;
  	}
  	Tcl_AppendObjToObj(psObj, Tcl_GetObjResult(interp));
  
  	if (fillStipple != None) {
  	    Tcl_AppendToObj(psObj, "clip ", -1);
  
  	    Tcl_ResetResult(interp);
  	    if (Tk_CanvasPsStipple(interp, canvas, fillStipple) != TCL_OK) {
  		goto error;
  	    }
  	    Tcl_AppendObjToObj(psObj, Tcl_GetObjResult(interp));
  
  	    if (arcPtr->outline.gc != NULL) {
  		Tcl_AppendToObj(psObj, "grestore gsave\n", -1);
  	    }
  	} else {
  	    Tcl_AppendToObj(psObj, "fill\n", -1);
  	}
      }
  
      /*
       * If there's an outline for the arc, draw it.
       */
  
      if (arcPtr->outline.gc != NULL) {
  	Tcl_AppendPrintfToObj(psObj,
  		"matrix currentmatrix\n"
  		"%.15g %.15g translate %.15g %.15g scale\n",
  		(arcPtr->bbox[0] + arcPtr->bbox[2])/2, (y1 + y2)/2,
  		(arcPtr->bbox[2] - arcPtr->bbox[0])/2, (y1 - y2)/2);
  	Tcl_AppendPrintfToObj(psObj,
  		"0 0 1 %.15g %.15g arc\nsetmatrix\n0 setlinecap\n",
  		ang1, ang2);
  
  	Tcl_ResetResult(interp);
  	if (Tk_CanvasPsOutline(canvas, itemPtr, &arcPtr->outline) != TCL_OK) {
  	    goto error;
  	}
  	Tcl_AppendObjToObj(psObj, Tcl_GetObjResult(interp));
  
  	if (arcPtr->style != ARC_STYLE) {
  	    Tcl_AppendToObj(psObj, "grestore gsave\n", -1);
  
  	    Tcl_ResetResult(interp);
  	    if (arcPtr->style == CHORD_STYLE) {
  		Tk_CanvasPsPath(interp, canvas, arcPtr->outlinePtr,
  			CHORD_OUTLINE_PTS);
  	    } else {
  		Tk_CanvasPsPath(interp, canvas, arcPtr->outlinePtr,
  			PIE_OUTLINE1_PTS);
  		if (Tk_CanvasPsColor(interp, canvas, color) != TCL_OK) {
  		    goto error;
  		}
  		Tcl_AppendObjToObj(psObj, Tcl_GetObjResult(interp));
  
  		if (stipple != None) {
  		    Tcl_AppendToObj(psObj, "clip ", -1);
  
  		    Tcl_ResetResult(interp);
  		    if (Tk_CanvasPsStipple(interp, canvas, stipple) !=TCL_OK){
  			goto error;
  		    }
  		    Tcl_AppendObjToObj(psObj, Tcl_GetObjResult(interp));
  		} else {
  		    Tcl_AppendToObj(psObj, "fill\n", -1);
  		}
  		Tcl_AppendToObj(psObj, "grestore gsave\n", -1);
  
  		Tcl_ResetResult(interp);
  		Tk_CanvasPsPath(interp, canvas,
  			arcPtr->outlinePtr + 2*PIE_OUTLINE1_PTS,
  			PIE_OUTLINE2_PTS);
  	    }
  	    if (Tk_CanvasPsColor(interp, canvas, color) != TCL_OK) {
  		goto error;
  	    }
  	    Tcl_AppendObjToObj(psObj, Tcl_GetObjResult(interp));
  
  	    if (stipple != None) {
  		Tcl_AppendToObj(psObj, "clip ", -1);
  
  		Tcl_ResetResult(interp);
  		if (Tk_CanvasPsStipple(interp, canvas, stipple) != TCL_OK) {
  		    goto error;
  		}
  		Tcl_AppendObjToObj(psObj, Tcl_GetObjResult(interp));
  	    } else {
  		Tcl_AppendToObj(psObj, "fill\n", -1);
  	    }
  	}
      }
  
      /*
       * Plug the accumulated postscript back into the result.
       */
  
      (void) Tcl_RestoreInterpState(interp, interpState);
      Tcl_AppendObjToObj(Tcl_GetObjResult(interp), psObj);
      Tcl_DecrRefCount(psObj);
      return TCL_OK;
  
    error:
      Tcl_DiscardInterpState(interpState);
      Tcl_DecrRefCount(psObj);
      return TCL_ERROR;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * StyleParseProc --
   *
   *	This function is invoked during option processing to handle the
   *	"-style" option.
   *
   * Results:
   *	A standard Tcl return value.
   *
   * Side effects:
   *	The state for a given item gets replaced by the state indicated in the
   *	value argument.
   *
   *--------------------------------------------------------------
   */
  
  static int
  StyleParseProc(
      ClientData clientData,	/* some flags.*/
      Tcl_Interp *interp,		/* Used for reporting errors. */
      Tk_Window tkwin,		/* Window containing canvas widget. */
      const char *value,		/* Value of option. */
      char *widgRec,		/* Pointer to record for item. */
      int offset)			/* Offset into item. */
  {
      int c;
      size_t length;
  
      register Style *stylePtr = (Style *) (widgRec + offset);
  
      if (value == NULL || *value == 0) {
  	*stylePtr = PIESLICE_STYLE;
  	return TCL_OK;
      }
  
      c = value[0];
      length = strlen(value);
  
      if ((c == 'a') && (strncmp(value, "arc", length) == 0)) {
  	*stylePtr = ARC_STYLE;
  	return TCL_OK;
      }
      if ((c == 'c') && (strncmp(value, "chord", length) == 0)) {
  	*stylePtr = CHORD_STYLE;
  	return TCL_OK;
      }
      if ((c == 'p') && (strncmp(value, "pieslice", length) == 0)) {
  	*stylePtr = PIESLICE_STYLE;
  	return TCL_OK;
      }
  
      Tcl_SetObjResult(interp, Tcl_ObjPrintf(
  	    "bad -style option \"%s\": must be arc, chord, or pieslice",
  	    value));
      Tcl_SetErrorCode(interp, "TK", "CANVAS", "ARC_STYLE", NULL);
      *stylePtr = PIESLICE_STYLE;
      return TCL_ERROR;
  }
  
  /*
   *--------------------------------------------------------------
   *
   * StylePrintProc --
   *
   *	This function is invoked by the Tk configuration code to produce a
   *	printable string for the "-style" configuration option.
   *
   * Results:
   *	The return value is a string describing the state for the item
   *	referred to by "widgRec". In addition, *freeProcPtr is filled in with
   *	the address of a function to call to free the result string when it's
   *	no longer needed (or NULL to indicate that the string doesn't need to
   *	be freed).
   *
   * Side effects:
   *	None.
   *
   *--------------------------------------------------------------
   */
  
  static const char *
  StylePrintProc(
      ClientData clientData,	/* Ignored. */
      Tk_Window tkwin,		/* Ignored. */
      char *widgRec,		/* Pointer to record for item. */
      int offset,			/* Offset into item. */
      Tcl_FreeProc **freeProcPtr)	/* Pointer to variable to fill in with
  				 * information about how to reclaim storage
  				 * for return string. */
  {
      register Style *stylePtr = (Style *) (widgRec + offset);
  
      if (*stylePtr == ARC_STYLE) {
  	return "arc";
      } else if (*stylePtr == CHORD_STYLE) {
  	return "chord";
      } else {
  	return "pieslice";
      }
  }
  
  /*
   * Local Variables:
   * mode: c
   * c-basic-offset: 4
   * fill-column: 78
   * End:
   */
  