/*
 * rbcGrAxis.c --
 *
 *      This module implements coordinate axes for the rbc graph widget.
 *
 * Copyright (c) 2009 Samuel Green, Nicholas Hudson, Stanton Sievers, Jarrod Stormo
 * All rights reserved.
 *
 * See "license.terms" for details.
 */

#include "rbcGraph.h"
#include "rbcGrElem.h"
#include <X11/Xutil.h>

#define DEF_NUM_TICKS		4	/* Each minor tick is 20% */
#define STATIC_TICK_SPACE	10

#define TICK_LABEL_SIZE		200
#define MAXTICKS		10001

#define CLAMP(val,low,high)	\
	(((val) < (low)) ? (low) : ((val) > (high)) ? (high) : (val))

/*
 * Round x in terms of units
 */
#define UROUND(x,u)		(Round((x)/(u))*(u))
#define UCEIL(x,u)		(ceil((x)/(u))*(u))
#define UFLOOR(x,u)		(floor((x)/(u))*(u))

#define LENGTH_MAJOR_TICK 	0.030	/* Length of a major tick */
#define LENGTH_MINOR_TICK 	0.015	/* Length of a minor (sub)tick */
#define LENGTH_LABEL_TICK 	0.040	/* Distance from graph to start of the
* label */
#define NUMDIGITS		15	/* Specifies the number of
* digits of accuracy used when
* outputting axis tick labels. */
#define AVG_TICK_NUM_CHARS	16	/* Assumed average tick label size */

#define TICK_RANGE_TIGHT	0
#define TICK_RANGE_LOOSE	1
#define TICK_RANGE_ALWAYS_LOOSE	2

#define AXIS_TITLE_PAD		2	/* Padding for axis title. */
#define AXIS_LINE_PAD		1	/* Padding for axis line. */

#define HORIZMARGIN(m)	(!((m)->site & 0x1))	/* Even sites are horizontal */

typedef enum AxisComponents {
    MAJOR_TICK, MINOR_TICK, TICK_LABEL, AXIS_LINE
} AxisComponent;


typedef struct {
    int axis; /* Length of the axis.  */
    int t1; /* Length of a major tick (in pixels). */
    int t2; /* Length of a minor tick (in pixels). */
    int label; /* Distance from axis to tick label.  */
} AxisInfo;

extern Tk_CustomOption rbcDistanceOption;
extern Tk_CustomOption rbcPositiveDistanceOption;
extern Tk_CustomOption rbcShadowOption;
extern Tk_CustomOption rbcListOption;

static Tk_OptionParseProc StringToLimit;
static Tk_OptionPrintProc LimitToString;
static Tk_OptionParseProc StringToTicks;
static Tk_OptionPrintProc TicksToString;
static Tk_OptionParseProc StringToAxis;
static Tk_OptionPrintProc AxisToString;
static Tk_OptionParseProc StringToAnyAxis;
static Tk_OptionParseProc StringToFormat;
static Tk_OptionPrintProc FormatToString;
static Tk_OptionParseProc StringToLoose;
static Tk_OptionPrintProc LooseToString;

static Tk_CustomOption limitOption = {
    StringToLimit, LimitToString, (ClientData)0
};

static Tk_CustomOption majorTicksOption = {
    StringToTicks, TicksToString, (ClientData)AXIS_CONFIG_MAJOR,
};
static Tk_CustomOption minorTicksOption = {
    StringToTicks, TicksToString, (ClientData)AXIS_CONFIG_MINOR,
};
Tk_CustomOption rbcXAxisOption = {
    StringToAxis, AxisToString, (ClientData)&rbcXAxisUid
};
Tk_CustomOption rbcYAxisOption = {
    StringToAxis, AxisToString, (ClientData)&rbcYAxisUid
};
Tk_CustomOption rbcAnyXAxisOption = {
    StringToAnyAxis, AxisToString, (ClientData)&rbcXAxisUid
};
Tk_CustomOption rbcAnyYAxisOption = {
    StringToAnyAxis, AxisToString, (ClientData)&rbcYAxisUid
};
static Tk_CustomOption formatOption = {
    StringToFormat, FormatToString, (ClientData)0,
};
static Tk_CustomOption looseOption = {
    StringToLoose, LooseToString, (ClientData)0,
};

/* Axis flags: */

#define DEF_AXIS_COMMAND		(char *)NULL
#define DEF_AXIS_DESCENDING		"no"
#define DEF_AXIS_FOREGROUND		RGB_BLACK
#define DEF_AXIS_FG_MONO		RGB_BLACK
#define DEF_AXIS_HIDE			"no"
#define DEF_AXIS_JUSTIFY		"center"
#define DEF_AXIS_LIMITS_FORMAT	        (char *)NULL
#define DEF_AXIS_LINE_WIDTH		"1"
#define DEF_AXIS_LOGSCALE		"no"
#define DEF_AXIS_LOOSE			"no"
#define DEF_AXIS_RANGE			"0.0"
#define DEF_AXIS_ROTATE			"0.0"
#define DEF_AXIS_SCROLL_INCREMENT 	"10"
#define DEF_AXIS_SHIFTBY		"0.0"
#define DEF_AXIS_SHOWTICKS		"yes"
#define DEF_AXIS_STEP			"0.0"
#define DEF_AXIS_STEP			"0.0"
#define DEF_AXIS_SUBDIVISIONS		"2"
#define DEF_AXIS_TAGS			"all"
#define DEF_AXIS_TICKS			"0"

#ifdef WIN32
#define DEF_AXIS_TICK_FONT		"{Arial Narrow} 8"
#else
#define DEF_AXIS_TICK_FONT		"TkSmallCaptionFont"
#endif

#define DEF_AXIS_TICK_LENGTH		"8"
#define DEF_AXIS_TITLE_ALTERNATE	"0"
#define DEF_AXIS_TITLE_FG		RGB_BLACK
#define DEF_AXIS_TITLE_FONT		STD_FONT
#define DEF_AXIS_X_STEP_BARCHART	"1.0"
#define DEF_AXIS_X_SUBDIVISIONS_BARCHART "0"
#define DEF_AXIS_BACKGROUND		(char *)NULL
#define DEF_AXIS_BORDERWIDTH		"0"
#define DEF_AXIS_RELIEF			"flat"

static Tk_ConfigSpec configSpecs[] = {
    {TK_CONFIG_DOUBLE, "-autorange", "autoRange", "AutoRange", DEF_AXIS_RANGE, offsetof(Axis, windowSize), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_BORDER, "-background", "background", "Background", DEF_AXIS_BACKGROUND, offsetof(Axis, border), ALL_GRAPHS | TK_CONFIG_NULL_OK},
    {TK_CONFIG_SYNONYM, "-bg", "background", (char *)NULL, (char *)NULL, 0, 0},
    {TK_CONFIG_CUSTOM, "-bindtags", "bindTags", "BindTags", DEF_AXIS_TAGS, offsetof(Axis, tags), ALL_GRAPHS | TK_CONFIG_NULL_OK, &rbcListOption},
    {TK_CONFIG_SYNONYM, "-bd", "borderWidth", (char *)NULL, (char *)NULL, 0, ALL_GRAPHS},
    {TK_CONFIG_CUSTOM, "-borderwidth", "borderWidth", "BorderWidth", DEF_AXIS_BORDERWIDTH, offsetof(Axis, borderWidth), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT, &rbcDistanceOption},
    {TK_CONFIG_COLOR, "-color", "color", "Color", DEF_AXIS_FOREGROUND, offsetof(Axis, tickTextStyle.color), TK_CONFIG_COLOR_ONLY | ALL_GRAPHS},
    {TK_CONFIG_COLOR, "-color", "color", "Color", DEF_AXIS_FG_MONO, offsetof(Axis, tickTextStyle.color), TK_CONFIG_MONO_ONLY | ALL_GRAPHS},
    {TK_CONFIG_STRING, "-command", "command", "Command", DEF_AXIS_COMMAND, offsetof(Axis, formatCmd), TK_CONFIG_NULL_OK | ALL_GRAPHS},
    {TK_CONFIG_BOOLEAN, "-descending", "descending", "Descending", DEF_AXIS_DESCENDING, offsetof(Axis, descending), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_BOOLEAN, "-hide", "hide", "Hide", DEF_AXIS_HIDE, offsetof(Axis, hidden), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_JUSTIFY, "-justify", "justify", "Justify", DEF_AXIS_JUSTIFY, offsetof(Axis, titleTextStyle.justify), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_BOOLEAN, "-labeloffset", "labelOffset", "LabelOffset", (char *)NULL, offsetof(Axis, labelOffset), ALL_GRAPHS},
    {TK_CONFIG_COLOR, "-limitscolor", "limitsColor", "Color", DEF_AXIS_FOREGROUND, offsetof(Axis, limitsTextStyle.color), TK_CONFIG_COLOR_ONLY | ALL_GRAPHS},
    {TK_CONFIG_COLOR, "-limitscolor", "limitsColor", "Color", DEF_AXIS_FG_MONO, offsetof(Axis, limitsTextStyle.color), TK_CONFIG_MONO_ONLY | ALL_GRAPHS},
    {TK_CONFIG_FONT, "-limitsfont", "limitsFont", "Font", DEF_AXIS_TICK_FONT, offsetof(Axis, limitsTextStyle.font), ALL_GRAPHS},
    {TK_CONFIG_CUSTOM, "-limitsformat", "limitsFormat", "LimitsFormat", (char *)NULL, offsetof(Axis, limitsFormats), TK_CONFIG_NULL_OK | ALL_GRAPHS, &formatOption},
    {TK_CONFIG_CUSTOM, "-limitsshadow", "limitsShadow", "Shadow", (char *)NULL, offsetof(Axis, limitsTextStyle.shadow), TK_CONFIG_COLOR_ONLY | ALL_GRAPHS, &rbcShadowOption},
    {TK_CONFIG_CUSTOM, "-limitsshadow", "limitsShadow", "Shadow", (char *)NULL, offsetof(Axis, limitsTextStyle.shadow), TK_CONFIG_MONO_ONLY | ALL_GRAPHS, &rbcShadowOption},
    {TK_CONFIG_CUSTOM, "-linewidth", "lineWidth", "LineWidth", DEF_AXIS_LINE_WIDTH, offsetof(Axis, lineWidth), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT, &rbcDistanceOption},
    {TK_CONFIG_BOOLEAN, "-logscale", "logScale", "LogScale", DEF_AXIS_LOGSCALE, offsetof(Axis, logScale), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_CUSTOM, "-loose", "loose", "Loose", DEF_AXIS_LOOSE, 0, ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT, &looseOption},
    {TK_CONFIG_CUSTOM, "-majorticks", "majorTicks", "MajorTicks", (char *)NULL, offsetof(Axis, t1Ptr), TK_CONFIG_NULL_OK | ALL_GRAPHS, &majorTicksOption},
    {TK_CONFIG_CUSTOM, "-max", "max", "Max", (char *)NULL, offsetof(Axis, reqMax), TK_CONFIG_NULL_OK | ALL_GRAPHS, &limitOption},
    {TK_CONFIG_CUSTOM, "-min", "min", "Min", (char *)NULL, offsetof(Axis, reqMin), TK_CONFIG_NULL_OK | ALL_GRAPHS, &limitOption},
    {TK_CONFIG_CUSTOM, "-minorticks", "minorTicks", "MinorTicks", (char *)NULL, offsetof(Axis, t2Ptr), TK_CONFIG_NULL_OK | ALL_GRAPHS, &minorTicksOption},
    {TK_CONFIG_RELIEF, "-relief", "relief", "Relief", DEF_AXIS_RELIEF, offsetof(Axis, relief), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_DOUBLE, "-rotate", "rotate", "Rotate", DEF_AXIS_ROTATE, offsetof(Axis, tickTextStyle.theta), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_STRING, "-scrollcommand", "scrollCommand", "ScrollCommand", (char *)NULL, offsetof(Axis, scrollCmdPrefix), ALL_GRAPHS | TK_CONFIG_NULL_OK},
    {TK_CONFIG_CUSTOM, "-scrollincrement", "scrollIncrement", "ScrollIncrement", DEF_AXIS_SCROLL_INCREMENT, offsetof(Axis, scrollUnits), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT, &rbcPositiveDistanceOption},
    {TK_CONFIG_CUSTOM, "-scrollmax", "scrollMax", "ScrollMax", (char *)NULL, offsetof(Axis, scrollMax), TK_CONFIG_NULL_OK | ALL_GRAPHS, &limitOption},
    {TK_CONFIG_CUSTOM, "-scrollmin", "scrollMin", "ScrollMin", (char *)NULL, offsetof(Axis, scrollMin), TK_CONFIG_NULL_OK | ALL_GRAPHS, &limitOption},
    {TK_CONFIG_DOUBLE, "-shiftby", "shiftBy", "ShiftBy", DEF_AXIS_SHIFTBY, offsetof(Axis, shiftBy), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_BOOLEAN, "-showticks", "showTicks", "ShowTicks", DEF_AXIS_SHOWTICKS, offsetof(Axis, showTicks), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_DOUBLE, "-stepsize", "stepSize", "StepSize", DEF_AXIS_STEP, offsetof(Axis, reqStep), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_DOUBLE, "-tickdivider", "tickDivider", "TickDivider", DEF_AXIS_STEP, offsetof(Axis, tickZoom), ALL_GRAPHS | TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_INT, "-subdivisions", "subdivisions", "Subdivisions", DEF_AXIS_SUBDIVISIONS, offsetof(Axis, reqNumMinorTicks), ALL_GRAPHS},
    {TK_CONFIG_FONT, "-tickfont", "tickFont", "Font", DEF_AXIS_TICK_FONT, offsetof(Axis, tickTextStyle.font), ALL_GRAPHS},
    {TK_CONFIG_PIXELS, "-ticklength", "tickLength", "TickLength", DEF_AXIS_TICK_LENGTH, offsetof(Axis, tickLength), ALL_GRAPHS},
    {TK_CONFIG_CUSTOM, "-tickshadow", "tickShadow", "Shadow", (char *)NULL, offsetof(Axis, tickTextStyle.shadow), TK_CONFIG_COLOR_ONLY | ALL_GRAPHS, &rbcShadowOption},
    {TK_CONFIG_CUSTOM, "-tickshadow", "tickShadow", "Shadow", (char *)NULL, offsetof(Axis, tickTextStyle.shadow), TK_CONFIG_MONO_ONLY | ALL_GRAPHS, &rbcShadowOption},
    {TK_CONFIG_STRING, "-title", "title", "Title", (char *)NULL, offsetof(Axis, title), TK_CONFIG_DONT_SET_DEFAULT | TK_CONFIG_NULL_OK | ALL_GRAPHS},
    {TK_CONFIG_BOOLEAN, "-titlealternate", "titleAlternate", "TitleAlternate", DEF_AXIS_TITLE_ALTERNATE, offsetof(Axis, titleAlternate), TK_CONFIG_DONT_SET_DEFAULT | ALL_GRAPHS},
    {TK_CONFIG_COLOR, "-titlecolor", "titleColor", "Color", DEF_AXIS_FOREGROUND, offsetof(Axis, titleTextStyle.color), TK_CONFIG_COLOR_ONLY | ALL_GRAPHS},
    {TK_CONFIG_COLOR, "-titlecolor", "titleColor", "TitleColor", DEF_AXIS_FG_MONO, offsetof(Axis, titleTextStyle.color), TK_CONFIG_MONO_ONLY | ALL_GRAPHS},
    {TK_CONFIG_FONT, "-titlefont", "titleFont", "Font", DEF_AXIS_TITLE_FONT, offsetof(Axis, titleTextStyle.font), ALL_GRAPHS},
    {TK_CONFIG_CUSTOM, "-titleshadow", "titleShadow", "Shadow", (char *)NULL, offsetof(Axis, titleTextStyle.shadow), TK_CONFIG_COLOR_ONLY | ALL_GRAPHS, &rbcShadowOption},
    {TK_CONFIG_CUSTOM, "-titleshadow", "titleShadow", "Shadow", (char *)NULL, offsetof(Axis, titleTextStyle.shadow), TK_CONFIG_MONO_ONLY | ALL_GRAPHS, &rbcShadowOption},
    {TK_CONFIG_END, NULL, NULL, NULL, NULL, 0, 0}
};

/* Rotation for each axis title */
static double titleRotate[4] = {
    0.0, 90.0, 0.0, 270.0
};

/* Forward declarations */
static int Round (register double x);
static void SetAxisRange (AxisRange *rangePtr, double min, double max);
static int InRange (register double x, AxisRange *rangePtr);
static int AxisIsHorizontal (Graph *graphPtr, Axis *axisPtr);
static void FreeLabels (Rbc_Chain *chainPtr);
static TickLabel *MakeLabel (Graph *graphPtr, Axis *axisPtr, double value);
static void GetDataLimits (Axis *axisPtr, double min, double max);
static void FixAxisRange (Axis *axisPtr);
static double NiceNum (double x, int round);
static Ticks *GenerateTicks (TickSweep *sweepPtr);
static void LogScaleAxis (Axis *axisPtr, double min, double max);
static void LinearScaleAxis (Axis *axisPtr, double min, double max);
static void SweepTicks (Axis *axisPtr);
static void ResetTextStyles (Graph *graphPtr, Axis *axisPtr);
static void DestroyAxis (Graph *graphPtr, Axis *axisPtr);
static void AxisOffsets (Graph *graphPtr, Axis *axisPtr, int margin, int axisOffset, AxisInfo *infoPtr);
static void MakeAxisLine (Graph *graphPtr, Axis *axisPtr, int line, Segment2D *segPtr);
static void MakeTick (Graph *graphPtr, Axis *axisPtr, double value, int tick, int line, Segment2D *segPtr);
static void MapAxis (Graph *graphPtr, Axis *axisPtr, int offset, int margin);
static double AdjustViewport (double offset, double windowSize);
static int GetAxisScrollInfo (Tcl_Interp *interp, int objc, Tcl_Obj *const objv[], double *offsetPtr, double windowSize, double scrollUnits);
static void DrawAxis (Graph *graphPtr, Drawable drawable, Axis *axisPtr);
static void AxisToPostScript (PsToken psToken, Axis *axisPtr);
static void MakeGridLine (Graph *graphPtr, Axis *axisPtr, double value, Segment2D *segPtr);
static void GetAxisGeometry (Graph *graphPtr, Axis *axisPtr);
static int GetMarginGeometry (Graph *graphPtr, Margin *marginPtr);
static void ComputeMargins (Graph *graphPtr);
static Axis *CreateAxis (Graph *graphPtr, char *name, int margin);
static int ConfigureAxis (Graph *graphPtr, Axis *axisPtr);
static int NameToAxis (Graph *graphPtr, const char *name, Axis **axisPtrPtr);
static int GetAxis (Graph *graphPtr, const char *name, Rbc_Uid classUid, Axis **axisPtrPtr);
static void FreeAxis (Graph *graphPtr, Axis *axisPtr);

typedef int (RbcGrAxisOp) (Graph *, Axis *, int, int, Tcl_Obj *const []);
static RbcGrAxisOp BindOp;
static RbcGrAxisOp CgetOp;
static RbcGrAxisOp ConfigureOp;
static RbcGrAxisOp InvTransformOp;
static RbcGrAxisOp LimitsOp;
static RbcGrAxisOp TransformOp;
static RbcGrAxisOp UseOp;

typedef int (RbcGrAxisVirtualOp) (Graph *, int, Tcl_Obj *const []);
static RbcGrAxisVirtualOp BindVirtualOp;
static RbcGrAxisVirtualOp CgetVirtualOp;
static RbcGrAxisVirtualOp ConfigureVirtualOp;
static RbcGrAxisVirtualOp CreateVirtualOp;
static RbcGrAxisVirtualOp DeleteVirtualOp;
static RbcGrAxisVirtualOp GetOp;
static RbcGrAxisVirtualOp InvTransformVirtualOp;
static RbcGrAxisVirtualOp LimitsVirtualOp;
static RbcGrAxisVirtualOp NamesVirtualOp;
static RbcGrAxisVirtualOp TransformVirtualOp;
static RbcGrAxisVirtualOp ViewOp;

/*
 *----------------------------------------------------------------------
 *
 * Round --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
Round(x)
    register double x;
{
    return (int) (x + ((x < 0.0) ? -0.5 : 0.5));
}

/*
 *----------------------------------------------------------------------
 *
 * SetAxisRange --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
SetAxisRange(rangePtr, min, max)
    AxisRange *rangePtr;
    double min, max;
{
    rangePtr->min = min;
    rangePtr->max = max;
    rangePtr->range = max - min;
    if (FABS(rangePtr->range) < DBL_EPSILON) {
	rangePtr->range = 1.0;
    }
    rangePtr->scale = 1.0 / rangePtr->range;
}

/*
 * ----------------------------------------------------------------------
 *
 * InRange --
 *
 *      Determines if a value lies within a given range.
 *
 *      The value is normalized and compared against the interval
 *      [0..1], where 0.0 is the minimum and 1.0 is the maximum.
 *      DBL_EPSILON is the smallest number that can be represented
 *      on the host machine, such that (1.0 + epsilon) != 1.0.
 *
 *      Please note, *max* can't equal *min*.
 *
 * Results:
 *      If the value is within the interval [min..max], 1 is
 *      returned; 0 otherwise.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
InRange(x, rangePtr)
    register double x;
    AxisRange *rangePtr;
{
    if (rangePtr->range < DBL_EPSILON) {
#ifdef notdef
	return (((rangePtr->max - x) >= (FABS(x) * DBL_EPSILON)) &&
		((x - rangePtr->min) >= (FABS(x) * DBL_EPSILON)));
#endif
	return (FABS(rangePtr->max - x) >= DBL_EPSILON);
    } else {
	double norm;

	norm = (x - rangePtr->min) * rangePtr->scale;
	return ((norm >= -DBL_EPSILON) && ((norm - 1.0) < DBL_EPSILON));
    }
}

static int
AxisIsHorizontal(graphPtr, axisPtr)
    Graph *graphPtr;
    Axis *axisPtr;
{
    return ((axisPtr->classUid == rbcYAxisUid) == graphPtr->inverted);
}


/* ----------------------------------------------------------------------
 * Custom option parse and print procedures
 * ----------------------------------------------------------------------
 */

/*
 *----------------------------------------------------------------------
 *
 * StringToAnyAxis --
 *
 *      Converts the name of an axis to a pointer to its axis structure.
 *
 * Results:
 *      The return value is a standard Tcl result.  The axis flags are
 *      written into the widget record.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
StringToAnyAxis(clientData, interp, tkwin, string, widgRec, offset)
    ClientData clientData; /* Class identifier of the type of
			    * axis we are looking for. */
    Tcl_Interp *interp; /* Interpreter to send results back to. */
    Tk_Window tkwin; /* Used to look up pointer to graph. */
    const char *string; /* String representing new value. */
    char *widgRec; /* Pointer to structure record. */
    Tcl_Size offset; /* Offset of field in structure. */
{
    Axis **axisPtrPtr = (Axis **)(widgRec + offset);
    Rbc_Uid classUid = *(Rbc_Uid *)clientData;
    Graph *graphPtr;
    Axis *axisPtr;

    graphPtr = Rbc_GetGraphFromWindowData(tkwin);
    if (*axisPtrPtr != NULL) {
	FreeAxis(graphPtr, *axisPtrPtr);
    }
    if (string[0] == '\0') {
	axisPtr = NULL;
    } else if (GetAxis(graphPtr, string, classUid, &axisPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    *axisPtrPtr = axisPtr;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * StringToAxis --
 *
 *      Converts the name of an axis to a pointer to its axis structure.
 *
 * Results:
 *      The return value is a standard Tcl result.  The axis flags are
 *      written into the widget record.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
StringToAxis(clientData, interp, tkwin, string, widgRec, offset)
    ClientData clientData; /* Class identifier of the type of
			    * axis we are looking for. */
    Tcl_Interp *interp; /* Interpreter to send results back to. */
    Tk_Window tkwin; /* Used to look up pointer to graph. */
    const char *string; /* String representing new value. */
    char *widgRec; /* Pointer to structure record. */
    Tcl_Size offset; /* Offset of field in structure. */
{
    Axis **axisPtrPtr = (Axis **)(widgRec + offset);
    Rbc_Uid classUid = *(Rbc_Uid *)clientData;
    Graph *graphPtr;

    graphPtr = Rbc_GetGraphFromWindowData(tkwin);
    if (*axisPtrPtr != NULL) {
	FreeAxis(graphPtr, *axisPtrPtr);
    }
    if (GetAxis(graphPtr, string, classUid, axisPtrPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * AxisToString --
 *
 *      Convert the window coordinates into a string.
 *
 * Results:
 *      The string representing the coordinate position is returned.
 *
 * Side Effects:
 *      TODO: Side Effects
 *----------------------------------------------------------------------
 */
static const char *
AxisToString(clientData, tkwin, widgRec, offset, freeProcPtr)
    ClientData clientData; /* Not used. */
    Tk_Window tkwin; /* Not used. */
    char *widgRec; /* Pointer to structure record .*/
    Tcl_Size offset; /* Offset of field in structure. */
    Tcl_FreeProc **freeProcPtr; /* Not used. */
{
    Axis *axisPtr = *(Axis **)(widgRec + offset);

    if (axisPtr == NULL) {
	return "";
    }
    return axisPtr->name;
}

/*
 *----------------------------------------------------------------------
 *
 * StringToFormat --
 *
 *      Convert the name of virtual axis to an pointer.
 *
 * Results:
 *      The return value is a standard Tcl result.  The axis flags are
 *      written into the widget record.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
StringToFormat(clientData, interp, tkwin, string, widgRec, offset)
    ClientData clientData; /* Not used. */
    Tcl_Interp *interp; /* Interpreter to send results back to. */
    Tk_Window tkwin; /* Used to look up pointer to graph */
    const char *string; /* String representing new value. */
    char *widgRec; /* Pointer to structure record. */
    Tcl_Size offset; /* Offset of field in structure. */
{
    Axis *axisPtr = (Axis *)(widgRec);
    char **argv;
    Tcl_Size argc;

    if (axisPtr->limitsFormats != NULL) {
	ckfree((char *)axisPtr->limitsFormats);
    }
    axisPtr->limitsFormats = NULL;
    axisPtr->nFormats = 0;

    if ((string == NULL) || (*string == '\0')) {
	return TCL_OK;
    }
    if (Tcl_SplitList(interp, string, &argc, (const char ***)&argv) != TCL_OK) {
	return TCL_ERROR;
    }
    if (argc > 2) {
	Tcl_AppendResult(interp, "too many elements in limits format list \"",
			 string, "\"", (char *)NULL);
	ckfree((char *)argv);
	return TCL_ERROR;
    }
    axisPtr->limitsFormats = argv;
    axisPtr->nFormats = argc;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * FormatToString --
 *
 *      Convert the window coordinates into a string.
 *
 * Results:
 *      The string representing the coordinate position is returned.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static const char *
FormatToString(clientData, tkwin, widgRec, offset, freeProcPtr)
    ClientData clientData; /* Not used. */
    Tk_Window tkwin; /* Not used. */
    char *widgRec; /* Widget record */
    Tcl_Size offset; /* offset of limits field */
    Tcl_FreeProc **freeProcPtr; /* Not used. */
{
    Axis *axisPtr = (Axis *)(widgRec);

    if (axisPtr->nFormats == 0) {
	return "";
    }
    *freeProcPtr = (Tcl_FreeProc *)Tcl_Free;
    return Tcl_Merge(axisPtr->nFormats, (const char *const *)axisPtr->limitsFormats);
}

/*
 * ----------------------------------------------------------------------
 *
 * StringToLimit --
 *
 *      Convert the string representation of an axis limit into its numeric
 *      form.
 *
 * Results:
 *      The return value is a standard Tcl result.  The symbol type is
 *      written into the widget record.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
StringToLimit(clientData, interp, tkwin, string, widgRec, offset)
    ClientData clientData; /* Either AXIS_CONFIG_MIN or AXIS_CONFIG_MAX.
			    * Indicates which axis limit to set. */
    Tcl_Interp *interp; /* Interpreter to send results back to */
    Tk_Window tkwin; /* Not used. */
    const char *string; /* String representing new value. */
    char *widgRec; /* Pointer to structure record. */
    Tcl_Size offset; /* Offset of field in structure. */
{
    double *limitPtr = (double *)(widgRec + offset);

    if ((string == NULL) || (*string == '\0')) {
	*limitPtr = VALUE_UNDEFINED;
    } else if (Tcl_ExprDouble(interp, string, limitPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 * ----------------------------------------------------------------------
 *
 * LimitToString --
 *
 *      Convert the floating point axis limits into a string.
 *
 * Results:
 *      The string representation of the limits is returned.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static const char *
LimitToString(clientData, tkwin, widgRec, offset, freeProcPtr)
    ClientData clientData; /* Either LMIN or LMAX */
    Tk_Window tkwin; /* Not used. */
    char *widgRec;
    Tcl_Size offset;
    Tcl_FreeProc **freeProcPtr;
{
    double limit = *(double *)(widgRec + offset);
    char *result;

    result = "";
    if (DEFINED(limit)) {
	char string[TCL_DOUBLE_SPACE + 1];
	Graph *graphPtr;

	graphPtr = Rbc_GetGraphFromWindowData(tkwin);
	Tcl_PrintDouble(graphPtr->interp, limit, string);
	result = RbcStrdup(string);
	if (result == NULL) {
	    return "";
	}
	*freeProcPtr = (Tcl_FreeProc *)Tcl_Free;
    }
    return result;
}

/*
 * ----------------------------------------------------------------------
 *
 * StringToTicks --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
StringToTicks(clientData, interp, tkwin, string, widgRec, offset)
    ClientData clientData; /* Not used. */
    Tcl_Interp *interp; /* Interpreter to send results back to */
    Tk_Window tkwin; /* Not used. */
    const char *string; /* String representing new value. */
    char *widgRec; /* Pointer to structure record. */
    Tcl_Size offset; /* Offset of field in structure. */
{
    unsigned int mask = PTR2UINT(clientData);
    Axis *axisPtr = (Axis *)widgRec;
    Ticks **ticksPtrPtr = (Ticks **) (widgRec + offset);
    int nTicks;
    Ticks *ticksPtr;

    nTicks = 0;
    ticksPtr = NULL;
    if ((string != NULL) && (*string != '\0')) {
	Tcl_Size nExprs;
	const char **exprArr;

	if (Tcl_SplitList(interp, string, &nExprs, &exprArr) != TCL_OK) {
	    return TCL_ERROR;
	}
	if (nExprs > 0) {
	    register int i;
	    int result = TCL_ERROR;
	    double value;

	    ticksPtr = (Ticks *)ckalloc(sizeof(Ticks) + (nExprs * sizeof(double)));
	    assert(ticksPtr);
	    for (i = 0; i < nExprs; i++) {
		result = Tcl_ExprDouble(interp, exprArr[i], &value);
		if (result != TCL_OK) {
		    break;
		}
		ticksPtr->values[i] = value;
	    }
	    ckfree((char *)exprArr);
	    if (result != TCL_OK) {
		ckfree((char *)ticksPtr);
		return TCL_ERROR;
	    }
	    nTicks = nExprs;
	}
    }
    axisPtr->flags &= ~mask;
    if (ticksPtr != NULL) {
	axisPtr->flags |= mask;
	ticksPtr->nTicks = nTicks;
    }
    if (*ticksPtrPtr != NULL) {
	ckfree((char *)*ticksPtrPtr);
    }
    *ticksPtrPtr = ticksPtr;
    return TCL_OK;
}

/*
 * ----------------------------------------------------------------------
 *
 * TicksToString --
 *
 *      Convert array of tick coordinates to a list.
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static const char *
TicksToString(clientData, tkwin, widgRec, offset, freeProcPtr)
    ClientData clientData; /* Not used. */
    Tk_Window tkwin; /* Not used. */
    char *widgRec;
    Tcl_Size offset;
    Tcl_FreeProc **freeProcPtr;
{
    Ticks *ticksPtr = *(Ticks **) (widgRec + offset);
    char string[TCL_DOUBLE_SPACE + 1];
    register int i;
    char *result;
    Tcl_DString dString;
    Graph *graphPtr;

    if (ticksPtr == NULL) {
	return "";
    }
    Tcl_DStringInit(&dString);
    graphPtr = Rbc_GetGraphFromWindowData(tkwin);
    for (i = 0; i < ticksPtr->nTicks; i++) {
	Tcl_PrintDouble(graphPtr->interp, ticksPtr->values[i], string);
	Tcl_DStringAppendElement(&dString, string);
    }
    *freeProcPtr = (Tcl_FreeProc *)Tcl_Free;
    result = RbcStrdup(Tcl_DStringValue(&dString));
    Tcl_DStringFree(&dString);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * StringToLoose --
 *
 *      Convert a string to one of three values.
 *      	0 - false, no, off
 *      	1 - true, yes, on
 *      	2 - always
 *
 * Results:
 *      If the string is successfully converted, TCL_OK is returned.
 *      Otherwise, TCL_ERROR is returned and an error message is left in
 *      interpreter's result field.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
StringToLoose(clientData, interp, tkwin, string, widgRec, offset)
    ClientData clientData; /* Not used. */
    Tcl_Interp *interp; /* Interpreter to send results back to */
    Tk_Window tkwin; /* Not used. */
    const char *string; /* String representing new value. */
    char *widgRec; /* Pointer to structure record. */
    Tcl_Size offset; /* Offset of field in structure. */
{
    Axis *axisPtr = (Axis *)(widgRec);
    register int i;
    Tcl_Size argc;
    const char **argv;
    int values[2];

    if (Tcl_SplitList(interp, string, &argc, &argv) != TCL_OK) {
	return TCL_ERROR;
    }
    if ((argc < 1) || (argc > 2)) {
	Tcl_AppendResult(interp, "wrong # elements in loose value \"",
			 string, "\"", (char *)NULL);
	return TCL_ERROR;
    }
    for (i = 0; i < argc; i++) {
	if ((argv[i][0] == 'a') && (strcmp(argv[i], "always") == 0)) {
	    values[i] = TICK_RANGE_ALWAYS_LOOSE;
	} else {
	    int boolVal;

	    if (Tcl_GetBoolean(interp, argv[i], &boolVal) != TCL_OK) {
		ckfree((char *)argv);
		return TCL_ERROR;
	    }
	    values[i] = boolVal;
	}
    }
    axisPtr->looseMin = axisPtr->looseMax = values[0];
    if (argc > 1) {
	axisPtr->looseMax = values[1];
    }
    ckfree((char *)argv);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * LooseToString --
 *
 *      TODO: Description
 *
 * Results:
 *      The string representation of the auto boolean is returned.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static const char *
LooseToString(clientData, tkwin, widgRec, offset, freeProcPtr)
    ClientData clientData; /* Not used. */
    Tk_Window tkwin; /* Not used. */
    char *widgRec; /* Widget record */
    Tcl_Size offset; /* offset of flags field in record */
    Tcl_FreeProc **freeProcPtr; /* Memory deallocation scheme to use */
{
    Axis *axisPtr = (Axis *)widgRec;
    Tcl_DString dString;
    char *result;

    Tcl_DStringInit(&dString);
    if (axisPtr->looseMin == TICK_RANGE_TIGHT) {
	Tcl_DStringAppendElement(&dString, "0");
    } else if (axisPtr->looseMin == TICK_RANGE_LOOSE) {
	Tcl_DStringAppendElement(&dString, "1");
    } else if (axisPtr->looseMin == TICK_RANGE_ALWAYS_LOOSE) {
	Tcl_DStringAppendElement(&dString, "always");
    }
    if (axisPtr->looseMin != axisPtr->looseMax) {
	if (axisPtr->looseMax == TICK_RANGE_TIGHT) {
	    Tcl_DStringAppendElement(&dString, "0");
	} else if (axisPtr->looseMax == TICK_RANGE_LOOSE) {
	    Tcl_DStringAppendElement(&dString, "1");
	} else if (axisPtr->looseMax == TICK_RANGE_ALWAYS_LOOSE) {
	    Tcl_DStringAppendElement(&dString, "always");
	}
    }
    result = RbcStrdup(Tcl_DStringValue(&dString));
    Tcl_DStringFree(&dString);
    *freeProcPtr = (Tcl_FreeProc *)Tcl_Free;
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * FreeLabels --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
FreeLabels(chainPtr)
    Rbc_Chain *chainPtr;
{
    Rbc_ChainLink *linkPtr;
    TickLabel *labelPtr;

    for (linkPtr = Rbc_ChainFirstLink(chainPtr); linkPtr != NULL;
	    linkPtr = Rbc_ChainNextLink(linkPtr)) {
	labelPtr = Rbc_ChainGetValue(linkPtr);
	ckfree((char *)labelPtr);
    }
    Rbc_ChainReset(chainPtr);
}

/*
 * ----------------------------------------------------------------------
 *
 * MakeLabel --
 *
 *      Converts a floating point tick value to a string to be used as its
 *      label.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Returns a new label in the string character buffer.  The formatted
 *      tick label will be displayed on the graph.
 *
 * ----------------------------------------------------------------------
 */
static TickLabel *
MakeLabel(graphPtr, axisPtr, value)
    Graph *graphPtr;
    Axis *axisPtr; /* Axis structure */
    double value; /* Value to be convert to a decimal string */
{
    char string[TICK_LABEL_SIZE + 1];
    TickLabel *labelPtr;

    /* Generate a default tick label based upon the tick value.  */
    if (axisPtr->logScale) {
	sprintf(string, "1E%d", ROUND(value));
    } else {
	sprintf(string, "%.*g", NUMDIGITS, value);
    }

    if (axisPtr->formatCmd != NULL) {
	Tcl_Interp *interp = graphPtr->interp;
	Tk_Window tkwin = graphPtr->tkwin;

	/*
	 * A Tcl proc was designated to format tick labels. Append the path
	 * name of the widget and the default tick label as arguments when
	 * invoking it. Copy and save the new label from the interpreter
	 * result.
	 */
	Tcl_ResetResult(interp);
	if (Tcl_VarEval(interp, axisPtr->formatCmd, " ", Tk_PathName(tkwin),
			" ", string, (char *)NULL) != TCL_OK) {
	    Tcl_BackgroundError(interp);
	} else {
	    /*
	     * The proc could return a string of any length, so arbitrarily
	     * limit it to what will fit in the return string.
	     */
	    strncpy(string, Tcl_GetStringResult(interp), TICK_LABEL_SIZE);
	    string[TICK_LABEL_SIZE] = '\0';

	    Tcl_ResetResult(interp); /* Clear the interpreter's result. */
	}
    }
    labelPtr = (TickLabel *)ckalloc(sizeof(TickLabel) + strlen(string));
    assert(labelPtr);
    strcpy(labelPtr->string, string);
    labelPtr->anchorPos.x = labelPtr->anchorPos.y = DBL_MAX;
    return labelPtr;
}

/*
 * ----------------------------------------------------------------------
 *
 * Rbc_InvHMap --
 *
 *      Maps the given screen coordinate back to a graph coordinate.
 *      Called by the graph locater routine.
 *
 * Results:
 *      Returns the graph coordinate value at the given window
 *      y-coordinate.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
double
Rbc_InvHMap(graphPtr, axisPtr, x)
    Graph *graphPtr;
    Axis *axisPtr;
    double x;
{
    double value;

    x = (double)(x - graphPtr->hOffset) * graphPtr->hScale;
    if (axisPtr->descending) {
	x = 1.0 - x;
    }
    value = (x * axisPtr->axisRange.range) + axisPtr->axisRange.min;
    if (axisPtr->logScale) {
	value = EXP10(value);
    }
    return value;
}

/*
 * ----------------------------------------------------------------------
 *
 * Rbc_InvVMap --
 *
 *      Maps the given window y-coordinate back to a graph coordinate
 *      value. Called by the graph locater routine.
 *
 * Results:
 *      Returns the graph coordinate value at the given window
 *      y-coordinate.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
double
Rbc_InvVMap(graphPtr, axisPtr, y)
    Graph *graphPtr;
    Axis *axisPtr;
    double y;
{
    double value;

    y = (double)(y - graphPtr->vOffset) * graphPtr->vScale;
    if (axisPtr->descending) {
	y = 1.0 - y;
    }
    value = ((1.0 - y) * axisPtr->axisRange.range) + axisPtr->axisRange.min;
    if (axisPtr->logScale) {
	value = EXP10(value);
    }
    return value;
}

/*
 * ----------------------------------------------------------------------
 *
 * Rbc_HMap --
 *
 *      Map the given graph coordinate value to its axis, returning a window
 *      position.
 *
 * Results:
 *      Returns a double precision number representing the window coordinate
 *      position on the given axis.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
double
Rbc_HMap(graphPtr, axisPtr, x)
    Graph *graphPtr;
    Axis *axisPtr;
    double x;
{
    if ((axisPtr->logScale) && (x != 0.0)) {
	x = log10(FABS(x));
    }
    /* Map graph coordinate to normalized coordinates [0..1] */
    x = (x - axisPtr->axisRange.min) * axisPtr->axisRange.scale;
    if (axisPtr->descending) {
	x = 1.0 - x;
    }
    return (x * graphPtr->hRange + graphPtr->hOffset);
}

/*
 * ----------------------------------------------------------------------
 *
 * Rbc_VMap --
 *
 *      Map the given graph coordinate value to its axis, returning a window
 *      position.
 *
 * Results:
 *      Returns a double precision number representing the window coordinate
 *      position on the given axis.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
double
Rbc_VMap(graphPtr, axisPtr, y)
    Graph *graphPtr;
    Axis *axisPtr;
    double y;
{
    if ((axisPtr->logScale) && (y != 0.0)) {
	y = log10(FABS(y));
    }
    /* Map graph coordinate to normalized coordinates [0..1] */
    y = (y - axisPtr->axisRange.min) * axisPtr->axisRange.scale;
    if (axisPtr->descending) {
	y = 1.0 - y;
    }
    return (((1.0 - y) * graphPtr->vRange) + graphPtr->vOffset);
}

/*
 * ----------------------------------------------------------------------
 *
 * Rbc_Map2D --
 *
 *      Maps the given graph x,y coordinate values to a window position.
 *
 * Results:
 *      Returns a XPoint structure containing the window coordinates of
 *      the given graph x,y coordinate.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
Point2D
Rbc_Map2D(graphPtr, x, y, axesPtr)
    Graph *graphPtr;
    double x, y; /* Graph x and y coordinates */
    Axis2D *axesPtr; /* Specifies which axes to use */
{
    Point2D point;

    if (graphPtr->inverted) {
	point.x = Rbc_HMap(graphPtr, axesPtr->y, y);
	point.y = Rbc_VMap(graphPtr, axesPtr->x, x);
    } else {
	point.x = Rbc_HMap(graphPtr, axesPtr->x, x);
	point.y = Rbc_VMap(graphPtr, axesPtr->y, y);
    }
    return point;
}

/*
 * ----------------------------------------------------------------------
 *
 * Rbc_InvMap2D --
 *
 *      Maps the given window x,y coordinates to graph values.
 *
 * Results:
 *      Returns a structure containing the graph coordinates of
 *      the given window x,y coordinate.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
Point2D
Rbc_InvMap2D(graphPtr, x, y, axesPtr)
    Graph *graphPtr;
    double x, y; /* Window x and y coordinates */
    Axis2D *axesPtr; /* Specifies which axes to use */
{
    Point2D point;

    if (graphPtr->inverted) {
	point.x = Rbc_InvVMap(graphPtr, axesPtr->x, y);
	point.y = Rbc_InvHMap(graphPtr, axesPtr->y, x);
    } else {
	point.x = Rbc_InvHMap(graphPtr, axesPtr->x, x);
	point.y = Rbc_InvVMap(graphPtr, axesPtr->y, y);
    }
    return point;
}

/*
 *----------------------------------------------------------------------
 *
 * GetDataLimits --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
GetDataLimits(axisPtr, min, max)
    Axis *axisPtr;
    double min, max;
{
    if (axisPtr->valueRange.min > min) {
	axisPtr->valueRange.min = min;
    }
    if (axisPtr->valueRange.max < max) {
	axisPtr->valueRange.max = max;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * FixAxisRange --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
FixAxisRange(axisPtr)
    Axis *axisPtr;
{
    double min, max;
    /*
     * When auto-scaling, the axis limits are the bounds of the element
     * data.  If no data exists, set arbitrary limits (wrt to log/linear
     * scale).
     */
    min = axisPtr->valueRange.min;
    max = axisPtr->valueRange.max;

    if (min == DBL_MAX) {
	if (DEFINED(axisPtr->reqMin)) {
	    min = axisPtr->reqMin;
	} else {
	    min = (axisPtr->logScale) ? 0.001 : 0.0;
	}
    }
    if (max == -DBL_MAX) {
	if (DEFINED(axisPtr->reqMax)) {
	    max = axisPtr->reqMax;
	} else {
	    max = 1.0;
	}
    }
    if (min >= max) {
	double value;

	/*
	 * There is no range of data (i.e. min is not less than max),
	 * so manufacture one.
	 */
	value = min;
	if (value == 0.0) {
	    min = -0.1, max = 0.1;
	} else {
	    double x;

	    x = FABS(value) * 0.1;
	    min = value - x, max = value + x;
	}
    }
    SetAxisRange(&axisPtr->valueRange, min, max);

    /*
     * The axis limits are either the current data range or overridden
     * by the values selected by the user with the -min or -max
     * options.
     */
    axisPtr->min = min;
    axisPtr->max = max;
    if (DEFINED(axisPtr->reqMin)) {
	axisPtr->min = axisPtr->reqMin;
    }
    if (DEFINED(axisPtr->reqMax)) {
	axisPtr->max = axisPtr->reqMax;
    }

    if (axisPtr->max < axisPtr->min) {

	/*
	 * If the limits still don't make sense, it's because one
	 * limit configuration option (-min or -max) was set and the
	 * other default (based upon the data) is too small or large.
	 * Remedy this by making up a new min or max from the
	 * user-defined limit.
	 */

	if (!DEFINED(axisPtr->reqMin)) {
	    axisPtr->min = axisPtr->max - (FABS(axisPtr->max) * 0.1);
	}
	if (!DEFINED(axisPtr->reqMax)) {
	    axisPtr->max = axisPtr->min + (FABS(axisPtr->max) * 0.1);
	}
    }
    /*
     * If a window size is defined, handle auto ranging by shifting
     * the axis limits.
     */
    if ((axisPtr->windowSize > 0.0) &&
	    (!DEFINED(axisPtr->reqMin)) && (!DEFINED(axisPtr->reqMax))) {
	if (axisPtr->shiftBy < 0.0) {
	    axisPtr->shiftBy = 0.0;
	}
	max = axisPtr->min + axisPtr->windowSize;
	if (axisPtr->max >= max) {
	    if (axisPtr->shiftBy > 0.0) {
		max = UCEIL(axisPtr->max, axisPtr->shiftBy);
	    }
	    axisPtr->min = max - axisPtr->windowSize;
	}
	axisPtr->max = max;
    }
    if ((axisPtr->max != axisPtr->prevMax) ||
	    (axisPtr->min != axisPtr->prevMin)) {
	/* Indicate if the axis limits have changed */
	axisPtr->flags |= AXIS_DIRTY;
	/* and save the previous minimum and maximum values */
	axisPtr->prevMin = axisPtr->min;
	axisPtr->prevMax = axisPtr->max;
    }
}

/*
 * ----------------------------------------------------------------------
 *
 * NiceNum --
 *
 *      Reference: Paul Heckbert, "Nice Numbers for Graph Labels",
 *             Graphics Gems, pp 61-63.
 *
 *      Finds a "nice" number approximately equal to x.
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static double
NiceNum(x, round)
    double x;
    int round; /* If non-zero, round. Otherwise take ceiling
		* of value. */
{
    double expt;		/* Exponent of x */
    double frac;		/* Fractional part of x */
    double nice;		/* Nice, rounded fraction */

    expt = floor(log10(x));
    frac = x / EXP10(expt);	/* between 1 and 10 */
    if (round) {
	if (frac < 1.5) {
	    nice = 1.0;
	} else if (frac < 3.0) {
	    nice = 2.0;
	} else if (frac < 7.0) {
	    nice = 5.0;
	} else {
	    nice = 10.0;
	}
    } else {
	if (frac <= 1.0) {
	    nice = 1.0;
	} else if (frac <= 2.0) {
	    nice = 2.0;
	} else if (frac <= 5.0) {
	    nice = 5.0;
	} else {
	    nice = 10.0;
	}
    }
    return nice * EXP10(expt);
}

/*
 *----------------------------------------------------------------------
 *
 * GenerateTicks --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static Ticks *
GenerateTicks(sweepPtr)
    TickSweep *sweepPtr;
{
    Ticks *ticksPtr;
    register int i;

    ticksPtr = (Ticks *)ckalloc(sizeof(Ticks) + (sweepPtr->nSteps * sizeof(double)));
    assert(ticksPtr);

    if (sweepPtr->step == 0.0) {
	static double logTable[] = { /* Precomputed log10 values [1..10] */
	    0.0,
	    0.301029995663981, 0.477121254719662,
	    0.602059991327962, 0.698970004336019,
	    0.778151250383644, 0.845098040014257,
	    0.903089986991944, 0.954242509439325,
	    1.0
	};
	/* Hack: A zero step indicates to use log values. */
	for (i = 0; i < sweepPtr->nSteps; i++) {
	    ticksPtr->values[i] = logTable[i];
	}
    } else {
	double value;

	value = sweepPtr->initial; /* Start from smallest axis tick */
	for (i = 0; i < sweepPtr->nSteps; i++) {
	    value = UROUND(value, sweepPtr->step);
	    ticksPtr->values[i] = value;
	    value += sweepPtr->step;
	}
    }
    ticksPtr->nTicks = sweepPtr->nSteps;
    return ticksPtr;
}

/*
 * ----------------------------------------------------------------------
 *
 * LogScaleAxis --
 *
 *      Determine the range and units of a log scaled axis.
 *
 *      Unless the axis limits are specified, the axis is scaled
 *      automatically, where the smallest and largest major ticks encompass
 *      the range of actual data values.  When an axis limit is specified,
 *      that value represents the smallest(min)/largest(max) value in the
 *      displayed range of values.
 *
 *      Both manual and automatic scaling are affected by the step used.  By
 *      default, the step is the largest power of ten to divide the range in
 *      more than one piece.
 *
 *      Automatic scaling:
 *      Find the smallest number of units which contain the range of values.
 *      The minimum and maximum major tick values will be represent the
 *      range of values for the axis. This greatest number of major ticks
 *      possible is 10.
 *
 *      Manual scaling:
 *          Make the minimum and maximum data values the represent the range of
 *          the values for the axis.  The minimum and maximum major ticks will be
 *          inclusive of this range.  This provides the largest area for plotting
 *          and the expected results when the axis min and max values have be set
 *          by the user (.e.g zooming).  The maximum number of major ticks is 20.
 *
 *          For log scale, there's the possibility that the minimum and
 *          maximum data values are the same magnitude.  To represent the
 *          points properly, at least one full decade should be shown.
 *          However, if you zoom a log scale plot, the results should be
 *          predictable. Therefore, in that case, show only minor ticks.
 *          Lastly, there should be an appropriate way to handle numbers
 *          <=0.
 *
 *              maxY
 *                |    units = magnitude (of least significant digit)
 *                |    high  = largest unit tick < max axis value
 *          high _|    low   = smallest unit tick > min axis value
 *                |
 *                |    range = high - low
 *                |    # ticks = greatest factor of range/units
 *               _|
 *            U   |
 *            n   |
 *            i   |
 *            t  _|
 *                |
 *                |
 *                |
 *           low _|
 *                |
 *                |_minX________________maxX__
 *                |   |       |      |       |
 *         minY  low                        high
 *               minY
 *
 *
 *      numTicks = Number of ticks
 *      min = Minimum value of axis
 *      max = Maximum value of axis
 *      range    = Range of values (max - min)
 *
 *      If the number of decades is greater than ten, it is assumed
 *      that the full set of log-style ticks can't be drawn properly.
 *
 * Results:
 *      None
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ---------------------------------------------------------------------- */
static void
LogScaleAxis(axisPtr, min, max)
    Axis *axisPtr;
    double min, max;
{
    double range;
    double tickMin, tickMax;
    double majorStep, minorStep;
    int nMajor, nMinor;

    min = (min != 0.0) ? log10(FABS(min)) : 0.0;
    max = (max != 0.0) ? log10(FABS(max)) : 1.0;

    tickMin = floor(min);
    tickMax = ceil(max);
    range = tickMax - tickMin;

    if (range > 10) {
	/* There are too many decades to display a major tick at every
	 * decade.  Instead, treat the axis as a linear scale.  */
	range = NiceNum(range, 0);
	majorStep = NiceNum(range / DEF_NUM_TICKS, 1);
	tickMin = UFLOOR(tickMin, majorStep);
	tickMax = UCEIL(tickMax, majorStep);
	nMajor = (int)((tickMax - tickMin) / majorStep) + 1;
	minorStep = EXP10(floor(log10(majorStep)));
	if (minorStep == majorStep) {
	    nMinor = 4, minorStep = 0.2;
	} else {
	    nMinor = Round(majorStep / minorStep) - 1;
	}
    } else {
	if (tickMin == tickMax) {
	    tickMax++;
	}
	majorStep = 1.0;
	nMajor = (int)(tickMax - tickMin + 1); /* FIXME: Check this. */

	minorStep = 0.0;	/* This is a special hack to pass
				 * information to the GenerateTicks
				 * routine. An interval of 0.0 tells
				 *	1) this is a minor sweep and
				 *	2) the axis is log scale.
				 */
	nMinor = 10;
    }
    if ((axisPtr->looseMin == TICK_RANGE_TIGHT) ||
	    ((axisPtr->looseMin == TICK_RANGE_LOOSE) &&
	     (DEFINED(axisPtr->reqMin)))) {
	tickMin = min;
	nMajor++;
    }
    if ((axisPtr->looseMax == TICK_RANGE_TIGHT) ||
	    ((axisPtr->looseMax == TICK_RANGE_LOOSE) &&
	     (DEFINED(axisPtr->reqMax)))) {
	tickMax = max;
    }
    axisPtr->majorSweep.step = majorStep;
    axisPtr->majorSweep.initial = floor(tickMin);
    axisPtr->majorSweep.nSteps = nMajor;
    axisPtr->minorSweep.initial = axisPtr->minorSweep.step = minorStep;
    axisPtr->minorSweep.nSteps = nMinor;

    SetAxisRange(&axisPtr->axisRange, tickMin, tickMax);
}

/*
 * ----------------------------------------------------------------------
 *
 * LinearScaleAxis --
 *
 *      Determine the units of a linear scaled axis.
 *
 *      The axis limits are either the range of the data values mapped
 *      to the axis (autoscaled), or the values specified by the -min
 *      and -max options (manual).
 *
 *      If autoscaled, the smallest and largest major ticks will
 *      encompass the range of data values.  If the -loose option is
 *      selected, the next outer ticks are choosen.  If tight, the
 *      ticks are at or inside of the data limits are used.
 *
 *      If manually set, the ticks are at or inside the data limits
 *      are used.  This makes sense for zooming.  You want the
 *      selected range to represent the next limit, not something a
 *      bit bigger.
 *
 *      Note: I added an "always" value to the -loose option to force
 *            the manually selected axes to be loose. It's probably
 *            not a good idea.
 *
 *              maxY
 *                |    units = magnitude (of least significant digit)
 *                |    high  = largest unit tick < max axis value
 *          high _|    low   = smallest unit tick > min axis value
 *                |
 *                |    range = high - low
 *                |    # ticks = greatest factor of range/units
 *               _|
 *            U   |
 *            n   |
 *            i   |
 *            t  _|
 *                |
 *                |
 *                |
 *           low _|
 *                |
 *                |_minX________________maxX__
 *                |   |       |      |       |
 *         minY  low                        high
 *               minY
 *
 *      numTicks = Number of ticks
 *      min = Minimum value of axis
 *      max = Maximum value of axis
 *      range    = Range of values (max - min)
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      The axis tick information is set.  The actual tick values will
 *      be generated later.
 *
 * ----------------------------------------------------------------------
 */
static void
LinearScaleAxis(axisPtr, min, max)
    Axis *axisPtr;
    double min, max;
{
    double range, step;
    double tickMin, tickMax;
    double axisMin, axisMax;
    int nTicks;

    range = max - min;

    /* Calculate the major tick stepping. */
    if (axisPtr->reqStep > 0.0) {
	/* An interval was designated by the user.  Keep scaling it
	 * until it fits comfortably within the current range of the
	 * axis.  */
	step = axisPtr->reqStep;
	while ((2 * step) >= range) {
	    step *= 0.5;
	}
    } else {
	range = NiceNum(range, 0);
	step = NiceNum(range / DEF_NUM_TICKS, 1);
    }

    /* Find the outer tick values. Add 0.0 to prevent getting -0.0. */
    axisMin = tickMin = floor(min / step) * step + 0.0;
    axisMax = tickMax = ceil(max / step) * step + 0.0;

    nTicks = Round((tickMax - tickMin) / step) + 1;
    axisPtr->majorSweep.step = step;
    axisPtr->majorSweep.initial = tickMin;
    axisPtr->majorSweep.nSteps = nTicks;

    /*
     * The limits of the axis are either the range of the data
     * ("tight") or at the next outer tick interval ("loose").  The
     * looseness or tightness has to do with how the axis fits the
     * range of data values.  This option is overridden when
     * the user sets an axis limit (by either -min or -max option).
     * The axis limit is always at the selected limit (otherwise we
     * assume that user would have picked a different number).
     */
    if ((axisPtr->looseMin == TICK_RANGE_TIGHT) ||
	    ((axisPtr->looseMin == TICK_RANGE_LOOSE) &&
	     (DEFINED(axisPtr->reqMin)))) {
	axisMin = min;
    }
    if ((axisPtr->looseMax == TICK_RANGE_TIGHT) ||
	    ((axisPtr->looseMax == TICK_RANGE_LOOSE) &&
	     (DEFINED(axisPtr->reqMax)))) {
	axisMax = max;
    }
    SetAxisRange(&axisPtr->axisRange, axisMin, axisMax);

    /* Now calculate the minor tick step and number. */

    if ((axisPtr->reqNumMinorTicks > 0) &&
	    ((axisPtr->flags & AXIS_CONFIG_MAJOR) == 0)) {
	nTicks = axisPtr->reqNumMinorTicks - 1;
	step = 1.0 / (nTicks + 1);
    } else {
	nTicks = 0;		/* No minor ticks. */
	step = 0.5;		/* Don't set the minor tick interval
				 * to 0.0. It makes the GenerateTicks
				 * routine create minor log-scale tick
				 * marks.  */
    }
    axisPtr->minorSweep.initial = axisPtr->minorSweep.step = step;
    axisPtr->minorSweep.nSteps = nTicks;
}

/*
 *----------------------------------------------------------------------
 *
 * SweepTicks --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
SweepTicks(axisPtr)
    Axis *axisPtr;
{
    if ((axisPtr->flags & AXIS_CONFIG_MAJOR) == 0) {
	if (axisPtr->t1Ptr != NULL) {
	    ckfree((char *)axisPtr->t1Ptr);
	}
	axisPtr->t1Ptr = GenerateTicks(&axisPtr->majorSweep);
    }
    if ((axisPtr->flags & AXIS_CONFIG_MINOR) == 0) {
	if (axisPtr->t2Ptr != NULL) {
	    ckfree((char *)axisPtr->t2Ptr);
	}
	axisPtr->t2Ptr = GenerateTicks(&axisPtr->minorSweep);
    }
}

/*
 * ----------------------------------------------------------------------
 *
 * Rbc_ResetAxes --
 *
 *      TODO: Description
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
void
Rbc_ResetAxes(graphPtr)
    Graph *graphPtr;
{
    Rbc_ChainLink *linkPtr;
    Element *elemPtr;
    Axis *axisPtr;
    Tcl_HashEntry *hPtr;
    Tcl_HashSearch cursor;
    Extents2D exts;
    double min, max;

    /* FIXME: This should be called whenever the display list of
     * elements change. Maybe yet another flag INIT_STACKS to
     * indicate that the element display list has changed.
     * Needs to be done before the axis limits are set.
     */
    Rbc_InitFreqTable(graphPtr);
    if ((graphPtr->mode == MODE_STACKED) && (graphPtr->nStacks > 0)) {
	Rbc_ComputeStacks(graphPtr);
    }
    /*
     * Step 1:  Reset all axes. Initialize the data limits of the axis to
     *		impossible values.
     */
    for (hPtr = Tcl_FirstHashEntry(&graphPtr->axes.table, &cursor);
	    hPtr != NULL; hPtr = Tcl_NextHashEntry(&cursor)) {
	axisPtr = (Axis *)Tcl_GetHashValue(hPtr);
	axisPtr->min = axisPtr->valueRange.min = DBL_MAX;
	axisPtr->max = axisPtr->valueRange.max = -DBL_MAX;
    }

    /*
     * Step 2:  For each element that's to be displayed, get the smallest
     *		and largest data values mapped to each X and Y-axis.  This
     *		will be the axis limits if the user doesn't override them
     *		with -min and -max options.
     */
    for (linkPtr = Rbc_ChainFirstLink(graphPtr->elements.displayList);
	    linkPtr != NULL; linkPtr = Rbc_ChainNextLink(linkPtr)) {
	elemPtr = Rbc_ChainGetValue(linkPtr);
	(*elemPtr->procsPtr->extentsProc) (elemPtr, &exts);
	GetDataLimits(elemPtr->axes.x, exts.left, exts.right);
	GetDataLimits(elemPtr->axes.y, exts.top, exts.bottom);
    }
    /*
     * Step 3:  Now that we know the range of data values for each axis,
     *		set axis limits and compute a sweep to generate tick values.
     */
    for (hPtr = Tcl_FirstHashEntry(&graphPtr->axes.table, &cursor);
	    hPtr != NULL; hPtr = Tcl_NextHashEntry(&cursor)) {
	axisPtr = (Axis *)Tcl_GetHashValue(hPtr);
	FixAxisRange(axisPtr);

	/* Calculate min/max tick (major/minor) layouts */
	min = axisPtr->min;
	max = axisPtr->max;
	if ((DEFINED(axisPtr->scrollMin)) && (min < axisPtr->scrollMin)) {
	    min = axisPtr->scrollMin;
	}
	if ((DEFINED(axisPtr->scrollMax)) && (max > axisPtr->scrollMax)) {
	    max = axisPtr->scrollMax;
	}
	if (axisPtr->logScale) {
	    LogScaleAxis(axisPtr, min, max);
	} else {
	    LinearScaleAxis(axisPtr, min, max);
	}

	if ((axisPtr->flags & (AXIS_DIRTY | AXIS_ONSCREEN)) ==
		(AXIS_DIRTY | AXIS_ONSCREEN)) {
	    graphPtr->flags |= REDRAW_BACKING_STORE;
	}
    }

    graphPtr->flags &= ~RESET_AXES;

    /*
     * When any axis changes, we need to layout the entire graph.
     */
    graphPtr->flags |= (GET_AXIS_GEOMETRY | LAYOUT_NEEDED |
			MAP_ALL | REDRAW_WORLD);
}

/*
 * ----------------------------------------------------------------------
 *
 * ResetTextStyles --
 *
 *      Configures axis attributes (font, line width, label, etc) and
 *      allocates a new (possibly shared) graphics context.  Line cap
 *      style is projecting.  This is for the problem of when a tick
 *      sits directly at the end point of the axis.
 *
 * Results:
 *      The return value is a standard Tcl result.
 *
 * Side Effects:
 *      Axis resources are allocated (GC, font). Axis layout is
 *      deferred until the height and width of the window are known.
 *
 * ----------------------------------------------------------------------
 */
static void
ResetTextStyles(graphPtr, axisPtr)
    Graph *graphPtr;
    Axis *axisPtr;
{
    GC newGC;
    XGCValues gcValues;
    unsigned long gcMask;

    Rbc_ResetTextStyle(graphPtr->tkwin, &axisPtr->titleTextStyle);
    Rbc_ResetTextStyle(graphPtr->tkwin, &axisPtr->tickTextStyle);
    Rbc_ResetTextStyle(graphPtr->tkwin, &axisPtr->limitsTextStyle);

    gcMask = (GCForeground | GCLineWidth | GCCapStyle);
    gcValues.foreground = axisPtr->tickTextStyle.color->pixel;
    gcValues.line_width = LineWidth(axisPtr->lineWidth);
    gcValues.cap_style = CapProjecting;

    newGC = Tk_GetGC(graphPtr->tkwin, gcMask, &gcValues);
    if (axisPtr->tickGC != NULL) {
	Tk_FreeGC(graphPtr->display, axisPtr->tickGC);
    }
    axisPtr->tickGC = newGC;
}

/*
 * ----------------------------------------------------------------------
 *
 * DestroyAxis --
 *
 *      TODO: Description
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Resources (font, color, gc, labels, etc.) associated with the
 *      axis are deallocated.
 *
 * ----------------------------------------------------------------------
 */
static void
DestroyAxis(graphPtr, axisPtr)
    Graph *graphPtr;
    Axis *axisPtr;
{
    int flags;

    flags = Rbc_GraphType(graphPtr);
    Tk_FreeOptions(configSpecs, (char *)axisPtr, graphPtr->display, flags);
    if (graphPtr->bindTable != NULL) {
	Rbc_DeleteBindings(graphPtr->bindTable, axisPtr);
    }
    if (axisPtr->linkPtr != NULL) {
	Rbc_ChainDeleteLink(axisPtr->chainPtr, axisPtr->linkPtr);
    }
    if (axisPtr->name != NULL) {
	ckfree((char *)axisPtr->name);
    }
    if (axisPtr->hashPtr != NULL) {
	Tcl_DeleteHashEntry(axisPtr->hashPtr);
    }
    Rbc_FreeTextStyle(graphPtr->display, &axisPtr->titleTextStyle);
    Rbc_FreeTextStyle(graphPtr->display, &axisPtr->limitsTextStyle);
    Rbc_FreeTextStyle(graphPtr->display, &axisPtr->tickTextStyle);

    if (axisPtr->tickGC != NULL) {
	Tk_FreeGC(graphPtr->display, axisPtr->tickGC);
    }
    if (axisPtr->t1Ptr != NULL) {
	ckfree((char *)axisPtr->t1Ptr);
    }
    if (axisPtr->t2Ptr != NULL) {
	ckfree((char *)axisPtr->t2Ptr);
    }
    if (axisPtr->limitsFormats != NULL) {
	ckfree((char *)axisPtr->limitsFormats);
    }
    FreeLabels(axisPtr->tickLabels);
    Rbc_ChainDestroy(axisPtr->tickLabels);
    if (axisPtr->segments != NULL) {
	ckfree((char *)axisPtr->segments);
    }
    if (axisPtr->tags != NULL) {
	ckfree((char *)axisPtr->tags);
    }
    ckfree((char *)axisPtr);
}

/*
 * ----------------------------------------------------------------------
 *
 * AxisOffsets --
 *
 *      Determines the sites of the axis, major and minor ticks,
 *      and title of the axis.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static void
AxisOffsets(graphPtr, axisPtr, margin, axisOffset, infoPtr)
    Graph *graphPtr;
    Axis *axisPtr;
    int margin;
    int axisOffset;
    AxisInfo *infoPtr;
{
    int pad;			/* Offset of axis from interior region. This
				 * includes a possible border and the axis
				 * line width. */
    int p;
    int majorOffset, minorOffset, labelOffset;
    int offset;
    int x, y;

    axisPtr->titleTextStyle.theta = titleRotate[margin];

    majorOffset = minorOffset = 0;
    labelOffset = AXIS_TITLE_PAD;
    if (axisPtr->lineWidth > 0) {
	majorOffset = ABS(axisPtr->tickLength);
	minorOffset = 10 * majorOffset / 15;
	labelOffset = majorOffset + AXIS_TITLE_PAD + axisPtr->lineWidth / 2;
    }
    /* Adjust offset for the interior border width and the line width */
    pad = axisPtr->lineWidth + 1;
    if (graphPtr->plotBorderWidth > 0) {
	pad += graphPtr->plotBorderWidth + 1;
    }
    offset = axisOffset + 1 + pad;
    if ((margin == MARGIN_LEFT) || (margin == MARGIN_TOP)) {
	majorOffset = -majorOffset;
	minorOffset = -minorOffset;
	labelOffset = -labelOffset;
    }
    /*
     * Pre-calculate the x-coordinate positions of the axis, tick labels, and
     * the individual major and minor ticks.
     */
    p = 0;		/* Suppress compiler warning */

    switch (margin) {
	case MARGIN_TOP:
	    p = graphPtr->top - axisOffset - pad;
	    if (axisPtr->titleAlternate) {
		x = graphPtr->right + AXIS_TITLE_PAD;
		y = graphPtr->top - axisOffset - (axisPtr->height  / 2);
		axisPtr->titleTextStyle.anchor = TK_ANCHOR_W;
	    } else {
		x = (graphPtr->right + graphPtr->left) / 2;
		y = graphPtr->top - axisOffset - axisPtr->height - AXIS_TITLE_PAD;
		axisPtr->titleTextStyle.anchor = TK_ANCHOR_N;
	    }
	    axisPtr->tickTextStyle.anchor = TK_ANCHOR_S;
	    offset = axisPtr->borderWidth + axisPtr->lineWidth / 2;
	    axisPtr->region.left = graphPtr->hOffset - offset - 2;
	    axisPtr->region.right = graphPtr->hOffset + graphPtr->hRange +
				    offset - 1;
	    axisPtr->region.top = p + labelOffset - 1;
	    axisPtr->region.bottom = p;
	    axisPtr->titlePos.x = x;
	    axisPtr->titlePos.y = y;
	    break;

	case MARGIN_BOTTOM:
	    p = graphPtr->bottom + axisOffset + pad;
	    if (axisPtr->titleAlternate) {
		x = graphPtr->right + AXIS_TITLE_PAD;
		y = graphPtr->bottom + axisOffset + (axisPtr->height / 2);
		axisPtr->titleTextStyle.anchor = TK_ANCHOR_W;
	    } else {
		x = (graphPtr->right + graphPtr->left) / 2;
		y = graphPtr->bottom + axisOffset + axisPtr->height +
		    AXIS_TITLE_PAD;
		axisPtr->titleTextStyle.anchor = TK_ANCHOR_S;
	    }
	    axisPtr->tickTextStyle.anchor = TK_ANCHOR_N;
	    offset = axisPtr->borderWidth + axisPtr->lineWidth / 2;
	    axisPtr->region.left = graphPtr->hOffset - offset - 2;
	    axisPtr->region.right = graphPtr->hOffset + graphPtr->hRange +
				    offset - 1;

	    axisPtr->region.top = graphPtr->bottom + axisOffset +
				  axisPtr->lineWidth - axisPtr->lineWidth / 2;
	    axisPtr->region.bottom = graphPtr->bottom + axisOffset +
				     axisPtr->lineWidth + labelOffset + 1;
	    axisPtr->titlePos.x = x;
	    axisPtr->titlePos.y = y;
	    break;

	case MARGIN_LEFT:
	    p = graphPtr->left - axisOffset - pad;
	    if (axisPtr->titleAlternate) {
		x = graphPtr->left - axisOffset - (axisPtr->width / 2);
		y = graphPtr->top - AXIS_TITLE_PAD;
		axisPtr->titleTextStyle.anchor = TK_ANCHOR_SW;
	    } else {
		x = graphPtr->left - axisOffset - axisPtr->width -
		    graphPtr->plotBorderWidth;
		y = (graphPtr->bottom + graphPtr->top) / 2;
		axisPtr->titleTextStyle.anchor = TK_ANCHOR_W;
	    }
	    axisPtr->tickTextStyle.anchor = TK_ANCHOR_E;
	    axisPtr->region.left = graphPtr->left - offset + labelOffset - 1;
	    axisPtr->region.right = graphPtr->left - offset + 2;

	    offset = axisPtr->borderWidth + axisPtr->lineWidth / 2;
	    axisPtr->region.top = graphPtr->vOffset - offset - 2;
	    axisPtr->region.bottom = graphPtr->vOffset + graphPtr->vRange +
				     offset - 1;
	    axisPtr->titlePos.x = x;
	    axisPtr->titlePos.y = y;
	    break;

	case MARGIN_RIGHT:
	    p = graphPtr->right + axisOffset + pad;
	    if (axisPtr->titleAlternate) {
		x = graphPtr->right + axisOffset + (axisPtr->width / 2);
		y = graphPtr->top - AXIS_TITLE_PAD;
		axisPtr->titleTextStyle.anchor = TK_ANCHOR_SE;
	    } else {
		x = graphPtr->right + axisOffset + axisPtr->width +
		    AXIS_TITLE_PAD;
		y = (graphPtr->bottom + graphPtr->top) / 2;
		axisPtr->titleTextStyle.anchor = TK_ANCHOR_E;
	    }
	    axisPtr->tickTextStyle.anchor = TK_ANCHOR_W;

	    axisPtr->region.left = graphPtr->right + axisOffset +
				   axisPtr->lineWidth - axisPtr->lineWidth / 2;
	    axisPtr->region.right = graphPtr->right + axisOffset +
				    labelOffset + axisPtr->lineWidth + 1;

	    offset = axisPtr->borderWidth + axisPtr->lineWidth / 2;
	    axisPtr->region.top = graphPtr->vOffset - offset - 2;
	    axisPtr->region.bottom = graphPtr->vOffset + graphPtr->vRange +
				     offset - 1;
	    axisPtr->titlePos.x = x;
	    axisPtr->titlePos.y = y;
	    break;

	case MARGIN_NONE:
	    break;
    }
    infoPtr->axis = p - (axisPtr->lineWidth / 2);
    infoPtr->t1 = p + majorOffset;
    infoPtr->t2 = p + minorOffset;
    infoPtr->label = p + labelOffset;

    if (axisPtr->tickLength < 0) {
	int hold;

	hold = infoPtr->t1;
	infoPtr->t1 = infoPtr->axis;
	infoPtr->axis = hold;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * MakeAxisLine --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
MakeAxisLine(graphPtr, axisPtr, line, segPtr)
    Graph *graphPtr;
    Axis *axisPtr; /* Axis information */
    int line;
    Segment2D *segPtr;
{
    double min, max;

    min = axisPtr->axisRange.min;
    max = axisPtr->axisRange.max;
    if (axisPtr->logScale) {
	min = EXP10(min);
	max = EXP10(max);
    }
    if (AxisIsHorizontal(graphPtr, axisPtr)) {
	segPtr->p.x = Rbc_HMap(graphPtr, axisPtr, min);
	segPtr->q.x = Rbc_HMap(graphPtr, axisPtr, max);
	segPtr->p.y = segPtr->q.y = line;
    } else {
	segPtr->q.x = segPtr->p.x = line;
	segPtr->p.y = Rbc_VMap(graphPtr, axisPtr, min);
	segPtr->q.y = Rbc_VMap(graphPtr, axisPtr, max);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * MakeTick --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
MakeTick(graphPtr, axisPtr, value, tick, line, segPtr)
    Graph *graphPtr;
    Axis *axisPtr;
    double value;
    int tick, line; /* Lengths of tick and axis line. */
    Segment2D *segPtr;
{
    if (axisPtr->logScale) {
	value = EXP10(value);
    }
    if (AxisIsHorizontal(graphPtr, axisPtr)) {
	segPtr->p.x = segPtr->q.x = Rbc_HMap(graphPtr, axisPtr, value);
	segPtr->p.y = line;
	segPtr->q.y = tick;
    } else {
	segPtr->p.x = line;
	segPtr->p.y = segPtr->q.y = Rbc_VMap(graphPtr, axisPtr, value);
	segPtr->q.x = tick;
    }
}

/*
 * -----------------------------------------------------------------
 *
 * MapAxis --
 *
 *      Pre-calculates positions of the axis, ticks, and labels (to be
 *      used later when displaying the axis).  Calculates the values
 *      for each major and minor tick and checks to see if they are in
 *      range (the outer ticks may be outside of the range of plotted
 *      values).
 *
 *      Line segments for the minor and major ticks are saved into one
 *      XSegment array so that they can be drawn by a single
 *      XDrawSegments call. The positions of the tick labels are also
 *      computed and saved.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Line segments and tick labels are saved and used later to draw
 *      the axis.
 *
 * -----------------------------------------------------------------
 */
static void
MapAxis(graphPtr, axisPtr, offset, margin)
    Graph *graphPtr;
    Axis *axisPtr;
    int offset;
    int margin;
{
    int arraySize;
    int nMajorTicks, nMinorTicks;
    AxisInfo info;
    Segment2D *segments;
    Segment2D *segPtr;

    AxisOffsets(graphPtr, axisPtr, margin, offset, &info);

    /* Save all line coordinates in an array of line segments. */

    if (axisPtr->segments != NULL) {
	ckfree((char *)axisPtr->segments);
    }
    nMajorTicks = nMinorTicks = 0;
    if (axisPtr->t1Ptr != NULL) {
	nMajorTicks = axisPtr->t1Ptr->nTicks;
    }
    if (axisPtr->t2Ptr != NULL) {
	nMinorTicks = axisPtr->t2Ptr->nTicks;
    }
    arraySize = 1 + (nMajorTicks * (nMinorTicks + 1));
    segments = (Segment2D *)ckalloc(arraySize * sizeof(Segment2D));
    assert(segments);

    segPtr = segments;
    if (axisPtr->lineWidth > 0) {
	/* Axis baseline */
	MakeAxisLine(graphPtr, axisPtr, info.axis, segPtr);
	segPtr++;
    }
    if (axisPtr->showTicks) {
	double t1, t2;
	double labelPos;
	register int i, j;
	int isHoriz;
	TickLabel *labelPtr;
	Rbc_ChainLink *linkPtr;
	Segment2D seg;

	isHoriz = AxisIsHorizontal(graphPtr, axisPtr);
	for (i = 0; i < axisPtr->t1Ptr->nTicks; i++) {
	    t1 = axisPtr->t1Ptr->values[i];
	    /* Minor ticks */
	    for (j = 0; j < axisPtr->t2Ptr->nTicks; j++) {
		t2 = t1 +
		     (axisPtr->majorSweep.step * axisPtr->t2Ptr->values[j]);
		if (InRange(t2, &axisPtr->axisRange)) {
		    MakeTick(graphPtr, axisPtr, t2, info.t2, info.axis,
			     segPtr);
		    segPtr++;
		}
	    }
	    if (!InRange(t1, &axisPtr->axisRange)) {
		continue;
	    }
	    /* Major tick */
	    MakeTick(graphPtr, axisPtr, t1, info.t1, info.axis, segPtr);
	    segPtr++;
	}

	linkPtr = Rbc_ChainFirstLink(axisPtr->tickLabels);
	labelPos = (double)info.label;

	for (i = 0; i < axisPtr->t1Ptr->nTicks; i++) {
	    t1 = axisPtr->t1Ptr->values[i];
	    if (axisPtr->labelOffset) {
		t1 += axisPtr->majorSweep.step * 0.5;
	    }
	    if (!InRange(t1, &axisPtr->axisRange)) {
		continue;
	    }
	    labelPtr = Rbc_ChainGetValue(linkPtr);
	    linkPtr = Rbc_ChainNextLink(linkPtr);
	    MakeTick(graphPtr, axisPtr, t1, info.t1, info.axis, &seg);
	    /* Save tick label X-Y position. */
	    if (isHoriz) {
		labelPtr->anchorPos.x = seg.p.x;
		labelPtr->anchorPos.y = labelPos;
	    } else {
		labelPtr->anchorPos.x = labelPos;
		labelPtr->anchorPos.y = seg.p.y;
	    }
	}
    }
    if (AxisIsHorizontal(graphPtr, axisPtr)) {
	axisPtr->width = graphPtr->right - graphPtr->left;
    } else {
	axisPtr->height = graphPtr->bottom - graphPtr->top;
    }
    axisPtr->segments = segments;
    axisPtr->nSegments = segPtr - segments;
    assert(axisPtr->nSegments <= arraySize);
}

/*
 *----------------------------------------------------------------------
 *
 * AdjustViewport --
 *
 *      Adjusts the offsets of the viewport according to the scroll mode.
 *      This is to accommodate both "listbox" and "canvas" style scrolling.
 *
 *      "canvas"	The viewport scrolls within the range of world
 *              coordinates.  This way the viewport always displays
 *              a full page of the world.  If the world is smaller
 *              than the viewport, then (bizarrely) the world and
 *              viewport are inverted so that the world moves up
 *              and down within the viewport.
 *
 *      "listbox"	The viewport can scroll beyond the range of world
 *              coordinates.  Every entry can be displayed at the
 *              top of the viewport.  This also means that the
 *              scrollbar thumb weirdly shrinks as the last entry
 *              is scrolled upward.
 *
 * Results:
 *      The corrected offset is returned.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static double
AdjustViewport(offset, windowSize)
    double offset, windowSize;
{
    /*
     * Canvas-style scrolling allows the world to be scrolled
     * within the window.
     */
    if (windowSize > 1.0) {
	if (windowSize < (1.0 - offset)) {
	    offset = 1.0 - windowSize;
	}
	if (offset > 0.0) {
	    offset = 0.0;
	}
    } else {
	if ((offset + windowSize) > 1.0) {
	    offset = 1.0 - windowSize;
	}
	if (offset < 0.0) {
	    offset = 0.0;
	}
    }
    return offset;
}

/*
 *----------------------------------------------------------------------
 *
 * GetAxisScrollInfo --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
GetAxisScrollInfo(
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const objv[],
    double *offsetPtr,
    double windowSize,
    double scrollUnits)
{
    char c;
    const char *s;
    unsigned int length;
    double offset;
    int count;
    double fract;

    offset = *offsetPtr;
    s = Tcl_GetString(objv[0]);
    c = s[0];
    length = strlen(s);
    if ((c == 's') && (strncmp(s, "scroll", length) == 0)) {
	assert(objc == 3);
	/* scroll number unit/page */
	if (Tcl_GetIntFromObj(interp, objv[1], &count) != TCL_OK) {
	    return TCL_ERROR;
	}
	s = Tcl_GetString(objv[2]);
	c = s[0];
	length = strlen(s);
	if ((c == 'u') && (strncmp(s, "units", length) == 0)) {
	    fract = (double)count * scrollUnits;
	} else if ((c == 'p') && (strncmp(s, "pages", length) == 0)) {
	    /* A page is 90% of the view-able window. */
	    fract = (double)count * windowSize * 0.9;
	} else {
	    Tcl_AppendResult(interp, "unknown \"scroll\" units \"", s,
			     "\"", (char *)NULL);
	    return TCL_ERROR;
	}
	offset += fract;
    } else if ((c == 'm') && (strncmp(s, "moveto", length) == 0)) {
	assert(objc == 2);
	/* moveto fraction */
	if (Tcl_GetDoubleFromObj(interp, objv[1], &fract) != TCL_OK) {
	    return TCL_ERROR;
	}
	offset = fract;
    } else {
	/* Treat like "scroll units" */
	if (Tcl_GetInt(interp, s, &count) != TCL_OK) {
	    return TCL_ERROR;
	}
	fract = (double)count * scrollUnits;
	offset += fract;
	/* CHECK THIS: return TCL_OK; */
    }
    *offsetPtr = AdjustViewport(offset, windowSize);
    return TCL_OK;
}

/*
 * -----------------------------------------------------------------
 *
 * DrawAxis --
 *
 *      Draws the axis, ticks, and labels onto the canvas.
 *
 *      Initializes and passes text attribute information through
 *      TextStyle structure.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Axis gets drawn on window.
 *
 * -----------------------------------------------------------------
 */
static void
DrawAxis(graphPtr, drawable, axisPtr)
    Graph *graphPtr;
    Drawable drawable;
    Axis *axisPtr;
{
    if (axisPtr->border != NULL) {
	Rbc_Fill3DRectangle(graphPtr->tkwin, drawable, axisPtr->border,
			    axisPtr->region.left + graphPtr->plotBorderWidth,
			    axisPtr->region.top + graphPtr->plotBorderWidth,
			    axisPtr->region.right - axisPtr->region.left,
			    axisPtr->region.bottom - axisPtr->region.top,
			    axisPtr->borderWidth, axisPtr->relief);
    }
    if (axisPtr->title != NULL) {
	Rbc_DrawText(graphPtr->tkwin, drawable, axisPtr->title,
		     &axisPtr->titleTextStyle, (int)axisPtr->titlePos.x,
		     (int)axisPtr->titlePos.y);
    }
    if (axisPtr->scrollCmdPrefix != NULL) {
	double viewWidth, viewMin, viewMax;
	double worldWidth, worldMin, worldMax;
	double fract;
	int isHoriz;

	worldMin = axisPtr->valueRange.min;
	worldMax = axisPtr->valueRange.max;
	if (DEFINED(axisPtr->scrollMin)) {
	    worldMin = axisPtr->scrollMin;
	}
	if (DEFINED(axisPtr->scrollMax)) {
	    worldMax = axisPtr->scrollMax;
	}
	viewMin = axisPtr->min;
	viewMax = axisPtr->max;
	if (viewMin < worldMin) {
	    viewMin = worldMin;
	}
	if (viewMax > worldMax) {
	    viewMax = worldMax;
	}
	if (axisPtr->logScale) {
	    worldMin = log10(worldMin);
	    worldMax = log10(worldMax);
	    viewMin = log10(viewMin);
	    viewMax = log10(viewMax);
	}
	worldWidth = worldMax - worldMin;
	viewWidth = viewMax - viewMin;
	isHoriz = AxisIsHorizontal(graphPtr, axisPtr);

	if (isHoriz != axisPtr->descending) {
	    fract = (viewMin - worldMin) / worldWidth;
	} else {
	    fract = (worldMax - viewMax) / worldWidth;
	}
	fract = AdjustViewport(fract, viewWidth / worldWidth);

	if (isHoriz != axisPtr->descending) {
	    viewMin = (fract * worldWidth);
	    axisPtr->min = viewMin + worldMin;
	    axisPtr->max = axisPtr->min + viewWidth;
	    viewMax = viewMin + viewWidth;
	    if (axisPtr->logScale) {
		axisPtr->min = EXP10(axisPtr->min);
		axisPtr->max = EXP10(axisPtr->max);
	    }
	    Rbc_UpdateScrollbar(graphPtr->interp, axisPtr->scrollCmdPrefix,
				(viewMin / worldWidth), (viewMax / worldWidth));
	} else {
	    viewMax = (fract * worldWidth);
	    axisPtr->max = worldMax - viewMax;
	    axisPtr->min = axisPtr->max - viewWidth;
	    viewMin = viewMax + viewWidth;
	    if (axisPtr->logScale) {
		axisPtr->min = EXP10(axisPtr->min);
		axisPtr->max = EXP10(axisPtr->max);
	    }
	    Rbc_UpdateScrollbar(graphPtr->interp, axisPtr->scrollCmdPrefix,
				(viewMax / worldWidth), (viewMin / worldWidth));
	}
    }
    if (axisPtr->showTicks) {
	register Rbc_ChainLink *linkPtr;
	TickLabel *labelPtr;

	for (linkPtr = Rbc_ChainFirstLink(axisPtr->tickLabels); linkPtr != NULL;
		linkPtr = Rbc_ChainNextLink(linkPtr)) {
	    /* Draw major tick labels */
	    labelPtr = Rbc_ChainGetValue(linkPtr);
	    Rbc_DrawText(graphPtr->tkwin, drawable, labelPtr->string,
			 &axisPtr->tickTextStyle, (int)labelPtr->anchorPos.x,
			 (int)labelPtr->anchorPos.y);
	}
    }
    if ((axisPtr->nSegments > 0) && (axisPtr->lineWidth > 0)) {
	/* Draw the tick marks and axis line. */
	Rbc_Draw2DSegments(graphPtr->display, drawable, axisPtr->tickGC,
			   axisPtr->segments, axisPtr->nSegments);
    }
}

/*
 * -----------------------------------------------------------------
 *
 * AxisToPostScript --
 *
 *      Generates PostScript output to draw the axis, ticks, and
 *      labels.
 *
 *      Initializes and passes text attribute information through
 *      TextStyle structure.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      PostScript output is left in the graphPtr->interp result;
 *
 * -----------------------------------------------------------------
 */
static void
AxisToPostScript(psToken, axisPtr)
    PsToken psToken;
    Axis *axisPtr;
{
    if (axisPtr->title != NULL) {
	Rbc_TextToPostScript(psToken, axisPtr->title, &axisPtr->titleTextStyle,
			     axisPtr->titlePos.x, axisPtr->titlePos.y);
    }
    if (axisPtr->showTicks) {
	register Rbc_ChainLink *linkPtr;
	TickLabel *labelPtr;

	for (linkPtr = Rbc_ChainFirstLink(axisPtr->tickLabels);
		linkPtr != NULL; linkPtr = Rbc_ChainNextLink(linkPtr)) {
	    labelPtr = Rbc_ChainGetValue(linkPtr);
	    Rbc_TextToPostScript(psToken, labelPtr->string,
				 &axisPtr->tickTextStyle, labelPtr->anchorPos.x,
				 labelPtr->anchorPos.y);
	}
    }
    if ((axisPtr->nSegments > 0) && (axisPtr->lineWidth > 0)) {
	Rbc_LineAttributesToPostScript(psToken, axisPtr->tickTextStyle.color,
				       axisPtr->lineWidth, (Rbc_Dashes *)NULL, CapButt, JoinMiter);
	Rbc_2DSegmentsToPostScript(psToken, axisPtr->segments,
				   axisPtr->nSegments);
    }
}


/*
 *----------------------------------------------------------------------
 *
 * MakeGridLine --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
MakeGridLine(graphPtr, axisPtr, value, segPtr)
    Graph *graphPtr;
    Axis *axisPtr;
    double value;
    Segment2D *segPtr;
{
    if (axisPtr->logScale) {
	value = EXP10(value);
    }
    /* Grid lines run orthogonally to the axis */
    if (AxisIsHorizontal(graphPtr, axisPtr)) {
	segPtr->p.y = graphPtr->top;
	segPtr->q.y = graphPtr->bottom;
	segPtr->p.x = segPtr->q.x = Rbc_HMap(graphPtr, axisPtr, value);
    } else {
	segPtr->p.x = graphPtr->left;
	segPtr->q.x = graphPtr->right;
	segPtr->p.y = segPtr->q.y = Rbc_VMap(graphPtr, axisPtr, value);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_GetAxisSegments --
 *
 *      Assembles the grid lines associated with an axis. Generates
 *      tick positions if necessary (this happens when the axis is
 *      not a logical axis too).
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
void
Rbc_GetAxisSegments(graphPtr, axisPtr, segPtrPtr, nSegmentsPtr)
    Graph *graphPtr;
    Axis *axisPtr;
    Segment2D **segPtrPtr;
    int *nSegmentsPtr;
{
    int needed;
    Ticks *t1Ptr, *t2Ptr;
    register int i;
    double value;
    Segment2D *segments, *segPtr;

    *nSegmentsPtr = 0;
    *segPtrPtr = NULL;
    if (axisPtr == NULL) {
	return;
    }
    t1Ptr = axisPtr->t1Ptr;
    if (t1Ptr == NULL) {
	t1Ptr = GenerateTicks(&axisPtr->majorSweep);
    }
    t2Ptr = axisPtr->t2Ptr;
    if (t2Ptr == NULL) {
	t2Ptr = GenerateTicks(&axisPtr->minorSweep);
    }

    needed = t1Ptr->nTicks;
    if (graphPtr->gridPtr->minorGrid) {
	needed += (t1Ptr->nTicks * t2Ptr->nTicks);
    }
    if (needed == 0) {
	return;
    }
    segments = (Segment2D *)ckalloc(sizeof(Segment2D) * needed);
    if (segments == NULL) {
	return;			/* Can't allocate memory for grid. */
    }

    segPtr = segments;
    for (i = 0; i < t1Ptr->nTicks; i++) {
	value = t1Ptr->values[i];
	if (graphPtr->gridPtr->minorGrid) {
	    register int j;
	    double subValue;

	    for (j = 0; j < t2Ptr->nTicks; j++) {
		subValue = value +
			   (axisPtr->majorSweep.step * t2Ptr->values[j]);
		if (InRange(subValue, &axisPtr->axisRange)) {
		    MakeGridLine(graphPtr, axisPtr, subValue, segPtr);
		    segPtr++;
		}
	    }
	}
	if (InRange(value, &axisPtr->axisRange)) {
	    MakeGridLine(graphPtr, axisPtr, value, segPtr);
	    segPtr++;
	}
    }

    if (t1Ptr != axisPtr->t1Ptr) {
	ckfree((char *)t1Ptr);	/* Free generated ticks. */
    }
    if (t2Ptr != axisPtr->t2Ptr) {
	ckfree((char *)t2Ptr);	/* Free generated ticks. */
    }
    *nSegmentsPtr = segPtr - segments;
    assert(*nSegmentsPtr <= needed);
    *segPtrPtr = segments;
}

/*
 *----------------------------------------------------------------------
 *
 * GetAxisGeometry --
 *
 *      TODO: Description
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
GetAxisGeometry(graphPtr, axisPtr)
    Graph *graphPtr;
    Axis *axisPtr;
{
    int height;

    FreeLabels(axisPtr->tickLabels);
    height = 0;
    if (axisPtr->lineWidth > 0) {
	/* Leave room for axis baseline (and pad) */
	height += axisPtr->lineWidth + 2;
    }
    if (axisPtr->showTicks) {
	int pad;
	register int i, nLabels;
	int lw, lh;
	double x, x2;
	int maxWidth, maxHeight;
	TickLabel *labelPtr;

	SweepTicks(axisPtr);

	if (axisPtr->t1Ptr->nTicks < 0) {
	    fprintf(stderr, "%s major ticks can't be %d\n",
		    axisPtr->name, axisPtr->t1Ptr->nTicks);
	    abort();
	}
	if (axisPtr->t1Ptr->nTicks > MAXTICKS) {
	    fprintf(stderr, "too big, %s major ticks can't be %d\n",
		    axisPtr->name, axisPtr->t1Ptr->nTicks);
	    abort();
	}

	maxHeight = maxWidth = 0;
	nLabels = 0;
	for (i = 0; i < axisPtr->t1Ptr->nTicks; i++) {
	    x2 = x = axisPtr->t1Ptr->values[i];
	    if (axisPtr->labelOffset) {
		x2 += axisPtr->majorSweep.step * 0.5;
	    }
	    if (!InRange(x2, &axisPtr->axisRange)) {
		continue;
	    }
	    labelPtr = MakeLabel(graphPtr, axisPtr, x);
	    Rbc_ChainAppend(axisPtr->tickLabels, labelPtr);
	    nLabels++;
	    /*
	     * Get the dimensions of each tick label.
	     * Remember tick labels can be multi-lined and/or rotated.
	     */
	    Rbc_GetTextExtents(&axisPtr->tickTextStyle, labelPtr->string,
			       &lw, &lh);
	    labelPtr->width = lw;
	    labelPtr->height = lh;

	    if (axisPtr->tickTextStyle.theta > 0.0) {
		double rotWidth, rotHeight;

		Rbc_GetBoundingBox(lw, lh, axisPtr->tickTextStyle.theta,
				   &rotWidth, &rotHeight, (Point2D *)NULL);
		lw = ROUND(rotWidth);
		lh = ROUND(rotHeight);
	    }
	    if (maxWidth < lw) {
		maxWidth = lw;
	    }
	    if (maxHeight < lh) {
		maxHeight = lh;
	    }
	}
	assert(nLabels <= axisPtr->t1Ptr->nTicks);

	/* Because the axis cap style is "CapProjecting", we need to
	 * account for an extra 1.5 linewidth at the end of each
	 * line.  */

	pad = ((axisPtr->lineWidth * 15) / 10);

	if (AxisIsHorizontal(graphPtr, axisPtr)) {
	    height += maxHeight + pad;
	} else {
	    height += maxWidth + pad;
	}
	if (axisPtr->lineWidth > 0) {
	    /* Distance from axis line to tick label. */
	    height += AXIS_TITLE_PAD;
	    height += ABS(axisPtr->tickLength);
	}
    }

    if (axisPtr->title != NULL) {
	if (axisPtr->titleAlternate) {
	    if (height < axisPtr->titleHeight) {
		height = axisPtr->titleHeight;
	    }
	} else {
	    height += axisPtr->titleHeight + AXIS_TITLE_PAD;
	}
    }

    /* Correct for orientation of the axis. */
    if (AxisIsHorizontal(graphPtr, axisPtr)) {
	axisPtr->height = height;
    } else {
	axisPtr->width = height;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * GetMarginGeometry --
 *
 *      Examines all the axes in the given margin and determines the
 *      area required to display them.
 *
 *      Note: For multiple axes, the titles are displayed in another
 *            margin. So we must keep track of the widest title.
 *
 * Results:
 *      Returns the width or height of the margin, depending if it
 *      runs horizontally along the graph or vertically.
 *
 * Side Effects:
 *      The area width and height set in the margin.  Note again that
 *      this may be corrected later (mulitple axes) to adjust for
 *      the longest title in another margin.
 *
 *----------------------------------------------------------------------
 */
static int
GetMarginGeometry(graphPtr, marginPtr)
    Graph *graphPtr;
    Margin *marginPtr;
{
    Rbc_ChainLink *linkPtr;
    Axis *axisPtr;
    int width, height;
    int isHoriz;
    int length, count;

    isHoriz = HORIZMARGIN(marginPtr);
    /* Count the number of visible axes. */
    count = 0;
    length = width = height = 0;
    for (linkPtr = Rbc_ChainFirstLink(marginPtr->axes); linkPtr != NULL;
	    linkPtr = Rbc_ChainNextLink(linkPtr)) {
	axisPtr = Rbc_ChainGetValue(linkPtr);
	if ((!axisPtr->hidden) && (axisPtr->flags & AXIS_ONSCREEN)) {
	    count++;
	    if (graphPtr->flags & GET_AXIS_GEOMETRY) {
		GetAxisGeometry(graphPtr, axisPtr);
	    }
	    if ((axisPtr->titleAlternate) && (length < axisPtr->titleWidth)) {
		length = axisPtr->titleWidth;
	    }
	    if (isHoriz) {
		height += axisPtr->height;
	    } else {
		width += axisPtr->width;
	    }
	}
    }
    /* Enforce a minimum size for margins. */
    if (width < 3) {
	width = 3;
    }
    if (height < 3) {
	height = 3;
    }
    marginPtr->nAxes = count;
    marginPtr->axesTitleLength = length;
    marginPtr->width = width;
    marginPtr->height = height;
    marginPtr->axesOffset = (HORIZMARGIN(marginPtr)) ? height : width;
    return marginPtr->axesOffset;
}

/*
 *----------------------------------------------------------------------
 *
 * ComputeMargins --
 *
 *      Computes the size of the margins and the plotting area.  We
 *      first compute the space needed for the axes in each margin.
 *      Then how much space the legend will occupy.  Finally, if the
 *      user has requested a margin size, we override the computed
 *      value.
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *---------------------------------------------------------------------- */
static void
ComputeMargins(graphPtr)
    Graph *graphPtr;
{
    int left, right, top, bottom;
    int width, height;
    int insets;

    /*
     * Step 1:	Compute the amount of space needed to display the
     *		axes (there many be 0 or more) associated with the
     *		margin.
     */
    top = GetMarginGeometry(graphPtr, &graphPtr->topMargin);
    bottom = GetMarginGeometry(graphPtr, &graphPtr->bottomMargin);
    left = GetMarginGeometry(graphPtr, &graphPtr->leftMargin);
    right = GetMarginGeometry(graphPtr, &graphPtr->rightMargin);

    /*
     * Step 2:  Add the graph title height to the top margin.
     */
    if (graphPtr->title != NULL) {
	top += graphPtr->titleTextStyle.height;
    }
    insets = 2 * (graphPtr->inset + graphPtr->plotBorderWidth);

    /*
     * Step 3:  Use the current estimate of the plot area to compute
     *		the legend size.  Add it to the proper margin.
     */
    width = graphPtr->width - (insets + left + right);
    height = graphPtr->height - (insets + top + bottom);
    Rbc_MapLegend(graphPtr->legend, width, height);
    if (!Rbc_LegendIsHidden(graphPtr->legend)) {
	switch (Rbc_LegendSite(graphPtr->legend)) {
	    case LEGEND_RIGHT:
		right += Rbc_LegendWidth(graphPtr->legend) + 2;
		break;
	    case LEGEND_LEFT:
		left += Rbc_LegendWidth(graphPtr->legend) + 2;
		break;
	    case LEGEND_TOP:
		top += Rbc_LegendHeight(graphPtr->legend) + 2;
		break;
	    case LEGEND_BOTTOM:
		bottom += Rbc_LegendHeight(graphPtr->legend) + 2;
		break;
	    case LEGEND_XY:
	    case LEGEND_PLOT:
	    case LEGEND_WINDOW:
		/* Do nothing. */
		break;
	}
    }

    /*
     * Recompute the plotarea, now accounting for the legend.
     */
    width = graphPtr->width - (insets + left + right);
    height = graphPtr->height - (insets + top + bottom);

    /*
     * Step 5:	If necessary, correct for the requested plot area
     *		aspect ratio.
     */
    if (graphPtr->aspect > 0.0) {
	double ratio;

	/*
	 * Shrink one dimension of the plotarea to fit the requested
	 * width/height aspect ratio.
	 */
	ratio = (double)width / (double)height;
	if (ratio > graphPtr->aspect) {
	    int scaledWidth;

	    /* Shrink the width. */
	    scaledWidth = (int)(height * graphPtr->aspect);
	    if (scaledWidth < 1) {
		scaledWidth = 1;
	    }
	    right += (width - scaledWidth); /* Add the difference to
					     * the right margin. */
	    /* CHECK THIS: width = scaledWidth; */
	} else {
	    int scaledHeight;

	    /* Shrink the height. */
	    scaledHeight = (int)(width / graphPtr->aspect);
	    if (scaledHeight < 1) {
		scaledHeight = 1;
	    }
	    top += (height - scaledHeight); /* Add the difference to
					    * the top margin. */
	    /* CHECK THIS: height = scaledHeight; */
	}
    }

    /*
     * Step 6:	If there's multiple axes in a margin, the axis
     *		titles will be displayed in the adjoining marging.
     *		Make sure there's room for the longest axis titles.
     */

    if (top < graphPtr->leftMargin.axesTitleLength) {
	top = graphPtr->leftMargin.axesTitleLength;
    }
    if (right < graphPtr->bottomMargin.axesTitleLength) {
	right = graphPtr->bottomMargin.axesTitleLength;
    }
    if (top < graphPtr->rightMargin.axesTitleLength) {
	top = graphPtr->rightMargin.axesTitleLength;
    }
    if (right < graphPtr->topMargin.axesTitleLength) {
	right = graphPtr->topMargin.axesTitleLength;
    }

    /*
     * Step 7:  Override calculated values with requested margin
     *		sizes.
     */

    graphPtr->leftMargin.width = left;
    graphPtr->rightMargin.width = right;
    graphPtr->topMargin.height =  top;
    graphPtr->bottomMargin.height = bottom;

    if (graphPtr->leftMargin.reqSize > 0) {
	graphPtr->leftMargin.width = graphPtr->leftMargin.reqSize;
    }
    if (graphPtr->rightMargin.reqSize > 0) {
	graphPtr->rightMargin.width = graphPtr->rightMargin.reqSize;
    }
    if (graphPtr->topMargin.reqSize > 0) {
	graphPtr->topMargin.height = graphPtr->topMargin.reqSize;
    }
    if (graphPtr->bottomMargin.reqSize > 0) {
	graphPtr->bottomMargin.height = graphPtr->bottomMargin.reqSize;
    }
}

/*
 * -----------------------------------------------------------------
 *
 * Rbc_LayoutMargins --
 *
 *      Calculate the layout of the graph.  Based upon the data,
 *      axis limits, X and Y titles, and title height, determine
 *      the cavity left which is the plotting surface.  The first
 *      step get the data and axis limits for calculating the space
 *      needed for the top, bottom, left, and right margins.
 *
 *      1) The LEFT margin is the area from the left border to the
 *         Y axis (not including ticks). It composes the border
 *         width, the width an optional Y axis label and its padding,
 *         and the tick numeric labels. The Y axis label is rotated
 *         90 degrees so that the width is the font height.
 *
 *      2) The RIGHT margin is the area from the end of the graph
 *         to the right window border. It composes the border width,
 *         some padding, the font height (this may be dubious. It
 *         appears to provide a more even border), the max of the
 *         legend width and 1/2 max X tick number. This last part is
 *         so that the last tick label is not clipped.
 *
 *               Window Width
 *          ___________________________________________________________
 *          |          |                               |               |
 *          |          |   TOP  height of title        |               |
 *          |          |                               |               |
 *          |          |           x2 title            |               |
 *          |          |                               |               |
 *          |          |        height of x2-axis      |               |
 *          |__________|_______________________________|_______________|  W
 *          |          | -plotpady                     |               |  i
 *          |__________|_______________________________|_______________|  n
 *          |          | top                   right   |               |  d
 *          |          |                               |               |  o
 *          |   LEFT   |                               |     RIGHT     |  w
 *          |          |                               |               |
 *          | y        |     Free area = 104%          |      y2       |  H
 *          |          |     Plotting surface = 100%   |               |  e
 *          | t        |     Tick length = 2 + 2%      |      t        |  i
 *          | i        |                               |      i        |  g
 *          | t        |                               |      t  legend|  h
 *          | l        |                               |      l   width|  t
 *          | e        |                               |      e        |
 *          |    height|                               |height         |
 *          |       of |                               | of            |
 *          |    y-axis|                               |y2-axis        |
 *          |          |                               |               |
 *          |          |origin 0,0                     |               |
 *          |__________|_left___________________bottom___|_______________|
 *          |          |-plotpady                      |               |
 *          |__________|_______________________________|_______________|
 *          |          | (xoffset, yoffset)            |               |
 *          |          |                               |               |
 *          |          |       height of x-axis        |               |
 *          |          |                               |               |
 *          |          |   BOTTOM   x title            |               |
 *          |__________|_______________________________|_______________|
 *
 *      3) The TOP margin is the area from the top window border to the top
 *         of the graph. It composes the border width, twice the height of
 *         the title font (if one is given) and some padding between the
 *         title.
 *
 *      4) The BOTTOM margin is area from the bottom window border to the
 *         X axis (not including ticks). It composes the border width, the height
 *         an optional X axis label and its padding, the height of the font
 *         of the tick labels.
 *
 *      The plotting area is between the margins which includes the X and Y axes
 *      including the ticks but not the tick numeric labels. The length of
 *      the ticks and its padding is 5% of the entire plotting area.  Hence the
 *      entire plotting area is scaled as 105% of the width and height of the
 *      area.
 *
 *      The axis labels, ticks labels, title, and legend may or may not be
 *      displayed which must be taken into account.
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * -----------------------------------------------------------------
 */
void
Rbc_LayoutMargins(graphPtr)
    Graph *graphPtr;
{
    int width, height;
    int titleY;
    int left, right, top, bottom;

    ComputeMargins(graphPtr);
    left = graphPtr->leftMargin.width + graphPtr->inset +
	   graphPtr->plotBorderWidth;
    right = graphPtr->rightMargin.width + graphPtr->inset +
	    graphPtr->plotBorderWidth;
    top = graphPtr->topMargin.height + graphPtr->inset +
	  graphPtr->plotBorderWidth;
    bottom = graphPtr->bottomMargin.height + graphPtr->inset +
	     graphPtr->plotBorderWidth;

    /* Based upon the margins, calculate the space left for the graph. */
    width = graphPtr->width - (left + right);
    height = graphPtr->height - (top + bottom);
    if (width < 1) {
	width = 1;
    }
    if (height < 1) {
	height = 1;
    }
    graphPtr->left = left;
    graphPtr->right = left + width;
    graphPtr->bottom = top + height;
    graphPtr->top = top;

    graphPtr->vOffset = top + graphPtr->padTop;
    graphPtr->vRange = height - PADDING(graphPtr->padY);
    graphPtr->hOffset = left + graphPtr->padLeft;
    graphPtr->hRange = width - PADDING(graphPtr->padX);

    if (graphPtr->vRange < 1) {
	graphPtr->vRange = 1;
    }
    if (graphPtr->hRange < 1) {
	graphPtr->hRange = 1;
    }
    graphPtr->hScale = 1.0 / (double)graphPtr->hRange;
    graphPtr->vScale = 1.0 / (double)graphPtr->vRange;

    /*
     * Calculate the placement of the graph title so it is centered within the
     * space provided for it in the top margin
     */
    titleY = graphPtr->titleTextStyle.height;
    graphPtr->titleY = (titleY / 2) + graphPtr->inset;
    graphPtr->titleX = (graphPtr->right + graphPtr->left) / 2;

}

/*
 * ----------------------------------------------------------------------
 *
 * ConfigureAxis --
 *
 *      Configures axis attributes (font, line width, label, etc).
 *
 * Results:
 *      The return value is a standard Tcl result.
 *
 * Side Effects:
 *      Axis layout is deferred until the height and width of the
 *      window are known.
 *
 * ----------------------------------------------------------------------
 */
static int
ConfigureAxis(graphPtr, axisPtr)
    Graph *graphPtr;
    Axis *axisPtr;
{
    char errMsg[200];

    /* Check the requested axis limits. Can't allow -min to be greater
     * than -max, or have undefined log scale limits.  */
    if (((DEFINED(axisPtr->reqMin)) && (DEFINED(axisPtr->reqMax))) &&
	    (axisPtr->reqMin >= axisPtr->reqMax)) {
	sprintf(errMsg, "impossible limits (min %g >= max %g) for axis \"%s\"",
		axisPtr->reqMin, axisPtr->reqMax, axisPtr->name);
	Tcl_AppendResult(graphPtr->interp, errMsg, (char *)NULL);
	/* Bad values, turn on axis auto-scaling */
	axisPtr->reqMin = axisPtr->reqMax = VALUE_UNDEFINED;
	return TCL_ERROR;
    }
    if ((axisPtr->logScale) && (DEFINED(axisPtr->reqMin)) &&
	    (axisPtr->reqMin <= 0.0)) {
	sprintf(errMsg, "bad logscale limits (min=%g,max=%g) for axis \"%s\"",
		axisPtr->reqMin, axisPtr->reqMax, axisPtr->name);
	Tcl_AppendResult(graphPtr->interp, errMsg, (char *)NULL);
	/* Bad minimum value, turn on auto-scaling */
	axisPtr->reqMin = VALUE_UNDEFINED;
	return TCL_ERROR;
    }
    axisPtr->tickTextStyle.theta = FMOD(axisPtr->tickTextStyle.theta, 360.0);
    if (axisPtr->tickTextStyle.theta < 0.0) {
	axisPtr->tickTextStyle.theta += 360.0;
    }
    ResetTextStyles(graphPtr, axisPtr);

    axisPtr->titleWidth = axisPtr->titleHeight = 0;
    if (axisPtr->title != NULL) {
	int w, h;

	Rbc_GetTextExtents(&axisPtr->titleTextStyle, axisPtr->title, &w, &h);
	axisPtr->titleWidth = (short int)w;
	axisPtr->titleHeight = (short int)h;
    }

    /*
     * Don't bother to check what configuration options have changed.
     * Almost every option changes the size of the plotting area
     * (except for -color and -titlecolor), requiring the graph and
     * its contents to be completely redrawn.
     *
     * Recompute the scale and offset of the axis in case -min, -max
     * options have changed.
     */
    graphPtr->flags |= REDRAW_WORLD;
    graphPtr->flags |= (MAP_WORLD | RESET_AXES);
    axisPtr->flags |= AXIS_DIRTY;
    Rbc_EventuallyRedrawGraph(graphPtr);

    return TCL_OK;
}

/*
 * ----------------------------------------------------------------------
 *
 * CreateAxis --
 *
 *      Create and initialize a structure containing information to
 *      display a graph axis.
 *
 * Results:
 *      The return value is a standard Tcl result.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static Axis *
CreateAxis(graphPtr, name, margin)
    Graph *graphPtr;
    char *name; /* Identifier for axis. */
    int margin;
{
    Axis *axisPtr;
    Tcl_HashEntry *hPtr;
    int isNew;

    if (name[0] == '-') {
	Tcl_AppendResult(graphPtr->interp, "name of axis \"", name,
			 "\" can't start with a '-'", (char *)NULL);
	return NULL;
    }
    hPtr = Tcl_CreateHashEntry(&graphPtr->axes.table, name, &isNew);
    if (!isNew) {
	axisPtr = (Axis *)Tcl_GetHashValue(hPtr);
	if (!axisPtr->deletePending) {
	    Tcl_AppendResult(graphPtr->interp, "axis \"", name,
			     "\" already exists in \"", Tk_PathName(graphPtr->tkwin), "\"",
			     (char *)NULL);
	    return NULL;
	}
	axisPtr->deletePending = FALSE;
    } else {
	axisPtr = RbcCalloc(1, sizeof(Axis));
	assert(axisPtr);

	axisPtr->name = RbcStrdup(name);
	axisPtr->hashPtr = hPtr;
	axisPtr->classUid = NULL;
	axisPtr->looseMin = axisPtr->looseMax = TICK_RANGE_TIGHT;
	axisPtr->reqNumMinorTicks = 2;
	axisPtr->scrollUnits = 10;
	axisPtr->showTicks = TRUE;
	axisPtr->reqMin = axisPtr->reqMax = VALUE_UNDEFINED;
	axisPtr->scrollMin = axisPtr->scrollMax = VALUE_UNDEFINED;

	if ((graphPtr->classUid == rbcBarElementUid) &&
		((margin == MARGIN_TOP) || (margin == MARGIN_BOTTOM))) {
	    axisPtr->reqStep = 1.0;
	    axisPtr->reqNumMinorTicks = 0;
	}
	if ((margin == MARGIN_RIGHT) || (margin == MARGIN_TOP)) {
	    axisPtr->hidden = TRUE;
	}
	Rbc_InitTextStyle(&axisPtr->titleTextStyle);
	Rbc_InitTextStyle(&axisPtr->limitsTextStyle);
	Rbc_InitTextStyle(&axisPtr->tickTextStyle);
	axisPtr->tickLabels = Rbc_ChainCreate();
	axisPtr->lineWidth = 1;
	axisPtr->tickTextStyle.padX.side1 = 2;
	axisPtr->tickTextStyle.padX.side2 = 2;
	Tcl_SetHashValue(hPtr, axisPtr);
    }
    return axisPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * NameToAxis --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
NameToAxis(
    Graph *graphPtr,	/* Graph widget record. */
    const char *name,	/* Name of the axis to be searched for. */
    Axis **axisPtrPtr)	/* (out) Pointer to found axis structure. */
{
    Tcl_HashEntry *hPtr;

    hPtr = Tcl_FindHashEntry(&graphPtr->axes.table, name);
    if (hPtr != NULL) {
	Axis *axisPtr;

	axisPtr = (Axis *)Tcl_GetHashValue(hPtr);
	if (!axisPtr->deletePending) {
	    *axisPtrPtr = axisPtr;
	    return TCL_OK;
	}
    }
    Tcl_AppendResult(graphPtr->interp, "can't find axis \"", name,
		     "\" in \"", Tk_PathName(graphPtr->tkwin), "\"", (char *)NULL);
    *axisPtrPtr = NULL;
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * GetAxis --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
GetAxis(graphPtr, axisName, classUid, axisPtrPtr)
    Graph *graphPtr;
    const char *axisName;
    Rbc_Uid classUid;
    Axis **axisPtrPtr;
{
    Axis *axisPtr;

    if (NameToAxis(graphPtr, axisName, &axisPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    if (classUid != NULL) {
	if ((axisPtr->refCount == 0) || (axisPtr->classUid == NULL)) {
	    /* Set the axis type on the first use of it. */
	    axisPtr->classUid = classUid;
	} else if (axisPtr->classUid != classUid) {
	    Tcl_AppendResult(graphPtr->interp, "axis \"", axisName,
			     "\" is already in use on an opposite ", axisPtr->classUid,
			     "-axis", (char *)NULL);
	    return TCL_ERROR;
	}
	axisPtr->refCount++;
    }
    *axisPtrPtr = axisPtr;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * FreeAxis --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static void
FreeAxis(graphPtr, axisPtr)
    Graph *graphPtr;
    Axis *axisPtr;
{
    axisPtr->refCount--;
    if ((axisPtr->deletePending) && (axisPtr->refCount == 0)) {
	DestroyAxis(graphPtr, axisPtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_DestroyAxes --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
void
Rbc_DestroyAxes(graphPtr)
    Graph *graphPtr;
{
    Tcl_HashEntry *hPtr;
    Tcl_HashSearch cursor;
    Axis *axisPtr;
    int i;

    for (hPtr = Tcl_FirstHashEntry(&graphPtr->axes.table, &cursor);
	    hPtr != NULL; hPtr = Tcl_NextHashEntry(&cursor)) {
	axisPtr = (Axis *)Tcl_GetHashValue(hPtr);
	axisPtr->hashPtr = NULL;
	DestroyAxis(graphPtr, axisPtr);
    }
    Tcl_DeleteHashTable(&graphPtr->axes.table);
    for (i = 0; i < 4; i++) {
	Rbc_ChainDestroy(graphPtr->axisChain[i]);
    }
    Tcl_DeleteHashTable(&graphPtr->axes.tagTable);
    Rbc_ChainDestroy(graphPtr->axes.displayList);
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_DefaultAxes --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
int
Rbc_DefaultAxes(graphPtr)
    Graph *graphPtr;
{
    register int i;
    Axis *axisPtr;
    Rbc_Chain *chainPtr;
    static char *axisNames[4] = { "x", "y", "x2", "y2" } ;
    int flags;

    flags = Rbc_GraphType(graphPtr);
    for (i = 0; i < 4; i++) {
	chainPtr = Rbc_ChainCreate();
	graphPtr->axisChain[i] = chainPtr;

	/* Create a default axis for each chain. */
	axisPtr = CreateAxis(graphPtr, axisNames[i], i);
	if (axisPtr == NULL) {
	    return TCL_ERROR;
	}
	axisPtr->refCount = 1;	/* Default axes are assumed in use. */
	axisPtr->classUid = (i & 1) ? rbcYAxisUid : rbcXAxisUid;
	axisPtr->flags |= AXIS_ONSCREEN;

	/*
	 * Rbc_ConfigureWidgetComponent creates a temporary child window
	 * by the name of the axis.  It's used so that the Tk routines
	 * that access the X resource database can describe a single
	 * component and not the entire graph.
	 */
	if (Rbc_ConfigureWidgetComponent(graphPtr->interp, graphPtr->tkwin,
		     axisPtr->name, "Axis", configSpecs, 0,
		     (Tcl_Obj *const *)NULL, (char *)axisPtr, flags) != TCL_OK) {
	    return TCL_ERROR;
	}
	if (ConfigureAxis(graphPtr, axisPtr) != TCL_OK) {
	    return TCL_ERROR;
	}
	axisPtr->linkPtr = Rbc_ChainAppend(chainPtr, axisPtr);
	axisPtr->chainPtr = chainPtr;
    }
    return TCL_OK;
}

/*----------------------------------------------------------------------
 *
 * BindOp --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
BindOp(
    Graph *graphPtr,
    Axis *axisPtr,
    int margin,
    int objc,
    Tcl_Obj *const objv[])
{
    Tcl_Interp *interp = graphPtr->interp;

    return Rbc_ConfigureBindingsFromObj(interp, graphPtr->bindTable,
	Rbc_MakeAxisTag(graphPtr, axisPtr->name), objc, objv);
}

/*
 * ----------------------------------------------------------------------
 *
 * CgetOp --
 *
 *      Queries axis attributes (font, line width, label, etc).
 *
 * Results:
 *      Return value is a standard Tcl result.  If querying configuration
 *      values, the interpreter result will contain the results.
 *
 * Side Effects:
 *      TODO: SIde Effects
 *
 * ----------------------------------------------------------------------
 */
static int
CgetOp(
    Graph *graphPtr,
    Axis *axisPtr,
    int margin,
    int objc,
    Tcl_Obj *const objv[])
{
    return Tk_ConfigureValue(graphPtr->interp, graphPtr->tkwin, configSpecs,
	(char *)axisPtr, Tcl_GetString(objv[0]), Rbc_GraphType(graphPtr));
}

/*
 * ----------------------------------------------------------------------
 *
 * ConfigureOp --
 *
 *      Queries or resets axis attributes (font, line width, label, etc).
 *
 * Results:
 *      Return value is a standard Tcl result.  If querying configuration
 *      values, the interppreter result will contain the results.
 *
 * Side Effects:
 *      Axis resources are possibly allocated (GC, font). Axis layout is
 *      deferred until the height and width of the window are known.
 *
 * ----------------------------------------------------------------------
 */
static int
ConfigureOp(
    Graph *graphPtr,
    Axis *axisPtr,
    int margin,
    int objc,
    Tcl_Obj *const objv[])
{
    int flags;

    flags = TK_CONFIG_ARGV_ONLY | Rbc_GraphType(graphPtr);
    if (objc == 0) {
	return Tk_ConfigureInfo(graphPtr->interp, graphPtr->tkwin, configSpecs,
		(char *)axisPtr, (char *)NULL, flags);
    } else if (objc == 1) {
	return Tk_ConfigureInfo(graphPtr->interp, graphPtr->tkwin, configSpecs,
		(char *)axisPtr, Tcl_GetString(objv[0]), flags);
    }
    if (Tk_ConfigureWidget(graphPtr->interp, graphPtr->tkwin, configSpecs,
	       objc, objv, axisPtr, flags) != TCL_OK) {
	return TCL_ERROR;
    }
    if (ConfigureAxis(graphPtr, axisPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    if (axisPtr->flags & AXIS_ONSCREEN) {
	if (!Rbc_ConfigModified(graphPtr->interp, configSpecs, "-*color", "-background", "-bg",
				(char *)NULL)) {
	    graphPtr->flags |= REDRAW_BACKING_STORE;
	}
	graphPtr->flags |= DRAW_MARGINS;
	Rbc_EventuallyRedrawGraph(graphPtr);
    }
    return TCL_OK;
}

/*
 *--------------------------------------------------------------
 *
 * LimitsOp --
 *
 *      This procedure returns a string representing the axis limits
 *      of the graph.  The format of the string is {left top right bottom}.
 *
 * Results:
 *      Always returns TCL_OK. The interpreter result is set to
 *      a list of the graph axis limits.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *--------------------------------------------------------------
 */
static int
LimitsOp(
    Graph *graphPtr,
    Axis *axisPtr,
    int margin,
    int objc,
    Tcl_Obj *const objv[])
{
    Tcl_Interp *interp = graphPtr->interp;
    double min, max;
    Tcl_Obj *resultObj = Tcl_NewListObj(0, NULL);

    if (graphPtr->flags & RESET_AXES) {
	Rbc_ResetAxes(graphPtr);
    }
    if (axisPtr->logScale) {
	min = EXP10(axisPtr->axisRange.min);
	max = EXP10(axisPtr->axisRange.max);
    } else {
	min = axisPtr->axisRange.min;
	max = axisPtr->axisRange.max;
    }
    Tcl_ListObjAppendElement(NULL, resultObj, Tcl_NewDoubleObj(min));
    Tcl_ListObjAppendElement(NULL, resultObj, Tcl_NewDoubleObj(max));
    Tcl_SetObjResult(interp, resultObj);
    return TCL_OK;
}

/*
 * ----------------------------------------------------------------------
 *
 * InvTransformOp --
 *
 *      Maps the given window coordinate into an axis-value.
 *
 * Results:
 *      Returns a standard Tcl result. The interpreter result contains
 *      the axis value. If an error occurred, TCL_ERROR is returned
 *      and the interpreter result will contain an error message.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
InvTransformOp(
    Graph *graphPtr,
    Axis *axisPtr,
    int margin,
    int objc,
    Tcl_Obj *const objv[])
{
    Tcl_Interp *interp = graphPtr->interp;
    int x;			/* Integer window coordinate*/
    double y;			/* Real graph coordinate */

    if (graphPtr->flags & RESET_AXES) {
	Rbc_ResetAxes(graphPtr);
    }
    if (Tcl_GetIntFromObj(interp, objv[0], &x) != TCL_OK) {
	return TCL_ERROR;
    }
    /*
     * Is the axis vertical or horizontal?
     *
     * Check the site where the axis was positioned.  If the axis is
     * virtual, all we have to go on is how it was mapped to an
     * element (using either -mapx or -mapy options).
     */
    if (AxisIsHorizontal(graphPtr, axisPtr)) {
	y = Rbc_InvHMap(graphPtr, axisPtr, (double)x);
    } else {
	y = Rbc_InvVMap(graphPtr, axisPtr, (double)x);
    }
    Tcl_SetObjResult(interp, Tcl_NewDoubleObj(y));
    return TCL_OK;
}

/*
 * ----------------------------------------------------------------------
 *
 * TransformOp --
 *
 *      Maps the given axis-value to a window coordinate.
 *
 * Results:
 *      Returns a standard Tcl result. The interpreter result contains
 *      the window coordinate. If an error occurred, TCL_ERROR
 *      is returned and the interpreter result will contain an error
 *      message.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
TransformOp(
    Graph *graphPtr,
    Axis *axisPtr,
    int margin,
    int objc, /* Not used. */
    Tcl_Obj *const objv[])
{
    Tcl_Interp *interp = graphPtr->interp;
    double x;

    if (graphPtr->flags & RESET_AXES) {
	Rbc_ResetAxes(graphPtr);
    }
    if (Tcl_ExprDoubleObj(interp, objv[0], &x) != TCL_OK) {
	return TCL_ERROR;
    }
    if (AxisIsHorizontal(graphPtr, axisPtr)) {
	x = Rbc_HMap(graphPtr, axisPtr, x);
    } else {
	x = Rbc_VMap(graphPtr, axisPtr, x);
    }
    Tcl_SetObjResult(interp, Tcl_NewIntObj((int)x));
    return TCL_OK;
}

/*
 *--------------------------------------------------------------
 *
 * UseOp --
 *
 *      Changes the virtual axis used by the logical axis.
 *
 * Results:
 *      A standard Tcl result.  If the named axis doesn't exist
 *      an error message is set in the interpreter result.
 *
 *      .g xaxis use "abc def gah"
 *      .g xaxis use [lappend abc [.g axis use]]
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *--------------------------------------------------------------
 */
static int
UseOp(
    Graph *graphPtr,
    Axis *axisPtr,
    int margin,
    int objc,
    Tcl_Obj *const objv[])
{
    Tcl_Interp *interp = graphPtr->interp;
    Rbc_Chain *chainPtr;
    Tcl_Size nNames, i;
    Tcl_Obj **names;
    Rbc_ChainLink *linkPtr;
    Rbc_Uid classUid;

    chainPtr = graphPtr->margins[margin].axes;
    if (objc == 0) {
	Tcl_Obj *resultObj = Tcl_NewListObj(0, NULL);

	for (linkPtr = Rbc_ChainFirstLink(chainPtr); linkPtr!= NULL;
		linkPtr = Rbc_ChainNextLink(linkPtr)) {
	    axisPtr = Rbc_ChainGetValue(linkPtr);
	    Tcl_ListObjAppendElement(NULL, resultObj,
		Tcl_NewStringObj(axisPtr->name, -1));
	}

	Tcl_SetObjResult(interp, resultObj);
	return TCL_OK;
    }
    if ((margin == MARGIN_BOTTOM) || (margin == MARGIN_TOP)) {
	classUid = (graphPtr->inverted) ? rbcYAxisUid : rbcXAxisUid;
    } else {
	classUid = (graphPtr->inverted) ? rbcXAxisUid : rbcYAxisUid;
    }
    if (Tcl_ListObjGetElements(interp, objv[0], &nNames, &names) != TCL_OK) {
	return TCL_ERROR;
    }

    for (linkPtr = Rbc_ChainFirstLink(chainPtr); linkPtr!= NULL;
	    linkPtr = Rbc_ChainNextLink(linkPtr)) {
	axisPtr = Rbc_ChainGetValue(linkPtr);
	axisPtr->linkPtr = NULL;
	axisPtr->flags &= ~AXIS_ONSCREEN;
	/* Clear the axis type if it's not currently used.*/
	if (axisPtr->refCount == 0) {
	    axisPtr->classUid = NULL;
	}
    }
    Rbc_ChainReset(chainPtr);
    for (i = 0; i < nNames; i++) {
	if (NameToAxis(graphPtr, Tcl_GetString(names[i]), &axisPtr) != TCL_OK) {
	    return TCL_ERROR;
	}
	if (axisPtr->classUid == NULL) {
	    axisPtr->classUid = classUid;
	} else if (axisPtr->classUid != classUid) {
	    Tcl_SetObjResult(interp, Tcl_ObjPrintf("wrong type axis \"%s\": "
		"can't use %s type axis.", axisPtr->name, classUid));
	    return TCL_ERROR;
	}
	if (axisPtr->linkPtr != NULL) {
	    /* Move the axis from the old margin's "use" list to the new. */
	    Rbc_ChainUnlinkLink(axisPtr->chainPtr, axisPtr->linkPtr);
	    Rbc_ChainAppendLink(chainPtr, axisPtr->linkPtr);
	} else {
	    axisPtr->linkPtr = Rbc_ChainAppend(chainPtr, axisPtr);
	}
	axisPtr->chainPtr = chainPtr;
	axisPtr->flags |= AXIS_ONSCREEN;
    }
    graphPtr->flags |= (GET_AXIS_GEOMETRY | LAYOUT_NEEDED | RESET_AXES);
    /* When any axis changes, we need to layout the entire graph.  */
    graphPtr->flags |= (MAP_WORLD | REDRAW_WORLD);
    Rbc_EventuallyRedrawGraph(graphPtr);

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * BindVirtualOp --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
BindVirtualOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Tcl_Interp *interp = graphPtr->interp;

    if (objc == 3) {
	Tcl_HashEntry *hPtr;
	Tcl_HashSearch cursor;
	char *tagName;
	Tcl_Obj *resultObj = Tcl_NewListObj(0, NULL);

	for (hPtr = Tcl_FirstHashEntry(&graphPtr->axes.tagTable, &cursor);
		hPtr != NULL; hPtr = Tcl_NextHashEntry(&cursor)) {
	    tagName = Tcl_GetHashKey(&graphPtr->axes.tagTable, hPtr);
	    Tcl_ListObjAppendElement(NULL, resultObj,
		Tcl_NewStringObj(tagName, -1));
	}
	Tcl_SetObjResult(interp, resultObj);
	return TCL_OK;
    }
    return Rbc_ConfigureBindingsFromObj(interp, graphPtr->bindTable,
	Rbc_MakeAxisTag(graphPtr, Tcl_GetString(objv[3])), objc-4, objv+4);
}

/*
 * ----------------------------------------------------------------------
 *
 * CreateVirtualOp --
 *
 *      Creates a new axis.
 *
 * Results:
 *      Returns a standard Tcl result.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
CreateVirtualOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Axis *axisPtr;
    int flags;

    axisPtr = CreateAxis(graphPtr, Tcl_GetString(objv[3]), MARGIN_NONE);
    if (axisPtr == NULL) {
	return TCL_ERROR;
    }
    flags = Rbc_GraphType(graphPtr);
    if (Rbc_ConfigureWidgetComponent(graphPtr->interp, graphPtr->tkwin,
		 axisPtr->name, "Axis", configSpecs, objc-4, objv+4,
		 (char *)axisPtr, flags) != TCL_OK) {
	goto error;
    }
    if (ConfigureAxis(graphPtr, axisPtr) != TCL_OK) {
	goto error;
    }
    Tcl_SetObjResult(graphPtr->interp, Tcl_NewStringObj(axisPtr->name, -1));
    return TCL_OK;
error:
    DestroyAxis(graphPtr, axisPtr);
    return TCL_ERROR;
}

/*
 * ----------------------------------------------------------------------
 *
 * CgetVirtualOp --
 *
 *      Queries axis attributes (font, line width, label, etc).
 *
 * Results:
 *      Return value is a standard Tcl result.  If querying configuration
 *      values, the interpreter result will contain the results.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
CgetVirtualOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Axis *axisPtr;

    if (NameToAxis(graphPtr, Tcl_GetString(objv[3]), &axisPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    return CgetOp(graphPtr, axisPtr, /*dummy*/0, objc-4, objv+4);
}

/*
 * ----------------------------------------------------------------------
 *
 * ConfigureVirtualOp --
 *
 *      Queries or resets axis attributes (font, line width, label, etc).
 *
 * Results:
 *      Return value is a standard Tcl result.  If querying configuration
 *      values, the interpreter result will contain the results.
 *
 * Side Effects:
 *      Axis resources are possibly allocated (GC, font). Axis layout is
 *      deferred until the height and width of the window are known.
 *
 * ----------------------------------------------------------------------
 */
static int
ConfigureVirtualOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Axis *axisPtr;
    int nNames, nOpts;
    Tcl_Obj *const *options;
    register int i;

    /* Figure out where the option value pairs begin */
    objc -= 3;
    objv += 3;
    for (i = 0; i < objc; i++) {
	const char *str = Tcl_GetString(objv[i]);
	if (str[0] == '-') {
	    break;
	}
	if (NameToAxis(graphPtr, str, &axisPtr) != TCL_OK) {
	    return TCL_ERROR;
	}
    }
    nNames = i;			/* Number of pen names specified */
    nOpts = objc - i;		/* Number of options specified */
    options = objv + i;		/* Start of options in objv  */

    for (i = 0; i < nNames; i++) {
	if (NameToAxis(graphPtr, Tcl_GetString(objv[i]), &axisPtr) != TCL_OK) {
	    return TCL_ERROR;
	}
	if (ConfigureOp(graphPtr, axisPtr, /*dummy*/0, nOpts, options) != TCL_OK) {
	    break;
	}
    }
    if (i < nNames) {
	return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 * ----------------------------------------------------------------------
 *
 * DeleteVirtualOp --
 *
 *      Deletes one or more axes.  The actual removal may be deferred
 *      until the axis is no longer used by any element. The axis
 *      can't be referenced by its name any longer and it may be
 *      recreated.
 *
 * Results:
 *      Returns a standard Tcl result.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
DeleteVirtualOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    register int i;
    Axis *axisPtr;

    for (i = 3; i < objc; i++) {
	if (NameToAxis(graphPtr, Tcl_GetString(objv[i]), &axisPtr) != TCL_OK) {
	    return TCL_ERROR;
	}
	axisPtr->deletePending = TRUE;
	if (axisPtr->refCount == 0) {
	    DestroyAxis(graphPtr, axisPtr);
	}
    }
    return TCL_OK;
}

/*
 * ----------------------------------------------------------------------
 *
 * GetOp --
 *
 *      Returns the name of the picked axis (using the axis
 *      bind operation).  Right now, the only name accepted is
 *      "current".
 *
 * Results:
 *      A standard Tcl result.  The interpreter result will contain
 *      the name of the axis.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
GetOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Tcl_Interp *interp = graphPtr->interp;
    register Axis *axisPtr;

    axisPtr = (Axis *)Rbc_GetCurrentItem(graphPtr->bindTable);
    /* Report only on axes. */
    if ((axisPtr != NULL) &&
	    ((axisPtr->classUid == rbcXAxisUid) ||
	     (axisPtr->classUid == rbcYAxisUid) ||
	     (axisPtr->classUid == NULL))) {
	const char *s = Tcl_GetString(objv[3]);
	const char c = s[0];

	if ((c == 'c') && (strcmp(s, "current") == 0)) {
//            Tcl_SetResult(interp, axisPtr->name, TCL_VOLATILE);
	    Tcl_SetObjResult(interp, Tcl_NewStringObj(axisPtr->name, -1));
	} else if ((c == 'd') && (strcmp(s, "detail") == 0)) {
//            Tcl_SetResult(interp, axisPtr->detail, TCL_VOLATILE);
	    Tcl_SetObjResult(interp, Tcl_NewStringObj(axisPtr->detail, -1));
	}
    }
    return TCL_OK;
}

/*
 * ----------------------------------------------------------------------
 *
 * InvTransformVirtualOp --
 *
 *      Maps the given window coordinate into an axis-value.
 *
 * Results:
 *      Returns a standard Tcl result. The interpreter result contains
 *      the axis value. If an error occurred, TCL_ERROR is returned
 *      and the interpreter result will contain an error message.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
InvTransformVirtualOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Axis *axisPtr;

    if (NameToAxis(graphPtr, Tcl_GetString(objv[3]), &axisPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    return InvTransformOp(graphPtr, axisPtr, /*dummy*/0, objc-4, objv+4);
}

/*
 *--------------------------------------------------------------
 *
 * LimitsVirtualOp --
 *
 *      This procedure returns a string representing the axis limits
 *      of the graph.  The format of the string is { left top right bottom}.
 *
 * Results:
 *      Always returns TCL_OK.  The interpreter result is set to
 *      a list of the graph axis limits.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *--------------------------------------------------------------
 */
static int
LimitsVirtualOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Axis *axisPtr;

    if (NameToAxis(graphPtr, Tcl_GetString(objv[3]), &axisPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    return LimitsOp(graphPtr, axisPtr, /*dummy*/0,  objc-4, objv+4);
}

/*
 * ----------------------------------------------------------------------
 *
 * NamesVirtualOp --
 *
 *      Return a list of the names of all the axes.
 *
 * Results:
 *      Returns a standard Tcl result.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
NamesVirtualOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Tcl_Interp *interp = graphPtr->interp;
    Tcl_HashEntry *hPtr;
    Tcl_HashSearch cursor;
    Axis *axisPtr;
    register int i;
    Tcl_Obj *resultObj = Tcl_NewListObj(0, NULL);

    for (hPtr = Tcl_FirstHashEntry(&graphPtr->axes.table, &cursor);
	    hPtr != NULL; hPtr = Tcl_NextHashEntry(&cursor)) {
	axisPtr = (Axis *)Tcl_GetHashValue(hPtr);
	if (axisPtr->deletePending) {
	    continue;
	}
	if (objc == 3) {
	    Tcl_ListObjAppendElement(NULL, resultObj,
		Tcl_NewStringObj(axisPtr->name, -1));
	    continue;
	}
	for (i = 3; i < objc; i++) {
	    if (Tcl_StringMatch(axisPtr->name, Tcl_GetString(objv[i]))) {
		Tcl_ListObjAppendElement(NULL, resultObj,
		    Tcl_NewStringObj(axisPtr->name, -1));
		break;
	    }
	}
    }
    Tcl_SetObjResult(interp, resultObj);
    return TCL_OK;
}

/*
 * ----------------------------------------------------------------------
 *
 * TransformVirtualOp --
 *
 *	Maps the given axis-value to a window coordinate.
 *
 * Results:
 *      Returns a standard Tcl result. The interpreter result contains
 *      the window coordinate. If an error occurred, TCL_ERROR
 *      is returned and the interpreter result will contain an error
 *      message.
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 * ----------------------------------------------------------------------
 */
static int
TransformVirtualOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Axis *axisPtr;

    if (NameToAxis(graphPtr, Tcl_GetString(objv[3]), &axisPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    return TransformOp(graphPtr, axisPtr, /*dummy*/0, objc-4, objv+4);
}

/*
 *----------------------------------------------------------------------
 *
 * ViewOp --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
static int
ViewOp(
    Graph *graphPtr,
    int objc,
    Tcl_Obj *const objv[])
{
    Axis *axisPtr;
    Tcl_Interp *interp = graphPtr->interp;
    double axisOffset, scrollUnits;
    double fract;
    double viewMin, viewMax, worldMin, worldMax;
    double viewWidth, worldWidth;

    if (NameToAxis(graphPtr, Tcl_GetString(objv[3]), &axisPtr) != TCL_OK) {
	return TCL_ERROR;
    }
    worldMin = axisPtr->valueRange.min;
    worldMax = axisPtr->valueRange.max;
    /* Override data dimensions with user-selected limits. */
    if (DEFINED(axisPtr->scrollMin)) {
	worldMin = axisPtr->scrollMin;
    }
    if (DEFINED(axisPtr->scrollMax)) {
	worldMax = axisPtr->scrollMax;
    }
    viewMin = axisPtr->min;
    viewMax = axisPtr->max;
    /* Bound the view within scroll region. */
    if (viewMin < worldMin) {
	viewMin = worldMin;
    }
    if (viewMax > worldMax) {
	viewMax = worldMax;
    }
    if (axisPtr->logScale) {
	worldMin = log10(worldMin);
	worldMax = log10(worldMax);
	viewMin = log10(viewMin);
	viewMax = log10(viewMax);
    }
    worldWidth = worldMax - worldMin;
    viewWidth = viewMax - viewMin;

    /* Unlike horizontal axes, vertical axis values run opposite of
     * the scrollbar first/last values.  So instead of pushing the
     * axis minimum around, we move the maximum instead. */

    if (AxisIsHorizontal(graphPtr, axisPtr) != axisPtr->descending) {
	axisOffset = viewMin - worldMin;
	scrollUnits = (double)axisPtr->scrollUnits * graphPtr->hScale;
    } else {
	axisOffset = worldMax - viewMax;
	scrollUnits = (double)axisPtr->scrollUnits * graphPtr->vScale;
    }
    if (objc == 4) {
	Tcl_Obj *resultObj = Tcl_NewListObj(0, NULL);

	/* Note: Bound the fractions between 0.0 and 1.0 to support
	 * "canvas"-style scrolling. */
	fract = axisOffset / worldWidth;
	Tcl_ListObjAppendElement(NULL, resultObj,
	    Tcl_NewDoubleObj(CLAMP(fract, 0.0, 1.0)));
	fract = (axisOffset + viewWidth) / worldWidth;
	Tcl_ListObjAppendElement(NULL, resultObj,
	    Tcl_NewDoubleObj(CLAMP(fract, 0.0, 1.0)));
	Tcl_SetObjResult(interp, resultObj);
	return TCL_OK;
    }
    fract = axisOffset / worldWidth;
    if (GetAxisScrollInfo(interp, objc-4, objv+4, &fract,
		viewWidth / worldWidth, scrollUnits) != TCL_OK) {
	return TCL_ERROR;
    }
    if (AxisIsHorizontal(graphPtr, axisPtr) != axisPtr->descending) {
	axisPtr->reqMin = (fract * worldWidth) + worldMin;
	axisPtr->reqMax = axisPtr->reqMin + viewWidth;
    } else {
	axisPtr->reqMax = worldMax - (fract * worldWidth);
	axisPtr->reqMin = axisPtr->reqMax - viewWidth;
    }
    if (axisPtr->logScale) {
	axisPtr->reqMin = EXP10(axisPtr->reqMin);
	axisPtr->reqMax = EXP10(axisPtr->reqMax);
    }
    graphPtr->flags |= (GET_AXIS_GEOMETRY | LAYOUT_NEEDED | RESET_AXES);
    Rbc_EventuallyRedrawGraph(graphPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_VirtualAxisOp --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
int
Rbc_VirtualAxisOp(
    Graph *graphPtr,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const objv[])
{
    Rbc_Op proc;
    int result;
    static Rbc_OpSpec axisOps[] = {
	{"bind",         (Rbc_Op)BindVirtualOp,         3, 6, "axisName sequence command"},
	{"cget",         (Rbc_Op)CgetVirtualOp,         5, 5, "axisName option"},
	{"configure",    (Rbc_Op)ConfigureVirtualOp,    4, 0, "axisName ?axisName?... ?option value?..."},
	{"create",       (Rbc_Op)CreateVirtualOp,       4, 0, "axisName ?option value?..."},
	{"delete",       (Rbc_Op)DeleteVirtualOp,       3, 0, "?axisName?..."},
	{"get",          (Rbc_Op)GetOp,                 4, 4, "name"},
	{"invtransform", (Rbc_Op)InvTransformVirtualOp, 5, 5, "axisName value"},
	{"limits",       (Rbc_Op)LimitsVirtualOp,       4, 4, "axisName"},
	{"names",        (Rbc_Op)NamesVirtualOp,        3, 0, "?pattern?..."},
	{"transform",    (Rbc_Op)TransformVirtualOp,    5, 5, "axisName value"},
	{"view",         (Rbc_Op)ViewOp,                4, 7, "axisName ?moveto fract? ?scroll number what?"},
	RBC_OPSPEC_END
    };

    proc = Rbc_GetOpFromObj(interp, axisOps, RBC_OP_ARG2, objc, objv);
    if (proc == NULL) {
	return TCL_ERROR;
    }
    result = (*proc) (graphPtr, objc, objv);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_AxisOp --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
int
Rbc_AxisOp(
    Graph *graphPtr,
    int margin,
    int objc,
    Tcl_Obj *const objv[])
{
    int result;
    Rbc_Op proc;
    Axis *axisPtr;
    static Rbc_OpSpec axisOps[] = {
	{"bind",         (Rbc_Op)BindOp,         2, 5, "sequence command"},
	{"cget",         (Rbc_Op)CgetOp,         4, 4, "option"},
	{"configure",    (Rbc_Op)ConfigureOp,    3, 0, "?option value?..."},
	{"invtransform", (Rbc_Op)InvTransformOp, 4, 4, "value"},
	{"limits",       (Rbc_Op)LimitsOp,       3, 3, ""},
	{"transform",    (Rbc_Op)TransformOp,    4, 4, "value"},
	{"use",          (Rbc_Op)UseOp,          3, 4, "?axisName?"},
	RBC_OPSPEC_END
    };

    proc = Rbc_GetOpFromObj(graphPtr->interp, axisOps, RBC_OP_ARG2, objc, objv);
    if (proc == NULL) {
	return TCL_ERROR;
    }
    axisPtr = Rbc_GetFirstAxis(graphPtr->margins[margin].axes);
    result = (*proc)(graphPtr, axisPtr, margin, objc-3, objv+3);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_MapAxes --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
void
Rbc_MapAxes(graphPtr)
    Graph *graphPtr;
{
    Axis *axisPtr;
    Rbc_Chain *chainPtr;
    Rbc_ChainLink *linkPtr;
    register int margin;
    int offset;

    for (margin = 0; margin < 4; margin++) {
	chainPtr = graphPtr->margins[margin].axes;
	offset = 0;
	for (linkPtr = Rbc_ChainFirstLink(chainPtr); linkPtr != NULL;
		linkPtr = Rbc_ChainNextLink(linkPtr)) {
	    axisPtr = Rbc_ChainGetValue(linkPtr);
	    if ((!axisPtr->hidden) && (axisPtr->flags & AXIS_ONSCREEN)) {
		MapAxis(graphPtr, axisPtr, offset, margin);
		if (AxisIsHorizontal(graphPtr, axisPtr)) {
		    offset += axisPtr->height;
		} else {
		    offset += axisPtr->width;
		}
	    }
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_DrawAxes --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
void
Rbc_DrawAxes(graphPtr, drawable)
    Graph *graphPtr;
    Drawable drawable;
{
    Axis *axisPtr;
    Rbc_ChainLink *linkPtr;
    register int i;

    for (i = 0; i < 4; i++) {
	for (linkPtr = Rbc_ChainFirstLink(graphPtr->margins[i].axes);
		linkPtr != NULL; linkPtr = Rbc_ChainNextLink(linkPtr)) {
	    axisPtr = Rbc_ChainGetValue(linkPtr);
	    if ((!axisPtr->hidden) && (axisPtr->flags & AXIS_ONSCREEN)) {
		DrawAxis(graphPtr, drawable, axisPtr);
	    }
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_AxesToPostScript --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
void
Rbc_AxesToPostScript(graphPtr, psToken)
    Graph *graphPtr;
    PsToken psToken;
{
    Axis *axisPtr;
    Rbc_ChainLink *linkPtr;
    register int i;

    for (i = 0; i < 4; i++) {
	for (linkPtr = Rbc_ChainFirstLink(graphPtr->margins[i].axes);
		linkPtr != NULL; linkPtr = Rbc_ChainNextLink(linkPtr)) {
	    axisPtr = Rbc_ChainGetValue(linkPtr);
	    if ((!axisPtr->hidden) && (axisPtr->flags & AXIS_ONSCREEN)) {
		AxisToPostScript(psToken, axisPtr);
	    }
	}
    }
}


/*
 * ----------------------------------------------------------------------
 *
 * Rbc_DrawAxisLimits --
 *
 *      Draws the min/max values of the axis in the plotting area.
 *      The text strings are formatted according to the "sprintf"
 *      format descriptors in the limitsFormats array.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Draws the numeric values of the axis limits into the outer
 *      regions of the plotting area.
 *
 * ----------------------------------------------------------------------
 */
void
Rbc_DrawAxisLimits(graphPtr, drawable)
    Graph *graphPtr;
    Drawable drawable;
{
    Axis *axisPtr;
    Tcl_HashEntry *hPtr;
    Tcl_HashSearch cursor;
    Dim2D textDim;
    int isHoriz;
    char *minPtr, *maxPtr;
    char *minFormat, *maxFormat;
    char minString[200], maxString[200];
    int vMin, hMin, vMax, hMax;

#define SPACING 8
    vMin = vMax = graphPtr->left + graphPtr->padLeft + 2;
    hMin = hMax = graphPtr->bottom - graphPtr->padBottom - 2;	/* Offsets */

    for (hPtr = Tcl_FirstHashEntry(&graphPtr->axes.table, &cursor);
	    hPtr != NULL; hPtr = Tcl_NextHashEntry(&cursor)) {
	axisPtr = (Axis *)Tcl_GetHashValue(hPtr);

	if (axisPtr->nFormats == 0) {
	    continue;
	}
	isHoriz = AxisIsHorizontal(graphPtr, axisPtr);
	minPtr = maxPtr = NULL;
	minFormat = maxFormat = axisPtr->limitsFormats[0];
	if (axisPtr->nFormats > 1) {
	    maxFormat = axisPtr->limitsFormats[1];
	}
	if (minFormat[0] != '\0') {
	    minPtr = minString;
	    sprintf(minString, minFormat, axisPtr->axisRange.min);
	}
	if (maxFormat[0] != '\0') {
	    maxPtr = maxString;
	    sprintf(maxString, maxFormat, axisPtr->axisRange.max);
	}
	if (axisPtr->descending) {
	    char *tmp;

	    tmp = minPtr, minPtr = maxPtr, maxPtr = tmp;
	}
	if (maxPtr != NULL) {
	    if (isHoriz) {
		axisPtr->limitsTextStyle.theta = 90.0;
		axisPtr->limitsTextStyle.anchor = TK_ANCHOR_SE;
		Rbc_DrawText2(graphPtr->tkwin, drawable, maxPtr,
			      &axisPtr->limitsTextStyle, graphPtr->right, hMax, &textDim);
		hMax -= (textDim.height + SPACING);
	    } else {
		axisPtr->limitsTextStyle.theta = 0.0;
		axisPtr->limitsTextStyle.anchor = TK_ANCHOR_NW;
		Rbc_DrawText2(graphPtr->tkwin, drawable, maxPtr,
			      &axisPtr->limitsTextStyle, vMax, graphPtr->top, &textDim);
		vMax += (textDim.width + SPACING);
	    }
	}
	if (minPtr != NULL) {
	    axisPtr->limitsTextStyle.anchor = TK_ANCHOR_SW;
	    if (isHoriz) {
		axisPtr->limitsTextStyle.theta = 90.0;
		Rbc_DrawText2(graphPtr->tkwin, drawable, minPtr,
			      &axisPtr->limitsTextStyle, graphPtr->left, hMin, &textDim);
		hMin -= (textDim.height + SPACING);
	    } else {
		axisPtr->limitsTextStyle.theta = 0.0;
		Rbc_DrawText2(graphPtr->tkwin, drawable, minPtr,
			      &axisPtr->limitsTextStyle, vMin, graphPtr->bottom, &textDim);
		vMin += (textDim.width + SPACING);
	    }
	}
    }				/* Loop on axes */
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_AxisLimitsToPostScript --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
void
Rbc_AxisLimitsToPostScript(graphPtr, psToken)
    Graph *graphPtr;
    PsToken psToken;
{
    Axis *axisPtr;
    Tcl_HashEntry *hPtr;
    Tcl_HashSearch cursor;
    double vMin, hMin, vMax, hMax;
    char string[200];
    int textWidth, textHeight;
    char *minFmt, *maxFmt;

#define SPACING 8
    vMin = vMax = graphPtr->left + graphPtr->padLeft + 2;
    hMin = hMax = graphPtr->bottom - graphPtr->padBottom - 2;	/* Offsets */
    for (hPtr = Tcl_FirstHashEntry(&graphPtr->axes.table, &cursor);
	    hPtr != NULL; hPtr = Tcl_NextHashEntry(&cursor)) {
	axisPtr = (Axis *)Tcl_GetHashValue(hPtr);

	if (axisPtr->nFormats == 0) {
	    continue;
	}
	minFmt = maxFmt = axisPtr->limitsFormats[0];
	if (axisPtr->nFormats > 1) {
	    maxFmt = axisPtr->limitsFormats[1];
	}
	if (*maxFmt != '\0') {
	    sprintf(string, maxFmt, axisPtr->axisRange.max);
	    Rbc_GetTextExtents(&axisPtr->tickTextStyle, string, &textWidth,
			       &textHeight);
	    if ((textWidth > 0) && (textHeight > 0)) {
		if (axisPtr->classUid == rbcXAxisUid) {
		    axisPtr->limitsTextStyle.theta = 90.0;
		    axisPtr->limitsTextStyle.anchor = TK_ANCHOR_SE;
		    Rbc_TextToPostScript(psToken, string,
					 &axisPtr->limitsTextStyle,
					 (double)graphPtr->right, hMax);
		    hMax -= (textWidth + SPACING);
		} else {
		    axisPtr->limitsTextStyle.theta = 0.0;
		    axisPtr->limitsTextStyle.anchor = TK_ANCHOR_NW;
		    Rbc_TextToPostScript(psToken, string,
					 &axisPtr->limitsTextStyle, vMax, (double)graphPtr->top);
		    vMax += (textWidth + SPACING);
		}
	    }
	}
	if (*minFmt != '\0') {
	    sprintf(string, minFmt, axisPtr->axisRange.min);
	    Rbc_GetTextExtents(&axisPtr->tickTextStyle, string, &textWidth,
			       &textHeight);
	    if ((textWidth > 0) && (textHeight > 0)) {
		axisPtr->limitsTextStyle.anchor = TK_ANCHOR_SW;
		if (axisPtr->classUid == rbcXAxisUid) {
		    axisPtr->limitsTextStyle.theta = 90.0;
		    Rbc_TextToPostScript(psToken, string,
					 &axisPtr->limitsTextStyle,
					 (double)graphPtr->left, hMin);
		    hMin -= (textWidth + SPACING);
		} else {
		    axisPtr->limitsTextStyle.theta = 0.0;
		    Rbc_TextToPostScript(psToken, string,
					 &axisPtr->limitsTextStyle,
					 vMin, (double)graphPtr->bottom);
		    vMin += (textWidth + SPACING);
		}
	    }
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_GetFirstAxis --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
Axis *
Rbc_GetFirstAxis(chainPtr)
    Rbc_Chain *chainPtr;
{
    Rbc_ChainLink *linkPtr;

    linkPtr = Rbc_ChainFirstLink(chainPtr);
    if (linkPtr == NULL) {
	return NULL;
    }
    return Rbc_ChainGetValue(linkPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_NearestAxis --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
Axis *
Rbc_NearestAxis(graphPtr, x, y)
    Graph *graphPtr;
    int x, y; /* Point to be tested */
{
    register Tcl_HashEntry *hPtr;
    Tcl_HashSearch cursor;
    Axis *axisPtr;
    int width, height;
    double rotWidth, rotHeight;
    Point2D bbox[5];

    for (hPtr = Tcl_FirstHashEntry(&graphPtr->axes.table, &cursor);
	    hPtr != NULL; hPtr = Tcl_NextHashEntry(&cursor)) {
	axisPtr = (Axis *)Tcl_GetHashValue(hPtr);
	if ((axisPtr->hidden) || (!(axisPtr->flags & AXIS_ONSCREEN))) {
	    continue;		/* Don't check hidden axes or axes
				 * that are virtual. */
	}
	if (axisPtr->showTicks) {
	    register Rbc_ChainLink *linkPtr;
	    TickLabel *labelPtr;
	    Point2D t;

	    for (linkPtr = Rbc_ChainFirstLink(axisPtr->tickLabels);
		    linkPtr != NULL; linkPtr = Rbc_ChainNextLink(linkPtr)) {
		labelPtr = Rbc_ChainGetValue(linkPtr);
		Rbc_GetBoundingBox(labelPtr->width, labelPtr->height,
				   axisPtr->tickTextStyle.theta, &rotWidth, &rotHeight, bbox);
		width = ROUND(rotWidth);
		height = ROUND(rotHeight);
		t = Rbc_TranslatePoint(&labelPtr->anchorPos, width, height, axisPtr->tickTextStyle.anchor);
		t.x = x - t.x - (width * 0.5);
		t.y = y - t.y - (height * 0.5);

		bbox[4] = bbox[0];
		if (Rbc_PointInPolygon(&t, bbox, 5)) {
		    axisPtr->detail = "label";
		    return axisPtr;
		}
	    }
	}
	if (axisPtr->title != NULL) { /* and then the title string. */
	    Point2D t;

	    Rbc_GetTextExtents(&axisPtr->titleTextStyle, axisPtr->title,&width,
			       &height);
	    Rbc_GetBoundingBox(width, height, axisPtr->titleTextStyle.theta,
			       &rotWidth, &rotHeight, bbox);
	    width = ROUND(rotWidth);
	    height = ROUND(rotHeight);
	    t = Rbc_TranslatePoint(&axisPtr->titlePos, width, height, axisPtr->titleTextStyle.anchor);
	    /* Translate the point so that the 0,0 is the upper left
	     * corner of the bounding box.  */
	    t.x = x - t.x - (width / 2);
	    t.y = y - t.y - (height / 2);

	    bbox[4] = bbox[0];
	    if (Rbc_PointInPolygon(&t, bbox, 5)) {
		axisPtr->detail = "title";
		return axisPtr;
	    }
	}
	if (axisPtr->lineWidth > 0) { /* Check for the axis region */
	    if (PointInRegion(&axisPtr->region, x, y)) {
		axisPtr->detail = "line";
		return axisPtr;
	    }
	}
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * Rbc_MakeAxisTag --
 *
 *      TODO: Description
 *
 * Results:
 *      TODO: Results
 *
 * Side Effects:
 *      TODO: Side Effects
 *
 *----------------------------------------------------------------------
 */
ClientData
Rbc_MakeAxisTag(graphPtr, tagName)
    Graph *graphPtr;
    char *tagName;
{
    Tcl_HashEntry *hPtr;
    int isNew;

    hPtr = Tcl_CreateHashEntry(&graphPtr->axes.tagTable, tagName, &isNew);
    assert(hPtr);
    return Tcl_GetHashKey(&graphPtr->axes.tagTable, hPtr);
}
