 * implemented by Tk_InitOptions, Tk_SetOptions, etc.
 */

typedef enum {
    TK_OPTION_BOOLEAN,
    TK_OPTION_INT,
    TK_OPTION_DOUBLE,
    TK_OPTION_STRING,
    TK_OPTION_STRING_TABLE,
    TK_OPTION_COLOR,
    TK_OPTION_FONT,
    TK_OPTION_BITMAP,
    TK_OPTION_BORDER,
    TK_OPTION_RELIEF,
    TK_OPTION_CURSOR,
    TK_OPTION_JUSTIFY,
    TK_OPTION_ANCHOR,
    TK_OPTION_SYNONYM,
    TK_OPTION_PIXELS,
    TK_OPTION_WINDOW,
    TK_OPTION_END,
    TK_OPTION_CUSTOM,
    TK_OPTION_STYLE
} Tk_OptionType;

/*
 * Structures of the following type are used by widgets to specify their
 * configuration options. Typically each widget has a static array of these
 * structures, where each element of the array describes a single
 * configuration option. The array is passed to Tk_CreateOptionTable.
 */

typedef struct Tk_OptionSpec {
    Tk_OptionType type;		/* Type of option, such as TK_OPTION_COLOR;
				 * see definitions above. Last option in table
				 * must have type TK_OPTION_END. */
    const char *optionName;	/* Name used to specify option in Tcl
				 * commands. */
    const char *dbName;		/* Name for option in option database. */
    const char *dbClass;	/* Class for option in database. */
    const char *defValue;	/* Default value for option if not specified
				 * in command line, the option database, or
				 * the system. */
    int objOffset;		/* Where in record to store a Tcl_Obj * that
				 * holds the value of this option, specified
				 * as an offset in bytes from the start of the
				 * record. Use the Tk_Offset macro to generate
				 * values for this. -1 means don't store the
				 * Tcl_Obj in the record. */
    int internalOffset;		/* Where in record to store the internal
				 * representation of the value of this option,
				 * such as an int or XColor *. This field is
				 * specified as an offset in bytes from the
				 * start of the record. Use the Tk_Offset
				 * macro to generate values for it. -1 means
				 * don't store the internal representation in
				 * the record. */
    int flags;			/* Any combination of the values defined
				 * below. */
    const void *clientData;	/* An alternate place to put option-specific
				 * data. Used for the monochrome default value
				 * for colors, etc. */
    int typeMask;		/* An arbitrary bit mask defined by the class
				 * manager; typically bits correspond to
				 * certain kinds of options such as all those
				 * that require a redisplay when they change.
				 * Tk_SetOptions returns the bit-wise OR of
				 * the typeMasks of all options that were
				 * changed. */
} Tk_OptionSpec;

/*
 * Flag values for Tk_OptionSpec structures. These flags are shared by
 * Tk_ConfigSpec structures, so be sure to coordinate any changes carefully.
 */

#define TK_OPTION_NULL_OK		(1 << 0)
#define TK_OPTION_DONT_SET_DEFAULT	(1 << 3)

/*
 * The following structure and function types are used by TK_OPTION_CUSTOM
 * options; the structure holds pointers to the functions needed by the Tk
 * option config code to handle a custom option.
 */

typedef int (Tk_CustomOptionSetProc) (ClientData clientData,
	Tcl_Interp *interp, Tk_Window tkwin, Tcl_Obj **value, char *widgRec,
	int offset, char *saveInternalPtr, int flags);
typedef Tcl_Obj *(Tk_CustomOptionGetProc) (ClientData clientData,
	Tk_Window tkwin, char *widgRec, int offset);
typedef void (Tk_CustomOptionRestoreProc) (ClientData clientData,
	Tk_Window tkwin, char *internalPtr, char *saveInternalPtr);
typedef void (Tk_CustomOptionFreeProc) (ClientData clientData, Tk_Window tkwin,
	char *internalPtr);

typedef struct Tk_ObjCustomOption {
    const char *name;		/* Name of the custom option. */
    Tk_CustomOptionSetProc *setProc;
				/* Function to use to set a record's option
				 * value from a Tcl_Obj */
    Tk_CustomOptionGetProc *getProc;
				/* Function to use to get a Tcl_Obj
				 * representation from an internal
				 * representation of an option. */
    Tk_CustomOptionRestoreProc *restoreProc;
				/* Function to use to restore a saved value
				 * for the internal representation. */
    Tk_CustomOptionFreeProc *freeProc;
				/* Function to use to free the internal
				 * representation of an option. */
    ClientData clientData;	/* Arbitrary one-word value passed to the
				 * handling procs. */
} Tk_ObjCustomOption;

/*
 * Macro to use to fill in "offset" fields of the Tk_OptionSpec structure.
 * Computes number of bytes from beginning of structure to a given field.
 */

#define Tk_Offset(type, field) ((int) offsetof(type, field))
/* Workaround for platforms missing offsetof(), e.g. VC++ 6.0 */
#ifndef offsetof
#   define offsetof(type, field) ((size_t) ((char *) &((type *) 0)->field))
#endif

/*
 * The following two structures are used for error handling. When config
 * options are being modified, the old values are saved in a Tk_SavedOptions
 * structure. If an error occurs, then the contents of the structure can be
 * used to restore all of the old values. The contents of this structure are
 * for the private use Tk. No-one outside Tk should ever read or write any of
 * the fields of these structures.
 */

typedef struct Tk_SavedOption {
    struct TkOption *optionPtr;	/* Points to information that describes the
				 * option. */
    Tcl_Obj *valuePtr;		/* The old value of the option, in the form of
				 * a Tcl object; may be NULL if the value was
				 * not saved as an object. */
    double internalForm;	/* The old value of the option, in some
				 * internal representation such as an int or
				 * (XColor *). Valid only if the field
				 * optionPtr->specPtr->objOffset is < 0. The
				 * space must be large enough to accommodate a
				 * double, a long, or a pointer; right now it
				 * looks like a double (i.e., 8 bytes) is big
				 * enough. Also, using a double guarantees
				 * that the field is properly aligned for
				 * storing large values. */
} Tk_SavedOption;

#ifdef TCL_MEM_DEBUG
#   define TK_NUM_SAVED_OPTIONS 2
#else
#   define TK_NUM_SAVED_OPTIONS 20
#endif

typedef struct Tk_SavedOptions {
    char *recordPtr;		/* The data structure in which to restore
				 * configuration options. */
    Tk_Window tkwin;		/* Window associated with recordPtr; needed to
				 * restore certain options. */
    int numItems;		/* The number of valid items in items field. */
    Tk_SavedOption items[TK_NUM_SAVED_OPTIONS];
				/* Items used to hold old values. */
    struct Tk_SavedOptions *nextPtr;
				/* Points to next structure in list; needed if
				 * too many options changed to hold all the
				 * old values in a single structure. NULL
				 * means no more structures. */
} Tk_SavedOptions;
