X User Tools

home *** CD-ROM | disk | FTP | other *** search

/ X User Tools / X User Tools (O'Reilly and Associates)(1994).ISO / sun4c / archive / tcltk.z / tcltk / man / cat3 / ConfigWidg.3 < prev next >

Wrap

Text File | 1994-09-20 | 38.4 KB | 859 lines

Tk_ConfigureWidget(3) Tk Library Procedures 3.3 _________________________________________________________________ NAME Tk_ConfigureWidget, Tk_Offset, Tk_ConfigureInfo, Tk_FreeOptions - process configuration options for widgets SYNOPSIS #include <tk.h> int Tk_ConfigureWidget(_i_n_t_e_r_p, _t_k_w_i_n, _s_p_e_c_s, _a_r_g_c, _a_r_g_v, _w_i_d_g_R_e_c, _f_l_a_g_s) int Tk_Offset(_t_y_p_e, _f_i_e_l_d) int Tk_ConfigureInfo(_i_n_t_e_r_p, _t_k_w_i_n, _s_p_e_c_s, _w_i_d_g_R_e_c, _a_r_g_v_N_a_m_e, _f_l_a_g_s) Tk_FreeOptions(_s_p_e_c_s, _w_i_d_g_R_e_c, _d_i_s_p_l_a_y, _f_l_a_g_s) | ARGUMENTS Tcl_Interp *_i_n_t_e_r_p (in) Interpreter to use for returning error mes- sages. Tk_Window _t_k_w_i_n (in) Window used to represent widget (needed to set up X resources). Tk_ConfigSpec *_s_p_e_c_s (in) Pointer to table speci- fying legal configura- tion options for this widget. int _a_r_g_c (in) Number of arguments in _a_r_g_v. char **_a_r_g_v (in) Command-line options for configuring widget. char *_w_i_d_g_R_e_c (in/out) Points to widget record structure. Fields in this structure get modified by Tk_ConfigureWidget to hold configuration information. int _f_l_a_g_s (in) If non-zero, then it specifies an OR-ed com- bination of flags that Tk 1 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 control the processing of configuration infor- mation. TK_CONFIG_ARGV_ONLY causes the option data- base and defaults to be ignored, and flag bits TK_CONFIG_USER_BIT and higher are used to selectively disable entries in _s_p_e_c_s. type name _t_y_p_e (in) The name of the type of a widget record. field name _f_i_e_l_d (in) The name of a field in records of type _t_y_p_e. char *_a_r_g_v_N_a_m_e (in) The name used on Tcl command lines to refer to a particular option (e.g. when creating a widget or invoking the configure widget com- mand). If non-NULL, then information is returned only for this option. If NULL, then information is returned for all available options. Display *_d_i_s_p_l_a_y (in) Display containing widget whose record is being freed; needed in order to free up resources. _________________________________________________________________ DESCRIPTION Tk_ConfigureWidget is called to configure various aspects of a widget, such as colors, fonts, border width, etc. It is intended as a convenience procedure to reduce the amount of code that must be written in individual widget managers to handle configuration information. It is typically invoked when widgets are created, and again when the configure com- mand is invoked for a widget. Although intended primarily for widgets, Tk_ConfigureWidget can be used in other situa- tions where _a_r_g_c-_a_r_g_v information is to be used to fill in a record structure, such as configuring graphical elements for a canvas widget or entries of a menu. Tk 2 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 Tk_ConfigureWidget processes a table specifying the confi- guration options that are supported (_s_p_e_c_s) and a collection of command-line arguments (_a_r_g_c and _a_r_g_v) to fill in fields of a record (_w_i_d_g_R_e_c). It uses the option database and defaults specified in _s_p_e_c_s to fill in fields of _w_i_d_g_R_e_c that are not specified in _a_r_g_v. Tk_ConfigureWidget normally returns the value TCL_OK; in this case it does not modify _i_n_t_e_r_p. If an error occurs then TCL_ERROR is returned and Tk_ConfigureWidget will leave an error message in _i_n_t_e_r_p- >_r_e_s_u_l_t in the standard Tcl fashion. In the event of an error return, some of the fields of _w_i_d_g_R_e_c could already have been set, if configuration information for them was successfully processed before the error occurred. The other | fields will be set to reasonable initial values so that | Tk_FreeOptions can be called for cleanup. The _s_p_e_c_s array specifies the kinds of configuration options expected by the widget. Each of its entries specifies one configuration option and has the following structure: typedef struct { int _t_y_p_e; char *_a_r_g_v_N_a_m_e; char *_d_b_N_a_m_e; char *_d_b_C_l_a_s_s; char *_d_e_f_V_a_l_u_e; int _o_f_f_s_e_t; int _s_p_e_c_F_l_a_g_s; Tk_CustomOption *_c_u_s_t_o_m_P_t_r; | } Tk_ConfigSpec; The _t_y_p_e field indicates what type of configuration option this is (e.g. TK_CONFIG_COLOR for a color value, or TK_CONFIG_INT for an integer value). The _t_y_p_e field indi- cates how to use the value of the option (more on this below). The _a_r_g_v_N_a_m_e field is a string such as ``-font'' or ``-bg'', which is compared with the values in _a_r_g_v (if _a_r_g_v_N_a_m_e is NULL it means this is a grouped entry; see GROUPED ENTRIES below). The _d_b_N_a_m_e and _d_b_C_l_a_s_s fields are used to look up a value for this option in the option data- base. The _d_e_f_V_a_l_u_e field specifies a default value for this configuration option if no value is specified in either _a_r_g_v or the option database. _O_f_f_s_e_t indicates where in _w_i_d_g_R_e_c to store information about this option, and _s_p_e_c_F_l_a_g_s con- tains additional information to control the processing of this configuration option (see FLAGS below). The last field, _c_u_s_t_o_m_P_t_r, is only used if _t_y_p_e is TK_CONFIG_CUSTOM; see CUSTOM OPTION TYPES below. Tk_ConfigureWidget first processes _a_r_g_v to see which (if any) configuration options are specified there. _A_r_g_v must contain an even number of fields; the first of each pair of Tk 3 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 fields must match the _a_r_g_v_N_a_m_e of some entry in _s_p_e_c_s (unique abbreviations are acceptable), and the second field of the pair contains the value for that configuration option. If there are entries in _s_p_e_c for which there were no matching entries in _a_r_g_v, Tk_ConfigureWidget uses the _d_b_N_a_m_e and _d_b_C_l_a_s_s fields of the _s_p_e_c_s entry to probe the option database; if a value is found, then it is used as the value for the option. Finally, if no entry is found in the option database, the _d_e_f_V_a_l_u_e field of the _s_p_e_c_s entry is used as the value for the configuration option. If the _d_e_f_V_a_l_u_e is NULL, or if the TK_CONFIG_DONT_SET_DEFAULT bit is set in _f_l_a_g_s, then there is no default value and this _s_p_e_c_s entry will be ignored if no value is specified in _a_r_g_v or the option database. Once a string value has been determined for a configuration option, Tk_ConfigureWidget translates the string value into a more useful form, such as a color if _t_y_p_e is TK_CONFIG_COLOR or an integer if _t_y_p_e is TK_CONFIG_INT. This value is then stored in the record pointed to by _w_i_d_g_R_e_c. This record is assumed to contain information relevant to the manager of the widget; its exact type is unknown to Tk_ConfigureWidget. The _o_f_f_s_e_t field of each _s_p_e_c_s entry indicates where in _w_i_d_g_R_e_c to store the informa- tion about this configuration option. You should use the Tk_Offset macro to generate _o_f_f_s_e_t values (see below for a description of Tk_Offset). The location indicated by _w_i_d_g_R_e_c and _o_f_f_s_e_t will be referred to as the ``target'' in the descriptions below. The _t_y_p_e field of each entry in _s_p_e_c_s determines what to do with the string value of that configuration option. The legal values for _t_y_p_e, and the corresponding actions, are: TK_CONFIG_ACTIVE_CURSOR The value must be an ASCII string identifying a cursor | in a form suitable for passing to Tk_GetCursor. The | value is converted to a Cursor by calling Tk_GetCursor | and the result is stored in the target. In addition, | the resulting cursor is made the active cursor for | _t_k_w_i_n by calling XDefineCursor. If TK_CONFIG_NULL_OK | is specified in _s_p_e_c_F_l_a_g_s then the value may be an | empty string, in which case the target and _t_k_w_i_n's | active cursor will be set to None. If the previous | value of the target wasn't None, then it is freed by | passing it to Tk_FreeCursor. | TK_CONFIG_ANCHOR || The value must be an ASCII string identifying an anchor | point in one of the ways accepted by Tk_GetAnchor. The | string is converted to a Tk_Anchor by calling | Tk_GetAnchor and the result is stored in the target. Tk 4 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 TK_CONFIG_BITMAP The value must be an ASCII string identifying a bitmap in a form suitable for passing to Tk_GetBitmap. The value is converted to a Pixmap by calling Tk_GetBitmap and the result is stored in the target. If | TK_CONFIG_NULL_OK is specified in _s_p_e_c_F_l_a_g_s then the | value may be an empty string, in which case the target | is set to None. If the previous value of the target wasn't None, then it is freed by passing it to Tk_FreeBitmap. TK_CONFIG_BOOLEAN The value must be an ASCII string specifying a boolean value. Any of the values ``true'', ``yes'', ``on'', or ``1'', or an abbreviation of one of these values, means true; any of the values ``false'', ``no'', ``off'', or ``0'', or an abbreviation of one of these values, means false. The target is expected to be an integer; for true values it will be set to 1 and for false values it will be set to 0. TK_CONFIG_BORDER The value must be an ASCII string identifying a border color in a form suitable for passing to Tk_Get3DBorder. The value is converted to a (Tk_3DBorder *) by calling Tk_Get3DBorder and the result is stored in the target. | If TK_CONFIG_NULL_OK is specified in _s_p_e_c_F_l_a_g_s then the | value may be an empty string, in which case the target | will be set to NULL. If the previous value of the tar- get wasn't NULL, then it is freed by passing it to Tk_Free3DBorder. TK_CONFIG_CAP_STYLE The value must be an ASCII string identifying a cap | style in one of the ways accepted by Tk_GetCapStyle. | The string is converted to an integer value correspond- | ing to the cap style by calling Tk_GetCapStyle and the | result is stored in the target. TK_CONFIG_COLOR The value must be an ASCII string identifying a color in a form suitable for passing to Tk_GetColor. The value is converted to an (XColor *) by calling Tk_GetColor and the result is stored in the target. If | TK_CONFIG_NULL_OK is specified in _s_p_e_c_F_l_a_g_s then the | value may be an empty string, in which case the target | will be set to None. If the previous value of the tar- get wasn't NULL, then it is freed by passing it to Tk_FreeColor. TK_CONFIG_CURSOR This option is identical to TK_CONFIG_ACTIVE_CURSOR Tk 5 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 except that the new cursor is not made the active one for _t_k_w_i_n. TK_CONFIG_CUSTOM This option allows applications to define new option | types. The _c_u_s_t_o_m_P_t_r field of the entry points to a | structure defining the new option type. See the sec- | tion CUSTOM OPTION TYPES below for details. TK_CONFIG_DOUBLE The value must be an ASCII floating-point number in the format accepted by strtol. The string is converted to a double value, and the value is stored in the target. TK_CONFIG_END Marks the end of the table. The last entry in _s_p_e_c_s must have this type; all of its other fields are ignored and it will never match any arguments. TK_CONFIG_FONT The value must be an ASCII string identifying a font in a form suitable for passing to Tk_GetFontStruct. The value is converted to an (XFontStruct *) by calling Tk_GetFontStruct and the result is stored in the tar- get. If TK_CONFIG_NULL_OK is specified in _s_p_e_c_F_l_a_g_s | then the value may be an empty string, in which case | the target will be set to NULL. If the previous value of the target wasn't NULL, then it is freed by passing it to Tk_FreeFontStruct. TK_CONFIG_INT The value must be an ASCII integer string in the format accepted by strtol (e.g. ``0'' and ``0x'' prefixes may be used to specify octal or hexadecimal numbers, respectively). The string is converted to an integer value and the integer is stored in the target. TK_CONFIG_JOIN_STYLE The value must be an ASCII string identifying a join | style in one of the ways accepted by Tk_GetJoinStyle. | The string is converted to an integer value correspond- | ing to the join style by calling Tk_GetJoinStyle and | the result is stored in the target. | TK_CONFIG_JUSTIFY || The value must be an ASCII string identifying a justif- | ication method in one of the ways accepted by | Tk_GetJustify. The string is converted to a Tk_Justify | by calling Tk_GetJustify and the result is stored in | the target. | TK_CONFIG_MM || Tk 6 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 The value must specify a screen distance in one of the | forms acceptable to Tk_GetScreenMM. The string is con- | verted to double-precision floating-point distance in | millimeters and the value is stored in the target. | TK_CONFIG_PIXELS || The value must specify screen units in one of the forms | acceptable to Tk_GetPixels. The string is converted to | an integer distance in pixels and the value is stored | in the target. TK_CONFIG_RELIEF The value must be an ASCII string identifying a relief in a form suitable for passing to Tk_GetRelief. The value is converted to an integer relief value by cal- ling Tk_GetRelief and the result is stored in the tar- get. TK_CONFIG_STRING A copy of the value is made by allocating memory space | with malloc and copying the value into the | dynamically-allocated space. A pointer to the new | string is stored in the target. If TK_CONFIG_NULL_OK | is specified in _s_p_e_c_F_l_a_g_s then the value may be an | empty string, in which case the target will be set to | NULL. If the previous value of the target wasn't NULL, | then it is freed by passing it to free. TK_CONFIG_SYNONYM This _t_y_p_e value identifies special entries in _s_p_e_c_s that are synonyms for other entries. If an _a_r_g_v value matches the _a_r_g_v_N_a_m_e of a TK_CONFIG_SYNONYM entry, the entry isn't used directly. Instead, Tk_ConfigureWidget searches _s_p_e_c_s for another entry whose _a_r_g_v_N_a_m_e is the same as the _d_b_N_a_m_e field in the TK_CONFIG_SYNONYM entry; this new entry is used just as if its _a_r_g_v_N_a_m_e had matched the _a_r_g_v value. The synonym mechanism allows multiple _a_r_g_v values to be used for a single configuration option, such as ``-background'' and ``-bg''. TK_CONFIG_UID The value is translated to a Tk_Uid (by passing it to Tk_GetUid). The resulting value is stored in the tar- get. If TK_CONFIG_NULL_OK is specified in _s_p_e_c_F_l_a_g_s | and the value is an empty string then the target will | be set to NULL. | TK_CONFIG_WINDOW || The value must be a window path name. It is translated | to a Tk_Window token and the token is stored in the | target. Tk 7 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 GROUPED ENTRIES In some cases it is useful to generate multiple resources from a single configuration value. For example, a color name might be used both to generate the background color for a widget (using TK_CONFIG_COLOR) and to generate a 3-D border to draw around the widget (using TK_CONFIG_BORDER). In cases like this it is possible to specify that several consecutive entries in _s_p_e_c_s are to be treated as a group. The first entry is used to determine a value (using its _a_r_g_v_N_a_m_e, _d_b_N_a_m_e, _d_b_C_l_a_s_s, and _d_e_f_V_a_l_u_e fields). The value will be processed several times (one for each entry in the group), generating multiple different resources and modify- ing multiple targets within _w_i_d_g_R_e_c. Each of the entries after the first must have a NULL value in its _a_r_g_v_N_a_m_e field; this indicates that the entry is to be grouped with the entry that precedes it. Only the _t_y_p_e and _o_f_f_s_e_t fields are used from these follow-on entries. FLAGS The _f_l_a_g_s argument passed to Tk_ConfigureWidget is used in conjunction with the _s_p_e_c_F_l_a_g_s fields in the entries of _s_p_e_c_s to provide additional control over the processing of configuration options. These values are used in three dif- ferent ways as described below. First, if the _f_l_a_g_s argument to Tk_ConfigureWidget has the TK_CONFIG_ARGV_ONLY bit set (i.e., _f_l_a_g_s | TK_CONFIG_ARGV_ONLY != 0), then the option database and _d_e_f_V_a_l_u_e fields are not used. In this case, if an entry in _s_p_e_c_s doesn't match a field in _a_r_g_v then nothing happens: the corresponding target isn't modified. This feature is useful when the goal is to modify certain configuration options while leaving others in their current state, such as when a configure widget command is being processed. Second, the _s_p_e_c_F_l_a_g_s field of an entry in _s_p_e_c_s may be used | to control the processing of that entry. Each _s_p_e_c_F_l_a_g_s | field may consists of an OR-ed combination of the following | values: | TK_CONFIG_COLOR_ONLY || If this bit is set then the entry will only be con- | sidered if the display for _t_k_w_i_n has more than one bit | plane. If the display is monochromatic then this _s_p_e_c_s | entry will be ignored. | TK_CONFIG_MONO_ONLY || If this bit is set then the entry will only be con- | sidered if the display for _t_k_w_i_n has exactly one bit | plane. If the display is not monochromatic then this | _s_p_e_c_s entry will be ignored. | Tk 8 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 TK_CONFIG_NULL_OK || This bit is only relevant for some types of entries | (see the descriptions of the various entry types | above). If this bit is set, it indicates that an empty | string value for the field is acceptable and if it | occurs then the target should be set to NULL or None, | depending on the type of the target. This flag is typ- | ically used to allow a feature to be turned off | entirely, e.g. set a cursor value to None so that a | window simply inherits its parent's cursor. If this | bit isn't set then empty strings are processed as | strings, which generally results in an error. | TK_CONFIG_DONT_SET_DEFAULT || If this bit is one, it means that the _d_e_f_V_a_l_u_e field of | the entry should only be used for returning the default | value in Tk_ConfigureInfo. In calls to | Tk_ConfigureWidget no default will be supplied for | entries with this flag set; it is assumed that the | caller has already supplied a default value in the tar- | get location. This flag provides a performance optimi- | zation where it is expensive to process the default | string: the client can compute the default once, save | the value, and provide it before calling | Tk_ConfigureWidget. | TK_CONFIG_OPTION_SPECIFIED || This bit is set and cleared by Tk_ConfigureWidget. | Whenever Tk_ConfigureWidget returns, this bit will be | set in all the entries where a value was specified in | _a_r_g_v. It will be zero in all other entries. This bit | provides a way for clients to determine which values | actually changed in a call to Tk_ConfigureWidget. The TK_CONFIG_MONO_ONLY and TK_CONFIG_COLOR_ONLY flags are typically used to specify different default values for mono- chrome and color displays. This is done by creating two entries in _s_p_e_c_s that are identical except for their _d_e_f_V_a_l_u_e and _s_p_e_c_F_l_a_g_s fields. One entry should have the value TK_CONFIG_MONO_ONLY in its _s_p_e_c_F_l_a_g_s and the default value for monochrome displays in its _d_e_f_V_a_l_u_e; the other entry entry should have the value TK_CONFIG_COLOR_ONLY in its _s_p_e_c_F_l_a_g_s and the appropriate _d_e_f_V_a_l_u_e for color displays. Third, it is possible to use _f_l_a_g_s and _s_p_e_c_F_l_a_g_s together to selectively disable some entries. This feature is not needed very often. It is useful in cases where several similar kinds of widgets are implemented in one place. It allows a single _s_p_e_c_s table to be created with all the con- figuration options for all the widget types. When process- ing a particular widget type, only entries relevant to that Tk 9 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 type will be used. This effect is achieved by setting the high-order bits (those in positions equal to or greater than TK_CONFIG_USER_BIT) in _s_p_e_c_F_l_a_g_s values or in _f_l_a_g_s. In order for a particular entry in _s_p_e_c_s to be used, its high- order bits must match exactly the high-order bits of the _f_l_a_g_s value passed to Tk_ConfigureWidget. If a _s_p_e_c_s table is being used for N different widget types, then N of the high-order bits will be used. Each _s_p_e_c_s entry will have one of more of those bits set in its _s_p_e_c_F_l_a_g_s field to indicate the widget types for which this entry is valid. When calling Tk_ConfigureWidget, _f_l_a_g_s will have a single one of these bits set to select the entries for the desired widget type. For a working example of this feature, see the code in tkButton.c. TK_OFFSET The Tk_Offset macro is provided as a safe way of generating the _o_f_f_s_e_t values for entries in Tk_ConfigSpec structures. It takes two arguments: the name of a type of record, and the name of a field in that record. It returns the byte offset of the named field in records of the given type. TK_CONFIGUREINFO The Tk_ConfigureInfo procedure may be used to obtain infor- mation about one or all of the options for a given widget. Given a token for a window (_t_k_w_i_n), a table describing the configuration options for a class of widgets (_s_p_e_c_s), a pointer to a widget record containing the current informa- tion for a widget (_w_i_d_g_R_e_c), and a NULL _a_r_g_v_N_a_m_e argument, Tk_ConfigureInfo generates a string describing all of the configuration options for the window. The string is placed in _i_n_t_e_r_p->_r_e_s_u_l_t. Under normal circumstances it returns TCL_OK; if an error occurs then it returns TCL_ERROR and _i_n_t_e_r_p->_r_e_s_u_l_t contains an error message. If _a_r_g_v_N_a_m_e is NULL, then the value left in _i_n_t_e_r_p->_r_e_s_u_l_t by Tk_ConfigureInfo consists of a list of one or more entries, each of which describes one configuration option (i.e. one entry in _s_p_e_c_s). Each entry in the list will con- tain either two or five values. If the corresponding entry in _s_p_e_c_s has type TK_CONFIG_SYNONYM, then the list will con- tain two values: the _a_r_g_v_N_a_m_e for the entry and the _d_b_N_a_m_e (synonym name). Otherwise the list will contain five values: _a_r_g_v_N_a_m_e, _d_b_N_a_m_e, _d_b_C_l_a_s_s, _d_e_f_V_a_l_u_e, and current value. The current value is computed from the appropriate field of _w_i_d_g_R_e_c by calling procedures like Tk_NameOfColor. If the _a_r_g_v_N_a_m_e argument to Tk_ConfigureInfo is non-NULL, then it indicates a single option, and information is returned only for that option. The string placed in Tk 10 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 _i_n_t_e_r_p->_r_e_s_u_l_t will be a list containing two or five values as described above; this will be identical to the corresponding sublist that would have been returned if _a_r_g_v_N_a_m_e had been NULL. The _f_l_a_g_s argument to Tk_ConfigureInfo is used to restrict the _s_p_e_c_s entries to consider, just as for Tk_ConfigureWidget. TK_FREEOPTIONS The Tk_FreeOptions procedure may be invoked during widget | cleanup to release all of the resources associated with con- | figuration options. It scans through _s_p_e_c_s and for each | entry corresponding to a resource that must be explicitly | freed (e.g. those with type TK_CONFIG_COLOR), it frees the | resource in the widget record. If the field in the widget | record doesn't refer to a resource (e.g. it contains a null | pointer) then no resource is freed for that entry. After | freeing a resource, Tk_FreeOptions sets the corresponding | field of the widget record to null. CUSTOM OPTION TYPES Applications can extend the built-in configuration types | with additional configuration types by writing procedures to | parse and print options of the a type and creating a struc- | ture pointing to those procedures: | typedef struct Tk_CustomOption { | Tk_OptionParseProc *_p_a_r_s_e_P_r_o_c; | Tk_OptionPrintProc *_p_r_i_n_t_P_r_o_c; | ClientData _c_l_i_e_n_t_D_a_t_a; | } Tk_CustomOption; | typedef int Tk_OptionParseProc( | ClientData _c_l_i_e_n_t_D_a_t_a, | Tcl_Interp *_i_n_t_e_r_p, | Tk_Window _t_k_w_i_n, | char *_v_a_l_u_e, | char *_w_i_d_g_R_e_c, | int _o_f_f_s_e_t); | typedef char *Tk_OptionPrintProc( | ClientData _c_l_i_e_n_t_D_a_t_a, | Tk_Window _t_k_w_i_n, | char *_w_i_d_g_R_e_c, | int _o_f_f_s_e_t, | Tcl_FreeProc **_f_r_e_e_P_r_o_c_P_t_r); | Tk 11 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 The Tk_CustomOption structure contains three fields, which | are pointers to the two procedures and a _c_l_i_e_n_t_D_a_t_a value to | be passed to those procedures when they are invoked. The | _c_l_i_e_n_t_D_a_t_a value typically points to a structure containing | information that is needed by the procedures when they are | parsing and printing options. | The _p_a_r_s_e_P_r_o_c procedure is invoked by Tk_ConfigureWidget to | parse a string and store the resulting value in the widget | record. The _c_l_i_e_n_t_D_a_t_a argument is a copy of the _c_l_i_e_n_t_D_a_t_a | field in the Tk_CustomOption structure. The _i_n_t_e_r_p argument | points to a Tcl interpreter used for error reporting. _T_k_w_i_n | is a copy of the _t_k_w_i_n argument to Tk_ConfigureWidget. The | _v_a_l_u_e argument is a string describing the value for the | option; it could have been specified explicitly in the call | to Tk_ConfigureWidget or it could come from the option data- | base or a default. _V_a_l_u_e will never be a null pointer but | it may point to an empty string. _R_e_c_o_r_d_P_t_r is the same as | the _w_i_d_g_R_e_c argument to Tk_ConfigureWidget; it points to | the start of the widget record to modify. The last argu- | ment, _o_f_f_s_e_t, gives the offset in bytes from the start of | the widget record to the location where the option value is | to be placed. The procedure should translate the string to | whatever form is appropriate for the option and store the | value in the widget record. It should normally return | TCL_OK, but if an error occurs in translating the string to | a value then it should return TCL_ERROR and store an error | message in _i_n_t_e_r_p->_r_e_s_u_l_t. | The _p_r_i_n_t_P_r_o_c procedure is called by Tk_ConfigureInfo to | produce a string value describing an existing option. Its | _c_l_i_e_n_t_D_a_t_a, _t_k_w_i_n, _w_i_d_g_R_e_c, and _o_f_f_s_e_t arguments all have | the same meaning as for Tk_OptionParseProc procedures. The | _p_r_i_n_t_P_r_o_c procedure should examine the option whose value is | stored at _o_f_f_s_e_t in _w_i_d_g_R_e_c, produce a string describing | that option, and return a pointer to the string. If the | string is stored in dynamically-allocated memory, then the | procedure must set *_f_r_e_e_P_r_o_c_P_t_r to the address of a pro- | cedure to call to free the string's memory; | Tk_ConfigureInfo will call this procedure when it is fin- | ished with the string. If the result string is stored in | static memory then _p_r_i_n_t_P_r_o_c need not do anything with the | _f_r_e_e_P_r_o_c_P_t_r argument. | Once _p_a_r_s_e_P_r_o_c and _p_r_i_n_t_P_r_o_c have been defined and a | Tk_CustomOption structure has been created for them, options | of this new type may be manipulated with Tk_ConfigSpec | entries whose _t_y_p_e fields are TK_CONFIG_CUSTOM and whose | _c_u_s_t_o_m_P_t_r fields point to the Tk_CustomOption structure. Tk 12 Tk_ConfigureWidget(3) Tk Library Procedures 3.3 EXAMPLES Although the explanation of Tk_ConfigureWidget is fairly complicated, its actual use is pretty straightforward. The easiest way to get started is to copy the code from an existing widget. The library implementation of frames (tkFrame.c) has a simple configuration table, and the library implementation of buttons (tkButton.c) has a much more complex table that uses many of the fancy _s_p_e_c_F_l_a_g_s mechanisms. KEYWORDS anchor, bitmap, boolean, border, cap style, color, confi- guration options, cursor, custom, double, font, integer, join style, justify, millimeters, pixels, relief, synonym, uid Tk 13