Add/retrieve window options to/from the option database

## NAME

option - Add/retrieve window options to/from the option database

## SYNOPSIS

$widget->optionAdd(pattern=>value ?,priority?)

$widget->optionClear

$widget->optionGet(name,class)

$widget->optionReadfile(fileName?,priority?)

## DESCRIPTION

The option methods allow you to add entries to the Tk option database or to retrieve options from the database. The optionAdd method adds a new option to the database. Pattern contains the option being specified, and consists of names and/or classes separated by asterisks or dots, in the usual X format. Value contains a text string to associate with pattern; this is the value that will be returned in calls to Tk_GetOption or by invocations of the optionGet method. If priority is specified, it indicates the priority level for this option (see below for legal values); it defaults to interactive. This method always returns an empty string.

The optionClear method clears the option database. Default options (from the RESOURCE_MANAGER property or the .Xdefaults file) will be reloaded automatically the next time an option is added to the database or removed from it. This method always returns an empty string.

The optionGet method returns the value of the option specified for $widget under name and class. The "pathname" to $widget from its MainWindow and the classes of the widgets that "path" passes through are used to determine the prefix to use when looking up the option. (The MainWindow's name is the appname and its class is (by default) derived from the name of the script.)

If several entries in the option database match $widget, name, and class, then the method returns whichever was created with highest priority level. If there are several matching entries at the same priority level, then it returns whichever entry was most recently entered into the option database. If there are no matching entries, then the empty string is returned.

The optionReadfile method reads fileName, which should have the standard format for an X resource database such as .Xdefaults, and adds all the options specified in that file to the option database. If priority is specified, it indicates the priority level at which to enter the options; priority defaults to interactive.

The priority arguments to the option methods are normally specified symbolically using one of the following values:

widgetDefault
  Level 20. Used for default values hard-coded into widgets.
startupFile
  Level 40. Used for options specified in application-specific startup files.
userDefault
  Level 60. Used for options specified in user-specific defaults files, such as .Xdefaults, resource databases loaded into the X server, or user-specific startup files.
interactive
  Level 80. Used for options specified interactively after the application starts running. If priority isn't specified, it defaults to this level.

Any of the above keywords may be abbreviated. In addition, priorities may be specified numerically using integers between 0 and 100, inclusive. The numeric form is probably a bad idea except for new priority levels other than the ones given above.

## BUGS

The priority scheme used by core Tk is not the same as used by normal Xlib routines. In particular is assumes that the order of the entries is defined, but user commands like xrdb -merge can change the order.

## KEYWORDS

database, option, priority, retrieve