option − Add/retrieve window options to/from the option database
option add pattern value ?priority?
option get window name class
option readfile fileName ?priority? _________________________________________________________________
The option command allows you to add entries to the Tk option database or to retrieve options from the database. The add form of the command 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 option get command. If priority is specified, it indicates the priority level for this option (see below for legal values); it defaults to interactive. This command always returns an empty string.
The option clear command 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 command always returns an empty string.
The option get command returns the value of the option specified for window under name and class. If several entries in the option database match window, name, and class, then the command 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 readfile form of the command 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 command are normally specified symbolically using one of the following values:
Level 20. Used for default values hard-coded into widgets.
Level 40. Used for options specified in application-specific startup files.
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.
Level 80. Used for options specified interactively after the application starts running. If priority is not 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.
Instruct every button in the application to have red text on it unless explicitly overridden:
option add *button.foreground red startupFile
Allow users to control what happens in an entry widget when the Return key is pressed by specifying a script in the option database and add a default option for that which rings the bell:
bind .e <Return> [option get .e returnCommand Command]
option add *.e.returnCommand bell widgetDefault
database, option, priority, retrieve