itclvars(n)							    [incr Tcl]							       itclvars(n)

NAME

       itclvars - variables used by [incr Tcl]

DESCRIPTION

       The  following global variables are created and managed automatically by the [incr Tcl] library.  Except where noted below, these variables
       should normally be treated as read-only by application-specific code and by users.

       itcl::library
	      When an interpreter is created, [incr Tcl] initializes this variable to hold the name of a directory containing the  system  library
	      of [incr Tcl] scripts.  The initial value of itcl::library is set from the ITCL_LIBRARY environment variable if it exists, or from a
	      compiled-in value otherwise.

       itcl::patchLevel
	      When an interpreter is created, [incr Tcl] initializes this variable to hold the current patch level for [incr Tcl].   For  example,
	      the value "2.0p1" indicates [incr Tcl] version 2.0 with the first set of patches applied.

       itcl::purist
	      When  an interpreter is created containing Tcl/Tk and the [incr Tcl] namespace facility, this variable controls a "backward-compati-
	      bility" mode for widget access.

	      In vanilla Tcl/Tk, there is a single pool of commands, so the access command for a widget is the same as the window  name.   When  a
	      widget  is created within a namespace, however, its access command is installed in that namespace, and should be accessed outside of
	      the namespace using a qualified name.  For example, namespace foo {
		  namespace bar {
		      button .b -text "Testing"
		  } } foo::bar::.b configure -background red pack .b Note that the window name ".b" is still used  in  conjunction  with  commands
	      like pack and destroy.  However, the access command for the widget (i.e., name that appears as the first argument on a command line)
	      must be more specific.

	      The "winfo command" command can be used to query the fully-qualified access command for any widget, so one can write: [winfo command
	      .b]  configure  -background  red and this is good practice when writing library procedures.  Also, in conjunction with the bind com-
	      mand, the "%q" field can be used in place of "%W" as the access command: bind Button <Key-Return> {%q flash; %q invoke}  While  this
	      behavior	makes  sense  from  the  standpoint of encapsulation, it causes problems with existing Tcl/Tk applications.  Many existing
	      applications are written with bindings that use "%W".  Many library procedures assume that the window name is the access command.

	      The itcl::purist variable controls a backward-compatibility mode.  By default, this variable is "0", and the window name can be used
	      as  an  access command in any context.  Whenever the unknown procedure stumbles across a widget name, it simply uses "winfo command"
	      to determine the appropriate command name.  If this variable is set to "1", this	backward-compatibility	mode  is  disabled.   This
	      gives better encapsulation, but using the window name as the access command may lead to "invalid command" errors.

       itcl::version
	      When  an interpreter is created, [incr Tcl] initializes this variable to hold the version number of the form x.y.  Changes to x rep-
	      resent major changes with probable incompatibilities and changes to y represent small enhancements and bug fixes that  retain  back-
	      ward compatibility.

KEYWORDS

       itcl, variables

itcl									3.0							       itclvars(n)