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

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NAME

       itclvars - variables used by [incr Tcl]
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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  wid-
       get (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 command, 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 encapsula-
       tion, 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)