itclvars(n) [redhat man page]

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)

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scope(n)							    [incr Tcl]								  scope(n)

__________________________________________________________________________________________________________________________________________________

NAME

       scope - capture the namespace context for a variable

SYNOPSIS

       itcl::scope name
_________________________________________________________________

DESCRIPTION

       Creates	a scoped value for the specified name, which must be a variable name.  If the name is an instance variable, then the scope command
       returns a string of the following form:
	      @itcl object varName
       This is recognized in any context as an instance variable belonging to object.  So with itcl3.0 and beyond, it is possible to use  instance
       variables in conjunction with widgets.  For example, if you have an object with a private variable x, and you can use x in conjunction with
       the -textvariable option of an entry widget.  Before itcl3.0, only common variables could be used in this manner.

       If the name is not an instance variable, then it must be a common variable or a global variable.  In that case, the scope  command  returns
       the fully qualified name of the variable, e.g., ::foo::bar::x.

       If the name is not recognized as a variable, the scope command returns an error.

       Ordinary  variable  names  refer to variables in the global namespace.  A scoped value captures a variable name together with its namespace
       context in a way that allows it to be referenced properly later.  It is needed, for example, to wrap up variable names when a Tk widget	is
       used within a namespace:
	      namespace foo {
		  private variable mode 1

		  radiobutton .rb1 -text "Mode #1"	   -variable [scope mode] -value 1
		  pack .rb1

		  radiobutton .rb2 -text "Mode #2"	   -variable [scope mode] -value 2
		  pack .rb2
	      }
       Radiobuttons .rb1 and .rb2 interact via the variable "mode" contained in the namespace "foo".  The scope command guarantees this by return-
       ing the fully qualified variable name ::foo::mode.

       You should never use the @itcl syntax directly.	For example, it is a bad idea to write code like this:
	      set {@itcl ::fred x} 3
	      puts "value = ${@itcl ::fred x}"
       Instead, you should always use the scope command to generate the variable name dynamically.  Then, you can pass that name to a widget or to
       any other bit of code in your program.

KEYWORDS

       code, namespace, variable

itcl																	  scope(n)

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itclvars(n) [redhat man page]

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