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



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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-spe-cific application-specific
       cific 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 com-piled-in compiled-in
              piled-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-compatibility" 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 com-mand command
       mand 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, command,
       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  exist-ing existing
       ing  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 bet-ter better
       ter 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 num-ber number
              ber of the form x.y.  Changes to x represent major changes with probable incompatibilities and
              changes to y represent small enhancements and bug fixes that retain backward compatibility.


KEYWORDS
       itcl, variables



itcl                                                 3.0                                         itclvars(n)