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.so man.macros

.TH itclvars n 3.0 itcl "[incr\ Tcl]"

.BS

'\" Note:  do not modify the .SH NAME line immediately below!

.SH NAME

itclvars \- variables used by [incr\ Tcl]

.BE

.SH DESCRIPTION

.PP

The following global variables are created and managed automatically

by the \fB[incr\ Tcl]\fR library.  Except where noted below, these

variables should normally be treated as read-only by application-specific

code and by users.

.TP

\fBitcl::library\fR

When an interpreter is created, \fB[incr\ Tcl]\fR initializes this variable

to hold the name of a directory containing the system library of

\fB[incr\ Tcl]\fR scripts.  The initial value of \fBitcl::library\fR

is set from the ITCL_LIBRARY environment variable if it exists,

or from a compiled-in value otherwise.

.TP

\fBitcl::patchLevel\fR

When an interpreter is created, \fB[incr\ Tcl]\fR initializes this

variable to hold the current patch level for \fB[incr\ Tcl]\fR.

For example, the value "\fB2.0p1\fR" indicates \fB[incr\ Tcl]\fR

version 2.0 with the first set of patches applied.

.TP

\fBitcl::purist\fR

When an interpreter is created containing Tcl/Tk and the

\fB[incr\ Tcl]\fR namespace facility, this variable controls

a "backward-compatibility" mode for widget access.

.sp

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,

.CS

namespace foo {

    namespace bar {

        button .b -text "Testing"

    }

}

foo::bar::.b configure -background red

pack .b

.CE

Note that the window name "\fC.b\fR" is still used in conjunction

with commands like \fBpack\fR and \fBdestroy\fR.  However, the

access command for the widget (i.e., name that appears as the

\fIfirst\fR argument on a command line) must be more specific.

.sp

The "\fBwinfo command\fR" command can be used to query the

fully-qualified access command for any widget, so one can write:

.CS

[winfo command .b] configure -background red

.CE

and this is good practice when writing library procedures.  Also,

in conjunction with the \fBbind\fR command, the "%q" field can be

used in place of "%W" as the access command:

.CS

bind Button  {%q flash; %q invoke}

.CE

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.

.sp

The \fBitcl::purist\fR 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

\fBunknown\fR procedure stumbles across a widget name, it simply

uses "\fBwinfo command\fR" 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.

.TP

\fBitcl::version\fR

When an interpreter is created, \fB[incr\ Tcl]\fR initializes this

variable to hold the version number of the form \fIx.y\fR.

Changes to \fIx\fR represent major changes with probable

incompatibilities and changes to \fIy\fR represent small enhancements

and bug fixes that retain backward compatibility.

.SH KEYWORDS

itcl, variables