107 lines
3.7 KiB
Plaintext
107 lines
3.7 KiB
Plaintext
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'\"
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'\" Copyright (c) 1993-1998 Lucent Technologies, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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.TH itclvars n 3.0 itcl "[incr\ Tcl]"
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.so man.macros
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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itclvars \- variables used by [incr\ Tcl]
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.BE
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.SH DESCRIPTION
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.PP
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The following global variables are created and managed automatically
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by the \fB[incr\ Tcl]\fR library. Except where noted below, these
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variables should normally be treated as read-only by application-specific
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code and by users.
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.TP
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\fBitcl::library\fR
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.
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When an interpreter is created, \fB[incr\ Tcl]\fR initializes this variable
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to hold the name of a directory containing the system library of
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\fB[incr\ Tcl]\fR scripts. The initial value of \fBitcl::library\fR
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is set from the ITCL_LIBRARY environment variable if it exists,
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or from a compiled-in value otherwise.
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.TP
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\fBitcl::patchLevel\fR
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.
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When an interpreter is created, \fB[incr\ Tcl]\fR initializes this
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variable to hold the current patch level for \fB[incr\ Tcl]\fR.
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For example, the value "\fB2.0p1\fR" indicates \fB[incr\ Tcl]\fR
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version 2.0 with the first set of patches applied.
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.TP
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\fBitcl::purist\fR
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.
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When an interpreter is created containing Tcl/Tk and the
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\fB[incr\ Tcl]\fR namespace facility, this variable controls
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a "backward-compatibility" mode for widget access.
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.RS
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.PP
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In vanilla Tcl/Tk, there is a single pool of commands, so the
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access command for a widget is the same as the window name.
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When a widget is created within a namespace, however, its access
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command is installed in that namespace, and should be accessed
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outside of the namespace using a qualified name. For example,
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.PP
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.CS
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namespace foo {
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namespace bar {
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button .b -text "Testing"
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}
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}
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foo::bar::.b configure -background red
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pack .b
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.CE
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.PP
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Note that the window name "\fC.b\fR" is still used in conjunction
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with commands like \fBpack\fR and \fBdestroy\fR. However, the
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access command for the widget (i.e., name that appears as the
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\fIfirst\fR argument on a command line) must be more specific.
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.PP
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The "\fBwinfo command\fR" command can be used to query the
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fully-qualified access command for any widget, so one can write:
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.PP
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.CS
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[winfo command .b] configure -background red
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.CE
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.PP
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and this is good practice when writing library procedures. Also,
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in conjunction with the \fBbind\fR command, the "%q" field can be
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used in place of "%W" as the access command:
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.PP
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.CS
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bind Button <Key-Return> {%q flash; %q invoke}
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.CE
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.PP
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While this behavior makes sense from the standpoint of encapsulation,
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it causes problems with existing Tcl/Tk applications. Many existing
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applications are written with bindings that use "%W". Many
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library procedures assume that the window name is the access
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command.
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.PP
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The \fBitcl::purist\fR variable controls a backward-compatibility
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mode. By default, this variable is "0", and the window name
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can be used as an access command in any context. Whenever the
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\fBunknown\fR procedure stumbles across a widget name, it simply
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uses "\fBwinfo command\fR" to determine the appropriate command
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name. If this variable is set to "1", this backward-compatibility
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mode is disabled. This gives better encapsulation, but using the
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window name as the access command may lead to "invalid command"
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errors.
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.RE
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.TP
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\fBitcl::version\fR
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.
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When an interpreter is created, \fB[incr\ Tcl]\fR initializes this
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variable to hold the version number of the form \fIx.y\fR.
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Changes to \fIx\fR represent major changes with probable
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incompatibilities and changes to \fIy\fR represent small enhancements
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and bug fixes that retain backward compatibility.
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.SH KEYWORDS
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itcl, variables
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