Tcl(3) Tcl extension module for Perl

SYNOPSIS


use Tcl;
$interp = Tcl->new;
$interp->Eval('puts "Hello world"');

DESCRIPTION

The Tcl extension module gives access to the Tcl library with functionality and interface similar to the C functions of Tcl. In other words, you can
  • create Tcl interpreters

    The Tcl interpreters so created are Perl objects whose destructors delete the interpreters cleanly when appropriate.

  • execute Tcl code in an interpreter

    The code can come from strings, files or Perl filehandles.

  • bind in new Tcl procedures

    The new procedures can be either C code (with addresses presumably obtained using dl_open and dl_find_symbol) or Perl subroutines (by name, reference or as anonymous subs). The (optional) deleteProc callback in the latter case is another perl subroutine which is called when the command is explicitly deleted by name or else when the destructor for the interpreter object is explicitly or implicitly called.

  • Manipulate the result field of a Tcl interpreter
  • Set and get values of variables in a Tcl interpreter
  • Tie perl variables to variables in a Tcl interpreter

    The variables can be either scalars or hashes.

Methods in class Tcl

To create a new Tcl interpreter, use 

    $interp = Tcl->new;

The following methods and routines can then be used on the Perl object returned (the object argument omitted in each case).

$interp->Init ()
Invoke Tcl_Init on the interpreter.
$interp->CreateSlave (NAME, SAFE)
Invoke Tcl_CreateSlave on the interpreter. Name is arbitrary. The safe variable, if true, creates a safe sandbox interpreter.
 See: http://www.tcl.tk/software/plugin/safetcl.html
      http://www.tcl.tk/man/tcl8.4/TclCmd/safe.htm

This command returns a new interpreter.

$interp->Eval (STRING, FLAGS)
Evaluate script STRING in the interpreter. If the script returns successfully (TCL_OK) then the Perl return value corresponds to Tcl interpreter's result otherwise a die exception is raised with the $@ variable corresponding to Tcl's interpreter result object. In each case, corresponds means that if the method is called in scalar context then the string result is returned but if the method is called in list context then the result is split as a Tcl list and returned as a Perl list. The FLAGS field is optional and can be a bitwise OR of the constants Tcl::EVAL_GLOBAL or Tcl::EVAL_DIRECT.
$interp->GlobalEval (STRING)
REMOVED. Evalulate script STRING at global level. Call Eval(STRING, Tcl::EVAL_GLOBAL) instead.
$interp->EvalFile (FILENAME)
Evaluate the contents of the file with name FILENAME. Otherwise, the same as Eval() above.
$interp->EvalFileHandle (FILEHANDLE)
Evaluate the contents of the Perl filehandle FILEHANDLE. Otherwise, the same as Eval() above. Useful when using the filehandle DATA to tack on a Tcl script following an __END__ token.
$interp->call (PROC, ARG, ...)
Looks up procedure PROC in the interpreter and invokes it using Tcl's eval semantics that does command tracing and will use the ::unknown (AUTOLOAD) mechanism. The arguments (ARG, ...) are not passed through the Tcl parser. For example, spaces embedded in any ARG will not cause it to be split into two Tcl arguments before being passed to PROC.

Before invoking procedure PROC special processing is performed on ARG list:

1. All subroutine references within ARG will be substituted with Tcl name which is responsible to invoke this subroutine. This Tcl name will be created using CreateCommand subroutine (see below).

2. All references to scalars will be substituted with names of Tcl variables transformed appropriately.

These first two items allow one to write and expect it to work properly such code as: 

  my $r = 'aaaa';
  button(".d", -textvariable => \$r, -command=>sub {$r++});

3. All references to hashes will be substituted with names of Tcl array variables transformed appropriately.

4. As a special case, there is a mechanism to deal with Tk's special event variables (they are mentioned as '%x', '%y' and so on throughout Tcl). When creating a subroutine reference that uses such variables, you must declare the desired variables using Tcl::Ev as the first argument to the subroutine. Example: 

  sub textPaste {
      my ($x,$y,$w) = @_;
      widget($w)->insert("\@$x,$y", $interp->Eval('selection get'));
  }
  $widget->bind('<2>', [\&textPaste, Tcl::Ev('%x', '%y'), $widget] );
$interp->return_ref (NAME)
returns a reference corresponding to NAME, which was associated during previously called "$interpnt->call(...)" preprocessing. As a typical example this could be variable associated with a widget.
$interp->delete_ref (NAME)
deletes and returns a reference corresponding to NAME, which was associated during previously called "$interpnt->call(...)" preprocessing.
$interp->icall (PROC, ARG, ...)
Looks up procedure PROC in the interpreter and invokes it using Tcl's eval semantics that does command tracing and will use the ::unknown (AUTOLOAD) mechanism. The arguments (ARG, ...) are not passed through the Tcl parser. For example, spaces embedded in any ARG will not cause it to be split into two Tcl arguments before being passed to PROC.

This is the lower-level procedure that the 'call' method uses. Arguments are converted efficiently from Perl SVs to Tcl_Objs. A Perl AV array becomes a Tcl_ListObj, an SvIV becomes a Tcl_IntObj, etc. The reverse conversion is done to the result.

$interp->invoke (PROC, ARG, ...)
Looks up procedure PROC in the interpreter and invokes it directly with arguments (ARG, ...) without passing through the Tcl parser. For example, spaces embedded in any ARG will not cause it to be split into two Tcl arguments before being passed to PROC. This differs from icall/call in that it directly invokes the command name without allowing for command tracing or making use of Tcl's unknown (AUTOLOAD) mechanism. If the command does not already exist in the interpreter, and error will be thrown.

Arguments are converted efficiently from Perl SVs to Tcl_Objs. A Perl AV array becomes a Tcl_ListObj, an SvIV becomes a Tcl_IntObj, etc. The reverse conversion is done to the result.

Tcl::Ev (FIELD, ...)
Used to declare %-substitution variables of interest to a subroutine callback. FIELD is expected to be of the form ``%#'' where # is a single character, and multiple fields may be specified. Returns a blessed object that the 'call' method will recognize when it is passed as the first argument to a subroutine in a callback. See description of 'call' method for details.
$interp->result ()
Returns the current Tcl interpreter result. List v. scalar context is handled as in Eval() above.
$interp->CreateCommand (CMDNAME, CMDPROC, CLIENTDATA, DELETEPROC, FLAGS)
Binds a new procedure named CMDNAME into the interpreter. The CLIENTDATA and DELETEPROC arguments are optional. There are two cases:

(1) CMDPROC is the address of a C function

(presumably obtained using dl_open and dl_find_symbol. In this case CLIENTDATA and DELETEPROC are taken to be raw data of the ClientData and deleteProc field presumably obtained in a similar way.

(2) CMDPROC is a Perl subroutine

(either a sub name, a sub reference or an anonymous sub). In this case CLIENTDATA can be any perl scalar (e.g. a ref to some other data) and DELETEPROC must be a perl sub too. When CMDNAME is invoked in the Tcl interpreter, the arguments passed to the Perl sub CMDPROC are 

    (CLIENTDATA, INTERP, LIST)

where INTERP is a Perl object for the Tcl interpreter which called out and LIST is a Perl list of the arguments CMDNAME was called with. If the 1-bit of FLAGS is set then the 3 first arguments on the call to CMDPROC are suppressed. As usual in Tcl, the first element of the list is CMDNAME itself. When CMDNAME is deleted from the interpreter (either explicitly with DeleteCommand or because the destructor for the interpreter object is called), it is passed the single argument CLIENTDATA.

$interp->DeleteCommand (CMDNAME)
Deletes command CMDNAME from the interpreter. If the command was created with a DELETEPROC (see CreateCommand above), then it is invoked at this point. When a Tcl interpreter object is destroyed either explicitly or implicitly, an implicit DeleteCommand happens on all its currently registered commands.
$interp->SetResult (STRING)
Sets Tcl interpreter result to STRING.
$interp->AppendResult (LIST)
Appends each element of LIST to Tcl's interpreter result object.
$interp->AppendElement (STRING)
Appends STRING to Tcl interpreter result object as an extra Tcl list element.
$interp->ResetResult ()
Resets Tcl interpreter result.
$interp->SplitList (STRING)
Splits STRING as a Tcl list. Returns a Perl list or the empty list if there was an error (i.e. STRING was not a properly formed Tcl list). In the latter case, the error message is left in Tcl's interpreter result object.
$interp->SetVar (VARNAME, VALUE, FLAGS)
The FLAGS field is optional. Sets Tcl variable VARNAME in the interpreter to VALUE. The FLAGS argument is the usual Tcl one and can be a bitwise OR of the constants Tcl::GLOBAL_ONLY, Tcl::LEAVE_ERR_MSG, Tcl::APPEND_VALUE, Tcl::LIST_ELEMENT.
$interp->SetVar2 (VARNAME1, VARNAME2, VALUE, FLAGS)
Sets the element VARNAME1(VARNAME2) of a Tcl array to VALUE. The optional argument FLAGS behaves as in SetVar above.
$interp->GetVar (VARNAME, FLAGS)
Returns the value of Tcl variable VARNAME. The optional argument FLAGS behaves as in SetVar above.
$interp->GetVar2 (VARNAME1, VARNAME2, FLAGS)
Returns the value of the element VARNAME1(VARNAME2) of a Tcl array. The optional argument FLAGS behaves as in SetVar above.
$interp->UnsetVar (VARNAME, FLAGS)
Unsets Tcl variable VARNAME. The optional argument FLAGS behaves as in SetVar above.
$interp->UnsetVar2 (VARNAME1, VARNAME2, FLAGS)
Unsets the element VARNAME1(VARNAME2) of a Tcl array. The optional argument FLAGS behaves as in SetVar above.

Linking Perl and Tcl variables

You can tie a Perl variable (scalar or hash) into class Tcl::Var so that changes to a Tcl variable automatically ``change'' the value of the Perl variable. In fact, as usual with Perl tied variables, its current value is just fetched from the Tcl variable when needed and setting the Perl variable triggers the setting of the Tcl variable.

To tie a Perl scalar $scalar to the Tcl variable tclscalar in interpreter $interp with optional flags $flags (see SetVar above), use 

        tie $scalar, "Tcl::Var", $interp, "tclscalar", $flags;

Omit the $flags argument if not wanted.

To tie a Perl hash %hash to the Tcl array variable array in interpreter $interp with optional flags $flags (see SetVar above), use 

        tie %hash, "Tcl::Var", $interp, "array", $flags;

Omit the $flags argument if not wanted. Any alteration to Perl variable $hash{``key''} affects the Tcl variable array(key) and vice versa.

Accessing Perl from within Tcl

After creation of Tcl interpreter, in addition to evaluation of Tcl/Tk commands within Perl, other way round also instantiated. Within a special namespace " ::perl " following objects are created: 

   ::perl::Eval

So it is possible to use Perl objects from within Tcl.

Moving Tcl/Tk around with Tcl.pm

NOTE: explanations below is for developers managing Tcl/Tk installations itself, users should skip this section.

In order to create Tcl/Tk application with this module, you need to make sure that Tcl/Tk is available within visibility of this module. There are many ways to achieve this, varying on ease of starting things up and providing flexible moveable archived files.

Following list enumerates them, in order of increased possibility to change location.

  • First method

    Install Tcl/Tk first, then install Perl module Tcl, so installed Tcl/Tk will be used. This is most normal approach, and no care of Tcl/Tk distribution is taken on Perl side (this is done on Tcl/Tk side)

  • Second method

    Copy installed Tcl/Tk binaries to some location, then install Perl module Tcl with a special action to make Tcl.pm know of this location. This approach makes sure that only chosen Tcl installation is used.

  • Third method

    During compiling Tcl Perl module, Tcl/Tk could be statically linked into module's shared library and all other files zipped into a single archive, so each file extracted when needed.

    To link Tcl/Tk binaries, prepare their libraries and then instruct Makefile.PL to use these libraries in a link stage. (TODO provide better detailed description)

Other Tcl interpreter methods

export_to_tcl method
An interpreter method, export_to_tcl, is used to expose a number of perl subroutines and variables all at once into tcl/tk.

export_to_tcl takes a hash as arguments, which represents named parameters, with following allowed values:

namespace => '...'
tcl namespace, where commands and variables are to be created, defaults to 'perl'. If '' is specified - then global namespace is used. A possible '::' at end is stripped.
subs => { ... }
anonymous hash of subs to be created in Tcl, in the form /tcl name/ => /code ref/
vars => { ... }
anonymous hash of vars to be created in Tcl, in the form /tcl name/ => /code ref/
subs_from => '...'
a name of Perl namespace, from where all existing subroutines will be searched and Tcl command will be created for each of them.
vars_from => '...'
a name of Perl namespace, from where all existing variables will be searched, and each such variable will be tied to Tcl.

An example: 

  use strict;
  use Tcl;
  
  my $int = Tcl->new;
  
  $tcl::foo = 'qwerty';
  $int->export_to_tcl(subs_from=>'tcl',vars_from=>'tcl');
  
  $int->Eval(<<'EOS');
  package require Tk
  
  button .b1 -text {a fluffy button} -command perl::fluffy_sub
  button .b2 -text {a foo button} -command perl::foo
  entry .e -textvariable perl::foo
  pack .b1 .b2 .e
  focus .b2
  
  tkwait window .
  EOS
  
  sub tcl::fluffy_sub {
      print "Hi, I am a fluffy sub\n";
  }
  sub tcl::foo {
      print "Hi, I am foo\n";
      $tcl::foo++;
  }
export_tcl_namespace
extra convenience sub, binds to tcl all subs and vars from perl tcl:: namespace

AUTHORS

 Malcolm Beattie, 23 Oct 1994
 Vadim Konovalov, 19 May 2003
 Jeff Hobbs, jeff (a) activestate . com, 22 Mar 2004
 Gisle Aas, gisle (a) activestate . com, 14 Apr 2004

Special thanks for contributions to Jan Dubois, Slaven Rezic, Paul Cochrane.

COPYRIGHT

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

See http://www.perl.com/perl/misc/Artistic.html

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