perl - very old suspect documentation on porting.

- NAME
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# NAME

Tcl vs perl - very old suspect documentation on porting.

# DESCRIPTION

This isn't really a .pod yet, nor is it Tcl vs perl it is a copy of John's comparison of Malcolm's original perl/Tk port with the current one. It is also out-of-date in places.

      From: john@WPI.EDU (John Stoffel )

      Here are some thoughts on the new Tk extension and how I think the
      organization of the commands looks.  Mostly, I'm happy with it, it
      makes some things more organized and more consistent with tcl/tk, but
      since the overlying language is so different, I don't think we need to
      follow exactly the tcl/tk model for how to call the language.

      The basic structure of the Tk program is:

          require Tk;

          $top = MainWindow->new();

          #
          # create widgets
          #

          Tk::MainLoop;

          sub method1 {
          }

          sub methodN {
          }

      This is pretty much the same as tkperl5a5, with some cosmetic naming
      changes, and some more useful command name and usage changes.  A quick
      comparison in no particular order follows:

      tkperl5a5                             Tk
      -------------------------------       -----------------------------------
      $top=tkinit(name,display,sync);       $top=MainWindow->new();

      tkpack $w, ... ;              $w->pack(...)

      $w = Class::new($top, ...);   $w = $top->Class(...);

      tkmainloop;                   Tk::MainLoop;

      tkbind($w,"<key>",sub);               $w->bind("<key>",sub);

      tkdelete($w, ...);            $w->delete(...);

      $w->scanmark(...);            $w->scan("mark", ...);

      $w->scandragto(...);          $w->scan("dragto", ...);

      $w->tkselect();                       $w->Select();

      $w->selectadjust(...);                $w->selection("adjust", ...);

      $w->selectto(...);            $w->selection("to", ...);

      $w->selectfrom(...);          $w->selection("from", ...);

      $w->tkindex(...);             $w->index(...);

      tclcmd("xxx",...);              &Tk::xxx(...)    # all Tk commands, but no Tcl at all

      tclcmd("winfo", xxx, $w, ...);  $w->xxx(...);

                                    $w->mark(...);

                                    $w->tag(...);

      $w->grabstatus();             $w->grab("status");

      $w->grabrelease(...);         $w->grab("release", ...);

      focus($w);                    $w->focus;

      update();                     Tk->update();

      idletasks();                  Tk->update("idletasks");

      wm("cmd",$w, ...);            $w->cmd(...);

      destroy($w);                  $w->destroy();

                                    Tk::option(...);
                                      $w->OptionGet(name,Class)

                                    $w->place(...)

                                    Tk::property(...);

      $w = Entry::new($parent,...)

      is now

      $w = $parent->Entry(...)

      As this allows new to be inherited from a Window class.

        -method=>x,-slave=>y

       is now

        -command => [x,y]

      1st element of list is treated as "method" if y is an object reference.
      (You can have -command => [a,b,c,d,e] too; b..e get passed as args).

      Object references are now hashes rather than scalars and there
      is only ever one such per window.  The Tcl_CmdInfo and PathName
      are entries in the hash.

      (This allows derived classes to
      re-bless the hash and keep their on stuff in it too.)

      Tk's "Tcl_Interp" is in fact a ref to "." window.
      You can find all the Tk windows descended from it as their object
      references get added (by PathName) into this hash.
      $w->MainWindow returns this hash from any window.

      I think that it should extend to multiple tkinits / Tk->news
      with different Display's - if Tk code does.

      Finally "bind" passes window as "extra" (or only)
      argument. Thus

      Tk::Button->bind(<Any-Enter>,"Enter");

      Binds Enter events to Tk::Button::Enter by default
      but gets called as $w->Enter so derived class of Button can just
      define its own Enter method. &EvWref and associated globals and race
      conditions are no longer needed.

      One thing to beware of : commands bound to events with $widget->bind
      follow same pattern, but get passed extra args :

      $widget->bind(<Any-1>,[sub {print shift}, $one, $two ]);

      When sub gets called it has :

         $widget $one $two

      passed.

      1st extra arg is reference to the per-widget hash that serves as the
      perl object for the widget.

      Every time an XEvent a reference to a special class is placed
      in the widget hash. It can be retrieved by $w->XEvent method.

      The methods of the XEvent class are the
      Tcl/Tk % special characters.

      Thus:

      $widget->bind(<Any-KeyPress>,
                    sub {
                     my $w = shift;
                     my $e = $w->XEvent;
                     print $w->PathName," ",$e->A," pressed ,$e->xy,"\n");
                    });

      XEvent->xy is a special case which returns "@" . $e->x . "," . $e->y
      which is common in Text package.

      Because of passing a blessed widget hash to "bound" subs they can be
      bound to (possibly inherited) methods of the widget's class:

      Class->bind(<Any-Down>,Down);

      sub Class::Down
      {
       my $w = shift;
       # handle down arrow
      }

      Also:

      -command and friends can take a list the 1st element can be a ref to
      as sub or a method name. Remaining elements are passed as args to the
      sub at "invoke" time. Thus :

      $b= $w->Button(blah blah, '-command' => [sub{print shift} , $fred ]);

      Should do the trick, provided $fred is defined at time of button creation.

      Thus 1st element of list is equivalent to Malcolm's -method and second
      would be his -slave.  Any further elements are a bonus and avoid
      having to pass ref to an array/hash as a slave.

perl - very old suspect documentation on porting.