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Tk::Tcl-perl.3pm

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 It is also out-of-date in places.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.