=head1 NAME

Tcl vs perl - very old suspect documentation on porting.

=head1 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 It is also out-of-date in places.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.
  
  
  
  
  
  
