NAME

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 It is also out-of-date in places.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


tkper5a5			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 decended 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 refence 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.