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 It is also out-of-date in places.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