RE: [tcltk-perl] Why is Tcl a subclass of Tck::Tk?

[Jeff H. <je...@Ac...>]

> Actually 'use Tcl::Tk q(:perlTk);' needed only to export 
> MainWindow, MainLoop functions and few other, and nothing 
> more. Most perlTk syntax is available even without that qw(:perlTk)
> 
> Currently you still can write using "perlTk syntax":
> 
> use Tcl::Tk;
> $mw = Tcl::Tk::MainWindow; 
> $mw->Button(-text=>'test',-command=>sub{print 'test'})->pack; 
> Tcl::Tk::MainLoop;

This is in fact how we are setting our preferred Perl/Tcl::Tk
coding style, to use $mw->Widgettype as the way to create
widgets.  While it's not as "simple" as the usual Tcl style,
it is "clean" from the Perl perspective and works well.

> > A separate module is cleaner.  I would actually prefer that, but it is 
> > certainly an API change.  If we then end up with two ways of doing 
> > this because we need to stay compatible I rather just keep as it is.
> 
> In case we'll move out perlTk compatibility to separate 
> module, what will stay in Tcl::Tk? Only few very old 
> subroutines like "label", "toplevel" and so on?

There are multiple levels of compatability.  The basic coding
style, as noted above, it worth keeping.  However, there are
a lot of Perl/Tk-isms that needn't be repeated in a "clean"
Tcl::Tk, like modifications to core commands that do not
reflect the usual behavior of Tk.  There is also a ton of
extra widgets that could be moved over.

I would also like to add a "DeclareWidget" sub in Tcl::Tk
that allows the use (or some submodule) to declare that it is
making a widget available (freeing up the need to hack the
ptk2tcltk hash).  Something like:

	Tcl::Tk::Declare('BWTree',    # name in Perl
			     'tree',      # name in Tcl
			     'BWidget',   # required Tcl package
			     'Tree::use', # extra code (if necessary)
			    )

There may be other options, but you get the idea.  Perhaps
even do it in option => value syntax to extend it easier in
the future.

> May be instead of doing special compatiiblity layer for 
> perlTk, may be it could be reasonable to just use perlTk 
> syntax as main way of doing GUI in perl? Many people just 
> used to using that syntax from perl, and there are books about it.

Right, as above, but with minor mods.  I've noticed that the
Perl/Tk docs aren't accurate often enough that if we start
to veer from them, it won't be a big deal.

> BTW (unrelated issue) if a line in Tk.pm "*{Tk::Exists} = 
> \&Tcl::Tk::Exists;" is commented out, it is possible to debug 
> Tcl::Tk code ising "ptkdb" debugger, which uses perlTk.

Cool, but why is that one line needed?  Are you actually
loading Perl/Tk as well?  I intentionally turn on the
tk_gestapo to avoid such interactions from occuring, as it
may lead to undesired consequences.

Jeff