| Date: | Thu, 1 Jan 2004 00:36:09 -0500 |
| From: | Rocco Caputo <rcaputo [...] pobox.com> |
| To: | poe [...] perl.org |
| CC: | bug-Tk [...] rt.cpan.org |
| Subject: | Re: Tk With POE - bind() function for keypresses |
On Wed, Dec 31, 2003 at 01:00:05PM +0000, James Brown wrote:
Show quoted text
> Hi All,
>
> I need a bit of help here. I'm trying get keyboard input (under UNIX
> and Windows) into a POE app which I'm developing. Having tried Curses
> and ReadLine, which work fine on UNIX, but won't install on Windows, I
> think I'll have to explore the POE-Tk route.
>
> I've managed to get the code working without POE, but (being new to POE)
> I struggle to understand how to use the postback() and bind() functions.
>
> ...etc...
[...]
Show quoted text> Basically, I see this error:
>
> Tk::Error: Can't call method "XEvent" on unblessed reference at **line
> 79.**Tk::After::once at D:/perl/site/lib/Tk/After.pm line 83
> [once,[{},after#43,0,once,[\&POE::Kernel::_loop_event_callback]]]
> ("after" script)
>
> I think my problem is that when the keypress event occurs, the "ev_key"
> happens, but I'm not so sure of how to extract the parameters that Tk
> would normally send along with this event.
Tk is not passing the event information to POE.
As you know, postbacks are anonymous subroutine references that post POE
events when they're called. They're used as a thin, flexible interface
between POE and Tk, among other things.
Postbacks are blessed, and their DESTROY methods are used to notify POE
when Tk is done with them. From Tk's point of view, the only difference
between a callback and a postback is this blessing.
For some reason, Tk does not pass parameters to a blessed callback. To
demonstrate:
#!/usr/bin/perl
use warnings;
use strict;
use Tk;
my $mw = Tk::MainWindow->new();
my $sub = \&callback;
$mw->bind("<Any-KeyPress>" => $sub);
Tk::MainLoop();
exit 0;
sub callback {
warn "@_";
}
displays
Tk::MainWindow=HASH(0x828b7e4) at tk-callback.perl line 18.
A subtle change
#!/usr/bin/perl
use warnings;
use strict;
use Tk;
my $mw = Tk::MainWindow->new();
my $sub = bless \&callback, "whatever";
$mw->bind("<Any-KeyPress>" => $sub);
Tk::MainLoop();
exit 0;
sub callback {
warn "@_";
}
changes the output to
Warning: something's wrong at tk-callback.perl line 18.
There is a workaround. Tk wants an unblessed callback, so you can hide
the blessed one inside a plain one.
##Start Event##
sub ui_start {
my $pb = $_[SESSION]->postback("ev_key");
$poe_main_window->bind (
'<Any-KeyPress>' => sub {
$pb->(@_);
}
)
}
A copy of this message has been Cc'd to <bug-Tk@rt.cpan.org>.
--
Rocco Caputo - rcaputo@pobox.com - http://poe.perl.org/