jfan8888 has asked for the wisdom of the Perl Monks concerning the following question:

I would like to programmatically trigger ButtonPress-1 event which is bind with a Listbox, but I can not get what I expected when eventGenerate is called. Below is my script:

use Tk; my $MW = MainWindow->new(); my $frame_lb = $MW->Frame(); $frame_lb->pack(-side => 'top', -pady => '20', -expand => 'n', -fill = +> 'both'); my $lbox = $frame_lb->Scrolled("Listbox", -scrollbars => "e", -selectmode => "single", -selectbackground => 'green', -height => 3)->pack(-side => 'left', -anchor => 'e'); my @list = ( "a", "b", "c", "d", "e", "f" ); $lbox->insert('end', @list ); $lbox->bind("<ButtonPress-1>" => sub { print "event trigged\n"; }); #trigger the event programmatically $lbox->eventGenerate("<ButtonPress-1>"); MainLoop;

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Re: eventGenerate for Listbox
by kcott (Archbishop) on Dec 30, 2021 at 06:34 UTC

    G'day jfan8888,

    Welcome to the Monastery.

    "... but I can not get what I expected when eventGenerate is called."

    Unfortunately, that's an entirely unhelpful report. What did you do? What did you get? What did you expect? Please read "How do I post a question effectively?". When you do, take note of what it says about strict and warnings in multiple places; in one, it's in big red letters — see "perlintro - Perl introduction for beginners" for more on that.

    Tk::Scrolled creates a composite megawidget (see Tk::mega) which, in this case, is a Tk::Frame containing the specified Tk::Listbox widget along with other widgets, such as scrollbars. You need to call eventGenerate() on the Tk::Listbox subwidget, not on the Tk::Frame — see "Tk::mega - Subwidget" for details.

    In the following code: I've removed all of the non-essential cosmetics (please also do this in any subsequent posts); show how to extract the Tk::Listbox subwidget; and, put eventGenerate() in a "Test" button so you can try this multiple times without needing to continually start and stop the application.

    #!/usr/bin/env perl use strict; use warnings; use Tk; my $mw = MainWindow::->new(); my $scrl_lbox = $mw->Scrolled('Listbox', -scrollbars => 'e', -selectmode => 'single', -height => 3, )->pack(); my $lbox = $scrl_lbox->Subwidget('scrolled'); $lbox->bind('<ButtonPress-1>', sub { print "Event: <ButtonPress-1>\n"; } ); $lbox->insert(end => 'a' .. 'f'); $mw->Button(-text => 'Test', -command => sub { $lbox->eventGenerate('<ButtonPress-1>'); } )->pack(); MainLoop;

    — Ken

      Thank you Ken, your information is really helpful! Just updated my script, it is working now.

Re: eventGenerate for Listbox
by Anonymous Monk on Dec 30, 2021 at 04:23 UTC