Hi all. I'm trying to give an old Tk application some love, and I noticed it had many tests that nobody had run for many years: many of them were failing.

I fixed all of them, and to prevent the same situation in the future, I decided to run the tests in GitHub Actions. One of the tests needs the Tk application to run, so I decided to run it headless in Xvfb.

The test failed in Xvfb, not only in GH Actions, but even when I ran it locally. In a real X session, it passed.

I was able to reduce the test to the following:

#!/usr/bin/perl
use strict;
use warnings;

use Tk;

my $mw = 'Tk::MainWindow'->new;

my $current = 0;

my @buttons = map { my $i = $_;
                    $mw->Button(-text    => $i,
                                -command => sub { $current = $i }
                    )->pack
                } 1, 2;

$mw->after(100, sub {
               $mw->eventGenerate('<KeyPress>', -keysym => $_)
                   for qw( Tab Return );
               $mw->idletasks();
               $mw->DESTROY;
});

Tk::MainLoop();

use Test::More tests => 1;
is $current, 1, 'Events processed';
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Steps to reproduce:

$ tktest.pl
1..1
ok 1 - Events processed
$ Xvfb :19 &
$ pid=$!
$ DISPLAY=:19 tktest.pl
1..1
not ok 1 - Events processed
#   Failed test 'Events processed'
#   at /home/choroba/tktest.pl line 27.
#          got: '0'
#     expected: '1'
# Looks like you failed 1 test of 1.
$ kill $pid
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Update: Under Xvnc, the behaviour is the same as under Xvfb, i.e. the events are ignored, even when I run the test from an xterm in a vnc viewer.