--- /dev/null
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • https://build.i3wm.org/docs/testsuite.html
+# (or docs/testsuite)
+#
+# • https://build.i3wm.org/docs/lib-i3test.html
+# (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • https://build.i3wm.org/docs/ipc.html
+# (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+# (unless you are already familiar with Perl)
+#
+# Verifies _NET_DESKTOP_NAMES, _NET_CURRENT_DESKTOP and _NET_CURRENT_DESKTOP
+# are updated properly when closing an inactive workspace container.
+# See github issue #3126
+
+use i3test;
+
+sub get_desktop_names {
+ sync_with_i3;
+
+ my $cookie = $x->get_property(
+ 0,
+ $x->get_root_window(),
+ $x->atom(name => '_NET_DESKTOP_NAMES')->id,
+ $x->atom(name => 'UTF8_STRING')->id,
+ 0,
+ 4096,
+ );
+
+ my $reply = $x->get_property_reply($cookie->{sequence});
+
+ return 0 if $reply->{value_len} == 0;
+
+ # the property is a null-delimited list of utf8 strings ;;
+ return split /\0/, $reply->{value};
+}
+
+sub get_num_of_desktops {
+ sync_with_i3;
+
+ my $cookie = $x->get_property(
+ 0,
+ $x->get_root_window(),
+ $x->atom(name => '_NET_NUMBER_OF_DESKTOPS')->id,
+ $x->atom(name => 'CARDINAL')->id,
+ 0,
+ 4,
+ );
+
+ my $reply = $x->get_property_reply($cookie->{sequence});
+
+ return undef if $reply->{value_len} != 1;
+ return undef if $reply->{format} != 32;
+ return undef if $reply->{type} != $x->atom(name => 'CARDINAL')->id,;
+
+ return unpack 'L', $reply->{value};
+}
+
+sub get_current_desktop {
+ sync_with_i3;
+
+ my $cookie = $x->get_property(
+ 0,
+ $x->get_root_window(),
+ $x->atom(name => '_NET_CURRENT_DESKTOP')->id,
+ $x->atom(name => 'CARDINAL')->id,
+ 0,
+ 4,
+ );
+
+ my $reply = $x->get_property_reply($cookie->{sequence});
+
+ return undef if $reply->{value_len} != 1;
+ return undef if $reply->{format} != 32;
+ return undef if $reply->{type} != $x->atom(name => 'CARDINAL')->id,;
+
+ return unpack 'L', $reply->{value};
+}
+
+cmd 'workspace 0';
+my $first = open_window;
+
+cmd 'workspace 1';
+my $second = open_window;
+
+cmd 'workspace 2';
+my $third = open_window;
+
+# Sanity check
+is(get_current_desktop, 2);
+is(get_num_of_desktops, 3);
+my @actual_names = get_desktop_names;
+my @expected_names = ('0', '1', '2');
+is_deeply(\@actual_names, \@expected_names);
+
+# Kill first window to close a workspace.
+cmd '[id="' . $second->id . '"] kill';
+
+is(get_current_desktop, 2, '_NET_CURRENT_DESKTOP should be updated');
+is(get_num_of_desktops, 2, '_NET_NUMBER_OF_DESKTOPS should be updated');
+my @actual_names = get_desktop_names;
+my @expected_names = ('0', '2');
+is_deeply(\@actual_names, \@expected_names, '_NET_DESKTOP_NAMES should be updated');
+
+
+done_testing;