Add testcase for EWMH desktop names

Test that the EWMH specified property _NET_DESKTOP_NAMES is updated
properly on the root window. We interpret this as a list of the open
workspace names.

This test is for this commit:

Implement EWMH desktop names

a9c094b731

testcases/t/234-ewmh-desktop-names.t

@@ -0,0 +1,72 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • http://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • http://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • http://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)
+#
+# Test that the EWMH specified property _NET_DESKTOP_NAMES is updated properly
+# on the root window. We interpret this as a list of the open workspace names.
+# Ticket: #1241
+use i3test;
+
+sub get_desktop_names {
+    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};
+}
+
+cmd 'workspace foo';
+
+my @expected_names = ('foo');
+my @desktop_names = get_desktop_names;
+
+is_deeply(\@desktop_names, \@expected_names, '_NET_DESKTOP_NAMES should be an array of the workspace names');
+
+# open a new workspace and see that the property is updated correctly
+open_window;
+cmd 'workspace bar';
+
+@desktop_names = get_desktop_names;
+@expected_names = ('foo', 'bar');
+
+is_deeply(\@desktop_names, \@expected_names, 'it should be updated when a new workspace appears');
+
+# rename the workspace and see that the property is updated correctly
+cmd 'rename workspace bar to baz';
+
+@desktop_names = get_desktop_names;
+@expected_names = ('foo', 'baz');
+
+is_deeply(\@desktop_names, \@expected_names, 'it should be updated when a workspace is renamed');
+
+# empty a workspace and see that the property is updated correctly
+cmd 'workspace foo';
+
+@desktop_names = get_desktop_names;
+@expected_names = ('foo');
+
+is_deeply(\@desktop_names, \@expected_names, 'it should be updated when a workspace is emptied');
+
+done_testing;