Allow multiple marks on windows.

This patch allows multiple marks to be set on a single window. The restriction that a mark may
only be on one window at a time is still upheld as this is necessary for commands like
"move window to mark" to make sense.

relates to #2014

testcases/t/255-multiple-marks.t

@@ -0,0 +1,96 @@
+#!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)
+#
+# Tests for mark/unmark with multiple marks on a single window.
+# Ticket: #2014
+use i3test;
+use List::Util qw(first);
+
+my ($ws, $con, $first, $second);
+
+sub get_marks {
+    return i3(get_socket_path())->get_marks->recv;
+}
+
+sub get_mark_for_window_on_workspace {
+    my ($ws, $con) = @_;
+
+    my $current = first { $_->{window} == $con->{id} } @{get_ws_content($ws)};
+    return $current->{marks};
+}
+
+###############################################################################
+# Verify that multiple marks can be set on a window.
+###############################################################################
+
+$ws = fresh_workspace;
+$con = open_window;
+cmd 'mark A';
+cmd 'mark B';
+
+is_deeply(sort(get_marks()), [ 'A', 'B' ], 'both marks exist');
+is_deeply(get_mark_for_window_on_workspace($ws, $con), [ 'A', 'B' ], 'both marks are on the same window');
+
+cmd 'unmark';
+
+###############################################################################
+# Verify that toggling a mark can affect only the specified mark.
+###############################################################################
+
+$ws = fresh_workspace;
+$con = open_window;
+cmd 'mark A';
+
+cmd 'mark --toggle B';
+is_deeply(get_mark_for_window_on_workspace($ws, $con), [ 'A', 'B' ], 'both marks are on the same window');
+cmd 'mark --toggle B';
+is_deeply(get_mark_for_window_on_workspace($ws, $con), [ 'A' ], 'only mark B has been removed');
+
+cmd 'unmark';
+
+###############################################################################
+# Verify that unmarking a mark leaves other marks on the same window intact.
+###############################################################################
+
+$ws = fresh_workspace;
+$con = open_window;
+cmd 'mark A';
+cmd 'mark B';
+cmd 'mark C';
+
+cmd 'unmark B';
+is_deeply(get_mark_for_window_on_workspace($ws, $con), [ 'A', 'C' ], 'only mark B has been removed');
+
+cmd 'unmark';
+
+###############################################################################
+# Verify that matching via mark works on windows with multiple marks.
+###############################################################################
+
+$ws = fresh_workspace;
+$con = open_window;
+cmd 'mark A';
+cmd 'mark B';
+open_window;
+
+cmd '[con_mark=B] mark C';
+is_deeply(get_mark_for_window_on_workspace($ws, $con), [ 'A', 'B', 'C' ], 'matching on a mark works with multiple marks');
+
+cmd 'unmark';
+
+###############################################################################
+
+done_testing;