Implement the window::close event

The window::close event should be emitted when a window closes.

docs/ipc

@@ -717,6 +717,7 @@ This event consists of a single serialized map containing a property
 +change (string)+ which indicates the type of the change
 
 * +new+ - the window has become managed by i3
+* +close+ - the window has closed
 * +focus+ - the window has received input focus
 * +title+ - the window's title has changed
 * +fullscreen_mode+ - the window has entered or exited fullscreen mode

src/tree.c

@@ -255,6 +255,7 @@ bool tree_close(Con *con, kill_window_t kill_window, bool dont_kill_parent, bool
              * X11 Errors are returned when the window was already destroyed */
             add_ignore_event(cookie.sequence, 0);
         }
+        ipc_send_window_event("close", con);
         FREE(con->window->class_class);
         FREE(con->window->class_instance);
         i3string_free(con->window->name);

testcases/t/231-ipc-window-close.t

@@ -0,0 +1,52 @@
+#!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 that the ipc close event works properly
+#
+# Bug still in: 4.8-7-gf4a8253
+use i3test;
+
+my $i3 = i3(get_socket_path());
+$i3->connect()->recv;
+
+my $cv;
+my $t;
+
+sub reset_test {
+    $cv = AE::cv;
+    $t = AE::timer(0.5, 0, sub { $cv->send(0); });
+}
+
+reset_test;
+
+$i3->subscribe({
+        window => sub {
+            my ($e) = @_;
+            if ($e->{change} eq 'close') {
+                $cv->send($e->{container});
+            }
+        },
+    })->recv;
+
+my $window = open_window;
+
+cmd 'kill';
+my $con = $cv->recv;
+
+ok($con, 'closing a window should send the window::close event');
+is($con->{window}, $window->{id}, 'the event should contain information about the window');
+
+done_testing;