Implement the ipc 'binding' event

The binding event will be triggered when a binding is run as a result of
some a user action. The binding event has the following properties:

change: (str) Currently this will only be "run" but may be expanded in
the future. Included for consistency with other events.

binding: (map) the serialized binding

The "binding" member will have these properties:

input_type: (str) either "keyboard" or "mouse"

input_code: (int) the xcb keycode of the keyboard binding if it was
provided or the mouse button if it is a mouse binding.

symbol: (str) the string representation of the input code

command: (str) the bound command

mods: (list of str) a list of the modifiers that were pressed as string
symbols

fixes #1210

testcases/t/238-ipc-binding-event.t

@@ -0,0 +1,86 @@
+#!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 binding event works properly
+# Ticket: #1210
+use i3test i3_autostart => 0;
+
+my $keysym = 't';
+my $command = 'nop';
+my @mods = ('Shift', 'Ctrl');
+my $binding_symbol = join("+", @mods) . "+$keysym";
+
+my $config = <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+
+bindsym $binding_symbol $command
+EOT
+
+SKIP: {
+    qx(which xdotool 2> /dev/null);
+
+    skip 'xdotool is required to test the binding event. `[apt-get install|pacman -S] xdotool`', 1 if $?;
+
+    my $pid = launch_with_config($config);
+
+    my $i3 = i3(get_socket_path());
+    $i3->connect->recv;
+
+    my $cv = AE::cv;
+    my $timer = AE::timer 0.5, 0, sub { $cv->send(0); };
+
+    $i3->subscribe({
+            binding => sub {
+                $cv->send(shift);
+            }
+        })->recv;
+
+    qx(xdotool key $binding_symbol);
+
+    my $e = $cv->recv;
+
+    does_i3_live;
+
+    diag "Event:\n", Dumper($e);
+
+    ok($e,
+        'the binding event should emit when user input triggers an i3 binding event');
+
+    is($e->{change}, 'run',
+        'the `change` field should indicate this binding has run');
+
+    ok($e->{binding},
+        'the `binding` field should be a hash that contains information about the binding');
+
+    is($e->{binding}->{input_type}, 'keyboard',
+        'the input_type field should be the input type of the binding (keyboard or mouse)');
+
+    note 'the `mods` field should contain the symbols for the modifiers of the binding';
+    foreach (@mods) {
+        ok(grep(/$_/i, @{$e->{binding}->{mods}}), "`mods` contains the modifier $_");
+    }
+
+    is($e->{binding}->{command}, $command,
+        'the `command` field should contain the command the binding ran');
+
+    is($e->{binding}->{input_code}, 0,
+        'the input_code should be the specified code if the key was bound with bindcode, and otherwise zero');
+
+    exit_gracefully($pid);
+
+}
+done_testing;