2010-03-11 21:06:40 -05:00
|
|
|
|
IPC interface (interprocess communication)
|
|
|
|
|
==========================================
|
|
|
|
|
Michael Stapelberg <michael+i3@stapelberg.de>
|
|
|
|
|
March 2010
|
|
|
|
|
|
|
|
|
|
This document describes how to interface with i3 from a separate process. This
|
|
|
|
|
is useful for example to remote-control i3 (to write test cases for example) or
|
|
|
|
|
to get various information like the current workspaces to implement an external
|
|
|
|
|
workspace bar.
|
|
|
|
|
|
|
|
|
|
The method of choice for IPC in our case is a unix socket because it has very
|
|
|
|
|
little overhead on both sides and is usually available without headaches in
|
|
|
|
|
most languages. In the default configuration file, no ipc-socket path is
|
|
|
|
|
specified and thus no socket is created. The standard path (which +i3-msg+ and
|
|
|
|
|
+i3-input+ use) is +/tmp/i3-ipc.sock+.
|
|
|
|
|
|
|
|
|
|
== Establishing a connection
|
|
|
|
|
|
|
|
|
|
To establish a connection, simply open the IPC socket. The following code
|
|
|
|
|
snippet illustrates this in Perl:
|
|
|
|
|
|
|
|
|
|
-------------------------------------------------------------
|
|
|
|
|
use IO::Socket::UNIX;
|
|
|
|
|
my $sock = IO::Socket::UNIX->new(Peer => '/tmp/i3-ipc.sock');
|
|
|
|
|
-------------------------------------------------------------
|
|
|
|
|
|
|
|
|
|
== Sending messages to i3
|
|
|
|
|
|
|
|
|
|
To send a message to i3, you have to format in the binary message format which
|
|
|
|
|
i3 expects. This format specifies a magic string in the beginning to ensure
|
|
|
|
|
the integrity of messages (to prevent follow-up errors). Afterwards follows
|
|
|
|
|
the length of the payload of the message as 32-bit integer and the type of
|
|
|
|
|
the message as 32-bit integer (the integers are not converted, so they are
|
|
|
|
|
in native byte order).
|
|
|
|
|
|
|
|
|
|
The magic string currently is "i3-ipc" and will only be changed when a change
|
|
|
|
|
in the IPC API is done which breaks compatibility (we hope that we don’t need
|
|
|
|
|
to do that).
|
|
|
|
|
|
|
|
|
|
Currently implemented message types are the following:
|
|
|
|
|
|
2010-03-13 13:09:49 -05:00
|
|
|
|
COMMAND (0)::
|
2010-03-11 21:06:40 -05:00
|
|
|
|
The payload of the message is a command for i3 (like the commands you
|
|
|
|
|
can bind to keys in the configuration file) and will be executed
|
|
|
|
|
directly after receiving it. There is no reply to this message.
|
2010-03-13 13:09:49 -05:00
|
|
|
|
GET_WORKSPACES (1)::
|
2010-03-11 21:06:40 -05:00
|
|
|
|
Gets the current workspaces. The reply will be a JSON-encoded list of
|
|
|
|
|
workspaces (see the reply section).
|
2010-03-13 13:09:49 -05:00
|
|
|
|
SUBSCRIBE (2)::
|
|
|
|
|
Subscribes your connection to certain events. See <<events>> for a
|
|
|
|
|
description of this message and the concept of events.
|
2010-03-11 21:06:40 -05:00
|
|
|
|
|
|
|
|
|
So, a typical message could look like this:
|
|
|
|
|
--------------------------------------------------
|
|
|
|
|
"i3-ipc" <message length> <message type> <payload>
|
|
|
|
|
--------------------------------------------------
|
|
|
|
|
|
|
|
|
|
Or, as a hexdump:
|
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
|
00000000 69 33 2d 69 70 63 04 00 00 00 00 00 00 00 65 78 |i3-ipc........ex|
|
|
|
|
|
00000010 69 74 0a |it.|
|
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
|
|
|
|
|
|
To generate and send such a message, you could use the following code in Perl:
|
|
|
|
|
------------------------------------------------------------
|
|
|
|
|
sub format_ipc_command {
|
|
|
|
|
my ($msg) = @_;
|
|
|
|
|
my $len;
|
|
|
|
|
# Get the real byte count (vs. amount of characters)
|
|
|
|
|
{ use bytes; $len = length($msg); }
|
|
|
|
|
return "i3-ipc" . pack("LL", $len, 0) . $msg;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
$sock->write(format_ipc_command("exit"));
|
|
|
|
|
------------------------------------------------------------
|
|
|
|
|
|
|
|
|
|
== Receiving replies from i3
|
|
|
|
|
|
|
|
|
|
Replies of i3 usually consist of a simple string (the length of the string
|
|
|
|
|
is the message_length, so you can consider them length-prefixed) which in turn
|
|
|
|
|
contain the JSON serialization of a data structure. For example, the
|
|
|
|
|
GET_WORKSPACES message returns an array of workspaces (each workspace is a map
|
|
|
|
|
with certain attributes).
|
|
|
|
|
|
|
|
|
|
=== Reply format
|
|
|
|
|
|
|
|
|
|
The reply format is identical to the normal message format. There also is
|
|
|
|
|
the magic string, then the message length, then the message type and the
|
|
|
|
|
payload.
|
|
|
|
|
|
|
|
|
|
The following reply types are implemented:
|
|
|
|
|
|
2010-03-13 13:09:49 -05:00
|
|
|
|
COMMAND (0)::
|
|
|
|
|
Confirmation/Error code for the COMMAND message.
|
|
|
|
|
GET_WORKSPACES (1)::
|
2010-03-11 21:06:40 -05:00
|
|
|
|
Reply to the GET_WORKSPACES message.
|
2010-03-13 13:09:49 -05:00
|
|
|
|
SUBSCRIBE (2)::
|
|
|
|
|
Confirmation/Error code for the SUBSCRIBE message.
|
|
|
|
|
|
|
|
|
|
=== COMMAND reply
|
|
|
|
|
|
|
|
|
|
The reply consists of a single serialized map. At the moment, the only
|
|
|
|
|
property is +success (bool)+, but this will be expanded in future versions.
|
|
|
|
|
|
|
|
|
|
*Example:*
|
|
|
|
|
-------------------
|
|
|
|
|
{ "success": true }
|
|
|
|
|
-------------------
|
2010-03-11 21:06:40 -05:00
|
|
|
|
|
|
|
|
|
=== GET_WORKSPACES reply
|
|
|
|
|
|
|
|
|
|
The reply consists of a serialized list of workspaces. Each workspace has the
|
|
|
|
|
following properties:
|
|
|
|
|
|
|
|
|
|
num (integer)::
|
2010-03-13 13:09:49 -05:00
|
|
|
|
The logical number of the workspace. Corresponds to the command
|
2010-03-11 21:06:40 -05:00
|
|
|
|
to switch to this workspace.
|
|
|
|
|
name (string)::
|
|
|
|
|
The name of this workspace (by default num+1), as changed by the
|
|
|
|
|
user. Encoded in UTF-8.
|
|
|
|
|
visible (boolean)::
|
|
|
|
|
Whether this workspace is currently visible on an output (multiple
|
|
|
|
|
workspaces can be visible at the same time).
|
|
|
|
|
focused (boolean)::
|
|
|
|
|
Whether this workspace currently has the focus (only one workspace
|
|
|
|
|
can have the focus at the same time).
|
|
|
|
|
rect (map)::
|
|
|
|
|
The rectangle of this workspace (equals the rect of the output it
|
|
|
|
|
is on), consists of x, y, width, height.
|
|
|
|
|
output (string)::
|
|
|
|
|
The video output this workspace is on (LVDS1, VGA1, …).
|
|
|
|
|
|
|
|
|
|
*Example:*
|
|
|
|
|
-------------------
|
|
|
|
|
[
|
|
|
|
|
{
|
|
|
|
|
"num": 0,
|
|
|
|
|
"name": "1",
|
|
|
|
|
"visible": true,
|
|
|
|
|
"focused": true,
|
|
|
|
|
"rect": {
|
|
|
|
|
"x": 0,
|
|
|
|
|
"y": 0,
|
|
|
|
|
"width": 1280,
|
|
|
|
|
"height": 800
|
|
|
|
|
},
|
|
|
|
|
"output": "LVDS1"
|
|
|
|
|
},
|
|
|
|
|
{
|
|
|
|
|
"num": 1,
|
|
|
|
|
"name": "2",
|
|
|
|
|
"visible": false,
|
|
|
|
|
"focused": false,
|
|
|
|
|
"rect": {
|
|
|
|
|
"x": 0,
|
|
|
|
|
"y": 0,
|
|
|
|
|
"width": 1280,
|
|
|
|
|
"height": 800
|
|
|
|
|
},
|
|
|
|
|
"output": "LVDS1"
|
|
|
|
|
}
|
|
|
|
|
]
|
|
|
|
|
-------------------
|
2010-03-13 13:09:49 -05:00
|
|
|
|
|
|
|
|
|
=== SUBSCRIBE reply
|
|
|
|
|
|
|
|
|
|
The reply consists of a single serialized map. The only property is
|
|
|
|
|
+success (bool)+, indicating whether the subscription was successful (the
|
|
|
|
|
default) or whether a JSON parse error occurred.
|
|
|
|
|
|
|
|
|
|
*Example:*
|
|
|
|
|
-------------------
|
|
|
|
|
{ "success": true }
|
|
|
|
|
-------------------
|
|
|
|
|
|
|
|
|
|
== Events
|
|
|
|
|
|
|
|
|
|
[[events]]
|
|
|
|
|
|
|
|
|
|
To get informed when certain things happen in i3, clients can subscribe to
|
|
|
|
|
events. Events consist of a name (like "workspace") and an event reply type
|
|
|
|
|
(like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
|
|
|
|
|
as replies to specific commands.
|
|
|
|
|
|
|
|
|
|
Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
|
|
|
|
|
that the requests to i3 are processed in order. This means, the following
|
|
|
|
|
situation can happen: You send a GET_WORKSPACES request but you receive a
|
|
|
|
|
"workspace" event before receiving the reply to GET_WORKSPACES. If your
|
|
|
|
|
program does not want to cope which such kinds of race conditions (an
|
|
|
|
|
event based library may not have a problem here), I advise to create a separate
|
|
|
|
|
connection to receive events.
|
|
|
|
|
|
|
|
|
|
=== Subscribing to events
|
|
|
|
|
|
|
|
|
|
By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
|
|
|
|
|
you can register to an event.
|
|
|
|
|
|
|
|
|
|
*Example:*
|
|
|
|
|
---------------------------------
|
|
|
|
|
type: SUBSCRIBE
|
|
|
|
|
payload: [ "workspace", "focus" ]
|
|
|
|
|
---------------------------------
|
|
|
|
|
|
|
|
|
|
=== Available events
|
|
|
|
|
|
|
|
|
|
workspace::
|
|
|
|
|
Sent when the user switches to a different workspace, when a new
|
|
|
|
|
workspace is initialized or when a workspace is removed (because the
|
|
|
|
|
last client vanished).
|
|
|
|
|
|
|
|
|
|
=== workspace event
|
|
|
|
|
|
|
|
|
|
This event consists of a single serialized map containing a property
|
|
|
|
|
+change (string)+ which indicates the type of the change ("focus", "init",
|
|
|
|
|
"empty").
|
|
|
|
|
|
|
|
|
|
*Example:*
|
|
|
|
|
---------------------
|
|
|
|
|
{ "change": "focus" }
|
|
|
|
|
---------------------
|
|
|
|
|
|
|
|
|
|
== See also
|
|
|
|
|
|
|
|
|
|
For some languages, libraries are available (so you don’t have to implement
|
|
|
|
|
all this on your own). This list names some (if you wrote one, please let me
|
|
|
|
|
know):
|
|
|
|
|
|
2010-03-15 19:13:40 -04:00
|
|
|
|
C::
|
|
|
|
|
i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
|
|
|
|
|
However, there is no library yet.
|
2010-03-13 13:09:49 -05:00
|
|
|
|
Ruby::
|
|
|
|
|
http://github.com/badboy/i3-ipc
|
|
|
|
|
Perl::
|
|
|
|
|
http://search.cpan.org/search?query=AnyEvent::I3
|