IPC interface (interprocess communication)
==========================================
Michael Stapelberg <michael+i3@stapelberg.de>
-March 2010
+October 2011
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
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+.
+most languages. In the default configuration file, the ipc-socket gets created
+in +/tmp/i3-%u/ipc-socket.%p+ where +%u+ is your UNIX username and +%p+ is the
+PID of i3. You can get the socketpath from i3 by calling +i3 --get-socketpath+.
+
+All i3 utilities, like +i3-msg+ and +i3-input+ will read the +I3_SOCKET_PATH+
+X11 property, stored on the X11 root window.
== Establishing a connection
-------------------------------------------------------------
use IO::Socket::UNIX;
-my $sock = IO::Socket::UNIX->new(Peer => '/tmp/i3-ipc.sock');
+chomp(my $path = qx(i3 --get-socketpath));
+my $sock = IO::Socket::UNIX->new(Peer => $path);
-------------------------------------------------------------
== 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 integrity of messages (to prevent follow-up errors). Following the magic
+string comes 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
GET_OUTPUTS (3)::
Gets the current outputs. The reply will be a JSON-encoded list of outputs
(see the reply section).
+GET_TREE (4)::
+ Gets the layout tree. i3 uses a tree as data structure which includes
+ every container. The reply will be the JSON-encoded tree (see the reply
+ section).
+GET_MARKS (5)::
+ Gets a list of marks (identifiers for containers to easily jump to them
+ later). The reply will be a JSON-encoded list of window marks (see
+ reply section).
+GET_BAR_CONFIG (6)::
+ Gets the configuration (as JSON map) of the workspace bar with the
+ given ID. If no ID is provided, an array with all configured bar IDs is
+ returned instead.
So, a typical message could look like this:
--------------------------------------------------
}
$sock->write(format_ipc_command("exit"));
-------------------------------------------------------------
+------------------------------------------------------------------------------
== Receiving replies from i3
-Replies of i3 usually consist of a simple string (the length of the string
+Replies from 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
Confirmation/Error code for the SUBSCRIBE message.
GET_OUTPUTS (3)::
Reply to the GET_OUTPUTS message.
+GET_TREE (4)::
+ Reply to the GET_TREE message.
+GET_MARKS (5)::
+ Reply to the GET_MARKS message.
+GET_BAR_CONFIG (6)::
+ Reply to the GET_BAR_CONFIG message.
=== COMMAND reply
]
-------------------
+=== GET_TREE reply
+
+The reply consists of a serialized tree. Each node in the tree (representing
+one container) has at least the properties listed below. While the nodes might
+have more properties, please do not use any properties which are not documented
+here. They are not yet finalized and will probably change!
+
+id (integer)::
+ The internal ID (actually a C pointer value) of this container. Do not
+ make any assumptions about it. You can use it to (re-)identify and
+ address containers when talking to i3.
+name (string)::
+ The internal name of this container. For all containers which are part
+ of the tree structure down to the workspace contents, this is set to a
+ nice human-readable name of the container.
+ For all other containers, the content is not defined (yet).
+border (string)::
+ Can be either "normal", "none" or "1pixel", dependending on the
+ container’s border style.
+layout (string)::
+ Can be either "default", "stacked", "tabbed", "dockarea" or "output".
+ Other values might be possible in the future, should we add new
+ layouts.
+orientation (string)::
+ Can be either "none" (for non-split containers), "horizontal" or
+ "vertical".
+percent (float)::
+ The percentage which this container takes in its parent. A value of
+ +null+ means that the percent property does not make sense for this
+ container, for example for the root container.
+rect (map)::
+ The absolute display coordinates for this container. Display
+ coordinates means that when you have two 1600x1200 monitors on a single
+ X11 Display (the standard way), the coordinates of the first window on
+ the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
+ 1200 }+.
+window_rect (map)::
+ The coordinates of the *actual client window* inside its container.
+ These coordinates are relative to the container and do not include the
+ window decoration (which is actually rendered on the parent container).
+ So, when using the +default+ layout, you will have a 2 pixel border on
+ each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
+ "height": 366 }+ (for example).
+geometry (map)::
+ The original geometry the window specified when i3 mapped it. Used when
+ switching a window to floating mode, for example.
+urgent (bool)::
+ Whether this container (window or workspace) has the urgency hint set.
+focused (bool)::
+ Whether this container is currently focused.
+
+Please note that in the following example, I have left out some keys/values
+which are not relevant for the type of the node. Otherwise, the example would
+be by far too long (it already is quite long, despite showing only 1 window and
+one dock window).
+
+It is useful to have an overview of the structure before taking a look at the
+JSON dump:
+
+* root
+** LVDS1
+*** topdock
+*** content
+**** workspace 1
+***** window 1
+*** bottomdock
+**** dock window 1
+** VGA1
+
+*Example:*
+-----------------------
+{
+ "id": 6875648,
+ "name": "root",
+ "rect": {
+ "x": 0,
+ "y": 0,
+ "width": 1280,
+ "height": 800
+ },
+ "nodes": [
+
+ {
+ "id": 6878320,
+ "name": "LVDS1",
+ "layout": "output",
+ "rect": {
+ "x": 0,
+ "y": 0,
+ "width": 1280,
+ "height": 800
+ },
+ "nodes": [
+
+ {
+ "id": 6878784,
+ "name": "topdock",
+ "layout": "dockarea",
+ "orientation": "vertical",
+ "rect": {
+ "x": 0,
+ "y": 0,
+ "width": 1280,
+ "height": 0
+ },
+ },
+
+ {
+ "id": 6879344,
+ "name": "content",
+ "rect": {
+ "x": 0,
+ "y": 0,
+ "width": 1280,
+ "height": 782
+ },
+ "nodes": [
+
+ {
+ "id": 6880464,
+ "name": "1",
+ "orientation": "horizontal",
+ "rect": {
+ "x": 0,
+ "y": 0,
+ "width": 1280,
+ "height": 782
+ },
+ "floating_nodes": [],
+ "nodes": [
+
+ {
+ "id": 6929968,
+ "name": "#aa0000",
+ "border": "normal",
+ "percent": 1,
+ "rect": {
+ "x": 0,
+ "y": 18,
+ "width": 1280,
+ "height": 782
+ }
+ }
+
+ ]
+ }
+
+ ]
+ },
+
+ {
+ "id": 6880208,
+ "name": "bottomdock",
+ "layout": "dockarea",
+ "orientation": "vertical",
+ "rect": {
+ "x": 0,
+ "y": 782,
+ "width": 1280,
+ "height": 18
+ },
+ "nodes": [
+
+ {
+ "id": 6931312,
+ "name": "#00aa00",
+ "percent": 1,
+ "rect": {
+ "x": 0,
+ "y": 782,
+ "width": 1280,
+ "height": 18
+ }
+ }
+
+ ]
+ }
+ ]
+ }
+ ]
+}
+------------------------
+
+=== GET_MARKS reply
+
+The reply consists of a single array of strings for each container that has a
+mark. The order of that array is undefined. If more than one container has the
+same mark, it will be represented multiple times in the reply (the array
+contents are not unique).
+
+If no window has a mark the response will be the empty array [].
+
+=== GET_BAR_CONFIG reply
+
+This can be used by third-party workspace bars (especially i3bar, but others
+are free to implement compatible alternatives) to get the +bar+ block
+configuration from i3.
+
+Depending on the input, the reply is either:
+
+empty input::
+ An array of configured bar IDs
+Bar ID::
+ A JSON map containing the configuration for the specified bar.
+
+Each bar configuration has the following properties:
+
+id (string)::
+ The ID for this bar. Included in case you request multiple
+ configurations and want to differentiate the different replies.
+mode (string)::
+ Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
+ does not show unless a specific key is pressed).
+position (string)::
+ Either +bottom+ or +top+ at the moment.
+status_command (string)::
+ Command which will be run to generate a statusline. Each line on stdout
+ of this command will be displayed in the bar. At the moment, no
+ formatting is supported.
+font (string)::
+ The font to use for text on the bar.
+workspace_buttons (boolean)::
+ Display workspace buttons or not? Defaults to true.
+verbose (boolean)::
+ Should the bar enable verbose output for debugging? Defaults to false.
+colors (map)::
+ Contains key/value pairs of colors. Each value is a color code in hex,
+ formatted #rrggbb (like in HTML).
+
+The following colors can be configured at the moment:
+
+background::
+ Background color of the bar.
+statusline::
+ Text color to be used for the statusline.
+focused_workspace_text/focused_workspace_bg::
+ Text color/background color for a workspace button when the workspace
+ has focus.
+active_workspace_text/active_workspace_bg::
+ Text color/background color for a workspace button when the workspace
+ is active (visible) on some output, but the focus is on another one.
+ You can only tell this apart from the focused workspace when you are
+ using multiple monitors.
+inactive_workspace_text/inactive_workspace_bg::
+ Text color/background color for a workspace button when the workspace
+ does not have focus and is not active (visible) on any output. This
+ will be the case for most workspaces.
+urgent_workspace_text/urgent_workspace_bar::
+ Text color/background color for workspaces which contain at least one
+ window with the urgency hint set.
+
+
+*Example of configured bars:*
+--------------
+["bar-bxuqzf"]
+--------------
+
+*Example of bar configuration:*
+--------------
+{
+ "id": "bar-bxuqzf",
+ "mode": "dock",
+ "position": "bottom",
+ "status_command": "i3status",
+ "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
+ "workspace_buttons": true,
+ "verbose": false,
+ "colors": {
+ "background": "#c0c0c0",
+ "statusline": "#00ff00",
+ "focused_workspace_text": "#ffffff",
+ "focused_workspace_bg": "#000000"
+ }
+}
+--------------
+
== 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.
+as replies to specific commands. However, the highest bit of the message type
+is set to 1 to indicate that this is an event reply instead of a normal reply.
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.
+event based library may not have a problem here), I suggest you create a
+separate connection to receive events.
=== Subscribing to events
payload: [ "workspace", "focus" ]
---------------------------------
+
=== Available events
-workspace::
+The numbers in parenthesis is the event type (keep in mind that you need to
+strip the highest bit first).
+
+workspace (0)::
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).
+output (1)::
+ Sent when RandR issues a change notification (of either screens,
+ outputs, CRTCs or output properties).
+
+*Example:*
+--------------------------------------------------------------------
+# the appropriate 4 bytes read from the socket are stored in $input
+
+# unpack a 32-bit unsigned integer
+my $message_type = unpack("L", $input);
+
+# check if the highest bit is 1
+my $is_event = (($message_type >> 31) == 1);
+
+# use the other bits
+my $event_type = ($message_type & 0x7F);
+
+if ($is_event) {
+ say "Received event of type $event_type";
+}
+--------------------------------------------------------------------
=== 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").
+"empty", "urgent").
*Example:*
---------------------
{ "change": "focus" }
---------------------
+=== output event
+
+This event consists of a single serialized map containing a property
++change (string)+ which indicates the type of the change (currently only
+"unspecified").
+
+*Example:*
+---------------------------
+{ "change": "unspecified" }
+---------------------------
+
== See also
For some languages, libraries are available (so you don’t have to implement
http://github.com/badboy/i3-ipc
Perl::
http://search.cpan.org/search?query=AnyEvent::I3
+Python::
+ http://github.com/thepub/i3ipc
projects / i3 / i3 / blobdiff