IPC interface (interprocess communication)
==========================================
Michael Stapelberg <michael@i3wm.org>
-February 2014
+September 2017
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
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:
-
-COMMAND (0)::
- 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.
-GET_WORKSPACES (1)::
- Gets the current workspaces. The reply will be a JSON-encoded list of
- workspaces (see the reply section).
-SUBSCRIBE (2)::
- Subscribes your connection to certain events. See <<events>> for a
- description of this message and the concept of events.
-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.
-GET_VERSION (7)::
- Gets the version of i3. The reply will be a JSON-encoded dictionary
- with the major, minor, patch and human-readable version.
+.Currently implemented message types
+[options="header",cols="^10%,^20%,^20%,^50%"]
+|======================================================
+| Type (numeric) | Type (name) | Reply type | Purpose
+| 0 | +RUN_COMMAND+ | <<_command_reply,COMMAND>> | Run the payload as an i3 command (like the commands you can bind to keys).
+| 1 | +GET_WORKSPACES+ | <<_workspaces_reply,WORKSPACES>> | Get the list of current workspaces.
+| 2 | +SUBSCRIBE+ | <<_subscribe_reply,SUBSCRIBE>> | Subscribe this IPC connection to the event types specified in the message payload. See <<events>>.
+| 3 | +GET_OUTPUTS+ | <<_outputs_reply,OUTPUTS>> | Get the list of current outputs.
+| 4 | +GET_TREE+ | <<_tree_reply,TREE>> | Get the i3 layout tree.
+| 5 | +GET_MARKS+ | <<_marks_reply,MARKS>> | Gets the names of all currently set marks.
+| 6 | +GET_BAR_CONFIG+ | <<_bar_config_reply,BAR_CONFIG>> | Gets the specified bar configuration or the names of all bar configurations if payload is empty.
+| 7 | +GET_VERSION+ | <<_version_reply,VERSION>> | Gets the i3 version.
+| 8 | +GET_BINDING_MODES+ | <<_binding_modes_reply,BINDING_MODES>> | Gets the names of all currently configured binding modes.
+| 9 | +GET_CONFIG+ | <<_config_reply,CONFIG>> | Returns the last loaded i3 config.
+| 10 | +SEND_TICK+ | <<_tick_reply,TICK>> | Sends a tick event with the specified payload.
+| 11 | +SYNC+ | <<_sync_reply,SYNC>> | Sends an i3 sync event with the specified random value to the specified window.
+|======================================================
So, a typical message could look like this:
--------------------------------------------------
The following reply types are implemented:
COMMAND (0)::
- Confirmation/Error code for the COMMAND message.
+ Confirmation/Error code for the RUN_COMMAND message.
WORKSPACES (1)::
Reply to the GET_WORKSPACES message.
SUBSCRIBE (2)::
Reply to the GET_BAR_CONFIG message.
VERSION (7)::
Reply to the GET_VERSION message.
-
+BINDING_MODES (8)::
+ Reply to the GET_BINDING_MODES message.
+GET_CONFIG (9)::
+ Reply to the GET_CONFIG message.
+TICK (10)::
+ Reply to the SEND_TICK message.
+
+[[_command_reply]]
=== COMMAND reply
The reply consists of a list of serialized maps for each command that was
[{ "success": true }]
-------------------
+[[_workspaces_reply]]
=== WORKSPACES reply
The reply consists of a serialized list of workspaces. Each workspace has the
num (integer)::
The logical number of the workspace. Corresponds to the command
- to switch to this workspace.
+ to switch to this workspace. For named workspaces, this will be -1.
name (string)::
The name of this workspace (by default num+1), as changed by the
user. Encoded in UTF-8.
]
-------------------
+[[_subscribe_reply]]
=== SUBSCRIBE reply
The reply consists of a single serialized map. The only property is
{ "success": true }
-------------------
+[[_outputs_reply]]
=== OUTPUTS reply
The reply consists of a serialized list of outputs. Each output has the
The name of this output (as seen in +xrandr(1)+). Encoded in UTF-8.
active (boolean)::
Whether this output is currently active (has a valid mode).
+primary (boolean)::
+ Whether this output is currently the primary output.
current_workspace (string)::
The name of the current workspace that is visible on this output. +null+ if
the output is not active.
"y": 0,
"width": 1280,
"height": 1024
- },
+ }
}
]
-------------------
+[[_tree_reply]]
=== TREE reply
The reply consists of a serialized tree. Each node in the tree (representing
Type of this container. Can be one of "root", "output", "con",
"floating_con", "workspace" or "dockarea".
border (string)::
- Can be either "normal", "none" or "1pixel", dependending on the
+ Can be either "normal", "none" or "pixel", depending on the
container’s border style.
current_border_width (integer)::
Number of pixels of the border width.
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).
+deco_rect (map)::
+ The coordinates of the *window decoration* inside its container. These
+ coordinates are relative to the container and do not include the actual
+ client window.
geometry (map)::
The original geometry the window specified when i3 mapped it. Used when
switching a window to floating mode, for example.
This field is set to null for split containers or otherwise empty
containers. This ID corresponds to what xwininfo(1) and other
X11-related tools display (usually in hex).
+window_properties (map)::
+ X11 window properties title, instance, class, window_role and transient_for.
urgent (bool)::
- Whether this container (window or workspace) has the urgency hint set.
+ Whether this container (window, split container, floating container or
+ workspace) has the urgency hint set, directly or indirectly. All parent
+ containers up until the workspace container will be marked urgent if they
+ have at least one urgent child.
focused (bool)::
Whether this container is currently focused.
+focus (array of integer)::
+ List of child node IDs (see +nodes+, +floating_nodes+ and +id+) in focus
+ order. Traversing the tree by following the first entry in this array
+ will result in eventually reaching the one node with +focused+ set to
+ true.
+nodes (array of node)::
+ The tiling (i.e. non-floating) child containers of this node.
+floating_nodes (array of node)::
+ The floating child containers of this node. Only non-empty on nodes with
+ type +workspace+.
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
"y": 0,
"width": 1280,
"height": 0
- },
+ }
},
{
"width": 1280,
"height": 782
},
+ "window_properties": {
+ "class": "Evince",
+ "instance": "evince",
+ "title": "Properties",
+ "transient_for": 52428808
+ },
"floating_nodes": [],
"nodes": [
}
------------------------
+[[_marks_reply]]
=== MARKS reply
The reply consists of a single array of strings for each container that has a
If no window has a mark the response will be the empty array [].
+[[_bar_config_reply]]
=== BAR_CONFIG reply
This can be used by third-party workspace bars (especially i3bar, but others
Text color to be used for the statusline.
separator::
Text color to be used for the separator.
-focused_workspace_text/focused_workspace_bg::
- Text color/background color for a workspace button when the workspace
+focused_background::
+ Background color of the bar on the currently focused monitor output.
+focused_statusline::
+ Text color to be used for the statusline on the currently focused
+ monitor output.
+focused_separator::
+ Text color to be used for the separator on the currently focused
+ monitor output.
+focused_workspace_text/focused_workspace_bg/focused_workspace_border::
+ Text/background/border 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
+active_workspace_text/active_workspace_bg/active_workspace_border::
+ Text/background/border 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
+inactive_workspace_text/inactive_workspace_bg/inactive_workspace_border::
+ Text/background/border 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
+urgent_workspace_text/urgent_workspace_bg/urgent_workspace_border::
+ Text/background/border color for workspaces which contain at least one
window with the urgency hint set.
+binding_mode_text/binding_mode_bg/binding_mode_border::
+ Text/background/border color for the binding mode indicator.
*Example of configured bars:*
}
--------------
+[[_version_reply]]
=== VERSION reply
The reply consists of a single JSON dictionary with the following keys:
build date and branch name. When you need to display the i3 version to
your users, use the human-readable version whenever possible (since
this is what +i3 --version+ displays, too).
+loaded_config_file_name (string)::
+ The current config path.
*Example:*
-------------------
{
"human_readable" : "4.2-169-gf80b877 (2012-08-05, branch \"next\")",
+ "loaded_config_file_name" : "/home/hwangcc23/.i3/config",
"minor" : 2,
"patch" : 0,
"major" : 4
}
-------------------
+[[_binding_modes_reply]]
+=== BINDING_MODES reply
+
+The reply consists of an array of all currently configured binding modes.
+
+*Example:*
+---------------------
+["default", "resize"]
+---------------------
+
+[[_config_reply]]
+=== CONFIG reply
+
+The config reply is a map which currently only contains the "config" member,
+which is a string containing the config file as loaded by i3 most recently.
+
+*Example:*
+-------------------
+{ "config": "font pango:monospace 8\nbindsym Mod4+q exit\n" }
+-------------------
+
+[[_tick_reply]]
+=== TICK reply
+
+The reply is a map containing the "success" member. After the reply was
+received, the tick event has been written to all IPC connections which subscribe
+to tick events. UNIX sockets are usually buffered, but you can be certain that
+once you receive the tick event you just triggered, you must have received all
+events generated prior to the +SEND_TICK+ message (happened-before relation).
+
+*Example:*
+-------------------
+{ "success": true }
+-------------------
+
+[[_sync_reply]]
+=== SYNC reply
+
+The reply is a map containing the "success" member. After the reply was
+received, the https://i3wm.org/docs/testsuite.html#i3_sync[i3 sync message] was
+responded to.
+
+*Example:*
+-------------------
+{ "success": true }
+-------------------
+
== Events
[[events]]
*Example:*
---------------------------------
type: SUBSCRIBE
-payload: [ "workspace", "focus" ]
+payload: [ "workspace", "output" ]
---------------------------------
barconfig_update (4)::
Sent when the hidden_state or mode field in the barconfig of any bar
instance was updated and when the config is reloaded.
+binding (5)::
+ Sent when a configured command binding is triggered with the keyboard or
+ mouse
+shutdown (6)::
+ Sent when the ipc shuts down because of a restart or exit by user command
+tick (7)::
+ Sent when the ipc client subscribes to the tick event (with +"first":
+ true+) or when any ipc client sends a SEND_TICK message (with +"first":
+ false+).
*Example:*
--------------------------------------------------------------------
This event consists of a single serialized map containing a property
+change (string)+ which indicates the type of the change ("focus", "init",
-"empty", "urgent").
+"empty", "urgent", "reload", "rename", "restored", "move"). A
++current (object)+ property will be present with the affected workspace
+whenever the type of event affects a workspace (otherwise, it will be +null).
-Moreover, when the change is "focus", an +old (object)+ and a +current
-(object)+ properties will be present with the previous and current
-workspace respectively. When the first switch occurs (when i3 focuses
-the workspace visible at the beginning) there is no previous
-workspace, and the +old+ property will be set to +null+. Also note
-that if the previous is empty it will get destroyed when switching,
-but will still be present in the "old" property.
+When the change is "focus", an +old (object)+ property will be present with the
+previous workspace. When the first switch occurs (when i3 focuses the
+workspace visible at the beginning) there is no previous workspace, and the
++old+ property will be set to +null+. Also note that if the previous is empty
+it will get destroyed when switching, but will still be present in the "old"
+property.
*Example:*
---------------------
This event consists of a single serialized map containing a property
+change (string)+ which holds the name of current mode in use. The name
is the same as specified in config when creating a mode. The default
-mode is simply named default.
+mode is simply named default. It contains a second property, +pango_markup+, which
+defines whether pango markup shall be used for displaying this mode.
*Example:*
---------------------------
-{ "change": "default" }
+{
+ "change": "default",
+ "pango_markup": true
+}
---------------------------
=== window event
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
-* +move+ - the window has changed its position in the tree
+* +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
+* +move+ – the window has changed its position in the tree
+* +floating+ – the window has transitioned to or from floating
+* +urgent+ – the window has become urgent or lost its urgent status
+* +mark+ – a mark has been added to or removed from the window
Additionally a +container (object)+ field will be present, which consists
of the window's parent container. Be aware that for the "new" event, the
barconfig of the specified bar_id that were updated in i3. This event is the
same as a +GET_BAR_CONFIG+ reply for the bar with the given id.
+=== binding event
+
+This event consists of a single serialized map reporting on the details of a
+binding that ran a command because of user input. The +change (string)+ field
+indicates what sort of binding event was triggered (right now it will always be
++"run"+ but may be expanded in the future).
+
+The +binding (object)+ field contains details about the binding that was run:
+
+command (string)::
+ The i3 command that is configured to run for this binding.
+event_state_mask (array of strings)::
+ The group and modifier keys that were configured with this binding.
+input_code (integer)::
+ If the binding was configured with +bindcode+, this will be the key code
+ that was given for the binding. If the binding is a mouse binding, it will be
+ the number of the mouse button that was pressed. Otherwise it will be 0.
+symbol (string or null)::
+ If this is a keyboard binding that was configured with +bindsym+, this
+ field will contain the given symbol. Otherwise it will be +null+.
+input_type (string)::
+ This will be +"keyboard"+ or +"mouse"+ depending on whether or not this was
+ a keyboard or a mouse binding.
+
+*Example:*
+---------------------------
+{
+ "change": "run",
+ "binding": {
+ "command": "nop",
+ "event_state_mask": [
+ "shift",
+ "ctrl"
+ ],
+ "input_code": 0,
+ "symbol": "t",
+ "input_type": "keyboard"
+ }
+}
+---------------------------
+
+=== shutdown event
+
+This event is triggered when the connection to the ipc is about to shutdown
+because of a user action such as a +restart+ or +exit+ command. The +change
+(string)+ field indicates why the ipc is shutting down. It can be either
++"restart"+ or +"exit"+.
+
+*Example:*
+---------------------------
+{
+ "change": "restart"
+}
+---------------------------
+
+=== tick event
+
+This event is triggered by a subscription to tick events or by a +SEND_TICK+
+message.
+
+*Example (upon subscription):*
+--------------------------------------------------------------------------------
+{
+ "first": true,
+ "payload": ""
+}
+--------------------------------------------------------------------------------
+
+*Example (upon +SEND_TICK+ with a payload of +arbitrary string+):*
+--------------------------------------------------------------------------------
+{
+ "first": false,
+ "payload": "arbitrary string"
+}
+--------------------------------------------------------------------------------
+
== See also (existing libraries)
[[libraries]]
C::
* i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
* https://github.com/acrisci/i3ipc-glib
+C++::
+ * https://github.com/drmgc/i3ipcpp
Go::
- * https://github.com/proxypoke/i3ipc
+ * https://github.com/mdirkse/i3ipc-go
+ * https://github.com/i3/go-i3
JavaScript::
* https://github.com/acrisci/i3ipc-gjs
Lua::
* https://github.com/whitelynx/i3ipc (not maintained)
* https://github.com/ziberna/i3-py (not maintained)
Ruby::
- * http://github.com/badboy/i3-ipc
+ * https://github.com/veelenga/i3ipc-ruby
+ * https://github.com/badboy/i3-ipc (not maintained)
+Rust::
+ * https://github.com/tmerr/i3ipc-rs
+OCaml::
+ * https://github.com/Armael/ocaml-i3ipc
+
+== Appendix A: Detecting byte order in memory-safe languages
+
+Some programming languages such as Go don’t offer a way to serialize data in the
+native byte order of the machine they’re running on without resorting to tricks
+involving the +unsafe+ package.
+
+The following technique can be used (and will not be broken by changes to i3) to
+detect the byte order i3 is using:
+
+1. The byte order dependent fields of an IPC message are message type and
+ payload length.
+
+ * The message type +RUN_COMMAND+ (0) is the same in big and little endian, so
+ we can use it in either byte order to elicit a reply from i3.
+
+ * The payload length 65536 + 256 (+0x00 01 01 00+) is the same in big and
+ little endian, and also small enough to not worry about memory allocations
+ of that size. We must use payloads of length 65536 + 256 in every message
+ we send, so that i3 will be able to read the entire message regardless of
+ the byte order it uses.
+
+2. Send a big endian encoded message of type +SUBSCRIBE+ (2) with payload `[]`
+ followed by 65536 + 256 - 2 +SPACE+ (ASCII 0x20) bytes.
+
+ * If i3 is running in big endian, this message is treated as a noop,
+ resulting in a +SUBSCRIBE+ reply with payload `{"success":true}`
+ footnote:[A small payload is important: that way, we circumvent dealing
+ with UNIX domain socket buffer sizes, whose size depends on the
+ implementation/operating system. Exhausting such a buffer results in an i3
+ deadlock unless you concurrently read and write, which — depending on the
+ programming language — makes the technique much more complicated.].
+
+ * If i3 is running in little endian, this message is read in its entirety due
+ to the byte order independent payload length, then
+ https://github.com/i3/i3/blob/d726d09d496577d1c337a4b97486f2c9fbc914f1/src/ipc.c#L1188[silently
+ discarded] due to the unknown message type.
+
+3. Send a byte order independent message, i.e. type +RUN_COMMAND+ (0) with
+ payload +nop byte order detection. padding:+, padded to 65536 + 256 bytes
+ with +a+ (ASCII 0x61) bytes. i3 will reply to this message with a reply of
+ type +COMMAND+ (0).
+
+ * The human-readable prefix is in there to not confuse readers of the i3 log.
+
+ * This messages serves as a synchronization primitive so that we know whether
+ i3 discarded the +SUBSCRIBE+ message or didn’t answer it yet.
+
+4. Receive a message header from i3, decoding the message type as big endian.
+
+ * If the message’s reply type is +COMMAND+ (0), i3 is running in little
+ endian (because the +SUBSCRIBE+ message was discarded). Decode the message
+ payload length as little endian, receive the message payload.
+
+ * If the message’s reply type is anything else, i3 is running in big endian
+ (because our big endian encoded +SUBSCRIBE+ message was answered). Decode
+ the message payload length in big endian, receive the message
+ payload. Then, receive the pending +COMMAND+ message reply in big endian.
+
+5. From here on out, send/receive all messages using the detected byte order.
+
+Find an example implementation of this technique in
+https://github.com/i3/go-i3/blob/master/byteorder.go
projects / i3 / i3 / blobdiff