665 lines
19 KiB
Plaintext
665 lines
19 KiB
Plaintext
IPC interface (interprocess communication)
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==========================================
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Michael Stapelberg <michael+i3@stapelberg.de>
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December 2011
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This document describes how to interface with i3 from a separate process. This
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is useful for example to remote-control i3 (to write test cases for example) or
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to get various information like the current workspaces to implement an external
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workspace bar.
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The method of choice for IPC in our case is a unix socket because it has very
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little overhead on both sides and is usually available without headaches in
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most languages. In the default configuration file, the ipc-socket gets created
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in +/tmp/i3-%u/ipc-socket.%p+ where +%u+ is your UNIX username and +%p+ is the
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PID of i3. You can get the socketpath from i3 by calling +i3 --get-socketpath+.
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All i3 utilities, like +i3-msg+ and +i3-input+ will read the +I3_SOCKET_PATH+
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X11 property, stored on the X11 root window.
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== Establishing a connection
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To establish a connection, simply open the IPC socket. The following code
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snippet illustrates this in Perl:
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-------------------------------------------------------------
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use IO::Socket::UNIX;
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chomp(my $path = qx(i3 --get-socketpath));
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my $sock = IO::Socket::UNIX->new(Peer => $path);
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-------------------------------------------------------------
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== Sending messages to i3
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To send a message to i3, you have to format in the binary message format which
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i3 expects. This format specifies a magic string in the beginning to ensure
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the integrity of messages (to prevent follow-up errors). Following the magic
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string comes the length of the payload of the message as 32-bit integer, and
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the type of the message as 32-bit integer (the integers are not converted, so
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they are in native byte order).
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The magic string currently is "i3-ipc" and will only be changed when a change
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in the IPC API is done which breaks compatibility (we hope that we don’t need
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to do that).
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Currently implemented message types are the following:
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COMMAND (0)::
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The payload of the message is a command for i3 (like the commands you
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can bind to keys in the configuration file) and will be executed
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directly after receiving it.
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GET_WORKSPACES (1)::
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Gets the current workspaces. The reply will be a JSON-encoded list of
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workspaces (see the reply section).
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SUBSCRIBE (2)::
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Subscribes your connection to certain events. See <<events>> for a
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description of this message and the concept of events.
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GET_OUTPUTS (3)::
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Gets the current outputs. The reply will be a JSON-encoded list of outputs
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(see the reply section).
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GET_TREE (4)::
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Gets the layout tree. i3 uses a tree as data structure which includes
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every container. The reply will be the JSON-encoded tree (see the reply
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section).
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GET_MARKS (5)::
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Gets a list of marks (identifiers for containers to easily jump to them
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later). The reply will be a JSON-encoded list of window marks (see
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reply section).
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GET_BAR_CONFIG (6)::
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Gets the configuration (as JSON map) of the workspace bar with the
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given ID. If no ID is provided, an array with all configured bar IDs is
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returned instead.
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GET_LOG_MARKERS (7)::
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Gets the SHM log markers for the current position, the last wrap, the
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SHM segment name and segment size. This is necessary for tools like
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i3-dump-log which want to display the SHM log.
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So, a typical message could look like this:
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--------------------------------------------------
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"i3-ipc" <message length> <message type> <payload>
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--------------------------------------------------
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Or, as a hexdump:
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------------------------------------------------------------------------------
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00000000 69 33 2d 69 70 63 04 00 00 00 00 00 00 00 65 78 |i3-ipc........ex|
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00000010 69 74 0a |it.|
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------------------------------------------------------------------------------
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To generate and send such a message, you could use the following code in Perl:
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------------------------------------------------------------
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sub format_ipc_command {
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my ($msg) = @_;
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my $len;
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# Get the real byte count (vs. amount of characters)
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{ use bytes; $len = length($msg); }
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return "i3-ipc" . pack("LL", $len, 0) . $msg;
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}
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$sock->write(format_ipc_command("exit"));
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------------------------------------------------------------------------------
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== Receiving replies from i3
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Replies from i3 usually consist of a simple string (the length of the string
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is the message_length, so you can consider them length-prefixed) which in turn
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contain the JSON serialization of a data structure. For example, the
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GET_WORKSPACES message returns an array of workspaces (each workspace is a map
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with certain attributes).
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=== Reply format
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The reply format is identical to the normal message format. There also is
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the magic string, then the message length, then the message type and the
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payload.
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The following reply types are implemented:
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COMMAND (0)::
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Confirmation/Error code for the COMMAND message.
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WORKSPACES (1)::
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Reply to the GET_WORKSPACES message.
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SUBSCRIBE (2)::
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Confirmation/Error code for the SUBSCRIBE message.
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OUTPUTS (3)::
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Reply to the GET_OUTPUTS message.
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TREE (4)::
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Reply to the GET_TREE message.
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MARKS (5)::
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Reply to the GET_MARKS message.
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BAR_CONFIG (6)::
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Reply to the GET_BAR_CONFIG message.
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LOG_MARKERS (7)::
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Reply to the GET_LOG_MARKERS message.
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=== COMMAND reply
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The reply consists of a single serialized map. At the moment, the only
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property is +success (bool)+, but this will be expanded in future versions.
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*Example:*
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-------------------
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{ "success": true }
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-------------------
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=== WORKSPACES reply
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The reply consists of a serialized list of workspaces. Each workspace has the
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following properties:
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num (integer)::
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The logical number of the workspace. Corresponds to the command
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to switch to this workspace.
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name (string)::
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The name of this workspace (by default num+1), as changed by the
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user. Encoded in UTF-8.
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visible (boolean)::
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Whether this workspace is currently visible on an output (multiple
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workspaces can be visible at the same time).
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focused (boolean)::
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Whether this workspace currently has the focus (only one workspace
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can have the focus at the same time).
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urgent (boolean)::
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Whether a window on this workspace has the "urgent" flag set.
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rect (map)::
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The rectangle of this workspace (equals the rect of the output it
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is on), consists of x, y, width, height.
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output (string)::
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The video output this workspace is on (LVDS1, VGA1, …).
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*Example:*
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-------------------
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[
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{
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"num": 0,
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"name": "1",
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"visible": true,
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"focused": true,
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"urgent": false,
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"rect": {
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"x": 0,
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"y": 0,
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"width": 1280,
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"height": 800
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},
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"output": "LVDS1"
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},
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{
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"num": 1,
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"name": "2",
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"visible": false,
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"focused": false,
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"urgent": false,
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"rect": {
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"x": 0,
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"y": 0,
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"width": 1280,
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"height": 800
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},
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"output": "LVDS1"
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}
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]
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-------------------
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=== SUBSCRIBE reply
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The reply consists of a single serialized map. The only property is
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+success (bool)+, indicating whether the subscription was successful (the
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default) or whether a JSON parse error occurred.
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*Example:*
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-------------------
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{ "success": true }
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-------------------
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=== GET_OUTPUTS reply
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The reply consists of a serialized list of outputs. Each output has the
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following properties:
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name (string)::
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The name of this output (as seen in +xrandr(1)+). Encoded in UTF-8.
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active (boolean)::
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Whether this output is currently active (has a valid mode).
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current_workspace (integer)::
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The current workspace which is visible on this output. +null+ if the
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output is not active.
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rect (map)::
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The rectangle of this output (equals the rect of the output it
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is on), consists of x, y, width, height.
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*Example:*
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-------------------
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[
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{
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"name": "LVDS1",
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"active": true,
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"current_workspace": 4,
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"rect": {
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"x": 0,
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"y": 0,
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"width": 1280,
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"height": 800
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}
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},
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{
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"name": "VGA1",
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"active": true,
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"current_workspace": 1,
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"rect": {
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"x": 1280,
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"y": 0,
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"width": 1280,
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"height": 1024
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},
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}
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]
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-------------------
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=== TREE reply
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The reply consists of a serialized tree. Each node in the tree (representing
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one container) has at least the properties listed below. While the nodes might
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have more properties, please do not use any properties which are not documented
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here. They are not yet finalized and will probably change!
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id (integer)::
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The internal ID (actually a C pointer value) of this container. Do not
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make any assumptions about it. You can use it to (re-)identify and
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address containers when talking to i3.
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name (string)::
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The internal name of this container. For all containers which are part
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of the tree structure down to the workspace contents, this is set to a
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nice human-readable name of the container.
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For all other containers, the content is not defined (yet).
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border (string)::
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Can be either "normal", "none" or "1pixel", dependending on the
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container’s border style.
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layout (string)::
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Can be either "default", "stacked", "tabbed", "dockarea" or "output".
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Other values might be possible in the future, should we add new
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layouts.
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orientation (string)::
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Can be either "none" (for non-split containers), "horizontal" or
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"vertical".
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percent (float)::
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The percentage which this container takes in its parent. A value of
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+null+ means that the percent property does not make sense for this
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container, for example for the root container.
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rect (map)::
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The absolute display coordinates for this container. Display
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coordinates means that when you have two 1600x1200 monitors on a single
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X11 Display (the standard way), the coordinates of the first window on
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the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
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1200 }+.
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window_rect (map)::
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The coordinates of the *actual client window* inside its container.
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These coordinates are relative to the container and do not include the
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window decoration (which is actually rendered on the parent container).
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So, when using the +default+ layout, you will have a 2 pixel border on
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each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
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"height": 366 }+ (for example).
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geometry (map)::
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The original geometry the window specified when i3 mapped it. Used when
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switching a window to floating mode, for example.
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urgent (bool)::
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Whether this container (window or workspace) has the urgency hint set.
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focused (bool)::
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Whether this container is currently focused.
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Please note that in the following example, I have left out some keys/values
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which are not relevant for the type of the node. Otherwise, the example would
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be by far too long (it already is quite long, despite showing only 1 window and
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one dock window).
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It is useful to have an overview of the structure before taking a look at the
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JSON dump:
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* root
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** LVDS1
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*** topdock
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*** content
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**** workspace 1
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***** window 1
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*** bottomdock
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**** dock window 1
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** VGA1
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*Example:*
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-----------------------
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{
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"id": 6875648,
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"name": "root",
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"rect": {
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"x": 0,
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"y": 0,
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"width": 1280,
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"height": 800
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},
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"nodes": [
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{
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"id": 6878320,
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"name": "LVDS1",
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"layout": "output",
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"rect": {
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"x": 0,
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"y": 0,
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"width": 1280,
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"height": 800
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},
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"nodes": [
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{
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"id": 6878784,
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"name": "topdock",
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"layout": "dockarea",
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"orientation": "vertical",
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"rect": {
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"x": 0,
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"y": 0,
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"width": 1280,
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"height": 0
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},
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},
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{
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"id": 6879344,
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"name": "content",
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"rect": {
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"x": 0,
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"y": 0,
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"width": 1280,
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"height": 782
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},
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"nodes": [
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{
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"id": 6880464,
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"name": "1",
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"orientation": "horizontal",
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"rect": {
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"x": 0,
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"y": 0,
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"width": 1280,
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"height": 782
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},
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"floating_nodes": [],
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"nodes": [
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{
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"id": 6929968,
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"name": "#aa0000",
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"border": "normal",
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"percent": 1,
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"rect": {
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"x": 0,
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"y": 18,
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"width": 1280,
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"height": 782
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}
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}
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]
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}
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]
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},
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{
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"id": 6880208,
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"name": "bottomdock",
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"layout": "dockarea",
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"orientation": "vertical",
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"rect": {
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"x": 0,
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"y": 782,
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"width": 1280,
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"height": 18
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},
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"nodes": [
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{
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"id": 6931312,
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"name": "#00aa00",
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"percent": 1,
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"rect": {
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"x": 0,
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"y": 782,
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"width": 1280,
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"height": 18
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}
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}
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]
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}
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]
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}
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]
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}
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------------------------
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=== MARKS reply
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The reply consists of a single array of strings for each container that has a
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mark. The order of that array is undefined. If more than one container has the
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same mark, it will be represented multiple times in the reply (the array
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contents are not unique).
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If no window has a mark the response will be the empty array [].
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=== BAR_CONFIG reply
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This can be used by third-party workspace bars (especially i3bar, but others
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are free to implement compatible alternatives) to get the +bar+ block
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configuration from i3.
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Depending on the input, the reply is either:
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empty input::
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An array of configured bar IDs
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Bar ID::
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A JSON map containing the configuration for the specified bar.
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Each bar configuration has the following properties:
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id (string)::
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The ID for this bar. Included in case you request multiple
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configurations and want to differentiate the different replies.
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mode (string)::
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Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
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does not show unless a specific key is pressed).
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position (string)::
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Either +bottom+ or +top+ at the moment.
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status_command (string)::
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Command which will be run to generate a statusline. Each line on stdout
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of this command will be displayed in the bar. At the moment, no
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formatting is supported.
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font (string)::
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The font to use for text on the bar.
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workspace_buttons (boolean)::
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Display workspace buttons or not? Defaults to true.
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verbose (boolean)::
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Should the bar enable verbose output for debugging? Defaults to false.
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colors (map)::
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Contains key/value pairs of colors. Each value is a color code in hex,
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formatted #rrggbb (like in HTML).
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The following colors can be configured at the moment:
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background::
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Background color of the bar.
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statusline::
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Text color to be used for the statusline.
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focused_workspace_text/focused_workspace_bg::
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Text color/background color for a workspace button when the workspace
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has focus.
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active_workspace_text/active_workspace_bg::
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Text color/background color for a workspace button when the workspace
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is active (visible) on some output, but the focus is on another one.
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You can only tell this apart from the focused workspace when you are
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using multiple monitors.
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inactive_workspace_text/inactive_workspace_bg::
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Text color/background color for a workspace button when the workspace
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does not have focus and is not active (visible) on any output. This
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will be the case for most workspaces.
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urgent_workspace_text/urgent_workspace_bar::
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Text color/background color for workspaces which contain at least one
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window with the urgency hint set.
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*Example of configured bars:*
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--------------
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["bar-bxuqzf"]
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--------------
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*Example of bar configuration:*
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--------------
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{
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"id": "bar-bxuqzf",
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"mode": "dock",
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"position": "bottom",
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"status_command": "i3status",
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"font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
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"workspace_buttons": true,
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"verbose": false,
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"colors": {
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"background": "#c0c0c0",
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"statusline": "#00ff00",
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"focused_workspace_text": "#ffffff",
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"focused_workspace_bg": "#000000"
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}
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}
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--------------
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=== LOG_MARKERS reply
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Gets the SHM log markers for the current position, the last wrap, the
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SHM segment name and segment size. This is necessary for tools like
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i3-dump-log which want to display the SHM log.
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The reply is a JSON map with the following entries:
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shmname (string)::
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The name of the SHM segment, will be of the format +/i3-log-<pid>+.
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size (integer)::
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The size (in bytes) of the SHM segment. If this is 0, SHM logging is
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disabled.
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offset_next_write (integer)::
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The offset in the SHM segment at which the next write will happen.
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Tools should start printing lines from here, since the bytes following
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this offset are the oldest log lines. However, the first line might be
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garbled, so it makes sense to skip all bytes until the first \0.
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offset_last_wrap (integer)::
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||
The offset in the SHM segment at which the last wrap occured. i3 only
|
||
stores entire messages in the SHM log, so it might waste a few bytes at
|
||
the end to be more efficient. Tools should not print content after the
|
||
offset_last_wrap.
|
||
|
||
*Example*:
|
||
-----------------------------
|
||
{
|
||
"offset_next_write":132839,
|
||
"offset_last_wrap":26214400,
|
||
"shmname":"/i3-log-3392",
|
||
"size":26214400
|
||
}
|
||
-----------------------------
|
||
|
||
== 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. 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 suggest you 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
|
||
|
||
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", "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
|
||
all this on your own). This list names some (if you wrote one, please let me
|
||
know):
|
||
|
||
C::
|
||
i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
|
||
However, there is no library yet.
|
||
Ruby::
|
||
http://github.com/badboy/i3-ipc
|
||
Perl::
|
||
http://search.cpan.org/search?query=AnyEvent::I3
|
||
Python::
|
||
http://github.com/thepub/i3ipc
|