149 lines
5.6 KiB
Plaintext
149 lines
5.6 KiB
Plaintext
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i3bar input protocol
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====================
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Michael Stapelberg <michael@i3wm.org>
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February 2012
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This document explains the protocol in which i3bar expects its input. It
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provides support for colors, urgency, shortening and easy manipulation.
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== Rationale for chosing JSON
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Before describing the protocol, let’s cover why JSON is a building block of
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this protocol.
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1. Other bar display programs such as dzen2 or xmobar are using in-band
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signaling: they recognize certain sequences (like ^fg(#330000) in your input
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text). We would like to avoid that and separate information from
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meta-information. By information, we mean the actual output, like the IP
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address of your ethernet adapter and by meta-information, we mean in which
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color it should be displayed right now.
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2. It is easy to write a simple script which manipulates part(s) of the input.
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Each block of information (like a block for the disk space indicator, a block
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for the current IP address, etc.) can be identified specifically and modified
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in whichever way you like.
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3. It remains easy to write a simple script which just suffixes (or prefixes) a
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status line input, because tools like i3status will output their JSON in
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such a way that each line array will be terminated by a newline. Therefore,
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you are not required to use a streaming JSON parser, but you can use any
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JSON parser and write your script in any programming language. In fact, you
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can decide to not bother with the JSON parsing at all and just inject your
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output at a specific position (beginning or end).
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4. Relying on JSON does not introduce any new dependencies. In fact, the IPC
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interface of i3 also uses JSON, therefore i3bar already depends on JSON.
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The only point against using JSON is computational complexity. If that really
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bothers you, just use the plain text input format (which i3bar will continue to
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support).
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== The protocol
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The first message of the protocol is a header block, which contains (at least)
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the version of the protocol to be used. In case there are significant changes
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(not only additions), the version will be incremented. i3bar will still
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understand the old protocol version, but in order to use the new one, you need
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to provide the correct version. The header block is terminated by a newline and
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consists of a single JSON hash:
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*Example*:
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----------------
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{ "version": 1 }
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----------------
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What follows is an infinite array (so it should be parsed by a streaming JSON
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parser, but as described above you can go for a simpler solution), whose
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elements are one array per status line. A status line is one unit of
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information which should be displayed at a time. i3bar will not display any
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input until the status line is complete. In each status line, every block will
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be represented by a JSON hash:
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*Example*:
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------
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[
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[
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{
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"full_text": "E: 10.0.0.1 (1000 Mbit/s)",
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"color": "#00ff00"
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},
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{
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"full_text": "2012-01-05 20:00:01"
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}
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],
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[
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{
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"full_text": "E: 10.0.0.1 (1000 Mbit/s)",
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"color": "#00ff00"
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},
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{
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"full_text": "2012-01-05 20:00:02"
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}
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],
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…
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------
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Please note that this example was pretty printed for human consumption.
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i3status and others will output single statuslines in one line, separated by
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\n.
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=== Blocks in detail
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full_text::
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The most simple block you can think of is one which just includes the
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only required key, the +full_text+ key. i3bar will display the string
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value and that’s it.
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short_text::
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Where appropriate, the +short_text+ (string) entry should also be
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provided. It will be used in case the status line needs to be shortened
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because it uses more space than your screen provides. For example, when
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displaying an IPv6 address, the prefix is usually (!) more relevant
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than the suffix, because the latter stays constant when using autoconf,
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while the prefix changes. When displaying the date, the time is more
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important than the date (it is more likely that you know which day it
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is than what time it is).
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color::
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To make the current state of the information easy to spot, colors can
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be used. For example, the wireless block could be displayed in red
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(using the +color+ (string) entry) if the card is not associated with
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any network and in green or yellow (depending on the signal strength)
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when it is associated.
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Colors are specified in hex (like in HTML), starting with a leading
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hash sign. For example, +#ff0000+ means red.
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name and instance::
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Every block should have a unique +name+ (string) entry so that it can
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be easily identified in scripts which process the output. i3bar
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completely ignores the name and instance fields. Make sure to also
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specify an +instance+ (string) entry where appropriate. For example,
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the user can have multiple disk space blocks for multiple mount points.
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urgent::
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A boolean which specifies whether the current value is urgent. Examples
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are battery charge values below 1 percent or no more available disk
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space (for non-root users). The presentation of urgency is up to i3bar.
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If you want to put in your own entries into a block, prefix the key with an
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underscore (_). i3bar will ignore all keys it doesn’t understand, and prefixing
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them with an underscore makes it clear in every script that they are not part
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of the i3bar protocol.
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*Example*:
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------------------------------------------
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{
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"full_text": "E: 10.0.0.1 (1000 Mbit/s)",
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"_ethernet_vendor": "Intel"
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}
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------------------------------------------
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An example of a block which uses all possible entries follows:
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*Example*:
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------------------------------------------
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{
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"full_text": "E: 10.0.0.1 (1000 Mbit/s)",
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"short_text": "10.0.0.1",
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"color": "#00ff00",
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"urgent": false,
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"name": "ethernet",
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"instance": "eth0"
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}
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------------------------------------------
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