Cockpit Coding Guidelines

Dominik Perpeet edited this page Jul 19, 2017 · 11 revisions


  • No trailing whitespace, no tab characters, except in files
  • Generally line length should be limited to 120 chars
  • Indentation: 4 spaces per level, no tabs


C style

  • Gtk+ coding standards

  • C99 is allowed and the default.

  • When in doubt, check the surrounding code and try to imitate it.

  • Exception: We don't require tabular alignment of function arguments like GTK and Glib do. Function definitions look like this:

static JsonArray *
interframe_compress_samples (int count,
                             JsonArray *samples)
  /* code */

Sample code

/* Store the code/data payload */
if (len >= 2)
    pv->peer_close_code = (guint16)data[0] << 8 | data[1];
if (len > 2)
    data += 2;
    len -= 2;
    if (g_utf8_validate ((gchar *)data, len, NULL))
      pv->peer_close_data = g_strndup ((gchar *)data, len);
      g_message ("received non-UTF8 close data: %d '%.*s' %d", (int)len, (int)len, (gchar *)data, (int)data[0]);

JavaScript style

  • Private scopes are only necessary in code that is not bundled with webpack.
  • "use strict" should be set on code that is not bundled with webpack.
  • Crockford with lots of exceptions
  • Chained calls may be placed on separate lines for readability (see example below)

Don't indent top level code, even if using a top level private scope (see above).

(function() {
"use strict";

console.log("not indented");


Variables should be declared outside of loops or condition braces.

  var demo = 1; /* here */
  while(false) {
     /* not here */

Function declarations and invocations should have no space after function name. Function starting brace goes on same line as function keyword.

function name(arg) {
   /* body */

Anonymous functions do not need a space between the function keyword and arguments.

div.onclick = function(e) {
   /* body */

Control flow keywords such as if for and while should have a space after them. If there is only one statement in a conditional or loop, you may leave out the braces.

while (false)
   console.log("never reached");

All binary operators except . (period) and ( (left parenthesis) and [ (left bracket) should be separated from their operands by a space.

More Sample code

/* if an image is older than two days, don't show the time */
var threshold_date = new Date(image.Created * 1000);
threshold_date.setDate(threshold_date.getDate() + 2);

if (threshold_date > (new Date())) {
    $(row[1]).text(new Date(image.Created * 1000).toLocaleString());
} else {
    var creation_date = new Date(image.Created * 1000);

    /* we hide the time, so put full timestamp in the hover text */
        .attr("title", creation_date.toLocaleString());

New javascript files should be in the Asyncronous Module Definition form. For example:

], function($, cockpit) {
    /* ... */

    var module = {
        api1: function api1() { /* ... */ },
        api2: function api2() { /* ... */ }

    return module;

As a general rule: Modules that return API (as above) should avoid global side-effects. And modules that have global side-effects should not return or define API.

React/JSX conventions:

  • Wrap multiline jsx in parentheses
  • Inside JSX code, simple variables or expressions don't require spaces in curly braces, complex ones do, {key.val} and {key} but { }
var panel = (
    <tr className="listing-panel">
        <td colSpan={ header_entries.length + (expand_toggle?1:0) }>
            <div className="listing-head">
                <div className="listing-actions">
                <ul className="nav nav-tabs nav-tabs-pf">

CSS/HTML style

  • Use dashes instead of underscores in ids
  • Use namespaces for ids if writing code that is consumed as part of a larger whole.

Sample code

/* Panels don't draw borders between them */
.panel > .table > tbody:first-child td {
    border-top: 1px solid rgb(221, 221, 221);

/* Table headers should not generate a double border */
.panel .table thead tr th {
    border-bottom: none;

Python style

Sample code

def run(self, proc, output=""):
    # Complete retrieval of the list of tests
    output +=
    if proc.returncode:
        sys.stderr.write("tap-gtester: listing GTest tests failed: %d\n" % proc.returncode)
        return proc.returncode
    self.test_remaining = []
    for line in output.split("\n"):
        if line.startswith("/"):
    if not self.test_remaining:
        print "Bail out! No tests found in GTest: %s" % self.command[0]
        return 0

    print "1..%d" % len(self.test_remaining)

Emacs setup

(setq indent-tabs-mode nil)
(add-hook 'before-save-hook 'delete-trailing-whitespace)
(setq whitespace-style '(face trailing lines-tail empty))
(setq whitespace-line-column 120)
Clone this wiki locally
You can’t perform that action at this time.
You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Reload to refresh your session.
Press h to open a hovercard with more details.