• 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)