SeaMonkey:MailNews:CodingStyle

This is just a draft and may change!

Basically, the Mozilla C++ coding style guide rules apply. But our MailNews code has grown evolved over the years and can be rather twisted complex, thus we favour readability over brevity.

JavaScript

In general, use the C++ rules above, but take care of these exceptions:

Default bracing style is "curly braces go on their own line"

To enhance readability, curly braces should be aligned vertically:

if (condition)
{
  let x = 23;
  CallSomething(x);
}
else
{
  CallSomethingElse();
}

There are quite some (old) files in our codebase which entirely adhere to the "opening curly braces go at the end of a line" style. If you do changes there, please keep the file's coding style consistent. Mixed coding styles only makes things worse.

If one if branch needs braces, the other should have braces as well

// Fine!
if (condition)
  CallSomething(23);
else
  CallSomethingElse();

// Bad! Don't do this!
if (condition)
{
  let x = 23;
  CallSomething(x);
}
else
  CallSomethingElse();

No one-line if contructs

Almost all contemporary debuggers are line debuggers and can't break amidst a line of code:

// Fine!
if (condition)
  return 42;

// Bad! Don't do this!
if (condition) return 42;

Use let for sub-scope variables

The scope of variables should as small as possible. Using the let keyword, the visibility can be restricted to the current block:

function CallSomething(ax)
{
  var x = 23;    // global to CallSomething!
  if (x < ax)
  {
    var y = 42;  // global to CallSomething!
    let z = 666; // local to this if
    for (let i = 0; i < ax; ++i) // i is local to the for loop
      CallSomethingElse(i);
  }
}

XML/XUL

Indent is two spaces per nesting level

<element>
  <element>
    <element/>
  </element>
</element>

Sort XUL attributes

XUL attributes should come in this rough order:

<element id="menu_showMessagePane"
         label="&showMessagePaneCmd.label;"
         accesskey="&showMessagePaneCmd.accesskey;"
         key="key_toggleMessagePane"
         random_other_attributes="put 'em here!"
         oncommand="MsgToggleMessagePane(true);"/>

Especially, id should be first, label/accesskey/key should go together and handlers should be last.

One attribute per line when folding

If the XML element definition (vastly) exceeds the 80 columns limit, it should be wrapped. In this case, put each attribute onto its own line and align them vertically:

<!-- Fine! -->
<element id="menu_showMessagePane" type="checkbox"/>

<!-- Bad! Don't do this! -->
<element id="menu_showMessagePane" type="checkbox" random_other_attribute1="1" random_other_attribute2="1" random_other_attribute3="1"/>

<!-- Fine! -->
<element id="menu_showMessagePane" 
         type="checkbox" 
         random_other_attribute1="1"
         random_other_attribute2="1"
         random_other_attribute3="1"/>

This page is maintained by Karsten "Mnyromyr" Düsterloh.