The Dillo Web Browser The Dillo Web Browser

Naming&Coding design

Dillo's code is divided into modules. For instance: bookmark, cache, dicache, gif.

Let's think of a module named "menu", then:

  • Every internal routine of the module, should start with "Menu_" prefix.
  • "Menu_" prefixed functions are not meant to be called from outside the module.
  • If the function is to be exported to other modules (i.e. it will be called from the outside), it should be wrapped with an "a_" prefix.

For instance: if the function name is "Menu_create", then it's an internal function, but if we need to call it from the outside, then it should be renamed to "a_Menu_create".

Why the "a_" prefix?

Because it reads better "a_Menu_create" than "d_Menu_create" cause the first one suggests "a Menu create" function!

Another way of understanding this is thinking of "a_" prefixed functions as Dillo's internal library, and the rest ("Menu_" prefixed in our example) as a private module-library.


Source code must be indented with 3 blank spaces, no Tabs.
Because different editors expand or treat tabs in several ways; 8 spaces being the most common, but that makes code really wide, and we want to keep it within the 80 columns bounds (printer friendly).

You can use:   indent -kr -sc -i3 -bad -nbbo -nut -l79 myfile.c

Function commenting

Every single function of the module should start with a short comment that explains its purpose; three lines should be enough, but if you think it requires more, enlarge it.

 * Try finding the url in the cache. If it hits, send contents
 * from there. If it misses, set up a new connection.
int a_Cache_open_url(const char *url, void *Data)
We also have the BUG:, TODO: and WORKAROUND: tags.
Use them within source code comments to spot hidden issues. For instance:
/* BUG: this counter is not accurate */

/* TODO: get color from the right place */
a = color;

/* WORKAROUND: the canonical way of doing it doesn't work yet. */
++a; ++a; ++a;

Function length

Let's try to keep functions within the 45 lines boundary. This eases code reading, following, understanding and maintenance.

Functions with a single exit

It's much easier to follow and maintain functions with a single exit point at the bottom (instead of multiple returns). The exception to the rule are calls like dReturn_if_fail() at its head.

dlib Functions

  • Dillo uses its own dlib library extensively. Before starting to code something new, a good starting point is to check what this library has to offer (check dlib/dlib.h).
  • Memory management must be done using dNew, dNew0, dMalloc, dFree and their relatives.
  • For debugging purposes and error catching (not for normal flow): dReturn_if_fail, dReturn_val_if_fail etc. are encouraged.
  • The MSG macro is extensively used to output additional information to the calling terminal.


Source code in C++ should follow the same rules with these exceptions:
  • Class method names are camel-cased and start with lowercase
      e.g. appendInputMultipart
  • Classes and types start uppercased
      e.g. class DilloHtmlReceiver
  • Class methods don't need to prefix its module name
      e.g. links->get()
We also try to keep the C++ relatively simple. Dillo does use inheritance and templates, but that's about all.

What do we get with this?

  • A clear module API for Dillo; every function prefixed "a_" is to be used outside the module.
  • A way to identify where the function came from (the capitalized word is the module name).
  • An inner ADT (Abstract data type) for the module that can be isolated, tested and replaced independently.
  • A two stage instance for bug-fixing. You can change the exported function algorithms while someone else fixes the internal module-ADT!
  • A coding standard ;)
Naming&Coding design by Jorge Arellano Cid