mutter/HACKING

GENERAL
=======

General notes and rules on clutter core hacking;

 - Follow the CODING_STYLE document.

 - *Really* follow the CODING_STYLE document.

 - All non static public API funcs should be documented in the source files
   via gtk-doc. Structures, enumerations and macros should be documented in
   the header files.

 - All non-trivial static and private API should be documented, especially
   the eventual lifetime handling of the arguments/return values or locking
   of mutexes.

 - Properties should always be in floating point (never fixed point).
   The preferred precision is double for angles, and single precision
   for size and position -- especially if they have to be passed down
   to COGL.

 - Properties should use pixels whenever is possible. Dimensional and
   positional properties can also use ClutterParamSpecUnits to define
   the units-based logical values with a unit type.

 - Public entry points must always check their arguments with
   g_return_if_fail() or g_return_val_if_fail().

 - Private entry points should use g_assert() or g_warn_if_fail() to
   verify internal state; do not use g_return_if_fail() or
   g_return_val_if_fail() as they might be compiled out.

 - If you need to share some state variable across source files use
   ClutterContext and a private accessor.

 - Private, non-static functions must begin with an underscore and
   be declared inside clutter-private.h.

 - Don't add direct GL calls but add API to COGL (both GL and GL|ES
   versions if possible).

 - Use the CLUTTER_NOTE() macro for debug statements in Clutter, and
   the COGL_NOTE() macro for debug statements in COGL. If necessary,
   add a value inside ClutterDebugFlags or CoglDebugFlags to specify
   the debug section.

 - New features should also include an exhaustive test unit under
   tests/conform and, eventually, a user-interactive test under
   tests/interactive.

 - When committing, use the standard git commit message format:

=== begin example commit ===
Short explanation of the commit

Longer explanation explaining exactly what's changed, whether any
external or private interfaces changed, what bugs were fixed (with bug
tracker reference if applicable) and so forth. Be concise but not too
brief.
=== end example commit ===

   Always add a brief description of the commit to the _first_ line of
   the commit and terminate by two newlines (it will work without the
   second newline, but that is not nice for the interfaces).

     short description          - MUST be less than 72 characters
     <newline>                  - MANDATORY empty line
     long description           - Each line MUST be less than 76 characters

   Do NOT put the commit message on the short description line. One line
   commit messages should be avoided, unless they can be *fully* explained
   in less than 72 characters (e.g. "Fix typo in
   clutter_actor_create_pango_context() docs").

   The brief description might optionally have a "tag", enclosed in
   square brackets, detailing what part of the repository the commit
   affected, e.g.:

      [alpha] Add :mode property
      [text] Emit ::cursor-event only on changes

   The tag counts as part of overall character count, so try using
   a short word. Optionally, you can also use the "tag:" form.

   Think of the commit message as an email sent to the maintainers explaining
   "what" you did and, more importantly, "why" you did it. The "how" is not
   important, since "git show" will show the patch inlined with the commit
   message.