# Style Guidelines


## Overall

Most of these rules are meant to be general guidelines.  The overriding
goal is for the code to _work_; if it doesn't do that, it's worthless.
Given that it works, it should be _readable_.  These guidelines are aimed
at achieving that goal; if you have to break a rule to be more readable,
then do it.  If you have to bend a rule to match surrounding code, do it.

ctwm is written in **C99**, to run in a generally **POSIX environment**,
and is intimately related with **X11**.  Those worlds, in roughly that
order, should be considered when making style choices.


## Automatic

http://astyle.sourceforge.net/[Artistic Style] is used to maintain
gross code styling.  The `make indent` target will run it over the
codebase, and should be used regularly to keep things in shape.

These are thus hard rules; in theory, at any given time, running `make
indent` should yield no changes.  This is the primary exception to the
"`break the rules`" guideline above.  Code should always follow these
rules, because it makes life simpler.


## Include files and ordering

* All source files should include `ctwm.h`, and always include it first.

* Includes should be generally ordered as:

** `ctwm.h`

** (some vertical whitespace separator)

** System includes (`stdio.h`, `X11/foo.h`, etc)

** (some vertical whitespace separator)

** Other local includes

** However some special cases exist where we have to pull system files
after the locals; _e.g._, when something in one of our headers is needed
to figure what else to `#include`.  That's fine.

* Generally, local includes should avoid ``#include``ing system includes
where possible, and avoid ``#include``ing other local includes where
practical.  If the file itself needs something from another header file
(_e.g._, a  prototype or var extern needs a type from elsewhere), it
should `#include` that; if however some `.c` file that ``#include``s the
`.h` needs something from another header, generally the `#include` should
be put there.
+
Bear in mind that this is a *guideline*.  There are extant exceptions,
and may be more over time.  Make it readable and maintainable.

* Try to avoid including things already brought in elsewhere.  For
instance, `ctwm.h` already includes our `types.h`, the system
`stdbool.h`, and many of Xlib's includes, so no other file in our tree
need `#include` them.


## Standards and Types

ctwm is written in C, and currently against the **C99** standard.  Types,
headers, functions, types, etc. defined there are assumed available, and
should be the initial goto choice for such.

It is also written to run in a **POSIX** environment, using **X11**, so
the headers, functions, and types related to them are also considered
available, and should be used when appropriate.

### Boolean

The case of boolean types gives a useful example.  C99 defines the `bool`
type for booleans, with the boolean values `true` and `false` (defined to
be numerically `1` and `0`).  The type and constants should be used in
code in ctwm itself needing boolean variables or values.

Xlib defined a `Bool` type, and the boolean values `True` and `False`
(which are also numerically `1` and `0`).  They should be used in
interactions with Xlib.  There are also some odder fringe cases we might
hit; libjpeg has a `boolean` type, and `TRUE`/`FALSE` values.  Xt
("Intrinsics") has a `Boolean` type, with `TRUE`/`FALSE` values.  When
dealing with an external lib, use its types and values.

Because of C's conversion rules, assigning values from one type to the
other, via boolean conditional expressions, or via literal or numeric
1/0, should always work as expected.  However, the type representations
aren't the same, so e.g.  passing a `+bool *+` to a function expecting a
`+Bool *+` will go *very badly*.


## Comments

There is no part of the codebase with too many comments.  I dream of the
day when we'll have to edit that line; please help hasten it!

C99 allows both `+/* enclosed */+` and `// to EOL` comment styles.  We
generally lean toward `+/* enclosed */+`, but `// to EOL` are acceptable
as well.  In particular comments at the end of the line (like
documentation of structure elements) are excellent candidates for `//`
comments, particularly when they would otherwise wrap.
