# Coding Standard for the ANGLE Project

## Google Style Guide

We generally use the [Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html) as a basis for
our Coding Standard, however we will deviate from it in a few areas, as noted
below.

Items marked {DEV} indicate a deviation from the Google guidelines. Items marked
{DO} are reiterating points from the Google guidelines.

Before you upload code to Gerrit, use `git cl format` to auto-format your code.
This will catch most of the trivial formatting errors and save you time.

### [Header Files](https://google.github.io/styleguide/cppguide.html#Header_Files)

*   We use **`.h`** for C++ headers.
*   {DEV} #define guards should be of the form: `<PATH>_<FILE>_H_`. (Compiler
    codebase is varied, including `<PROJECT>_` makes the names excessively
    long).

### [Scoping](https://google.github.io/styleguide/cppguide.html#Scoping)

*   {DO} avoid globally scoped variables, unless absolutely necessary.

### [Classes](https://google.github.io/styleguide/cppguide.html#Classes)

*   {DEV} Inherit (privately) from angle::NonCopyable helper class (defined in
    common/angleutils.h) to disable default copy and assignment operators.

### [Other C++ Features](https://google.github.io/styleguide/cppguide.html#Other_C++_Features)

*   {DEV} all parameters passed by reference, except for STL containers (e.g.
    std::vector, std::list), must be labeled `const`. For return parameters
    other than STL containers, use a pointer.
*   {DO} avoid use of default arguments.
*   {DONT} use C++ exceptions, they are disabled in the builds and not caught.
*   {DO} use nullptr (instead of 0 or NULL) for pointers.
*   {DO} use size\_t for loop iterators and size values.
*   {DO} use uint8\_t pointers instead of void pointers to denote binary data.
*   {DO} use C++11/14 according to the [Chromium c++ 11/14 guide]
    (http://chromium-cpp.appspot.com/).

### [Naming](https://google.github.io/styleguide/cppguide.html#Naming)

#### File Names

*   {DEV} Filenames should be all lowercase and can include underscores (`_`).
    If the file is an implementation of a class, the filename may be capitalized
    the same as the major class.
*   {DEV} We use .cpp (instead of .cc), .h and .inl (inlined files) for C++
    files and headers.

#### Directory Names
*   Directory names should be all lowercase, unless following an externally
    imposed capitalization (eg include/EGL, or src/libGLESv2, etc)

#### Variable Names

Use the following guidelines, they do deviate somewhat from the [Google
guidelines](https://google.github.io/styleguide/cppguide.html#Naming).

* Class and type names: start with capital letter and use CamelCase.
* {DEV} Class member variables: use an **`m`** prefix instead of trailing
underscore and use CamelCase.
* Global variables (if they must be used): use a **`g`** prefix.
* {DEV} Variable names: start with lower case and use CamelCase (chosen for consistency)
* {DEV} Function names: Member functions start with lower case and use CamelCase. Non-member and static member functions start with capital letter and
use CamelCase (chosen for consistency)
* {DO} Constants: start with a **`k`** and use CamelCase
* Namespaces: short names. use all lower case
* {DEV} Enum Names: use strongly typed class enums when possible. Use CamelCase for class enum members. See [official docs][EnumsOfficial].
* Macros: all uppercase with underscores
* Exceptions to naming: use common sense!

[EnumsOfficial]: https://google.github.io/styleguide/cppguide.html#Enumerator_Names

### [Comments](https://google.github.io/styleguide/cppguide.html#Comments)

*   {DO} read and follow Google's recommendations.
*   Each file **must** start with the following boilerplate notice:

```
//
//  Copyright $YEAR The ANGLE Project Authors. All rights reserved.
//  Use of this source code is governed by a BSD-style license that can be
//  found in the LICENSE file.
//
```

* $YEAR should be set to the current year at the time a file is created, and not changed thereafter.

### [Formatting](https://google.github.io/styleguide/cppguide.html#Formatting)

*   {DEV} Avoid excessively long lines. Please keep lines under 100 columns
    long.
*   Use unix-style newlines.
*   {DO} use only spaces. No tab characters. Configure your editor to emit
    spaces when you hit the TAB-key.
*   {DEV} indent 4 spaces at a time.
*   conditionals: place space outside the parenthesis. No spaces inside.
*   switch statements: use the output of `git cl format`.
*   class format(eg private, public, protected): indent by 2 spaces. Regular
    4-space indent from the outer scope for declarations/definitions.
*   pointers and references: **`*`** and **`&`** tight against the variable
*   namespaces: are not indented.
*   extern code blocks: are not indented.
*   {DEV} braces should go on a separate line, except for functions defined in a
    header file where the whole function declaration and definition fit on one
    line.

Examples:

```
if (conditional)
{
    stuff();
}
else
{
    otherstuff()
}
```

```
switch (conditional)
{
  case foo:
    dostuff();
    break;
  case bar:
    otherstuff();
    break;
  default:
    WTFBBQ();
}
```

```
class MyClass : public Foo
{
  public:
    MyClass();
    ~MyClass() {};
  private:
    DISALLOW_COPY_AND_ASSIGN(MyClass);
};
```

```
char *c;
const string &str;
```

### [Exceptions to the Rules](https://google.github.io/styleguide/cppguide.html#Exceptions_to_the_Rules)

*   If modifying pre-existing code that does not match the standard, the altered
    portions of the code should be changed to match the standard.

### Generated Source Files

Prefer storing generated sources as baked files in the repository. Avoid using
GN actions to run Python scripts.

**Definition:**

Sometimes helper scripts can create compilable sources more easily from XML or
JSON data sources than maintaining source files by hand. These scripts are often
written in Python and output generated sources.

**Decision**

Storing generated sources in the repository makes integration easier for non-GN
users. Python scripts can be expensive and slow to run at compile-time.
Generated sources can be a pain point for messing up builds.

It could be possible to solve the build clobbering problem. And we could replace
Python with something faster. But to allow for easier integration with our tools
and customers we should bake generated files into the repository.