path: root/CODING_GUIDELINES.dox

/*!

\page code_guidelines Code guidelines and formatting conventions

@brief \doc_header{ Code guidelines and formatting conventions }

\tableofcontents

These are conventions which we try to follow when writing code for Kodi. They
are this way mainly for reasons of taste, however, sticking to a common set of
formatting rules also makes it slightly easier to read through our sources. If
you want to submit patches, please try to follow these rules.

As such we don't follow these rules slavishly, in certain cases it is ok (and
in fact favorable) to stray from them.

================================================================================
\section code_guidelines_1 Indentation

Use spaces as tab policy with an indentation size of 2

--------------------------------------------------------------------------------
\subsection code_guidelines_1_1 Statements

No multiple statements on a single line, like this:
~~~~~~~~~~~~~
std::vector<std::string> test; test.push_back("foobar"); // This is the bad way
~~~~~~~~~~~~~

Always use a new line for a new statement:
~~~~~~~~~~~~~
std::vector<std::string> test;
test.push_back("foobar");
~~~~~~~~~~~~~

With them becomes it much more easy for debugging of faults to see direct on the
line what has created the fault.


--------------------------------------------------------------------------------
\subsection code_guidelines_1_2 Namespaces

Namespaces are not required to use any indentation to simplify nested namespaces
and wrapping `.cpp` files in a namespace

~~~~~~~~~~~~~
namespace KODI
{
namespace UTILS
{
class ILogger
{
  void Log(...) = 0;
}
}
}
~~~~~~~~~~~~~

\subsection code_guidelines_1_3 Headers

Included header files `*.h`, are to sort alphabetical to prevent double used file
definition and allow better overview

- On cpp define used header first to confirm needed headers are present on them itself
- As next use the global system headers e.g. `<cassert>` or `"system.h"`
- Then insert all the headers needed for the file itself

~~~~~~~~~~~~~
#include "PVRManager.h"

#include <cassert>
#include <utility>

#include "Application.h"
#include "Util.h"
#include "addons/AddonInstaller.h"
#include "dialogs/GUIDialogExtendedProgressBar.h"
#include "messaging/helpers/DialogHelper.h"
#include "music/tags/MusicInfoTag.h"
#include "network/Network.h"
#include "pvr/addons/PVRClients.h"
#include "pvr/channels/PVRChannel.h"
#include "settings/Settings.h"
#include "threads/SingleLock.h"
#include "utils/JobManager.h"
#include "utils/log.h"
#include "utils/Variant.h"
#include "video/VideoDatabase.h"
~~~~~~~~~~~~~

================================================================================
\section code_guidelines_2 Braces

Braces should go to newline and your code should look like the following example:

~~~~~~~~~~~~~
if (int i = 0; i < t; i++)
{
  [...]
}
else
{
  [...]
}

class Dummy()
{
  [...]
}
~~~~~~~~~~~~~

================================================================================
\section code_guidelines_3 Whitespaces

Conventional operators should be surrounded by a whitespace.

~~~~~~~~~~~~~
a = (b + c) * d;
~~~~~~~~~~~~~

Reserved words should be separated from opening parentheses by a whitespace.

~~~~~~~~~~~~~
while (true)
for (int i = 0; i < x; ++i)
~~~~~~~~~~~~~

Commas should be followed by a whitespace.

~~~~~~~~~~~~~
void Dummy::Method(int a, int b, int c);
int d, e;
~~~~~~~~~~~~~

Semicolons should be followed by a whitespace if there is more than one
expression per line.

~~~~~~~~~~~~~
for (int i = 0; i < x; ++i)
doSomething(e); doSomething(f); // this is probably bad style anyway
~~~~~~~~~~~~~

--------------------------------------------------------------------------------
\subsection code_guidelines_3_1 No vertical alignment

Do not use whitespaces to align value names together, this becomes problematic
on updates to see the change, if the whitspaces need to change on all.

This should be not used:
~~~~~~~~~~~~~
...

int                  value1             = 0;
int                  value2             = 0;
CExampleClass       *exampleClass       = nullptr;
CBiggerExampleClass *biggerExampleClass = nullptr;

exampleClass       = new CExampleClass      (value1, value2);
biggerExampleClass = new CBiggerExampleClass(value1, value2);

exampleClass      ->InitExample();
biggerExampleClass->InitExample();

...
~~~~~~~~~~~~~

Use it as:
~~~~~~~~~~~~~
...

int value1 = 0;
int value2 = 0;
CExampleClass *exampleClass = nullptr;
CBiggerExampleClass *biggerExampleClass = nullptr;

exampleClass = new CExampleClass(value1, value2);
biggerExampleClass = new CBiggerExampleClass(value1, value2);

exampleClass->InitExample();
biggerExampleClass->InitExample();

...
~~~~~~~~~~~~~

================================================================================
\section code_guidelines_4 Control statements

Insert new line before

- else in an if statement
- catch in a try statement
- while in a do statement


--------------------------------------------------------------------------------
\subsection code_guidelines_4_1 if else

- put then statement, return or throw to new line
- keep else if on one line 

~~~~~~~~~~~~~
if (true)
  return;

if (true)
{
  [...]
} 
else if (false)
{
  return;
} 
else
  return;
~~~~~~~~~~~~~

--------------------------------------------------------------------------------
\subsection code_guidelines_4_2 switch / case

~~~~~~~~~~~~~[.cpp}
switch (cmd)
{
  case x:
  {
    doSomething();
    break;
  }
  case x:
  case z:
    return true;
  default:
    doSomething();
}
~~~~~~~~~~~~~

================================================================================
\section code_guidelines_5 Naming
\subsection code_guidelines_5_1 Namespaces

Namespaces should be in uppercase letters

~~~~~~~~~~~~~
namespace KODI
{
...
}
~~~~~~~~~~~~~

\subsection code_guidelines_5_2 Constants

Use upper case with underscore spacing where necessary.

~~~~~~~~~~~~~
const int MY_CONSTANT = 1;
~~~~~~~~~~~~~

--------------------------------------------------------------------------------
\subsection code_guidelines_5_3 Enums

Use CamelCase for the enum name and upper case for the values.

~~~~~~~~~~~~~
enum Dummy
{
  VALUE_X,
  VALUE_Y
};
~~~~~~~~~~~~~

--------------------------------------------------------------------------------
\subsection code_guidelines_5_4 Interfaces

We use CamelCase for interface names and they should be prefixed with an
uppercase I. Filename should match the interface name, e.g. `ILogger.h`

~~~~~~~~~~~~~
class ILogger
{
  void Log(...) = 0;
}
~~~~~~~~~~~~~

--------------------------------------------------------------------------------
\subsection code_guidelines_5_5 Classes

We use CamelCase for class names and they should be prefixed with an uppercase C.
Filename should match the class name without the prefixed C, e.g. `Logger.cpp`

~~~~~~~~~~~~~
class CLogger : public ILogger
{
  void Log(...)
}
~~~~~~~~~~~~~

--------------------------------------------------------------------------------
\subsection code_guidelines_5_6 Methods

We use CamelCase for method names and first letter should always be upper case.
Even if the methods are private or protected.

~~~~~~~~~~~~~
void MyDummyClass::DoSomething();
~~~~~~~~~~~~~

--------------------------------------------------------------------------------
\subsection code_guidelines_5_7 Variables

We use CamelCase for variables. Type prefixing is optional.
\subsubsection code_guidelines_5_7_1 Global Variables

Prefix global variables with g_

~~~~~~~~~~~~~
int g_globalVariableA;
~~~~~~~~~~~~~

\warning Use of globals reduces the chance of submitted code to be accepted to a minimum

\subsubsection code_guidelines_5_7_2 Member Variables

Prefix member variables with m_

~~~~~~~~~~~~~
int m_variableA;
~~~~~~~~~~~~~

================================================================================
\section code_guidelines_6 Conventions

--------------------------------------------------------------------------------
\subsection code_guidelines_6_1 Casts

New code should use C++ style casts and not older C style casts. When modifying
existing code the developer can choose to update it to C++ style casts or leave
as is. Remember that whenever a dynamic_cast is used the result can be a nullptr
and needs to be checked accordingly.

--------------------------------------------------------------------------------
\subsection code_guidelines_6_2 NULL vs nullptr

Prefer the use of nullptr instead of NULL. nullptr is a typesafe version and as
such can't be implicitly converted to int or anything else.

--------------------------------------------------------------------------------
\subsection code_guidelines_6_3 auto

Feel free to use auto wherever it improves readability. Good places are
iterators or when dealing with containers.

~~~~~~~~~~~~~
std::map<std::string, std::vector<int>>::iterator i = var.begin();
vs
auto i = var.being();
~~~~~~~~~~~~~

--------------------------------------------------------------------------------
\subsection code_guidelines_6_4 for loops

Use newer style foreach loops whenever it makes sense. If iterators are used see
above about using auto.

~~~~~~~~~~~~~
for (auto& : var)
{
  ...
}
~~~~~~~~~~~~~

Use const auto& if there's no reason to modify the value.

*/