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clang-format

We use clang-format to keep formatting in the code base consistent. Please run clang-format on your patches before submitting.

clang-format ships with a Python script clang/tools/clang-format-diff.py that can be used to reformat patches. For example the following command will reformat all the lines in the latest commit

git diff -U0 HEAD^ | clang-format-diff.py -i -p1

clang-format also provides git-clang-format, a script that more closely integrates with git. If you add this script to your path you can using the following command to reformat all the lines in the latest commit.

git clang-format HEAD~1

clang-format-diff locations by platform

The exact location of the Python script varies by platform/distro. The table below provides the location on some common platform/distro's

Platform/Distro. Location
Arch Linux /usr/share/clang/clang-format-diff.py
Ubuntu /usr/bin/clang-format-diff-3.8

The script can also be downloaded here.

Code style

This project is developed primarily in C++ and Python. Please follow these code style guidelines when contributing code to our project.

  • Alphabetize includes

  • Use #include "xxx" for local includes, #include <xxx> for external includes.

  • Do not add comment separators before function definitions.

  • Split long lines, when reasonable, to avoid going over 80 characters per line.

  • Add a space after the commas in parameter lists, e.g., function(a, b, c), not function(a,b,c)

  • Add spaces between operators, e.g. 5 - 2, not 5-2.

  • For class names, use CamelCase, starting their names with an upper-case letter.

  • For local variables and function names, use camelCase, starting names with a lower-case letter.

  • For member variables, prefix them with m_, i.e. m_camelCase, starting the name with a lower-case letter.

  • For comments, add a space between // and the beginning of the comment, e.g.,

    • // A comment
    • # Python comment

  • Use 2 spaces when indenting C++ code, 4 spaces for Python code.

  • Do not indent inside namespaces, e.g.,

        namespace Avogadro {
        namespace Core {
        void foo();
        }
        }
  • Curly braces marking the start and end of a code block should be on separate lines and aligned vertically with the statement preceding the block, e.g.,
        if (condition) {
          statement;
        }

        for (int i = 0; i < n; ++i) {
          statement;
        }

  • Assume that C++11 features are available, and prefer them over legacy macros, defines, etc. A few examples follow, but are not exhaustive.

    • Use override to specify member overrides in derived classes.
    • Set default values of member variables directly in definitions.
    • Use nullptr instead of NULL.

C++ Features

  • Don't use exceptions
  • Prefer solutions from the Qt library over others in Qt dependent code
  • Minimize dependencies on third party libraries, think carefully before adding more
  • Use templates where they make sense

Including Headers

  • In public headers, always use this form to include project headers: #include <avogadro/core/something.h>
  • Prefer declaration of types in public headers over including headers for the type
        namespace Avogadro {
        class MyClass;
        }
  • In source files include specialized headers first, then dependency headers, then generic headers
        #include "myapiheader.h" // Our header
        #include <avogadro/core/molecule.h> // Avogadro header from a different module
        #include <QtCore/QString> // Qt header
        #include <vector> // STL
  • If you need to include the export header for the module do it as the first include
        #include "avogadrorenderingexport.h"
  • Private headers are denoted by _p.h endings, and should not be included in public headers
  • Use the Qt module and camel-cased header
  • Never include Qt module headers such as QtGui, instead include the header for the class being used
        #include <QtGui> // WRONG (module header)!
        #include <QtGui/QDialog> // Correct

Namespaces

  • Avogadro uses nested namespaces
    • Everything is inside the Avogadro namespace
    • Code in the core module is in the Avogadro::Core namespace
  • Don't overspecify, i.e. code in the Avogadro namespace doesn't need to use Avogadro::
    • Qt signals and slots are one exception where MOC often needs a little help
  • Never use using inside a public header
    • Only pull in specific symbols in source files, i.e. using Avogadro::Core::Molecule;

Casting

  • Avoid C-style casts, prefer C++ (static_cast, dynamic_cast, const_cast, reinterpret_cast)
  • For Qt classes, and Qt derived classes prefer qobject_cast over dynamic_cast

Aesthetics

  • Prefer enums to define constants over static const int or defines
  • Prefer verbose argument names in headers
    • Most IDEs show the argument names in their autocompletion
    • It looks better in the generated documentation
    • Poor style making people guess what an argument is for
  • Avoid abbreviations, as they are often ambiguous and we can afford the extra bytes