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Since 1999, people have been hacking on Krita. Everyone brought their
own coding style, their own code conventions, their own likes and
dislikes. Me, (Boudewijn that is), I like indents of four spaces, and
no scope prefixes for variables. However, in the interests of
consistency, these are the rules new code should adhere to:

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See also http://techbase.kde.org/Policies/Kdelibs_Coding_Style -- that document
is leading.

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Qt vs STD vs Boost:

    In general, use the Qt classes wherever possible, even if someone tells you
    that the STD class is better or whatever. We're dealing with a big project
    with lots of developers here and we should keep the code as consistent and
    easy to grasp as possible. Since people need to know Qt in the first place,
    keep to Qt. Discuss deviations on #krita

C++11 and C++14

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    Yes, but. Avoid lambdas (except when replacing the use of
    QSignalMapper. Sigh.).  Avoid the new sig/slot connection syntax
    _unless_ you are porting all of Krita to the new syntax. Sure, it
    has some advantages, but having two different ways of doing the same
    thing is begging for trouble and comprehension problems. For now,
    keep using Q_FOREACH, we're using it all over the place. auto is fine,
    when using in for loops. Don't go use it in other places.
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    Before using other new features, discuss on #krita so we can expand this list.

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    Our minimum gcc version is 4.5, shipped with Ubuntu 12.04


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	With four spaces. Use the default kdelibs indentation 
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	Avoid as much as possible #includes in header files; use forward declarations
	of classes.


	Avoid as much as possible initializers in the body of the constructor. Use
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	initializer lists instead. Write the initializers as follows
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    Class(A a, B b)
        : Subclass(a)
        , m_b(b)

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    Note the location of the colon and comma.

    It is also okay to use initializers like, and maybe even preferred where it works.

    int m_something {0};

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Scope prefixes

	Use only m_ for class-level variables. No other scope prefixes; no g_, l_,
	no 'p' for pointer variables.

Shared pointers

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	Use shared pointers wherever possible. Prefer Qt's shared pointer classes
    to our home-grown shared ppointer classes.
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	Krita doesn't use Qt's properties -- yet. If you want to introduce use of
	properties, convert any and all classes in Krita before committing.

	Getter/setters are named 'x() for getters and setX(int x) for setters. If you
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	come across violations of this rule, change the code.	

Class naming

	If you use a well-known design pattern, name the class according to the design
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	pattern. All files should start with 'Kis', all classes with the 'Kis' prefix.
    This filename should be the same as the classname: KisNewClass.h, KisNewClass.

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Function naming

	Functions should be named in camelBackedFashion, to conform to Qt's standards.
	If you encounter functions in c_style_like_this, feel free to rename. Also:
	verbNoun -- i.e., rotateLayer, not layer_rotate. The latter is a true c-ism,
	introduced by a language that needs to prefix the 'class' name to every function
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	in order to have something that's not quite OO.

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Variable/Parameter names

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	Variable/parameter names start with a lower case letter. A name composed of different
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	words is done in camelBackedStyle.

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	Krita has started to use designer. All dialogs and all widgets that have a layout
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	manager must be done in designer. Do not add code or signal/slot connections
	in designer.
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	All enums should be prefixed with 'enum'.


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	Currently, we only use anonymous namespaces for things like undo
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	commands. For the rest, some classes have a 'Kis' prefix, others don't. This should
	be made consistent, and we might want to use namespaces to keep all of Krita
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Files and classes

	It's preferred (and strongly preferred) to have only one class per .h/.cpp file.
	(Which is logical, because otherwise you won't be able to keep to the naming scheme.)

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	Keep the source airy and open. In particular, there should be empty lines between function
    declarations and definitions.
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Slots and signals

	Prefix slots with slot and signals with sig: slotUpdateSelection, sigSelectionUpdated.

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Boolean operators

    Use the standard !, !=, ==, && etc style, not the "not", "and" etc. style. Keep krita code
    using one, easily recognizable, C++ style.

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With Krita now supporting Python scripting, we need guidelines for these as well.
These guidelines are preliminary and may be further refined in the future.

To keep it simple, we have chosen to follow the style guide suggested by Python: PEP8.

All rules should be followed, except the max limit of 79 characters per line. As this
can reduce readability in some cases, this rule is optional.

The full PEP8 specification is available here: https://www.python.org/dev/peps/pep-0008/

To check compliance you can run pep8.py against the code.
You can also use autopep8.py to automatically fix detected compliance issues.

pep8.py can be downloaded via Python's package manager (pip) [https://pypi.python.org/pypi/pep8],
or your distribution's package manager.
autopep8.py can also be downloaded via Python's package manager [https://pypi.python.org/pypi/autopep8],
or your distribution's package manager.

Both of these scripts come bundled with the PyDev plugin, which is available for Eclipse and other IDEs.
The PyDev integration can be configured to visually highlight portions of the code which is not in compliance,
as well as run autopep8 via shortcuts.

pep8.py and autopep8.py can suppress select rules via the "--ignore" command line argument.
To ignore the 79 charachers per line rule, pep8.py can be called like this:

pep8.py --ignore=E501

You can read more about the error codes and what they mean here: