Policies/Kdelibs Coding Style: Difference between revisions

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           --indent-labels --pad=oper --unpad=paren \
           --keep-one-line-statements --convert-tabs \
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    Revision as of 14:14, 19 September 2011

    This document describes the recommended coding style for kdelibs. Nobody is forced to use this style, but to have consistent formatting of the source code files it is recommended to make use of it.

    In short: Kdelibs coding style follows the Qt 4 coding style.

    Indentation

    • No tabs
    • 4 Spaces instead of one tab

    Variable declaration

    • Each variable declaration on a new line
    • Each new word in a variable name starts with a capital letter (so-called camelCase)
    • Avoid abbreviations
    • Take useful names. No short names, except:
      • Single character variable names can denote counters and temporary variables whose purpose is obvious
      • Variables and functions start with a lowercase letter

    Example:

    // wrong
    KProgressBar *prbar;
    QString prtxt, errstr;
    
    // correct
    KProgressBar *downloadProgressBar;
    QString progressText;
    QString errorString;
    

    Whitespace

    • Use blank lines to group statements
    • Use only one empty line
    • Use one space after each keyword
    • For pointers or references, use a single space before '*' or '&', but not after
    • No space after a cast

    Example:

    // wrong
    QString* myString;
    if(true){
    }
    
    // correct
    QString *myString;
    if (true) {
    }
    

    Braces

    As a base rule, the left curly brace goes on the same line as the start of the statement.

    Example:

    // wrong
    if (true)
    {
    }
    
    // correct
    if (true) {
    }
    

    Exception: Function implementations, class, struct and namespace declarations always have the opening brace on the start of a line.

    Example:

    void debug(int i)
    {
        qDebug("foo: %i", i);
    }
    
    class Debug
    {
    };
    

    Use curly braces even when the body of a conditional statement contains only one line.

    Example:

    // wrong
    if (true)
        return true;
    
    for (int i = 0; i < 10; ++i)
        qDebug("%i", i);
    
    // correct
    if (true) {
        return true;
    }
    
    for (int i = 0; i < 10; ++i) {
        qDebug("%i", i);
    }
    

    Switch statements

    Case labels are on the same column as the switch

    Example:

    switch (myEnum) {
    case Value1:
        doSomething();
        break;
    case Value2:
        doSomethingElse();
        // fall through
    default:
        defaultHandling();
        break;
    }
    

    Line breaks

    Try to keep lines shorter than 100 characters, inserting line breaks as necessary.

    Qt Includes

    • If you add #includes for Qt classes, use both the module and class name. This allows library code to be used by applications without excessive compiler include paths.

    Example:

    // wrong
    #include <QString>
    
    // correct
    #include <QtCore/QString>
    

    Artistic Style (astyle) automatic code formatting

    You can use astyle (>=1.23) to format code or to test if you have followed this document. Run the following command:

    astyle --indent=spaces=4 --brackets=linux \
           --indent-labels --pad=oper --unpad=paren \
           --one-line=keep-statements --convert-tabs \
           --indent-preprocessor \
           `find -type f -name '*.cpp'` `find -type f -name '*.cc'` `find -type f -name '*.h'`
    

    With astyle (>=2.01) you need to run the following command:

    astyle --indent=spaces=4 --brackets=linux \
           --indent-labels --pad=oper --unpad=paren \
           --keep-one-line-statements --convert-tabs \
           --indent-preprocessor \
           `find -type f -name '*.cpp'` `find -type f -name '*.cc'` `find -type f -name '*.h'`
    

    A related shell script could be found for unix in kdesdk/scripts/astyle-kdelibs and for windows in kdesdk/scripts/astyle-kdelibs.bat.

    Emacs and Vim scripts

    The "scripts" directory in the kdesdk module contains, among other useful things, some useful additions to the Emacs and Vim text editors that make it easier to edit KDE code with them.

    Emacs

    The kde-emacs directory contains a set of key bindings, macros and general useful code. It is compatible with both GNU Emacs and XEmacs.

    To start using kde-emacs, add the following to your .emacs:

    (add-to-list 'load-path "/path/to/kde-emacs")
    (require 'kde-emacs)
    

    Many settings can be changed by editing the "kde-emacs" group via M-x customize-group.

    For more information, including what the key bindings are and what additional settings you could add to your .emacs, please check kde-emacs.el itself.

    Vim

    You can find a vim script in kdesdk/scripts/kde-devel-vim.vim that helps you to keep the coding style correct. In addition to defaulting to the kdelibs coding style it will automatically use the correct style for Solid and kdepim code. If you want to add rules for other projects feel free to add them in the SetCodingStyle function.

    To use the script, include it in your ~/.vimrc like this:

    source /path/to/kde/sources/kdesdk/scripts/kde-devel-vim.vim
    


    Document started by Urs Wolfer. Some parts of this document have been adopted from the Qt Coding Style document posted by Zack Rusin on kde-core-devel.