Policies/Kdelibs Coding Style: Difference between revisions

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    This document describes the recommended coding style for kdelibs. Nobody is forced to use this style, but to have consistent formating of the source code files it is recommended to make use of it.
    <languages />
    <translate>
    <!--T:1-->
    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.'''
    <!--T:2-->
    '''In short: Kdelibs coding style follows the [http://wiki.qt-project.org/Coding_Style Qt 4 coding style], with one main difference: using curly braces even when the body of a conditional statement contains only one line.'''


    == Indentation ==
    == Indentation == <!--T:3-->
    * No tabs
    * No tabs
    * 4 Spaces instead of one tab
    * 4 Spaces instead of one tab


    == Variable declaration ==
    == Variable declaration == <!--T:4-->
    * Each variable declaration on a new line
    * Each variable declaration on a new line
    * Each new word in a variable name starts with a capital letter
    * Each new word in a variable name starts with a capital letter (so-called camelCase)
    * Avoid abbreviations
    * Avoid abbreviations
    * Take useful names. No short names, except:
    * Take useful names. No short names, except:
    ** Single character variable names can denote counters and temporary variables whose purpose is obvious
    ** Single character variable names can denote counters and temporary variables whose purpose is obvious
    ** Variables and functions start with a small letter
    * Variables and functions start with a lowercase letter


    <!--T:5-->
    Example:
    Example:
    <code cppqt>
    </translate>
    // wrong
    <syntaxhighlight lang="cpp-qt">
    <translate><!--T:6-->
    // wrong</translate>
    KProgressBar *prbar;
    KProgressBar *prbar;
    QString prtxt, errstr;
    QString prtxt, errstr;


    // correct
    <translate><!--T:7-->
    // correct</translate>
    KProgressBar *downloadProgressBar;
    KProgressBar *downloadProgressBar;
    QString progressText;
    QString progressText;
    QString errorString;
    QString errorString;
    </code>
    </syntaxhighlight>


    == Whitespace ==
    <translate>
     
    == Whitespace == <!--T:8-->
    * Use blank lines to group statements
    * Use blank lines to group statements
    * Use only one empty line
    * Use only one empty line
    Line 34: Line 44:
    * No space after a cast
    * No space after a cast


    <!--T:9-->
    Example:
    Example:
    <code cppqt>
    </translate>
    // wrong
    <syntaxhighlight lang="cpp-qt">
    <translate><!--T:10-->
    // wrong</translate>
    QString* myString;
    QString* myString;
    if(true){
    if(true){
    }
    }


    // correct
    <translate><!--T:11-->
    // correct</translate>
    QString *myString;
    QString *myString;
    if (true) {
    if (true) {
    }
    }
    </code>
    </syntaxhighlight>


    == Braces ==
    <translate>
    == Braces == <!--T:12-->
    As a base rule, the left curly brace goes on the same line as the start of the statement.
    As a base rule, the left curly brace goes on the same line as the start of the statement.


    <!--T:13-->
    Example:
    Example:
    <code cppqt>
    </translate>
    // wrong
    <syntaxhighlight lang="cpp-qt">
    <translate><!--T:14-->
    // wrong</translate>
    if (true)
    if (true)
    {
    {
    }
    }


    // correct
    <translate><!--T:15-->
    // correct</translate>
    if (true) {
    if (true) {
    }
    }
    </code>
    </syntaxhighlight>


    <translate>
    <!--T:16-->
    Exception: Function implementations, class, struct and namespace declarations always have the opening brace on the start of a line.
    Exception: Function implementations, class, struct and namespace declarations always have the opening brace on the start of a line.


    <!--T:17-->
    Example:
    Example:
    <code cppqt>
    </translate>
    <syntaxhighlight lang="cpp-qt">
    void debug(int i)
    void debug(int i)
    {
    {
    Line 74: Line 97:
    {
    {
    };
    };
    </code>
    </syntaxhighlight>


    <translate>
    <!--T:18-->
    Use curly braces even when the body of a conditional statement contains only one line.
    Use curly braces even when the body of a conditional statement contains only one line.


    <!--T:19-->
    Example:
    Example:
    <code cppqt>
    </translate>
    // wrong
    <syntaxhighlight lang="cpp-qt">
    <translate><!--T:20-->
    // wrong</translate>
    if (true)
    if (true)
         return true;
         return true;
    Line 87: Line 115:
         qDebug("%i", i);
         qDebug("%i", i);


    // correct
    <translate><!--T:21-->
    // correct</translate>
    if (true) {
    if (true) {
         return true;
         return true;
    Line 95: Line 124:
         qDebug("%i", i);
         qDebug("%i", i);
    }
    }
    </code>
    </syntaxhighlight>


    == Switch statements ==
    <translate>
    == Switch statements == <!--T:22-->
    Case labels are on the same column as the switch
    Case labels are on the same column as the switch


    <!--T:23-->
    Example:
    Example:
    <code cppqt>
    </translate>
    <syntaxhighlight lang="cpp-qt">
    switch (myEnum) {
    switch (myEnum) {
    case Value1:
    case Value1:
    Line 113: Line 145:
         break;
         break;
    }
    }
    </code>
    </syntaxhighlight>


    == Line breaks ==
    <translate>
    == Line breaks == <!--T:24-->
    Try to keep lines shorter than 100 characters, inserting line breaks as necessary.
    Try to keep lines shorter than 100 characters, inserting line breaks as necessary.


    == Artistic Style (astyle) automatic code formatting ==
    == Qt Includes == <!--T:25-->
    You can use [http://astyle.sourceforge.net/ astyle] (<=1.19) to format code or to test if you have followed this document. Run the following command:
    * 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.
    <code>
     
    <!--T:26-->
    Example:
    </translate>
    <syntaxhighlight lang="cpp-qt">
    <translate><!--T:27-->
    // wrong</translate>
    #include <QString>
     
    <translate><!--T:28-->
    // correct</translate>
    #include <QtCore/QString>
    </syntaxhighlight>
     
    <translate>
    == Artistic Style (astyle) automatic code formatting == <!--T:29-->
    You can use [http://astyle.sourceforge.net/ astyle] (>=1.23) to format code or to test if you have followed this document. Run the following command:
    </translate>
    <syntaxhighlight lang="text">
    astyle --indent=spaces=4 --brackets=linux \
    astyle --indent=spaces=4 --brackets=linux \
           --indent-labels --pad=oper --unpad=paren \
           --indent-labels --pad=oper --unpad=paren \
           --one-line=keep-statements --convert-tabs \
           --one-line=keep-statements --convert-tabs \
           --indent-preprocessor \
           --indent-preprocessor \
           `find -type f -name '*.cpp'` `find -type f -name '*.h'`
           `find -type f -name '*.cpp'-or -name '*.cc' -or -name '*.h'`
    </code>
    </syntaxhighlight>
     
    <translate>
    <!--T:30-->
    With astyle (>=2.01) you need to run the following command:
    </translate>
    <syntaxhighlight lang="text">
    astyle --indent=spaces=4 --brackets=linux \
          --indent-labels --pad-oper --unpad-paren --pad-header \
          --keep-one-line-statements --convert-tabs \
          --indent-preprocessor \
          `find -type f -name '*.cpp' -or -name '*.cc' -or -name '*.h'`
    </syntaxhighlight>
     
    <translate>
    <!--T:31-->
    You can find a shell script to run this command in:
     
    <!--T:40-->
    * [https://projects.kde.org/projects/kde/kdesdk/kde-dev-scripts/repository/revisions/master/raw/astyle-kdelibs kde-dev-scripts/astyle-kdelibs] (POSIX)
    * [https://projects.kde.org/projects/kde/kdesdk/kde-dev-scripts/repository/revisions/master/raw/astyle-kdelibs.bat kde-dev-scripts/astyle-kdelibs.bat] (Windows)
     
    == Emacs and Vim scripts == <!--T:32-->
    The [https://projects.kde.org/projects/kde/kdesdk/kde-dev-scripts/repository/revisions/master/show kde-dev-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 [https://projects.kde.org/projects/kde/kdesdk/kde-dev-scripts/repository/revisions/master/show/kde-emacs kde-emacs] directory contains a set of key bindings, macros and general useful code. It is compatible with both GNU Emacs and XEmacs.
     
    <!--T:33-->
    To start using kde-emacs, add the following to your .emacs:
    </translate>
     
    <syntaxhighlight lang="text">
    (add-to-list 'load-path "/path/to/kde-emacs")
    (require 'kde-emacs)
    </syntaxhighlight>
     
    <translate>
    <!--T:34-->
    Many settings can be changed by editing the "kde-emacs" group via <tt>M-x customize-group</tt>.
     
    <!--T:35-->
    For more information, including what the key bindings are and what additional settings you could add to your .emacs, please check <tt>kde-emacs.el</tt> itself.


    == Vim script ==
    === Vim === <!--T:36-->
    You can find a vim script in [http://websvn.kde.org/kde/*checkout*/trunk/KDE/kdesdk/scripts/kde-devel-vim.vim 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.
    You can find a vim script in [https://projects.kde.org/projects/kde/kdesdk/kde-dev-scripts/repository/revisions/master/raw/kde-devel-vim.vim 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.


    <!--T:37-->
    To use the script, include it in your {{path|~/.vimrc}} like this:
    To use the script, include it in your {{path|~/.vimrc}} like this:
    <code>
    </translate>
    <syntaxhighlight lang="text">
    source /path/to/kde/sources/kdesdk/scripts/kde-devel-vim.vim
    source /path/to/kde/sources/kdesdk/scripts/kde-devel-vim.vim
    </code>
    </syntaxhighlight>




    <translate>
    <!--T:38-->
    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.
    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.


    <!--T:39-->
    [[Category:Policies]] [[Category:C++]]
    [[Category:Policies]] [[Category:C++]]
    </translate>

    Revision as of 10:08, 27 May 2013

    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, with one main difference: using curly braces even when the body of a conditional statement contains only one line.

    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'-or -name '*.cc' -or -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 --pad-header \
           --keep-one-line-statements --convert-tabs \
           --indent-preprocessor \
           `find -type f -name '*.cpp' -or -name '*.cc' -or -name '*.h'`
    

    You can find a shell script to run this command in:

    Emacs and Vim scripts

    The kde-dev-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 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.