Policies/Kdelibs Coding Style: Difference between revisions

    From KDE TechBase
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    <!--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.
    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.


    <!--T:2-->
    '''In short: Kdelibs coding style follows the Qt 4 coding style.'''
    '''In short: Kdelibs coding style follows the Qt 4 coding style.'''


    == 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 (so-called camelCase)
    * Each new word in a variable name starts with a capital letter (so-called camelCase)
    Line 16: Line 18:
    ** Variables and functions start with a lowercase letter
    ** Variables and functions start with a lowercase letter


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


    <translate>// correct</translate>
    <translate><!--T:7-->
    // correct</translate>
    KProgressBar *downloadProgressBar;
    KProgressBar *downloadProgressBar;
    QString progressText;
    QString progressText;
    Line 30: Line 35:


    <translate>
    <translate>
    == Whitespace ==
    == 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 37: Line 42:
    * No space after a cast
    * No space after a cast


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


    <translate>// correct</translate>
    <translate><!--T:11-->
    // correct</translate>
    QString *myString;
    QString *myString;
    if (true) {
    if (true) {
    Line 52: Line 60:


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


    <translate>// correct</translate>
    <translate><!--T:15-->
    // correct</translate>
    if (true) {
    if (true) {
    }
    }
    Line 69: Line 80:


    <translate>
    <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:
    </translate>
    </translate>
    Line 85: Line 98:


    <translate>
    <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:
    </translate>
    </translate>
    <syntaxhighlight lang="cpp-qt">
    <syntaxhighlight lang="cpp-qt">
    <translate>// wrong</translate>
    <translate><!--T:20-->
    // wrong</translate>
    if (true)
    if (true)
         return true;
         return true;
    Line 97: Line 113:
         qDebug("%i", i);
         qDebug("%i", i);


    <translate>// correct</translate>
    <translate><!--T:21-->
    // correct</translate>
    if (true) {
    if (true) {
         return true;
         return true;
    Line 108: Line 125:


    <translate>
    <translate>
    == Switch statements ==
    == 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:
    </translate>
    </translate>
    Line 128: Line 146:


    <translate>
    <translate>
    == Line breaks ==
    == 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.


    == Qt Includes ==
    == Qt Includes == <!--T:25-->
    * 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.
    * 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.


    <!--T:26-->
    Example:
    Example:
    </translate>
    </translate>
    <syntaxhighlight lang="cpp-qt">
    <syntaxhighlight lang="cpp-qt">
    <translate>// wrong</translate>
    <translate><!--T:27-->
    // wrong</translate>
    #include <QString>
    #include <QString>


    <translate>// correct</translate>
    <translate><!--T:28-->
    // correct</translate>
    #include <QtCore/QString>
    #include <QtCore/QString>
    </syntaxhighlight>
    </syntaxhighlight>


    <translate>
    <translate>
    == Artistic Style (astyle) automatic code formatting ==
    == 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:
    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>
    </translate>
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    <translate>
    <translate>
    <!--T:30-->
    With astyle (>=2.01) you need to run the following command:
    With astyle (>=2.01) you need to run the following command:
    </translate>
    </translate>
    Line 168: Line 190:


    <translate>
    <translate>
    <!--T:31-->
    A related shell script could be found for unix in [http://websvn.kde.org/*checkout*/trunk/KDE/kdesdk/scripts/astyle-kdelibs kdesdk/scripts/astyle-kdelibs] and for windows in [http://websvn.kde.org/*checkout*/trunk/KDE/kdesdk/scripts/astyle-kdelibs.bat kdesdk/scripts/astyle-kdelibs.bat].
    A related shell script could be found for unix in [http://websvn.kde.org/*checkout*/trunk/KDE/kdesdk/scripts/astyle-kdelibs kdesdk/scripts/astyle-kdelibs] and for windows in [http://websvn.kde.org/*checkout*/trunk/KDE/kdesdk/scripts/astyle-kdelibs.bat kdesdk/scripts/astyle-kdelibs.bat].


    == Emacs and Vim scripts ==
    == Emacs and Vim scripts == <!--T:32-->
    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.
    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.
       
       
    Line 176: Line 199:
    The [http://websvn.kde.org/trunk/KDE/kdesdk/scripts/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.
    The [http://websvn.kde.org/trunk/KDE/kdesdk/scripts/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:
    To start using kde-emacs, add the following to your .emacs:
    </translate>
    </translate>
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    <translate>
    <translate>
    <!--T:34-->
    Many settings can be changed by editing the "kde-emacs" group via <tt>M-x customize-group</tt>.
    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.
    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 ===
    === Vim === <!--T:36-->
    You can find a vim script in [http://websvn.kde.org/*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 [http://websvn.kde.org/*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.


    <!--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:
    </translate>
    </translate>
    Line 200: Line 227:


    <translate>
    <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>
    </translate>

    Revision as of 13:18, 5 July 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.