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Policies/Frameworks Coding Style

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 take use of it.

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


  • No tabs
  • 4 Spaces instead of one tab

Variable delclaration

  • Each variable declaration on a new line
  • Take useful names, no short names, except:
  • Single character variable names can be used for counters and temporary variables, where the purpose is obvious
  • Variables and functions start with a small letter
  • Each new word in a variable name starts with a capital letter
  • Avoid abbreviations

Example: // wrong KProgressBar *prbar; QString prtxt, errstr;

// correct KProgressBar *downloadProgressBar; QString progressText; QString errorString;


  • 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) { }


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 and class declarations always have the left brace on the start of a line.

Example: void debug(int i) {

   qDebug("foo: %i", i);


class Debug { };

Use curly braces when the body of a conditional statement contains more than one line, and also if a single line statement is somewhat complex.

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);

Exception 1: Use braces also if the parent statement covers several lines or wraps.

Example: if (address.isEmpty() || !isValid()

   || !codec) {
   return false;


Exception 2: Use braces also in if-then-else blocks where either the if-code or the else-code covers several lines.

Example: // wrong if (true)

   return true;

else {

   return false;


// correct if (true) {

   return true;

} else {

   return false;


Switch statements

Case labels are on the same column as the switch

Example: switch (myEnum) { case Value1:


case Value2:

   // fall through




Artistic Style (astyle) automatic code formatting

You can use astyle (<=1.19) 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 '*.h'`

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.

This page was last edited on 15 April 2021, at 11:15. Content is available under Creative Commons License SA 4.0 unless otherwise noted.