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 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
- 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 small 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.
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'`
Vim script
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.