WebKit Coding Style Guidelines

Indentation

  1. Use spaces, not tabs. Tabs should only appear in files that require them for semantic meaning, like Makefiles.
  2. The indent size is 4 spaces.

    Right:

    int main()
    {
        return 0;
    }
    

    Wrong:

    int main() 
    {
            return 0;
    }
    
  3. In a header, code inside a namespace should be indented.

    Right:

    // Document.h
    namespace WebCore {
    
        class Document {
            Document();
            ...
        };
    
    } // namespace WebCore
    

    Wrong:

    // Document.h
    namespace WebCore {
    
    class Document {
        Document();
        ...
    };
    
    } // namespace WebCore
    
  4. In an implementation file, code inside a namespace should not be indented.

    Right:

    // Document.cpp
    namespace WebCore {
    
    Document::Document()
    {
        ...
    }
    
    } // namespace WebCore
    

    Wrong:

    // Document.cpp
    namespace WebCore {
    
        Document::Document()
        {
            ...
        }
    
    } // namespace WebCore
    
  5. A case label should line up with its switch statement. The case statement is indented.

    Right:

    switch (condition) {
    case fooCondition:
    case barCondition:
        i++;
        break;
    default:
        i--;
    }
    

    Wrong:

    switch (condition) {
        case fooCondition:
        case barCondition:
            i++;
            break;
        default:
            i--;
    }
    

Spacing

  1. Do not place spaces around unary operators.

    Right:

    i++;
    

    Wrong:

    i ++;
    
  2. Do place spaces around binary and ternary operators.

    Right:

    y = m * x + b;
    f(a, b);
    c = a | b;
    return condition ? 1 : 0;
    

    Wrong:

    y=m*x+b;
    f(a,b);
    c = a|b;
    return condition ? 1:0;
    
  3. Place spaces between control statements and their parentheses.

    Right:

    if (condition)
        doIt();
    

    Wrong:

    if(condition)
        doIt();
    
  4. Do not place spaces between a function and its parentheses, or between a parenthesis and its content.

    Right:

    f(a, b);
    

    Wrong:

    f (a, b);
    f( a, b );
    

Line breaking

  1. Each statement should get its own line.

    Right:

    x++;
    y++;
    if (condition)
        doIt();
    

    Wrong:

    x++; y++;
    if (condition) doIt();
    
  2. An else statement should go on the same line as a preceding close brace.

    Right:

    if (condition) {
        ...
    } else {
        ...
    }
    

    Wrong:

    if (condition) {
        ...
    }
    else {
        ...
    }
    

Braces

  1. Function definitions: place each brace on its own line.

    Right:

    int main()
    {
        ...
    }
    

    Wrong:

    int main() {
        ...
    }
    
  2. Other braces: place the open brace on the line preceding the code block; place the close brace on its own line.

    Right:

    class MyClass {
        ...
    };
    
    namespace WebCore {
        ...
    }
    
    for (int i = 0; i < 10; i++) {
        ...
    }
    

    Wrong:

    class MyClass 
    {
        ...
    };
    
  3. One-line control clauses should not use braces

    Right:

    if (condition)
        doIt();
    

    Wrong:

    if (condition) {
        doIt();
    }
    
  4. Control clauses without a body should use empty braces:

    Right:

    for ( ; current; current = current->next) { }
    

    Wrong:

    for ( ; current; current = current->next);
    

Null, false and 0

  1. In C++, the null pointer value should be written as 0. In C, it should be written as NULL. In Objective-C and Objective-C++, follow the guideline for C or C++, respectively, but use nil to represent a null Objective-C object.
  2. C++ and C bool values should be written as true and false. Objective-C BOOL values should be written as YES and NO.
  3. Tests for true/false, null/non-null, and zero/non-zero should all be done without equality comparisons.

    Right:

    if (condition)
        doIt();
        
    if (!ptr)
        return;
    
    if (!count)
        return;
    

    Wrong:

    if (condition == true)
        doIt();
        
    if (ptr == NULL)
        return;
        
    if (count == 0)
        return;
    

Names

  1. Use CamelCase. Capitalize the first letter of a class, struct, protocol, or namespace name. Lower-case the first letter of a variable or function name. Fully capitalize acronyms.

    Right:

    struct Data;
    size_t bufferSize;
    class HTMLDocument;
    

    Wrong:

    struct data;
    size_t buffer_size;
    class HtmlDocument;
    
  2. Use full words, except in the rare case where an abbreviation would be more canonical and easier to understand.

    Right:

    size_t characterSize;
    size_t length;
    short tabIndex; // more canonical
    

    Wrong:

    size_t charSize;
    size_t len;
    short tabulationIndex; // bizarre
    
  3. Prefix C++ data members with "m_".

    Right:

    class String {
        ...
        short m_length;
    };
    

    Wrong:

    class String {
        ...
        short length;
    };
    
  4. Prefix Objective-C instance variables with "_".

    Right:

    @class String
        ...
        short _length;
    @end
    

    Wrong:

    @class String
        ...
        short length;
    @end
    
  5. Precede boolean values with words like "is" and "did".

    Right:

    bool isValid;
    bool didSendData;
    

    Wrong:

    bool valid;
    bool sentData;
    
  6. Precede setters with the word "set". Use bare words for getters. Setter and getter names should match the names of the variables being set/gotten.

    Right:

    void setCount(size_t); // sets m_count
    size_t count(); // returns m_count
    

    Wrong:

    void setCount(size_t); // sets m_theCount
    size_t getCount();
    
  7. Use descriptive verbs in function names.

    Right:

    bool convertToASCII(short*, size_t);
    

    Wrong:

    bool toASCII(short*, size_t);
    
  8. Leave meaningless variable names out of function declarations.

    Right:

    void setCount(size_t);
    

    Wrong:

    void setCount(size_t count);
    
  9. Objective-C method names should follow the Cocoa naming guidelines — they should read like a phrase and each piece of the selector should start with a lowercase letter and use intercaps.
  10. Enum members should user InterCaps with an initial capital letter.
  11. Prefer const to #define. Prefer inline functions to macros.
  12. #defined constants should use all uppercase names with words separated by underscores.
  13. Macros that expand to function calls or other non-constant computation: these should be named like functions, and should have parentheses at the end, even if they take no arguments (with the exception of some special macros like ASSERT). Note that usually it is preferable to use an inline function in such cases instead of a macro.

    Right:

    #define WBStopButtonTitle() \
            NSLocalizedString(@"Stop", @"Stop button title")
    

    Wrong:

    #define WB_STOP_BUTTON_TITLE \
            NSLocalizedString(@"Stop", @"Stop button title")
    
    #define WBStopButtontitle \
            NSLocalizedString(@"Stop", @"Stop button title")
    
  14. #define, #ifdef "header guards" should be named exactly the same as the file (including case), replacing the '.' with a '_'.

    Right:

    // HTMLDocument.h
    #ifndef HTMLDocument_h
    #define HTMLDocument_h
    

    Wrong:

    // HTMLDocument.h
    #ifndef _HTML_DOCUMENT_H_
    #define _HTML_DOCUMENT_H_
    

Other Punctuation

  1. Constructors for C++ classes should initialize all of their members using C++ initializer syntax. Each member (and superclass) should be indented on a separate line, with the colon or comma preceding the member on that line.

    Right:

    MyClass::MyClass(Document* doc)
        : MySuperClass()
        , m_myMember(0)
        , m_doc(doc)
    {
    }
    
    MyOtherClass::MyOtherClass()
        : MySuperClass()
    {
    }
    

    Wrong:

    MyClass::MyClass(Document* doc) : MySuperClass()
    {
        m_myMember = 0;
        m_doc = doc;
    }
    
    MyOtherClass::MyOtherClass() : MySuperClass() {}
    
  2. Pointer types in non-C++ code — Pointer types should be written with a space between the type and the * (so the * is adjacent to the following identifier if any).
  3. Pointer and reference types in C++ code — Both pointer types and reference types should be written with no space between the type name and the * or &.

    Right:

    Image* SVGStyledElement::doSomething(PaintInfo& paintInfo)
    {
      SVGStyledElement* element = static_cast<SVGStyledElement*>(node());
      const KCDashArray& dashes = dashArray();
    

    Wrong:

    Image *SVGStyledElement::doSomething(PaintInfo &paintInfo)
    {
        SVGStyledElement *element = static_cast<SVGStyledElement *>(node());
        const KCDashArray &dashes = dashArray();
    

#include Statements

  1. All files must #include "config.h" first.
  2. All files must #include the primary header second, just after "config.h". So for example, Node.cpp should include Node.h first, before other files. This guarantees that each header's completeness is tested, to make sure it can be compiled without requiring any other header files be included first.
  3. Other #include statements should be in sorted order (case sensitive, as done by the command-line sort tool or the Xcode sort selection command). Don't bother to organize them in a logical order.