donner::css::Specificity Class Reference

A CSS specificity value (id, class, type), as defined in https://www.w3.org/TR/selectors-4/#specificity-rules, which is used during cascading to determine which style takes precedence. More...

#include "donner/css/Specificity.h"

Classes
struct	ABC
	A 3-tuple of integers representing the specificity before modifiers such as the "!important" flag have been applied. More...

Public Types
enum class	SpecialType {   UserAgent ,   None ,   StyleAttribute ,   Important ,   Override }
	Special values for specificity, which take precedence over the 3-tuple. More...

Public Member Functions
constexpr	Specificity ()=default
	Default constructor, creates a specificity of (0, 0, 0).
constexpr	Specificity (const ABC &abc)
	Constructs a specificity from a ABC 3-tuple.
	~Specificity ()=default
	Destructor.
	Specificity (const Specificity &other)=default
	Copy constructor.
	Specificity (Specificity &&other) noexcept=default
	Move constructor.
Specificity &	operator= (const Specificity &other)=default
	Assignment operator.
Specificity &	operator= (Specificity &&other) noexcept=default
	Move assignment operator.
auto	operator<=> (const Specificity &other) const
	Spaceship operator.
bool	operator== (const Specificity &other) const
	Equality operator, for gtest.
const ABC &	abc () const
	Gets the 3-tuple of integers.
SpecialType	specialValue () const
	Gets the special value of the specificity, defaults to SpecialType::None.
Specificity	toUserAgentSpecificity () const
	Converts this Specificity into a UserAgent-specific Specificity (lowering the priority).

Static Public Member Functions
static constexpr Specificity	FromABC (uint32_t a, uint32_t b, uint32_t c)
	Creates a specificity from the 3-tuple of integers.
static constexpr Specificity	Important ()
	Creates a specificity for an !important declaration.
static constexpr Specificity	StyleAttribute ()
	Creates a specificity for a style attribute.
static constexpr Specificity	Override ()
	Creates a specificity that overrides any other value, for overriding styles from the C++ API.

Friends
std::ostream &	operator<< (std::ostream &os, const SpecialType &type)
	Output stream operator.
std::ostream &	operator<< (std::ostream &os, const Specificity &obj)
	Ostream output operator.

Detailed Description

A CSS specificity value (id, class, type), as defined in https://www.w3.org/TR/selectors-4/#specificity-rules, which is used during cascading to determine which style takes precedence.

The specificity is a 3-tuple of integers, where the first integer is the most significant, plus a few special values such as "!important" which override.

The 3-tuple is defined as:

• a: The number of ID selectors in the selector.
• b: The number of class selectors, attributes selectors, and pseudo-classes in the selector.
• c: The number of type selectors and pseudo-elements in the selector.

Examples

Selector	Specificity
#id	(1, 0, 0)
.class	(0, 1, 0)
div	(0, 0, 1)
#id.class	(1, 1, 0)
#id.class div	(1, 1, 1)
#id.class > div	(1, 1, 1)
[class=~"class"]	(1, 1, 1)

For example, the selector #id.class has a specificity of (1, 1, 0), while div > p has a specificity of (0, 0, 2).

To construct from a 3-tuple:

const Specificity spec = Specificity::FromABC(1, 2, 3);

To construct from "!important":

const Specificity spec = Specificity::Important();

Member Enumeration Documentation

SpecialType

enum class donner::css::Specificity::SpecialType

strong

Special values for specificity, which take precedence over the 3-tuple.

The order of these values is important, since operator<=> considers later enum values to be greater.

Enumerator
UserAgent	User agent stylesheet, lowest precedence in CSS.
None	No special value.
StyleAttribute	Style attribute, second highest precedence in CSS.
Important	!important declaration, highest precedence in CSS.
Override	Values set from C++ API, which overrides all other values.

Member Function Documentation

FromABC()

static constexpr Specificity donner::css::Specificity::FromABC ( uint32_t a, uint32_t b, uint32_t c )

inlinestaticconstexpr

Creates a specificity from the 3-tuple of integers.

Parameters

a	The number of ID selectors in the selector.
b	The number of class selectors, attributes selectors, and pseudo-classes in the selector.
c	The number of type selectors and pseudo-elements in the selector.

Friends And Related Symbol Documentation

operator<<

std::ostream & operator<< ( std::ostream & os, const Specificity & obj )

friend

Ostream output operator.

Example output:

Specificity(1, 2, 3)

or

Specificity(!important)

Parameters

os	Output stream.
obj	Specificity to output.

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The documentation for this class was generated from the following file:

• donner/css/Specificity.h