QFont::Tag Class Reference

The QFont::Tag type provides access to advanced font features. More...

#include <qfont.h>

Collaboration diagram for QFont::Tag:

Public Member Functions
constexpr	Tag ()=default
	Default constructor, producing an invalid tag.
template<size_t N>
constexpr Q_IMPLICIT	Tag (const char(&str)[N]) noexcept
	Constructs a tag from a string literal, str.
constexpr bool	isValid () const noexcept
	Returns whether the tag is valid.
constexpr quint32	value () const noexcept
	Returns the numerical value of this tag.
QByteArray	toString () const
	Returns the string representation of this tag as a byte array.

Static Public Member Functions
static constexpr std::optional< Tag >	fromValue (quint32 value) noexcept
	Returns a tag constructed from value, or std::nullopt if the tag produced would be invalid.
static Q_GUI_EXPORT std::optional< Tag >	fromString (QAnyStringView view) noexcept
	Returns a tag constructed from the string in view.

Friends
Q_GUI_EXPORT QDataStream &	operator<< (QDataStream &stream, QFont::Tag tag)
Q_GUI_EXPORT QDataStream &	operator>> (QDataStream &stream, QFont::Tag &tag)
	Data stream operators for QFont::Tag.
Q_GUI_EXPORT QDebug	operator<< (QDebug debug, QFont::Tag tag)
constexpr size_t	qHash (Tag key, size_t seed=0) noexcept
	\qhash{QFont::Tag}
constexpr bool	comparesEqual (const Tag &lhs, const Tag &rhs) noexcept
constexpr Qt::strong_ordering	compareThreeWay (const Tag &lhs, const Tag &rhs) noexcept
	Compare lhs with rhs for equality and ordering.

Detailed Description

The QFont::Tag type provides access to advanced font features.

Since

6.7 \inmodule QtGui

QFont provides access to advanced features when shaping text. A feature is defined by a tag, which can be represented as a four-character string, or as a 32bit integer value. This type represents such a tag in a type-safe way. It can be constructed from a four-character, 8bit string literal, or from a corresponding 32bit integer value. Using a shorter or longer string literal will result in a compile-time error.

QFont font;
// Correct
font.setFeature("frac");
 
// Wrong - won't compile
font.setFeature("fraction");
 
// Wrong - will produce runtime warning and fail
font.setFeature(u"fraction"_s);

The named constructors allow to create a tag from an 32bit integer or string value, and will return a std::nullopt when the input is invalid.

See also

QFont::setFeature(), QFont::featureTags()

Definition at line 215 of file qfont.h.

Constructor & Destructor Documentation

Tag() [1/2]

QFont::Tag::Tag ( )

constexprdefault

Default constructor, producing an invalid tag.

Tag() [2/2]

template<size_t N>

Q_IMPLICIT QFont::Tag::Tag ( const char(&) str[N] )

inlineconstexprnoexcept

Constructs a tag from a string literal, str.

The literal must be exactly four characters long.

font.setFeature("frac", 1);

See also

fromString(), fromValue()

Definition at line 220 of file qfont.h.

Member Function Documentation

fromString()

std::optional< QFont::Tag > QFont::Tag::fromString ( QAnyStringView view )

staticnoexcept

Returns a tag constructed from the string in view.

The string must be exactly four characters long.

Returns std::nullopt if the input is not four characters long, or if the tag produced would be invalid.

See also

isValid(), fromValue()

Definition at line 2388 of file qfont.cpp.

fromValue()

static constexpr std::optional< Tag > QFont::Tag::fromValue ( quint32 value )

inlinestaticconstexprnoexcept

Returns a tag constructed from value, or std::nullopt if the tag produced would be invalid.

See also

isValid()

Definition at line 240 of file qfont.h.

isValid()

bool QFont::Tag::isValid ( ) const

inlineconstexprnoexcept

Returns whether the tag is valid.

A tag is valid if its value is not zero.

See also

value(), fromValue(), fromString()

Definition at line 227 of file qfont.h.

toString()

QByteArray QFont::Tag::toString ( ) const

inline

Returns the string representation of this tag as a byte array.

See also

fromString()

Definition at line 230 of file qfont.h.

value()

quint32 QFont::Tag::value ( ) const

inlineconstexprnoexcept

Returns the numerical value of this tag.

See also

isValid(), fromValue()

Definition at line 228 of file qfont.h.

Friends And Related Symbol Documentation

comparesEqual

bool comparesEqual ( const Tag & lhs, const Tag & rhs )

friend

Definition at line 261 of file qfont.h.

compareThreeWay

Qt::strong_ordering compareThreeWay ( const Tag & lhs, const Tag & rhs )

friend

Compare lhs with rhs for equality and ordering.

Definition at line 263 of file qfont.h.

operator<< [1/2]

Q_GUI_EXPORT QDataStream & operator<< ( QDataStream & stream, QFont::Tag tag )

friend

Definition at line 2951 of file qfont.cpp.

operator<< [2/2]

Q_GUI_EXPORT QDebug operator<< ( QDebug debug, QFont::Tag tag )

friend

Definition at line 3849 of file qfont.cpp.

operator>>

Q_GUI_EXPORT QDataStream & operator>> ( QDataStream & stream, QFont::Tag & tag )

friend

Data stream operators for QFont::Tag.

Definition at line 2957 of file qfont.cpp.

qHash

size_t qHash ( QFont::Tag key, size_t seed = 0 )

friend

\qhash{QFont::Tag}

Definition at line 257 of file qfont.h.

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

• qtbase/src/gui/text/qfont.h (1bc78f7739ca4319323de5e7e07f88ef5cbd52bc)
• qtbase/src/gui/text/qfont.cpp (906aa1533f2267b091615d21c2d31e1742f0a520)