Tag Struct

struct QFont ::Tag

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

This struct was introduced in Qt 6.7.

• 所有成员列表，包括继承成员

公共函数

	Tag ()
	Tag (const char (&)[N] str )
bool	isValid () const
QByteArray	toString () const
quint32	value () const

静态公共成员

std::optional<QFont::Tag>	fromString (QAnyStringView view )
std::optional<QFont::Tag>	fromValue (quint32 value )

相关非成员

Qt::strong_ordering	compareThreeWay (const QFont::Tag & lhs , const QFont::Tag & rhs )
bool	comparesEqual (const QFont::Tag & lhs , const QFont::Tag & rhs )
size_t	qHash (QFont::Tag key , size_t seed = 0)

详细描述

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.

另请参阅 QFont::setFeature () 和 QFont::featureTags ().

成员函数文档编制

[constexpr noexcept] Tag:: Tag ()

Default constructor, producing an invalid tag.

[constexpr noexcept] template <size_t N> Tag:: Tag (const char (&)[ N ] str )

Constructs a tag from a string literal, str . The literal must be exactly four characters long.

font.setFeature("frac", 1);
					

另请参阅 fromString () 和 fromValue ().

[static noexcept] std::optional < QFont::Tag > Tag:: fromString ( QAnyStringView view )

Returns a tag constructed from the string in view . The string must be exactly four characters long.

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

另请参阅 isValid () 和 fromValue ().

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

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

另请参阅 isValid ().

[constexpr noexcept] bool Tag:: isValid () const

Returns whether the tag is valid. A tag is valid if its value is not zero.

另请参阅 value (), fromValue ()，和 fromString ().

QByteArray Tag:: toString () const

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

另请参阅 fromString ().

[constexpr noexcept] quint32 Tag:: value () const

Returns the numerical value of this tag.

另请参阅 isValid () 和 fromValue ().

相关非成员

[constexpr noexcept] Qt::strong_ordering compareThreeWay (const QFont::Tag & lhs , const QFont::Tag & rhs )

[constexpr noexcept] bool comparesEqual (const QFont::Tag & lhs , const QFont::Tag & rhs )

比较 lhs with rhs for equality and ordering.

[constexpr noexcept] size_t qHash ( QFont::Tag key , size_t seed = 0)

返回哈希值为 key ，使用 seed 做计算种子。

内容

• 公共函数

• 静态公共成员

• 相关非成员

• 详细描述