path: root/src/corelib/global/qflags.qdoc

// Copyright (C) 2022 The Qt Company Ltd. // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only /*! \class QFlag \inmodule QtCore \brief The QFlag class is a helper data type for QFlags. It is equivalent to a plain \c int, except with respect to function overloading and type conversions. You should never need to use this class in your applications. \sa QFlags */ /*! \fn QFlag::QFlag(int value) Constructs a QFlag object that stores the \a value. */ /*! \fn QFlag::QFlag(uint value) \since 5.3 Constructs a QFlag object that stores the \a value. */ /*! \fn QFlag::QFlag(short value) \since 5.3 Constructs a QFlag object that stores the \a value. */ /*! \fn QFlag::QFlag(ushort value) \since 5.3 Constructs a QFlag object that stores the \a value. */ /*! \fn QFlag::operator int() const Returns the value stored by the QFlag object. */ /*! \fn QFlag::operator uint() const \since 5.3 Returns the value stored by the QFlag object. */ /*! \class QFlags \inmodule QtCore \brief The QFlags class provides a type-safe way of storing OR-combinations of enum values. \ingroup tools The QFlags<Enum> class is a template class, where Enum is an enum type. QFlags is used throughout Qt for storing combinations of enum values. The traditional C++ approach for storing OR-combinations of enum values is to use an \c int or \c uint variable. The inconvenience with this approach is that there's no type checking at all; any enum value can be OR'd with any other enum value and passed on to a function that takes an \c int or \c uint. Since Qt 6.9, QFlags supports 64-bit enumerations. It is recommended to use explicit (fixed) underlying types when going above 32 bits, to ensure neither the enumeration nor the QFlags type change sizes if an enumerator is removed. Some compilers will also only make the \c enum type larger than 32 bits with explicit underlying types. Qt uses QFlags to provide type safety. For example, the Qt::Alignment type is simply a typedef for QFlags<Qt::AlignmentFlag>. QLabel::setAlignment() takes a Qt::Alignment parameter, which means that any combination of Qt::AlignmentFlag values, or \c{{ }}, is legal: \snippet code/src_corelib_global_qglobal.cpp 0 If you try to pass a value from another enum or just a plain integer other than 0, the compiler will report an error. If you need to cast integer values to flags in a untyped fashion, you can use the explicit QFlags constructor as cast operator. If you want to use QFlags for your own enum types, use the Q_DECLARE_FLAGS() and Q_DECLARE_OPERATORS_FOR_FLAGS(). Example: \snippet code/src_corelib_global_qglobal.cpp 1 You can then use the \c MyClass::Options type to store combinations of \c MyClass::Option values. \section1 Flags and the Meta-Object System The Q_DECLARE_FLAGS() macro does not expose the flags to the meta-object system, so they cannot be used by Qt Script or edited in \QD. To make the flags available for these purposes, the Q_FLAG() macro must be used: \snippet code/src_corelib_global_qglobal.cpp meta-object flags \section1 Naming Convention A sensible naming convention for enum types and associated QFlags types is to give a singular name to the enum type (e.g., \c Option) and a plural name to the QFlags type (e.g., \c Options). When a singular name is desired for the QFlags type (e.g., \c Alignment), you can use \c Flag as the suffix for the enum type (e.g., \c AlignmentFlag). */ /*! \typedef QFlags::Int \since 5.0 Typedef for the integer type used for storage as well as for implicit conversion. Either \c qintXX or \c quintXX, depending on whether the enum's underlying type is signed or unsigned and, since Qt 6.9, the enum's size. Typically, it will be \c qint32 (\c{int}) or \c quint32 (\c{unsigned}). */ /*! \typedef QFlags::enum_type Typedef for the Enum template type. */ /*! \fn template<typename Enum> QFlags<Enum>::QFlags(const QFlags &other) Constructs a copy of \a other. */ /*! \fn template <typename Enum> QFlags<Enum>::QFlags(Enum flags) Constructs a QFlags object storing the \a flags. */ /*! \fn template <typename Enum> QFlags<Enum>::QFlags() \since 5.15 Constructs a QFlags object with no flags set. */ /*! \fn template <typename Enum> QFlags<Enum>::QFlags(QFlag flag) Constructs a QFlags object initialized with the integer \a flag. The QFlag type is a helper type. By using it here instead of \c int, we effectively ensure that arbitrary enum values cannot be cast to a QFlags, whereas untyped enum values (i.e., \c int values) can. This constructor is only present for 32-bit \c Enum types. To support all enum sizes, consider the constructor using \c{std::in_place_t}. */ /*! \fn template <typename Enum> QFlags<Enum>::QFlags(std::in_place_t, Int flags) \since 6.9 Constructs a QFlags object initialized with the integer \a flags. */ /*! \fn template <typename Enum> QFlags<Enum>::QFlags(std::initializer_list<Enum> flags) \since 5.4 Constructs a QFlags object initialized with all \a flags combined using the bitwise OR operator. \sa operator|=(), operator|() */ /*! \fn template <typename Enum> QFlags &QFlags<Enum>::operator=(const QFlags &other) Assigns \a other to this object and returns a reference to this object. */ /*! \fn template <typename Enum> QFlags &QFlags<Enum>::operator&=(int mask) Performs a bitwise AND operation with \a mask and stores the result in this QFlags object. Returns a reference to this object. //! [unsafe-integer] This operator is disabled if the \c{QT_TYPESAFE_FLAGS} macro is defined. Note that it is not extended to 64-bit for 64-bit QFlags either: for 64-bit support, use the type-safe overload. //! [unsafe-integer] \sa operator&(), operator|=(), operator^=() */ /*! \fn template <typename Enum> QFlags &QFlags<Enum>::operator&=(uint mask) \overload \include qflags.qdoc unsafe-integer */ /*! \fn template <typename Enum> QFlags &QFlags<Enum>::operator&=(Enum mask) \overload */ /*! \fn template <typename Enum> QFlags &QFlags<Enum>::operator&=(QFlags mask) \since 6.2 \overload */ /*! \fn template <typename Enum> QFlags &QFlags<Enum>::operator|=(QFlags other) Performs a bitwise OR operation with \a other and stores the result in this QFlags object. Returns a reference to this object. \sa operator|(), operator&=(), operator^=() */ /*! \fn template <typename Enum> QFlags &QFlags<Enum>::operator|=(Enum other) \overload */ /*! \fn template <typename Enum> QFlags &QFlags<Enum>::operator^=(QFlags other) Performs a bitwise XOR operation with \a other and stores the result in this QFlags object. Returns a reference to this object. \sa operator^(), operator&=(), operator|=() */ /*! \fn template <typename Enum> QFlags &QFlags<Enum>::operator^=(Enum other) \overload */ /*! \fn template <typename Enum> QFlags<Enum>::operator Int() const Returns the value stored in the QFlags object as an integer. \sa Int */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::operator|(QFlags other) const Returns a QFlags object containing the result of the bitwise OR operation on this object and \a other. \sa operator|=(), operator^(), operator&(), operator~() */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::operator|(Enum other) const \overload */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::operator^(QFlags other) const Returns a QFlags object containing the result of the bitwise XOR operation on this object and \a other. \sa operator^=(), operator&(), operator|(), operator~() */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::operator^(Enum other) const \overload */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::operator&(int mask) const Returns a QFlags object containing the result of the bitwise AND operation on this object and \a mask. \include qflags.qdoc unsafe-integer \sa operator&=(), operator|(), operator^(), operator~() */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::operator&(uint mask) const \overload \include qflags.qdoc unsafe-integer */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::operator&(Enum mask) const \overload */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::operator&(QFlags mask) const \since 6.2 \overload */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::operator~() const Returns a QFlags object that contains the bitwise negation of this object. \sa operator&(), operator|(), operator^() */ /*! \fn template <typename Enum> bool QFlags<Enum>::operator!() const Returns \c true if no flag is set (i.e., if the value stored by the QFlags object is 0); otherwise returns \c false. */ /*! \fn template <typename Enum> bool QFlags<Enum>::testFlag(Enum flag) const \since 4.2 Returns \c true if the flag \a flag is set, otherwise \c false. \note if \a flag contains multiple bits set to 1 (for instance, if it's an enumerator equal to the bitwise-OR of other enumerators) then this function will return \c true if and only if all the bits are set in this flags object. On the other hand, if \a flag contains no bits set to 1 (that is, its value as a integer is 0), then this function will return \c true if and only if this flags object also has no bits set to 1. \sa testAnyFlag() */ /*! \fn template <typename Enum> bool QFlags<Enum>::testFlags(QFlags flags) const noexcept \since 6.2 Returns \c true if this flags object matches the given \a flags. If \a flags has any flags set, this flags object matches precisely if all flags set in \a flags are also set in this flags object. Otherwise, when \a flags has no flags set, this flags object only matches if it also has no flags set. \sa testAnyFlags() */ /*! \fn template <typename Enum> bool QFlags<Enum>::testAnyFlag(Enum flag) const noexcept \since 6.2 Returns \c true if \b any flag set in \a flag is also set in this flags object, otherwise \c false. If \a flag has no flags set, the return will always be \c false. \sa testFlag() */ /*! \fn template <typename Enum> bool QFlags<Enum>::testAnyFlags(QFlags flags) const noexcept \since 6.2 Returns \c true if \b any flag set in \a flags is also set in this flags object, otherwise \c false. If \a flags has no flags set, the return will always be \c false. \sa testFlags() */ /*! \fn template <typename Enum> QFlags QFlags<Enum>::setFlag(Enum flag, bool on) \since 5.7 Sets the flag \a flag if \a on is \c true or unsets it if \a on is \c false. Returns a reference to this object. */ /*! \fn template <typename Enum> QFlags<Enum> QFlags<Enum>::fromInt(Int i) noexcept \since 6.2 Constructs a QFlags object representing the integer value \a i. */ /*! \fn template <typename Enum> Int QFlags<Enum>::toInt() const noexcept \since 6.2 Returns the value stored in the QFlags object as an integer. Note that the returned integer may be signed or unsigned, depending on whether the enum's underlying type is signed or unsigned. \sa Int */ /*! \fn template <typename Enum> size_t qHash(QFlags<Enum> key, size_t seed) \since 6.2 \qhashold{QFlags} */ /*! \fn template <typename Enum> bool QFlags<Enum>::operator==(QFlags<Enum> lhs, QFlags<Enum> rhs) \fn template <typename Enum> bool QFlags<Enum>::operator==(QFlags<Enum> lhs, Enum rhs) \fn template <typename Enum> bool QFlags<Enum>::operator==(Enum lhs, QFlags<Enum> rhs) \since 6.2 Compares \a lhs and \a rhs for equality; the two arguments are considered equal if they represent exactly the same value (bitmask). */ /*! \fn template <typename Enum> bool QFlags<Enum>::operator!=(QFlags<Enum> lhs, QFlags<Enum> rhs) \fn template <typename Enum> bool QFlags<Enum>::operator!=(QFlags<Enum> lhs, Enum rhs) \fn template <typename Enum> bool QFlags<Enum>::operator!=(Enum lhs, QFlags<Enum> rhs) \since 6.2 Compares \a lhs and \a rhs for inequality; the two arguments are considered different if they don't represent exactly the same value (bitmask). */ /*! \macro Q_DECLARE_FLAGS(Flags, Enum) \relates QFlags The Q_DECLARE_FLAGS() macro expands to \snippet code/src_corelib_global_qglobal.cpp 2 \a Enum is the name of an existing enum type, whereas \a Flags is the name of the QFlags<\e{Enum}> typedef. See the QFlags documentation for details. \sa Q_DECLARE_OPERATORS_FOR_FLAGS() */ /*! \macro Q_DECLARE_OPERATORS_FOR_FLAGS(Flags) \relates QFlags The Q_DECLARE_OPERATORS_FOR_FLAGS() macro declares global \c operator|() functions for \a Flags, which is of type QFlags<T>. See the QFlags documentation for details. \sa Q_DECLARE_FLAGS() */