Some of the changes listed in this file include issue tracking numbers corresponding to tasks in the Qt Bug Tracker: http://bugreports.qt-project.org/ Each of these identifiers can be entered in the bug tracker to obtain more information about a particular change. **************************************************************************** * Source incompatible changes * **************************************************************************** - QObject * The signatures of the connectNotify() and disconnectNotify() functions have changed. The functions now get passed a QMetaMethod that identifies the signal, rather than a const char *. - QSslCertificate::subjectInfo() and QSslCertificate::issuerInfo() now return a QStringList instead of a QString - QSslCertificate::isValid() has been deprecated. Originally it only checked the certificate dates, but later checking for blacklisting was added. Now there's a more specific QSslCertificate::isBlacklisted() method. - Unite clipping support has been removed from QPainter. The alternative is to unite QRegion's and using the result on QPainter. - QLibrary::resolve() now returns a function pointer instead of a void pointer. - QSslCertificate::alternateSubjectNames() is deprecated (but can be enabled via QT_DISABLE_DEPRECATED_BEFORE), use QSslCertificate::subjectAlternativeNames() instead. - QLibraryInfo::buildKey() has been removed. Likewise, the QT_BUILD_KEY preprocessor #define has also been removed. The build-key is obsolete and is no longer necessary. - QCoreApplication::translate() will no longer return the source text when the translation is empty. Use lrelease -removeidentical for optimization. - QString and QByteArray constructors that take a size argument will now treat negative sizes to indicate nul-terminated strings (a nul-terminated array of QChar, in the case of QString). In Qt 4, negative sizes were ignored and result in empty QString and QByteArray, respectively. The size argument to those constructors now has a default value of -1, thus replacing the separate constructors that did the same. - Qt::escape() is deprecated (but can be enabled via QT_DISABLE_DEPRECATED_BEFORE), use QString::toHtmlEscaped() instead. - QBool is gone. QString::contains, QByteArray::contains, and QList::contains used to return an internal QBool class so that the Qt3 code "if (a.contains() == 2)" wouldn't compile anymore. Such code cannot exist in Qt4, so these methods return a bool now. If your code used the undocumented QBool, simply replace it with bool. - qIsDetached<> has been removed without replacement. - QMetaType: * QMetaType::construct() has been renamed to QMetaType::create(). * QMetaType::unregisterType() has been removed. - QMetaMethod: * QMetaMethod::signature() has been renamed to QMetaMethod::methodSignature(), and the return type has been changed to QByteArray. This was done to be able to generate the signature string on demand, rather than always storing it in the meta-data. * QMetaMethod::typeName() no longer returns an empty string when the return type is void; it returns "void". The recommended way of checking whether a method returns void is to compare the return value of QMetaMethod::returnType() to QMetaType::Void. - QVariant: * Inconsistent constructor taking Qt::GlobalColor and producing QVariant(QColor) instance was removed. Code constructing such variants can be migrated by explicitly calling QColor constructor. For example from "QVariant(Qt::red)" to "QVariant(QColor(Qt::red))" - QTestLib: * The plain-text, xml and lightxml test output formats have been changed to show a test result for every row of test data in data-driven tests. In Qt4, only fails and skips were shown for individual data rows and passes were not shown for individual data rows, preventing accurate calculation of test run rates and pass rates. * The QTRY_VERIFY and QTRY_COMPARE macros have been moved into QTestLib. These macros formerly lived in tests/shared/util.h but are now provided by including the header. In addition, QTRY_VERIFY_WITH_TIMEOUT and QTRY_COMPARE_WITH_TIMEOUT are provided, allowing for specifying custom timeout values. * The QTEST_NOOP_MAIN macro has been removed from the API. If a test is known at compile-time to be inapplicable for a particular build it should be omitted via .pro file logic, or the test should call QSKIP in the initTestCase() method to skip the entire test and report a meaningful explanation in the test log. * The DEPENDS_ON macro has been removed from the API. This macro did nothing and misled some users to believe that they could make test functions depend on each other or impose an execution order on test functions. * The QTest::qt_snprintf function has been removed from the API. This was an internal testlib function that was exposed in the public API due to its use in a public macro. Any calls to this function should be replaced by a call to qsnprintf(), which comes from the header. * The QTest::pixmapsAreEqual() function has been removed from the API. Comparison of QPixmap objects should be done using QCOMPARE, which provides more informative output in the event of a failure. * The QSKIP macro no longer has the "mode" parameter, which caused problems for calculating test metrics, as the SkipAll mode hid information about what test data was skipped. Calling QSKIP in a test function now behaves like SkipSingle -- skipping a non-data-driven test function or skipping only the current data row of a data-driven test function. Every skipped data row is now reported in the test log. - The QSsl::TlsV1 enum value was renamed to QSsl::TlsV1_0 . - QAccessible: * Internal QAccessible::State enum value HasInvokeExtension removed - QAccessibleInterface: * The "child" integer parameters have been removed. This moves the api to be closer to IAccessible2. This means several functions lose their integer parameter: text(Text t, int child) -> text(Text t), rect(int child) -> rect() setText(Text t, int child, const QString &text) -> setText(Text t, const QString &text) role(int child) -> role(), state(int child) -> state() * parent() and child() was added in order to do hierarchical navigation. * relations() was added as a replacement to relationTo() * As a consequence of the above two points, navigate() was removed. * Accessible-Action related functions have been removed. QAccessibleInterface subclasses are expected to implement the QAccessibleActionInterface instead. These functions have been removed: QAccessibleInterface::userActionCount, QAccessibleInterface::actionText, QAccessibleInterface::doAction - QAccessibleEvent also loses the child parameter. QAccessibleEvent(Type type, int child) -> QAccessibleEvent(Type type) QAccessibleEvent::child() removed. - QAccessibleActionInterface: * Refactored to be based on action names. All functions have been changed from using int parameters to strings. - QSound has been moved from QtGui to QtMultimedia - QTabletEvent::QTabletEvent does not take a hiResGlobalPos argument anymore, as all coordinates are floating point based now. - QTouchEvent: * The DeviceType enum and deviceType() have been deprecated due to the introduction of QTouchDevice. * The signature of the constructor has changed. It now takes a QTouchDevice pointer instead of just a DeviceType value. * TouchPointState no longer includes TouchPointStateMask and TouchPointPrimary. QTouchEvent::TouchPoint::isPrimary() has been removed. * QWidget *widget() has been removed and is replaced by QObject *target() in order to avoid QWidget dependencies. * QEvent::TouchCancel has been introduced. On systems where it makes sense this event type can be used to differentiate between a regular TouchEnd and abrupt touch sequence cancellations caused by the compositor, for example when a system gesture gets recognized. - QMetaType * Q_DECLARE_METATYPE(Foo*) now requires that Foo is fully defined. In cases where a forward declared type should be used as a metatype, Q_DECLARE_OPAQUE_POINTER(Foo*) can be used to allow that. * Similarly, Q_DECLARE_METATYPE(QSharedPointer), and Q_DECLARE_METATYPE(QWeakPointer) require Foo to be fully defined. Again though, Q_DECLARE_OPAQUE_POINTER(Foo*) can be used to allow that. - QItemEditorFactory * The signature of the createEditor and valuePropertyName methods have been changed to take arguments of type int instead of QVariant::Type. - QWindowSystemInterface: * The signature of all handleTouchEvent() variants have changed, taking a QTouchDevice* instead of just a DeviceType value. Platform or generic plug-ins have to create and register at least one QTouchDevice before sending the first touch event. * The event type parameter is removed from handleTouchEvent(). - The previously exported function qt_translateRawTouchEvent() has been removed. Use QWindowSystemInterface::handleTouchEvent() instead. - QAbstractEventDispatcher * The signature for the pure-virtual registerTimer() has changed. Subclasses of QAbstractEventDispatcher will need to be updated to reimplement the new pure-virtual 'virtual void registerTimer(int timerId, int interval, Qt::TimerType timerType, QObject *object) = 0;' * QAbstractEventDispatcher::TimerInfo is no longer a QPair. It is now a struct with 3 members: struct TimerInfo { int timerId; int interval; Qt::TimerType timerType; }; Reimplementations of QAbstractEventDispatcher::registeredTimers() will need to be updated to pass 3 arguments to the TimerInfo constructor (instead of 2). - QUuid * Removed implicit conversion operator QUuid::operator QString(), instead QUuid::toString() function should be used. - The QHttp, QHttpHeader, QHttpResponseHeader and QHttpRequestHeader classes have been removed, QNetworkAccessManager should be used instead. - The QFtp and QUrlInfo classes are no longer exported, QNetworkAccessManager should be used instead. These classes are available in a separate module, qtftp. - QProcess * On Windows, QProcess::ForwardedChannels will not forward the output of GUI applications anymore, if they do not create a console. - QAbstractSocket's connectToHost() and disconnectFromHost() are now virtual and connectToHostImplementation() and disconnectFromHostImplementation() don't exist. - QTcpServer::incomingConnection() now takes a qintptr instead of an int. - QNetworkConfiguration::bearerName() removed, and bearerTypeName() should be used. - QDir::convertSeparators() (deprecated since Qt 4.2) has been removed. Use QDir::toNativeSeparators() instead. - QIconEngineV2 was merged into QIconEngine You might need to adjust your code if it used a QIconEngine. - qmake * Projects which explicitly set an empty TARGET are considered broken now. * The makespec and .qmake.cache do not see build pass specific variables any more. * load()/include() with a target namespace and infile()/$$fromfile() now start with an entirely pristine context. * Configure's -sysroot and -hostprefix are now handled slightly differently. The QT_INSTALL_... properties are now automatically prefixed with the sysroot; the raw values are available as QT_INSTALL_.../raw and the sysroot as QT_SYSROOT. The new QT_HOST_... properties can be used to refer to the Qt host tools. * Several functions and built-in variables were modified to return normalized paths. * The -(no-)exception flags in configure have been removed. Qt modules are now compiled without exceptions by default, as they do not use them and can neither handle them properly. Qt Core still has exceptions enabled to correctly throw bad_alloc exceptions in our tool classes. Whether code should be compiled with exception support enabled or disabled can be controlled by a CONFIG += exceptions/exceptions_off setting in the .pro file. - QTextCodecPlugin has been removed since it is no longer used. All text codecs are now built into QtCore. - QDir::NoDotAndDotDot is QDir::NoDot|QDir::NoDotDot therefore there is no need to use or check both. - QFSFileEngine, QAbstractFileEngine, QAbstractFileEngineIterator and QAbstractFileEngineHandler were removed from public API and are no longer exported. They may temporarily live as private implementation details, but they may be altogether dropped or otherwise changed at will in the future. - QLocale * toShort(), toUShort(), toInt(), toUInt(), toLongLong() and toULongLong() no longer take a parameter for base, they will only perform localised base 10 conversions. For converting other bases use the QString methods instead. - QSystemLocale has been removed from the public API. - QSqlQueryModel::indexInQuery() is now virtual. See note below under QtSql. - QSqlDriver::subscribeToNotification, unsubscribeFromNotification, subscribedToNotifications, isIdentifierEscaped, and stripDelimiters are now virtual. See note below under QtSql. - qMacVersion() has been removed. Use QSysInfo::macVersion() or QSysInfo::MacintoshVersion instead. - QColorDialog::customColor() now returns a QColor value instead of QRgb. QColorDialog::setCustomColor() and QColorDialog::setStandardColor() now take a QColor value for their second parameter instead of QRgb. - QPageSetupDialog has had the PageSetupDialogOption enum and the api to set and get the enum removed as none of the Options are used any more. **************************************************************************** * General * **************************************************************************** General Improvements -------------------- - The directory structure of the qtbase unit-tests has been reworked to more closely match the directory structure of the code under test. Integration tests have been moved to tests/auto/integrationtests. - Qt is compiled with C++11 support enabled by default, provided the compiler supports C++11. Qmake based projects can enable C++11 support explicitly using 'CONFIG+=c++11' in their .pro files. To enable it conditionally, use 'contains(QT_CONFIG,c++11):CONFIG+=c++11'. This will enable C++11 support only if Qt was built with C++11 support. Third party components ---------------------- - SQLITE_ENABLE_FTS3,SQLITE_ENABLE_FTS3_PARENTHESIS and SQLITE_ENABLE_RTREE flags are now enabled by default on all platforms, for the sqlite3 copy under the 3rdparty directory. **************************************************************************** * Library * **************************************************************************** QtCore ------ * drop a bogus QChar::NoCategory enum value; the proper QChar::Other_NotAssigned value is returned for an unassigned codepoints now. * layoutAboutToBeChanged is no longer emitted by QAbstractItemModel::beginMoveRows. layoutChanged is no longer emitted by QAbstractItemModel::endMoveRows. Proxy models should now also connect to (and disconnect from) the rowsAboutToBeMoved and rowsMoved signals. * The default value of the property QSortFilterProxyModel::dynamicSortFilter was changed from false to true. * The signature of the virtual QAbstractItemView::dataChanged method has changed to include the roles which have changed. The signature is consistent with the dataChanged signal in the model. * QFileSystemWatcher is now able to return failure in case of errors whilst altering the watchlist in both the singular and QStringList overloads of addPath and removePath. * QString::mid, QString::midRef and QByteArray::mid, if the position passed is equal to the length (that is, right after the last character/byte), now return an empty QString, QStringRef or QByteArray respectively. in Qt 4 they returned a null QString or a null QStringRef. * QString methods toLongLong(), toULongLong(), toLong(), toULong(), toInt(), toUInt(), toShort(), toUShort(), toDouble(), and toFloat() no longer use the default or system locale, they will always use the C locale. This is to guarantee consistent default conversion of strings. For locale-aware conversions use the equivalent QLocale methods. * QDate, QTime, and QDateTime have undergone important behavioural changes: * QDate only implements the Gregorian calendar, the switch to the Julian calendar before 1582 has been removed. This means all QDate methods will return different results for dates prior to 15 October 1582, and there is no longer a gap between 4 October 1582 and 15 October 1582. * QDate::setYMD() is deprecated, use QDate::setDate() instead * Most methods now apply strict validity checks and will return appropriate and consistent values when invalid. For example, QDate::year() will return 0 and QDate::shortMonthName() will return QString(). * Adding days to a null QDate or seconds to a null QTime will no longer return a valid QDate/QTime. * QDate stores the Julian Day as a qint64 extending date support across a more interesting range, see the class documentation for details. * Conversion to YMD form dates is only accurate between to 4800 BCE to 1.4 million CE * The QDate::addDays() and QDateTime::addDays() methods now take a qint64 * The QDate::daysTo() and QDateTime::daysTo() methods now return a qint64 * QTextCodec::codecForCStrings() and QTextCodec::setCodecForCStrings() have both been removed. This was removed due to issues with breaking other code from libraries, creating uncertainty/bugs in using QString easily, and (to a lesser extent) performance issues. * QTextCodec::codecForTr() and QTextCodec::setCodecForTr() have been removed. QObject::trUtf8 and QCoreApplication::Encoding enum are now obsolete. Qt assumes that the source code is encoded in UTF-8. * QFile::setEncodingFunction and QFile::setDecodingFunction are obsolete and do nothing in Qt 5. The QFile::encodeName and QFile::decodeName functions are now hardcoded to operate on QString::fromLocal8Bit and QString::toLocal8Bit only. Therefore, it's still possible to obtain the old behaviour by calling QTextCodec::setCodecForLocale. However, that is not recommended: new code should not make assumptions about the filesystem encoding and older code should have those assumptions removed. * QIntValidator and QDoubleValidator no longer fall back to using the C locale if the requested locale fails to validate the input. * A new set of classes for doing pattern matching with Perl-compatible regular expressions has been added: QRegularExpression, QRegularExpressionMatch and QRegularExpressionMatchIterator. They aim to replace QRegExp with a more powerful and flexible regular expression engine. * QEvent::AccessibilityPrepare, AccessibilityHelp and AccessibilityDescription removed: * The enum values simply didn't make sense in the first place and should simply be dropped. * [QTBUG-23529] QHash is now more resilient to a family of denial of service attacks exploiting algorithmic complexity, by supporting two-arguments overloads of the qHash() hashing function. QtGui ----- * Accessibility has been refactored. The hierachy of accessible objects is implemented via proper parent/child functions instead of using navigate which has been deprecated for this purpose. Table and cell interfaces have been added to qaccessible2.h * Touch events and points have been extended to hold additional information like capability flags, point-specific flags, velocity, and raw positions. * A new set of enabler classes have been added, most importantly QWindow, QScreen, QSurfaceFormat, and QOpenGLContext. * Most of the useful QtOpenGL classes have been polished and moved into QtGui. See QOpenGLFramebufferObject, QOpenGLShaderProgram, QOpenGLFunctions, etc. * QOpenGLPaintDevice has been added to be able to use QPainter to render into the currently bound context. QtWidgets --------- * QInputContext removed as well as related getters and setters on QWidget and QApplication. Input contexts are now platform specific. * QInputDialog::getInteger() has been obsoleted. Use QInputDialog::getInt() instead. * In Qt 4, many QStyleOption subclasses were introduced in order to keep binary compatibility -- QStyleOption was designed to be extended this way, in fact it embeds a version number. In Qt 5 the various QStyleOption*V{2,3,4} classes have been removed, and their members merged into the respective base classes. Those classes were left as typedefs to keep existing code working. Still, some minor adjustements could be necessary, especially in code that uses QStyleOption directly and does not initialize all the members using the proper Qt API: due to the version bump, QStyle will try to use the additional QStyleOption members, which are left default-initialized. * QHeaderView - The following functions have been obsoleted. * void setMovable(bool movable) - use void setSectionsMovable(bool movable) instead. * bool isMovable() const - use bool sectionsMovable() const instead. * void setClickable(bool clickable) - use void setSectionsClickable(bool clickable) instead. * bool isClickable() const - use bool sectionsClickable() instead. * void setResizeMode(int logicalindex, ResizeMode mode) - use setSectionResizeMode(logicalindex, mode) instead. * ResizeMode resizeMode(int logicalindex) const - use sectionResizeMode(int logicalindex) instead. * QDateEdit and QTimeEdit have re-gained a USER property. These were originally removed before Qt 4.7.0, and are re-added for 5.0. This means that the userProperty for those classes are now QDate and QTime respectively, not QDateTime as they have been for the 4.7 and 4.8 releases. QtNetwork --------- * QHostAddress::isLoopback() API added. Returns true if the address is one of the IP loopback addresses. * QSslCertificate::serialNumber() now always returns the serial number in hexadecimal format. * The openssl network backend now reads the ssl configuration file allowing the use of openssl engines. QtDBus ------ * QtDBus now generates property annotations for the Qt type names in the org.qtproject.QtDBus namespace. When parsing such annotations both the old and new namespaces are accepted. * QtDBus error codes have been updated to be on the org.qtproject.QtDBus.Error namespace. QtOpenGL -------- * Most of the classes in this module (with the notable exception of QGLWidget) now have equivalents in QtGui, along with the naming change QGL -> QOpenGL. The classes in QtOpenGL that have equivalents in QtGui can now be considered deprecated. QtScript -------- QTestLib -------- * [QTBUG-20615] Autotests can now log test output to multiple destinations and log formats simultaneously. QtSql ----- QSqlQueryModel/QSqlTableModel/QSqlRelationalTableModel * The dataChanged() signal is now emitted for changes made to an inserted record that has not yet been committed. Previously, dataChanged() was suppressed in this case for OnRowChange and OnFieldChange. This was probably an attempt to avoid trouble if setData() was called while handling primeInsert(). By emitting dataChanged(), we ensure that all views are aware of the change. * While handling primeInsert() signal, the record must be manipulated using the provided reference. Do not attempt to manipulate the records using the model methods setData() or setRecord(). * removeRows() no longer emits extra beforeDelete signal for out of range row. * removeRows() now requires the whole range of targetted rows to be valid before doing anything. Previously, it would remove what it could and ignore the rest of the range. * removeRows(), for OnFieldChange and OnRowChange, allows only 1 row to be removed and only if there are no other changed rows. * setRecord() and insertRecord() -Only use fields where generated flag is set to true. This is is consistent with the meaning of the flag. -Require all fields to map correctly. Previously fields that didn't map were simply ignored. -For OnManualSubmit, insertRecord() no longer leaves behind an empty row if setRecord() fails. -setRecord() now automatically submits for OnRowChange. * QSqlQueryModel::indexInQuery() is now virtual. See QSqlTableModel::indexInQuery() as example of how to implement in a subclass. * QSqlQueryMode::setQuery() emits fewer signals. The modelAboutToBeReset() and modelReset() signals suffice to inform views that they must reinterrogate the model. * QSqlTableModel::selectRow(): This is a new method that refreshes a single row in the model from the database. * QSqlTableModel edit strategies OnFieldChange/OnRowChange QTBUG-2875 Previously, after changes were submitted in these edit strategies, select() was called which removed and inserted all rows. This ruined navigation in QTableView. Now, with these edit strategies, there is no implicit select() done after committing. This includes deleted rows which remain in the model as blank rows until the application calls select(). Instead, selectRow() is called to refresh only the affected row. * QSqlTableModel::isDirty(): New overloaded method to check whether model has any changes to submit. QTBUG-3108 * QSqlTableModel::setData() and setRecord() no longer revert pending changes that fail upon resubmitting for edit strategies OnFieldChange and OnRowChange. Instead, pending (failed) changes cause new changes inappropriate to the edit strategy to be refused. The application should resolve or revert pending changes. insertRows() and insertRecord() also respect the edit strategy. * QSqlTableModel::setData() and setRecord() in OnRowChange no longer have the side effect of submitting the cached row when invoked on a different row. * QSqlDriver::subscribeToNotification, unsubscribeFromNotification, subscribedToNotifications, isIdentifierEscaped, and stripDelimiters are now virtual. Their xxxImplemenation counterparts have been removed now that QSqlDriver subclasses can reimplement these directly. **************************************************************************** * Database Drivers * **************************************************************************** sqlite ------ * QVariant::Bool type now mapped to integers 0/1 in SQL instead of strings 'true' and 'false'. Sqlite does not have a boolean column type and it is customary to use integer. QTBUG-23895 postgres -------- * the error message returned in QSqlError::text() has the SQLSTATE error code appended in parantheses. **************************************************************************** * Platform Specific Changes * **************************************************************************** Qt for Linux/X11 ---------------- Qt for Windows -------------- * Accessibility framework uses IAccessible2 * ANGLE can be used to provide Open GL ES 2.0 (see http://code.google.com/p/angleproject/) Qt for Mac OS X --------------- Qt for Embedded Linux --------------------- Qt for Windows CE ----------------- **************************************************************************** * Compiler Specific Changes * **************************************************************************** **************************************************************************** * Tools * **************************************************************************** - Build System * Remove qttest_p4.prf file. From now on we should explicitly enable the things from it which we want. Autotest .pro files should stop using 'load(qttest_p4)' and start using 'CONFIG+=testcase' instead. - Assistant - Designer * [QTBUG-8926] [QTBUG-20440] Properties of type QStringList now have translation attributes which apply to all items. They are by default translatable. - Linguist - rcc - moc * [QTBUG-20785] The moc now has a -b option to #include an additional file at the beginning of the generated file. - uic - uic3 - qmake * QMAKE_MOC_OPTIONS variable is now available for passing additional parameters to the moc. - configure * The Mac OS X -dwarf2 configure argument has been removed. DWARF2 is always used on Mac OS X now. - qtconfig **************************************************************************** * Plugins * **************************************************************************** - The text codecs that were previously plugins are now built into QtCore. - Code using Q_EXPORT_PLUGIN macros will no longer compile. Use Q_PLUGIN_METADATA instead. Note that this requires that the class be default-constructible. **************************************************************************** * Important Behavior Changes * **************************************************************************** - QPointer * The implementation of QPointer has been changed to use QWeakPointer. The old guard mechanism has been removed. This causes a slight change in behavior when using QPointer: * When using QPointer on a QWidget (or a subclass of QWidget), previously the QPointer would be cleared by the QWidget destructor. Now, the QPointer is cleared by the QObject destructor (since this is when QWeakPointers are cleared). Any QPointers tracking a widget will NOT be cleared before the QWidget destructor destroys the children for the widget being tracked. - QUrl * QUrl has been changed to operate only on percent-encoded forms. Fully-decoded forms, where the percent character stands for itself, are no longer possible. For that reason, the getters and setters with "encoded" in the name are deprecated, except for QUrl::toEncoded() and QUrl::fromEncoded(). QUrl now operates in a mode where it decodes as much as it can of the percent-encoding sequences. In addition, the setter methods possess a mode in which a '%' character not part of a percent-encoding sequence will cause the parser to correct the input. Therefore, most software will not require changes to adapt, since the getter methods will continue returning the components in their most-decoded form as they did before and the setter methods will accept input as they did before.. The most notable difference is when dealing with QUrl::toString(). Previously, this function would return percent characters in the URL by themselves. Now, it will return "%25", like QUrl::toEncoded(). - QVariant * Definition of QVariant::UserType changed. Currently it is the same as QMetaType::User, which means that it points to the first registered custom type, instead of a nonexistent type. - QMetaType * Interpretation of QMetaType::Void was changed. Before, in some cases it was returned as an invalid type id, but sometimes it was used as a valid type (C++ "void"). In Qt5, new QMetaType::UnknownType was introduced to distinguish between these two. QMetaType::UnknownType is an invalid type id signaling that a type is unknown to QMetaType, and QMetaType::Void is a valid type id of C++ void type. The difference will be visible for example in call to QMetaType::typeName(), this function will return null for QMetaType::UnknownType and a pointer to "void" string for QMetaType::Void. Please, notice that QMetaType::UnknownType has value 0, which previously was reserved for QMetaType::Void. - QMessageBox * The static function QMessageBox::question has changed the default argument for buttons. Before the default was to have an Ok button. That is changed to having a yes and a no button.