/**************************************************************************** ** ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). ** All rights reserved. ** Contact: Nokia Corporation (qt-info@nokia.com) ** ** This file is part of the documentation of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:FDL$ ** No Commercial Usage ** This file contains pre-release code and may not be distributed. ** You may use this file in accordance with the terms and conditions ** contained in the Technology Preview License Agreement accompanying ** this package. ** ** GNU Free Documentation License ** Alternatively, this file may be used under the terms of the GNU Free ** Documentation License version 1.3 as published by the Free Software ** Foundation and appearing in the file included in the packaging of this ** file. ** ** If you have questions regarding the use of this file, please contact ** Nokia at qt-info@nokia.com. ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \group porting \title Porting Guides \brief Guides related to porting Qt applications and libraries. \ingroup best-practices A number of guides and documents are available that cover porting issues, from detailed coverage of API differences between Qt 3 and Qt 4 to platform and tool-specific documentation. \generatelist{related} */ /*! \page porting4.html \title Porting to Qt 4 \contentspage {Porting Guides}{Contents} \previouspage Porting Guides \nextpage Porting to Qt 4 - Virtual Functions \ingroup porting \brief An overview of issues and techniques to consider when porting from Qt 3 to Qt 4. \omit ### QFileInfo::PermissionSpec -> QFile::Permission(s?) ### refer to porting4-renamedfunctions.qdoc ### QApplication library mutex is gone ### no integral conversion for containers? strings? ### QVector etc. are initialized to 0 by default? ### How to port from Qt 2.3 to Qt 4. ### missing sort() functions? ### QToolTipGroup ### QServerSocket -> Q3ServerSocket ### remove these when the classes are re-ported ### QApplication::eventLoop() \row \o void QCheckListItem::paintCell(QPainter *, const QColorGroup &, int, int, int)\row \o void Q3CheckListItem::paintCell(QPainter *, const QPalette &, int, int, int) \row \o void QCheckListItem::paintFocus(QPainter *, const QColorGroup &, const QRect &) \o void Q3CheckListItem::paintFocus(QPainter *, const QPalette &, const QRect &) \row \o QDataTable: a whole bunch of virtual functions have a different signature < Function: void QIconViewItem::paintFocus(QPainter *, const QColorGroup &) > Function: void QIconViewItem::paintFocus(QPainter *, const QPalette &) < Function: void QIconViewItem::paintItem(QPainter *, const QColorGroup &) > Function: void QIconViewItem::paintItem(QPainter *, const QPalette &) < Function: bool QUrlOperator::checkValid() < Function: void QWSInputMethod::setFont(const QFont &) ### OpenMode or OpenMode ### QWSDecoration \endomit This document describes the process of porting applications from Qt 3 to Qt 4. If you haven't yet made the decision about porting, or are unsure about whether it is worth it, take a look at the \l{What's New in Qt 4}{key features} offered by Qt 4. See also \l{Moving from Qt 3 to Qt 4} for tips on how to write Qt 3 code that is easy to port to Qt 4. \bold{Other porting guides:} \list \o \l{Moving from Qt 3 to Qt 4} \mdash covers some high level topics relevant to developers porting from Qt 3 to Qt 4. \o \l{Porting to Qt 4 - Drag and Drop} \mdash covers differences in the way drag and drop is handled between Qt 3 and Qt 4. \o \l{Porting UI Files to Qt 4} \mdash describes the new format used to describe forms created with \QD. \o \l{Porting to Graphics View} \mdash provides a class-by-class overview of the differences between Qt 3's canvas API and Qt 4's Graphics View framework. \o \l{qt3to4 - The Qt 3 to 4 Porting Tool} \mdash provides an overview of a tool aimed at helping developers start the process of porting an application to Qt 4. \endlist The Qt 4 series is not binary compatible with the 3 series. This means programs compiled for Qt 3 must be recompiled to work with Qt 4. Qt 4 is also not completely \e source compatible with 3, however nearly all points of incompatibility cause compiler errors or run-time messages (rather than mysterious results). Qt 4 includes many additional features and discards obsolete functionality. Porting from Qt 3 to Qt 4 requires some effort, but once completed the considerable additional power and flexibility of Qt 4 is available for use in your applications. To port code from Qt 3 to Qt 4: \list 1 \o Briefly read the porting notes below to get an idea of what to expect. \o Be sure that your code compiles and runs well on all your target platforms with Qt 3. \o Add the line \c{QT += qt3support} to your \c .pro file if you use \c qmake; otherwise, edit your makefile or project file to link against the Qt3Support library and add \c -DQT3_SUPPORT to your compiler flags. (You might also need to specify other libraries. See \l{What's New in Qt 4} for details.) \o Run the \l qt3to4 porting tool. The tool will go through your source code and adapt it to Qt 4. \o Follow the instructions in the \l{Porting UI Files to Qt 4} page to port Qt Designer files. \o Recompile with Qt 4. For each error, search below for related identifiers (e.g., function names, class names). This document mentions all relevant identifiers to help you get the information you need at the cost of being a little verbose. \endlist The \l qt3to4 porting tool replaces occurrences of Qt 3 classes that don't exist anymore in Qt 4 with the corresponding Qt 3 support class; for example, \c QListBox is turned into \c Q3ListBox. At some point, you might want to stop linking against the Qt 3 support library (\l{Qt3Support}) and take advantage of Qt 4's new features. The instructions below explain how to do that for each compatibility class. In addition to the Qt3Support classes (such as \c Q3Action, \c Q3ListBox, and \c Q3ValueList), Qt 4 provides compatibility functions when it's possible for an old API to cohabit with the new one. For example, QString provides a QString::simplifyWhiteSpace() compatibility function that's implemented inline and that simply calls QString::simplified(). \bold{The compatibility functions are not documented here; instead, they are documented for each class.} If you have the line \c{QT += qt3support} in your \c .pro file, \c qmake will automatically define the \c QT3_SUPPORT symbol, turning on compatibility function support. You can also define the symbol manually (e.g., if you don't want to link against the \c Qt3Support library), or you can define \c QT3_SUPPORT_WARNINGS instead, telling the compiler to emit a warning when a compatibility function is called. (This works only with GCC 3.2+ and MSVC 7.) If you get stuck, ask on the \l{http://qt.nokia.com/lists/qt-interest/}{qt-interest} mailing list. If you are a licensed customer, you can also contact Qt's technical support team. \omit ### what to do with slots that aren't slots anymore ### what to do with virtual functions that aren't virtual anymore ### what to do with virtual functions that changed signature \endomit \omit ### -- stuff that vanished? ### implicit sharing ### uint -> int indexes \endomit Table of contents: \tableofcontents{4} \omit \section1 Header Files ### New style of headers \table \header \o Old header \o New header \row \o \c{} \o \c{} or \c{} \endtable ### Some headers don't include each other anymore... \endomit \section1 Casting and Object Types In Qt 3, it was possible to use the \c qt_cast() function to determine whether instances of QObject subclasses could be safely cast to derived types of those subclasses. For example, if a QFrame instance is passed to a function whose signature specifies a QWidget pointer as its argument, \c qt_cast() could be used to obtain a QFrame pointer so that the instance's functions can be accessed. In Qt 4, much of this functionality is provided by the qobject_cast() function, and additional functions also provide similar functionality for certain non-QObject types: \table \header \o Qt 3 function \o Qt 4 function \row \o T *qt_cast(QObject *) \o \l{qobject_cast()}{T *qobject_cast(QObject *)} \row \o \o \l{qgraphicsitem_cast()}{T qgraphicsitem_cast(QGraphicsItem *)} \row \o \o \l{qstyleoption_cast()}{T qstyleoption_cast(QStyleOption *)} \row \o \o \l{qvariant_cast()}{T qvariant_cast(const QVariant &)} \row \o \o \l{qdbus_cast()}{T qdbus_cast(const QDBusArgument &)} \endtable \omit \section1 Global Functions \table \header \o Qt 3 function \o Qt 4 function \row \o cstrcmp() \o strcmp() \row \o cstrcpy() \o strcpy() \row \o cstrlen() \o strlen() \row \o cstrncmp() \o strncmp() \row \o qmemmove() \o memmove() \endtable qGLVersion() ### copyBlt() ### bitBlt() #ifdef compat classes: * QLayoutIterator * QColorGroup * QMenuItem QWidget visibleRect property compat QWidget::BackgroundOrigin compat \endomit \section1 Type Names The table below lists the classes that have been renamed in Qt 4. If you compile your applications with \c QT3_SUPPORT defined, the old names will be available. Whenever you see an occurrence of the name on the left, you can safely replace it with the Qt 4 equivalent in your program. The \l qt3to4 tool performs the conversion automatically. \table \header \o Qt 3 class name \o Qt 4 class name \input porting/porting4-renamedclasses.qdocinc \endtable The table below lists the enums and typedefs that have been renamed in Qt 4. If you compile your applications with \c QT3_SUPPORT defined, the old names will be available. Whenever you see an occurrence of the name on the left, you can safely replace it with the Qt 4 equivalent in your program. The \l qt3to4 tool performs the conversion automatically. \table \header \o Qt 3 type name \o Qt 4 type name \input porting/porting4-renamedtypes.qdocinc \endtable \omit ### \row \o QButton::ToggleState \o Use QCheckBox::ToggleState instead. \endomit \section1 Enum Values The table below lists the enum values that have been renamed in Qt 4. If you compile your applications with \c QT3_SUPPORT defined, the old names will be available. Whenever you see an occurrence of the name on the left, you can safely replace it with the Qt 4 equivalent in your program. The \l qt3to4 tool performs the conversion automatically. \table \header \o Qt 3 enum value name \o Qt 4 enum value name \input porting/porting4-renamedenumvalues.qdocinc \endtable In addition, the following \l{Qt::WindowFlags}{window flags} have been either replaced with \l{Qt::WidgetAttribute}{widget attributes} or have been deprecated: \table \header \o Qt 3 type \o Qt 4 equivalent \row \o Qt::WDestructiveClose \o Use QWidget::setAttribute(Qt::WA_DeleteOnClose) instead. \row \o Qt::WStaticContents \o{1,2} Use QWidget::setAttribute(Qt::WA_StaticContents) instead. \row \o Qt::WNorthWestGravity \row \o Qt::WNoAutoErase \o{1,3} Use QWidget::setAttribute(Qt::WA_NoBackground) instead. \row \o Qt::WResizeNoErase \row \o Qt::WRepaintNoErase \row \o Qt::WPaintClever \o Unnecessary in Qt 4. \omit ### Check with Matthias \endomit \row \o Qt::WMacNoSheet \o Unnecessary in Qt 4. \omit ### Check with Sam \endomit \endtable In Qt 4.1, the widget flags used to determine window modality were replaced by a single enum that can be used to specify the modal behavior of top-level widgets: \table \header \o Qt 3 type \o Qt 4 equivalent \row \o Qt::WShowModal \o Use QWidget::setWindowModality(Qt::ApplicationModal) instead. \row \o Qt::WGroupLeader \o Use QWidget::setWindowModality(Qt::WindowModal) for each child dialog of the group leader, but do not change the modality of the group leader itself. \endtable \target properties \section1 Properties Some properties have been renamed in Qt 4, to make Qt's API more consistent and more intuitive. For example, QWidget's \c caption property has been renamed \c windowTitle to make it clear that it refers to the title shown in the window's title bar. In addition, the property system has been extended to allow properties to be redefined in subclasses with the \l Q_PROPERTY() macro, removing the need for a \c Q_OVERRIDE() macro. The table below lists the Qt properties that have been renamed in Qt 4. Occurrences of these in \e{Qt Designer} UI files are automatically converted to the new name by \c uic. \table \header \o Qt 3 name \o Qt 4 name \row \o QButton::accel \o QButton::shortcut \row \o QButton::on \o QButton::checked \row \o QButton::toggleButton \o QAbstractButton::checkable \row \o QDial::lineStep \o QDial::singleStep \row \o QDial::maxValue \o QDial::maximum \row \o QDial::minValue \o QDial::minimum \row \o QDialog::modal \o QDialog::isModal \row \o QLineEdit::edited \o QLineEdit::modified \row \o QLineEdit::hasMarkedText \o QLineEdit::hasSelectedText \row \o QLineEdit::markedText \o QLineEdit::selectedText \row \o QObject::name \o QObject::objectName \row \o QProgressDialog::progress \o QProgressDialog::value \row \o QProgressDialog::totalSteps \o QProgressDialog::maximum \row \o QProgressDialog::wasCancelled \o QProgressDialog::wasCanceled \row \o QPushButton::iconSet \o QPushButton::icon \row \o QScrollBar::draggingSlider \o QScrollBar::sliderDown \row \o QScrollBar::lineStep \o QScrollBar::singleStep \row \o QScrollBar::maxValue \o QScrollBar::maximum \row \o QScrollBar::minValue \o QScrollBar::minimum \row \o QSlider::lineStep \o QSlider::singleStep \row \o QSlider::maxValue \o QSlider::maximum \row \o QSlider::minValue \o QSlider::minimum \row \o QSpinBox::lineStep \o QSpinBox::singleStep \row \o QSpinBox::maxValue \o QSpinBox::maximum \row \o QSpinBox::minValue \o QSpinBox::minimum \row \o QTabBar::currentTab \o QTabBar::currentIndex \row \o QTabWidget::currentPage \o QTabWidget::currentWidget \row \o QToolButton::iconSet \o QToolButton::icon \row \o QToolButton::textLabel \o QToolButton::text \row \o QWidget::caption \o QWidget::windowTitle \row \o QWidget::icon \o QWidget::windowIcon \row \o QWidget::iconText \o QWidget::windowIconText \endtable A handful of properties in Qt 3 are no longer properties in Qt 4, but the access functions still exist as part of the Qt 4 API. These are not used by \e{Qt Designer}; the only case where you need to worry about them is in highly dynamic applications that use Qt's meta-object system to access properties. Here's the list of these properties with the read and write functions that you can use instead: \table \header \o Qt 3 property \o Qt 4 read function \o Qt 4 write function \row \o QSqlDatabase::connectOptions \o QSqlDatabase::connectOptions() \o QSqlDatabase::setConnectOptions() \row \o QSqlDatabase::databaseName \o QSqlDatabase::databaseName() \o QSqlDatabase::setDatabaseName() \row \o QSqlDatabase::hostName \o QSqlDatabase::hostName() \o QSqlDatabase::setHostName() \row \o QSqlDatabase::password \o QSqlDatabase::password() \o QSqlDatabase::setPassword() \row \o QSqlDatabase::port \o QSqlDatabase::port() \o QSqlDatabase::setPort() \row \o QSqlDatabase::userName \o QSqlDatabase::userName() \o QSqlDatabase::setUserName() \endtable Some properties have been removed from Qt 4, but the associated access functions are provided if \c QT3_SUPPORT is defined to help porting to Qt 4. When converting Qt 3 UI files to Qt 4, \c uic generates calls to the Qt 3 compatibility functions. Note that this only applies to the properties of the Qt3Support library, i.e. \c QT3_SUPPORT properties of the other libraries must be ported manually when converting Qt 3 UI files to Qt 4. The table below lists these properties with the read and write functions that you can use instead. The documentation for the individual functions explains how to replace them with non-compatibility Qt 4 functions. \table \header \o Qt 3 property \o Qt 4 read function (\c QT3_SUPPORT)\o Qt 4 write function (\c QT3_SUPPORT) \row \o QMenuBar::separator \o QMenuBar::separator() \o QMenuBar::setSeparator() \row \o QPushButton::menuButton \o QPushButton::isMenuButton() \o N/A \row \o QTabWidget::margin \o QTabWidget::margin() \o QTabWidget::setMargin() \row \o QTextEdit::textFormat \o QTextEdit::textFormat() \o QTextEdit::setTextFormat() \row \o QWidget::backgroundBrush \o QWidget::backgroundBrush() \o N/A \row \o QWidget::backgroundMode \o QWidget::backgroundMode() \o QWidget::setBackgroundMode() \row \o QWidget::backgroundOrigin \o QWidget::backgroundOrigin() \o QWidget::setBackgroundOrigin() \row \o QWidget::colorGroup \o QWidget::colorGroup() \o QWidget::setColorGroup() \row \o QWidget::customWhatsThis \o QWidget::customWhatsThis() \o QWidget::setCustomWhatsThis() \row \o QWidget::inputMethodEnabled \o QWidget::inputMethodEnabled() \o QWidget::setInputMethodEnabled() \row \o QWidget::ownCursor \o QWidget::ownCursor() \o N/A \row \o QWidget::ownFont \o QWidget::ownFont() \o N/A \row \o QWidget::ownPalette \o QWidget::ownPalette() \o N/A \row \o QWidget::paletteBackgroundColor \o QWidget::paletteBackgroundColor() \o QWidget::setPaletteBackgroundColor() \row \o QWidget::paletteBackgroundPixmap \o QWidget::paletteBackgroundPixmap() \o QWidget::setPaletteBackgroundPixmap() \row \o QWidget::paletteForegroundColor \o QWidget::paletteForegroundColor() \o QWidget::setPaletteForegroundColor() \row \o QWidget::underMouse \o QWidget::underMouse() \o N/A \endtable The following Qt 3 properties and their access functions are no longer available in Qt 4. In most cases, Qt 4 provides similar functionality. \table \header \o Qt 3 property \o Qt 4 equivalent \row \o QButton::autoRepeat \o N/A \row \o QButton::autoResize \o Call QWidget:setFixedSize(QWidget::sizeHint()) whenever you change the contents. \row \o QButton::exclusiveToggle \o See \l QAbstractButton::autoExclusive. \row \o QButton::pixmap \o Use QAbstractButton::icon instead. \row \o QButton::toggleState \o Use QCheckBox::setState() and QCheckBox::state() instead. \row \o QButton::toggleType \o Use QCheckBox::setTristate() instead. \row \o QComboBox::autoResize \o Call QWidget:setFixedSize(QWidget::sizeHint()) whenever you change the contents. \row \o QFrame::contentsRect \o Use Q3Frame::contentsRect() instead. \row \o QFrame::margin \o Use QWidget::setContentsMargins() instead. \row \o QTabBar::keyboardFocusTab \o N/A \row \o QToolButton::offIconSet \o Use the \l{QIcon::Off}{off component} of QAbstractButton::icon instead. \row \o QToolButton::onIconSet \o Use the \l{QIcon::On}{on component} of QAbstractButton::icon instead. \row \o QWidget::microFocusHint \o N/A \row \o QMimeSource::serialNumber () \o N/A \endtable \omit \section1 Inheritance Chain ### QMenuBar, etc. \section1 Null vs. Empty ### \endomit \section1 Explicit Sharing Qt 4 is the first version of Qt that contains no \link http://doc.qt.nokia.com/3.3/shclass.html explicitly shared \endlink classes. All classes that were explicitly shared in Qt 3 are \e implicitly shared in Qt 4: \list \o QImage \o QBitArray \o QByteArray \o Q3PointArray \endlist This means that if you took a copy of an instance of the class (using operator=() or the class's copy constructor), any modification to the copy would affect the original and vice versa. Needless to say, this behavior is rarely desirable. Fortunately, nearly all Qt 3 applications don't rely on explicit sharing. When porting, you typically only need to remove calls to detach() and/or copy(), which aren't necessary anymore. If you deliberately rely on explicit sharing in your application, you can use pointers or references to achieve the same result in Qt 4. \oldcode void asciify(QByteArray array) { for (int i = 0; i < (int)array.size(); ++i) { if ((uchar)array[i] >= 128) array[i] = '?'; } } \newcode void asciify(QByteArray &array) { for (int i = 0; i < array.size(); ++i) { if ((uchar)array[i] >= 128) array[i] = '?'; } } \endcode (Notice the \c & in the parameter declaration.) \omit \section1 Qt Designer UI Files ### \endomit \section1 Painting and Redrawing Widgets When implementing custom widgets in Qt 3, it was possible to use QPainter to draw on a widget outside paint events. This made it possible to integrate Qt applications with third party libraries and tools that impose their own rendering models. For example, a widget might be repainted in a slot using data obtained from an external source. In Qt 4, it is only possible to paint on a widget from within its \l{QWidget::}{paintEvent()} handler function. This restriction simplifies Qt's interaction with native window systems, improves the performance of applications by reducing the number of redraw operations, and also enables features to be implemented to improve the appearance of widgets, such as a backing store. Generally, we recommend redesigning applications to perform all painting operations in \l{QWidget::}{paintEvent()} functions, deferring actual painting until the next time this function is called. Applications can post paint events to trigger repaints, and it may be possible to examine your widget's internal state to determine which part of the widget needs to be repainted. If asynchronous repaints are used extensively by your application, and it is not practical to redesign the rendering model to perform all painting operations from within a widget's \l{QWidget::}{paintEvent()} function, it may be necessary to consider using an intermediate painting step. In this approach, one or more images can be updated asynchronously and painted on the widget in the paint event. To avoid excessive buffering, it may be worthwhile disabling the backing store by setting the widget's Qt::WA_PaintOnScreen widget attribute. On certain platforms, the Qt::WA_PaintOutsidePaintEvent widget attribute can be set to allow a widget to be painted from outside paint events. \note Setting widget attributes to disable key features of Qt's widget rendering model may also cause other features to be disabled. \section1 Compatibility Signals and Slots When \c QT3_SUPPORT is defined, the default connection type for signals and slots is the Qt::AutoCompatConnection type. This allows so-called \e compatibility signals and slots (defined in Qt 3 support mode to provide Qt 3 compatibility features) to be connected to other signals and slots. However, if Qt is compiled with debugging output enabled, and the developer uses other connection types to connect to compatibility signals and slots (perhaps by building their application without Qt 3 support enabled), then Qt will output warnings to the console to indicate that compatibility connections are being made. This is intended to be used as an aid in the process of porting a Qt 3 application to Qt 4. \section1 QAccel The \c QAccel class has been renamed Q3Accel and moved to the Qt3Support module. In new applications, you have three options: \list 1 \o You can use QAction and set a key sequence using QAction::setShortcut(). \o You can use QShortcut, a class that provides similar functionality to Q3Accel. \o You can use QWidget::grabShortcut() and process "shortcut" events by reimplementing QWidget::event(). \endlist The Q3Accel class also supports multiple accelerators using the same object, by calling Q3Accel::insertItem() multiple times. In Qt 4, the solution is to create multiple QShortcut objects. \section1 QAccessibleInterface The QAccessibleInterface class has undergone some API changes in Qt 4, to make it more consistent with the rest of the Qt API. If you have classes that inherit QAccessibleInterface or one of its subclasses (QAccessibleObject, QAccessibleWidget, etc.), you must port them the new QAccessibleInterface API. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QAccessibleInterface virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QAccessibleTitleBar The \c QAccessibleTitleBar has been renamed Q3AccessibleTitleBar and moved to the Qt3Support library. \target qaction.section \section1 QAction The QAction class has been redesigned in Qt 4 to integrate better with the rest of the menu system. It unifies the old \c QMenuItem class and the old \c QAction class into one class, avoiding unnecessary data duplication and the need to learn two different APIs. The old \c QAction and \c QActionGroup classes have been renamed Q3Action and Q3ActionGroup and moved to Qt3Support. In addition, the new QAction class has compatibility functions to ease transition to Qt 4. Note that when using Q3ToolBar and Q3PopupMenu, their actions must be \l {Q3Action}s. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QAction virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QActionGroup The QAction class has been completely redesigned in Qt 4 to integrate better with the rest of the menu system. See the \l{#qaction.section}{section on QAction} for details. \section1 QApplication The QApplication class has been split into two classes: QCoreApplication and QApplication. The new QApplication class inherits QCoreApplication and adds GUI-related functionality. In practice, this has no consequences for existing Qt applications. In addition, the following API changes were made: \list 1 \o QApplication::allWidgets() and QApplication::topLevelWidgets() used to return a pointer to a QWidgetList. Now they return a QWidgetList. Also, QWidgetList has changed from being a typedef for QPtrList to being a typedef for QList. See the \l{#qwidgetlist.section}{section on QWidgetList} below for details. \oldcode QWidgetList *list = QApplication::topLevelWidgets(); QWidgetListIt it(*list); QWidget *widget; while ((widget = it.current())) { if (widget->inherits("MainWindow")) ((MainWindow *)widget)->updateRecentFileItems(); ++it; } delete list; \newcode QWidgetList list = QApplication::topLevelWidgets(); for (int i = 0; i < list.size(); ++i) { if (MainWindow *mainWin = qobject_cast(list.at(i))) mainWin->updateRecentFileItems(); } \endcode \o QApplication::setMainWidget() is no longer used. When all an application's windows are closed, the application will exit normally. \endlist \section1 QAquaStyle The \c QAquaStyle class first appeared in Qt 3.0, when the Qt for Mac OS X port was first released. It emulated Apple's "Aqua" theme. In Qt 3.1, QAquaStyle was obsoleted by QMacStyle, which uses Appearance Manager to perform its drawing. The \c QAquaStyle class is no longer provided in Qt 4. Use QMacStyle instead. \target qasciidict.section \section1 QAsciiCache \c QAsciiCache has been renamed Q3AsciiCache and moved to the Qt3Support library. It has been replaced by QCache. For details, read the \l{#qcache.section}{section on QCache}, mentally substituting QByteArray for QString. \section1 QAsciiDict QAsciiDict and QAsciiDictIterator have been renamed Q3AsciiDict and Q3AsciiDictIterator and moved to the Qt3Support library. They have been replaced by the more modern QHash and QMultiHash classes and their associated iterator classes. When porting old code that uses Q3AsciiDict to Qt 4, there are four classes that you can use: \list \o QMultiHash \o QMultiHash \o QHash \o QHash \endlist For details, read the \l{#qdict.section}{section on QDict}, mentally substituting QByteArray for QString. \section1 QAsyncIO The \c QAsyncIO class was used internally in Qt 2.x in conjunction with QImageConsumer. It was obsoleted in Qt 3.0. \input porting/porting4-obsoletedmechanism.qdocinc \section1 QBackInsertIterator The undocumented \c QBackInsertIterator class has been removed from the Qt library. If you need it in your application, feel free to copy the source code from the Qt 3 \c header file. \section1 QBitArray In Qt 3, QBitArray inherited from QByteArray. In Qt 4, QBitArray is a totally independent class. This makes very little difference to the user, except that the new QBitArray doesn't provide any of QByteArray's byte-based API anymore. These calls will result in a compile-time error, except calls to QBitArray::truncate(), whose parameter was a number of \e bytes in Qt 3 and a number of bits in Qt 4. QBitArray was an explicitly shared class in Qt 3. See \l{Explicit Sharing} for more information. The \c QBitVal class has been renamed QBitRef. \section1 QButton The \c QButton class has been replaced by QAbstractButton in Qt 4. Classes like QPushButton and QRadioButton inherit from QAbstractButton. As a help when porting older Qt applications, the Qt3Support library contains a Q3Button class implemented in terms of the new QAbstractButton. If you used the \c QButton class as a base class for your own button type and want to port your code to the newer QAbstractButton, you need to be aware that QAbstractButton has no equivalent for the Q3Button::drawButton(QPainter *) virtual function. The solution is to reimplement QWidget::paintEvent() in your QAbstractButton subclass as follows: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 0 \table \header \o Q3Button function \o QAbstractButton equivalent \row \o Q3Button::autoResize() \o Call QWidget:setFixedSize(QWidget::sizeHint()) whenever you change the contents. \row \o Q3Button::isExclusiveToggle() \o Use QAbstractButton::group() or QAbstractButton::autoExclusive() instead. \row \o Q3Button::pixmap() const \o QAbstractButton::icon() \row \o Q3Button::setAutoResize() \o N/A \row \o Q3Button::setPixmap(const QPixmap &) \o QAbstractButton::setIcon(const QIcon &) \row \o Q3Button::setState(ToggleState) \o See remark below \row \o Q3Button::setToggleType(ToggleType) \o See remark below \row \o Q3Button::state() \o See remark below \row \o Q3Button::stateChanged(int) \o See remark below \row \o Q3Button::toggleType() \o See remark below \endtable Remarks: \list 1 \o In Qt 3, \c QButton had a "toggle type", which could be QButton::SingleShot, QButton::Toggle, or QButton::Tristate. The new QAbstractButton class doesn't support "tristate" directly; this feature is implemented in QCheckBox instead. The two other "toggle types" (\c QButton::SingleShot and \c QButton::Toggle) are replaced by a QAbstractButton::checkable property. \o In Qt 3, QButton had a "toggle state", which could be \c QButton::Off, \c QButton::NoChange, or \c QButton::On. In Qt 4, this mechanism has been moved to QCheckBox. \endlist See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of \c QButton virtual member functions in Qt 3 that aren't virtual in Qt 4. See \l{#properties}{Properties} for a list of \c QButton properties in Qt 3 that have changed in Qt 4. \section1 QButtonGroup The \c QButtonGroup class has been completely redesigned in Qt 4. For compatibility, the old \c QButtonGroup class has been renamed Q3ButtonGroup and has been moved to Qt3Support. Likewise, the \c QHButtonGroup and \c QVButtonGroup convenience subclasses have been renamed \c Q3HButtonGroup and \c Q3VButtonGroup and moved to the Qt3Support library. The old \c QButtonGroup, as well as Q3ButtonGroup, can be used in two ways: \list 1 \o The button group is the parent widget of a number of buttons, i.e. the button group is the parent argument in the button constructor. The buttons are assigned identifiers 0, 1, 2, etc., in the order they are created. A Q3ButtonGroup can display a frame and a title because it inherits Q3GroupBox. \o The button group is an invisible widget and the contained buttons have some other parent widget. In this usage, each button must be manually inserted, using Q3ButtonGroup::insert(), into the button group and given an ID number. \endlist Unlike Q3ButtonGroup, the new QButtonGroup doesn't inherit QWidget. It is very similar to a "hidden Q3ButtonGroup". If you use a Q3ButtonGroup, Q3HButtonGroup, or Q3VButtonGroup as a widget and want to port to Qt 4, you can replace it with QGroupBox. In Qt 4, radio buttons with the same parent are automatically part of an exclusive group, so you normally don't need to do anything else. See also the \l{#qgroupbox.section}{section on QGroupBox} below. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QButtonGroup virtual member functions in Qt 3 that are no longer virtual in Qt 4. \target qbytearray.section \section1 QByteArray In Qt 3, QByteArray was simply a typedef for QMemArray. In Qt 4, QByteArray is a class in its own right, with a higher-level API in the style of QString. Here are the main issues to be aware of when porting to Qt 4: \list 1 \o The QMemArray(int size) constructor has been replaced with QByteArray(int size, char ch). The second argument specifies which character should be used for initializing the array; pass '\\0' if you have no specific needs. \oldcode QByteArray ba(64); \newcode QByteArray ba(64, '\0'); \endcode \o QMemArray::at() returned a non-const reference, whereas the new QByteArray::at() returns a const value. Code like \snippet doc/src/snippets/code/doc_src_porting4.qdoc 1 will no longer compile. Instead, use QByteArray::operator[]: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 2 \o The QMemArray::contains(char) function has been renamed QByteArray::count(char). In addition, there now exists a QByteArray::contains(char) function that returns a boolean value. Replace old calls to contains() with either count() or contains(), depending on whether you care about the specific number of occurrences of a character in the byte array or only care about whether the array contains that character or not. \o The new QByteArray has no assign() function. Calls to QMemArray::assign(const QMemArray &) can be replaced by calls to QByteArray::operator=(). Calls to QMemArray::assign(const T *, uint) have no equivalent in Qt 4; if you use it, the solution is either to use QByteArray::fromRawData() and to call free() yourself to avoid a memory leak, or to use the QByteArray(const char *, int) constructor, which will take a deep copy of the data. \o QMemArray::bsearch() and QMemArray::sort() have no equivalent in the new QByteArray class. Use \l qBinaryFind() and \l qSort() if you need that functionality. \endlist QByteArray was an explicitly shared class in Qt 3. See \l{Explicit Sharing} for more information. \target qcache.section \section1 QCache QCache has been renamed Q3Cache and moved to Qt3Support. The new QCache class has a different API, and takes different template parameters: QCache. When porting to Qt 4, QCache is the obvious substitute for Q3Cache. The following table summarizes the API differences. \table \header \o Q3Cache function \o QCache equivalent \row \o Q3Cache::Q3Cache(int maxCost, int size, bool caseSensitive) \o See remark below \row \o Q3Cache::autoDelete() \o N/A \row \o Q3Cache::count() \o QCache::count() or QCache::size() (equivalent) \row \o Q3Cache::setAutoDelete() \o See remark below \row \o Q3Cache::size() \o N/A \row \o Q3Cache::statistics() \o N/A \row \o Q3Cache::operator=() \o See remark below \endtable Remarks: \list 1 \o Q3Cache requires the user to allocate a specific number of buckets by passing a prime number (17 by default) to the constructor. In contrast, the new QCache's hash table automatically grows and shrinks as needed, and the constructor doesn't take a prime number. \o Q3Cache supportes case-insensitive lookups by passing false as second argument to the constructor. This feature has no equivalent in QMultiHash. Instead, call QString::toLower() before you insert or lookup a key in the hash. \o The Q3Cache::insert() function returns a \c bool value that indicates whether or not the item actually was inserted in the cache. If the item wasn't inserted, it was the caller's responsibility to delete the item. The new QCache::insert() function returns \c void and either adds it to the cache or deletes it right away. Old code like \snippet doc/src/snippets/code/doc_src_porting4.qdoc 3 becomes \snippet doc/src/snippets/code/doc_src_porting4.qdoc 4 \o The new QCache class \e always takes ownership of the items it stores (i.e. auto-delete is always on). If you use Q3Cache with auto-delete turned off (the rarely useful default), you cannot use QCache as a direct substitute. One unelegant trick that works well in practice is to use QCache instead of QCache. In that case, QCache owns the pointers, not the objects that the pointers refer to. For example, \snippet doc/src/snippets/code/doc_src_porting4.qdoc 5 becomes \snippet doc/src/snippets/code/doc_src_porting4.qdoc 6 An alternative is to stick to using Q3Cache. \endlist QCacheIterator has been renamed Q3CacheIterator and moved to the Qt3Support library. The new QCache class doesn't offer any iterator types. \section1 QCanvas The canvas module classes have been renamed and moved to the Qt3Support library. \table \header \o Qt 3 class name \o Compatibility class in Qt 4 \row \o \c QCanvas \o Q3Canvas \row \o \c QCanvasEllipse \o Q3CanvasEllipse \row \o \c QCanvasItem \o Q3CanvasItem \row \o \c QCanvasItemList \o Q3CanvasItemList \row \o \c QCanvasLine \o Q3CanvasLine \row \o \c QCanvasPixmap \o Q3CanvasPixmap \row \o \c QCanvasPixmapArray \o Q3CanvasPixmapArray \row \o \c QCanvasPolygon \o Q3CanvasPolygon \row \o \c QCanvasPolygonalItem \o Q3CanvasPolygonalItem \row \o \c QCanvasRectangle \o Q3CanvasRectangle \row \o \c QCanvasSpline \o Q3CanvasSpline \row \o \c QCanvasSprite \o Q3CanvasSprite \row \o \c QCanvasText \o Q3CanvasText \row \o \c QCanvasView \o Q3CanvasView \endtable The \l{Graphics View Framework} replaces QCanvas. For more on porting to Graphics View, see \l{Porting to Graphics View}. \section1 QColor In Qt 4, QColor is a value type like QPoint or QRect. Graphics system-specific code has been implemented in QColormap. The \c QColor::maxColors() function has been replaced by QColormap::size(). The \c QColor::numBitPlanes() function has been replaced by QColormap::depth(). The \c QColor::setNamedColor() function no longer supports the named color in the same way as Qt 3. Qt 4's \l{QColor::}{setNamedColor()} uses the new W3C convention as stated \l{http://www.w3.org/TR/SVG/types.html#ColorKeywords}{here}. \table \header \o{4,1} Predefined Qt Colors \row \o Qt::color0 \o Qt::color1 \o Qt::black \o Qt::white \row \o Qt::darkGray \o Qt::gray \o Qt::lightGray \o Qt::red \row \o Qt::green \o Qt::blue \o Qt::cyan \o Qt::magenta \row \o Qt::yellow \o Qt::darkRed \o Qt::darkGreen \o Qt::darkBlue \row \o Qt::darkCyan \o Qt::darkMagenta \o Qt::darkYellow \o Qt::transparent \endtable The predefined colors listed in the table above were static QColor objects in Qt 3. In Qt 4, they are enum values of type Qt::GlobalColor. Thanks to the implicit QColor(Qt::GlobalColor) constructor, the enum values are automatically converted to \l{QColor}s in most contexts. Occasionally, you might need a cast. \oldcode QColor lightCyan = Qt::cyan.light(180); \newcode QColor lightCyan = QColor(Qt::cyan).light(180); \endcode \section1 QColorGroup In Qt 3, a QPalette consisted of three QColorGroup objects. In Qt 4, the (rarely used) QColorGroup abstraction has been eliminated. For source compatibility, a QColorGroup class is available when \c QT3_SUPPORT is defined. The new QPalette still works in terms of color groups, specified through enum values (QPalette::Active, QPalette::Disabled, and QPalette::Inactive). It also has the concept of a \e current color group, which you can set using QPalette::setCurrentColorGroup(). The QPalette object returned by QWidget::palette() returns a QPalette initialized with the correct current color group for the widget. This means that if you had code like \badcode painter.setBrush(colorGroup().brush(QColorGroup::Text)); \endcode you can simply replace colorGroup() with palette(): \snippet doc/src/snippets/code/doc_src_porting4.qdoc 7 \section1 QColorDrag The \c QColorDrag class has been renamed Q3ColorDrag and moved to the Qt3Support library. In Qt 4, use QMimeData instead and call QMimeData::setColor() to set the color. \section1 QComboBox In Qt 3, the list box used to display the contents of a \c QComboBox widget could be accessed by using the \c listBox() function. In Qt 4, the standard list box is provided by a QListView widget, and can be accessed with the \l{QComboBox::view()}{view()} function. \omit ### \endomit See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QComboBox virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QCString In Qt 3, QCString inherited from QByteArray. The main drawback of this approach is that the user had the responsibility of ensuring that the string is '\\0'-terminated. Another important issue was that conversions between \c QCString and QByteArray often gave confusing results. (See the \l{http://doc.qt.nokia.com/qq/qq05-achtung.html#qcstringisastringofchars}{Achtung! Binary and Character Data} article in \e{Qt Quarterly} for an overview of the pitfalls.) Qt 4 solves that problem by merging the QByteArray and \c QCString classes into one class called QByteArray. Most functions that were in \c QCString previously have been moved to QByteArray. The '\\0' issue is handled by having QByteArray allocate one extra byte that it always sets to '\\0'. For example: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 8 The Qt3Support library contains a class called Q3CString that inherits from the new QByteArray class and that extends it to provide an API that is as close to the old \c QCString class as possible. Note that the following functions aren't provided by Q3CString: \list \o QCString::find(const QRegExp &, int) \o QCString::findRev(const QRegExp &, int) \o QCString::contains(const QRegExp &) \o QCString::replace(const QRegExp &, const char *) \endlist The following functions have lost their last parameter, which specified whether the search was case sensitive or not: \list \o QByteArray::find(char, int) \o QByteArray::find(const char *, int) \o QByteArray::findRev(char, int) \o QByteArray::findRev(const char *, int) \o QByteArray::contains(char) \o QByteArray::contains(const char *) \endlist In both cases, the solution is to convert the \c QCString to a QString and use the corresponding QString functions instead. Also be aware that \c QCString::size() (inherited from QByteArray) used to return the size of the character data \e including the '\\0'-terminator, whereas the new QByteArray::size() is just a synonym for QByteArray::length(). This brings QByteArray in line with QString. When porting to Qt 4, occurrences of \c QCString should be replaced with QByteArray or QString. The following table summarizes the API differences between the Q3CString class and the Qt 4 QByteArray and QString classes: \table \header \o Q3CString function \o Qt 4 equivalent \row \o Q3CString::Q3CString(const char *, uint) \o See remark below \row \o Q3CString::Q3CString(int) \o QByteArray::QByteArray(int, char) \row \o Q3CString::leftJustify() \o QString::leftJustified() \row \o Q3CString::length() \o QByteArray::length() or QByteArray::size() (equivalent) \row \o Q3CString::lower() \o QByteArray::toLower() \row \o Q3CString::rightJustify() \o QString::rightJustified() \row \o Q3CString::setExpand() \o See remark below \row \o Q3CString::simplifyWhiteSpace() \o QByteArray::simplified() \row \o Q3CString::sprintf() \o QString::sprintf() \row \o Q3CString::stripWhiteSpace() \o QByteArray::trimmed() \row \o Q3CString::toDouble() \o QString::toDouble() \row \o Q3CString::toFloat() \o QString::toFloat() \row \o Q3CString::toInt() \o QString::toInt() \row \o Q3CString::toLong() \o QString::toLong() \row \o Q3CString::toShort() \o QString::toShort() \row \o Q3CString::toUInt() \o QString::toUInt() \row \o Q3CString::toULong() \o QString::toULong() \row \o Q3CString::toUShort() \o QString::toUShort() \row \o Q3CString::upper() \o QByteArray::toUpper() \endtable Remarks: \list 1 \o Q3CString(const char *str, uint max) constructs a string of length strlen(str) or \e max - 1, whichever is shorter. QByteArray(const char *data, int size) constructs a byte array containing exactly \e size bytes. \oldcode QCString str1("Hello", 4); // "Hel" QCString str2("Hello world!", n); \newcode QByteArray str1("Hello", 3); QByteArray str2("Hello world!"); str2.truncate(n - 1); \endcode \o Q3CString::setExpand(uint index, char ch) has no equivalent in Qt 4. \oldcode QCString str("Hello world"); str.setExpand(16, '\n'); // "Hello world \n" \newcode QByteArray str("Hello world"); while (str.size() < 16) str += ' '; str += '\n'; \endcode \endlist Since the old \c QCString class inherited from QByteArray, everything that is said in the \l{#qbytearray.section}{QByteArray section} applies for \c QCString as well. \section1 QCustomEvent In Qt 3, developers could create a custom event by constructing a new QCustomEvent, and send relevant data to other components in the application by passing a void pointer, either on construction or using the setData() function. Objects could receive custom events by reimplementing the \l{QObject::customEvent()}{customEvent()} function, and access the stored data using the event's data() function. In Qt 4, custom events are created by subclassing QEvent. Event-specific data can be stored in a way that is appropriate for your application. Custom events are still delivered to each object's \l{QObject::customEvent()}{customEvent()} handler function, but as QEvent objects rather than as deprecated QCustomEvent objects. \section1 QDataBrowser The \c QDataBrowser class has been renamed Q3DataBrowser and moved to the Qt3Support library. In Qt 4.2, you should use the QDataWidgetMapper class to create data-aware forms. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QDataPump The \c QDataPump class was used internally in Qt 2.x in conjunction with QImageConsumer. It was obsoleted in Qt 3.0. \input porting/porting4-obsoletedmechanism.qdocinc \section1 QDataSink The \c QDataSink class was used internally in Qt 2.x in conjunction with QImageConsumer. It was obsoleted in Qt 3.0. \input porting/porting4-obsoletedmechanism.qdocinc \section1 QDataSource The \c QDataSource class was used internally in Qt 2.x in conjunction with QImageConsumer. It was obsoleted in Qt 3.0. \input porting/porting4-obsoletedmechanism.qdocinc \section1 QDataTable The \c QDataTable class has been renamed Q3DataTable and moved to the Qt3Support library. In Qt 4.2, you should use the QDataWidgetMapper class to create data-aware forms. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QDataView The \c QDataView class has been renamed Q3DataView and moved to the Qt3Support library. In Qt 4.2, you should use the QDataWidgetMapper class to create data-aware forms. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QDateEdit The QDateEdit class in Qt 4 is a convenience class based on QDateTimeEdit. The old class has been renamed Q3DateEdit and moved to the Qt3Support library. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of \c QDateEdit virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QDateTimeEditBase The \c QDateTimeEditBase class has been renamed Q3DateTimeEditBase and moved to Qt3Support. Use QDateTimeEdit or QAbstractSpinBox instead. \section1 QDateTimeEdit The old \c QDateTimeEdit class has been renamed Q3DateTimeEditBase and moved to Qt3Support. The new QDateTimeEdit in Qt 4 has been rewritten from scratch to provide a more flexible and powerful API. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QDateTimeEdit virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QDeepCopy The \c QDeepCopy class in Qt 3 provided a means of ensuring that implicitly shared and explicitly shared classes referenced unique data. This was necessary because the reference counting in Qt's container classes was done in a thread-unsafe manner. With Qt 4, \c QDeepCopy has been renamed Q3DeepCopy and moved to the Qt3Support library. Removing it from existing code is straightforward. \oldcode QString str1 = "I am a string"; QDeepCopy str2 = str1; QString str3 = QDeepCopy(str2); \newcode QString str1 = "I am a string"; QString str2 = str1; QString str3 = str2; \endcode \section1 QDial See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QDial virtual member functions in Qt 3 that are no longer virtual in Qt 4. See \l{#properties}{Properties} for a list of QDial properties in Qt 3 that have changed in Qt 4. \target qdict.section \section1 QDict \c QDict has been renamed Q3Dict and moved to Qt3Support. It has been replaced by the more modern QHash and QMultiHash classes. When porting old code that uses QDict to Qt 4, there are four classes that you can use: \table \header \o Qt 4 class \o When to use it \row \o QMultiHash \o Since Q3Dict is pointer-based and allows duplicate keys, this is usually the most straightforward conversion. \row \o QMultiHash \o If type \c T is an \l{assignable data type}, you can use \c T as the value type rather than \c{T *}. This often leads to nicer code. \row \o QHash \o{1,2} If you don't use duplicate keys, you can use QHash instead of QMultiHash. QMultiHash inherits from QHash. \row \o QHash \endtable The APIs of Q3Dict and QMultiHash are quite similar. The main issue is that Q3Dict supports auto-delete whereas QMultiHash doesn't. \omit (See \l{What's Wrong with Auto-Delete} for an explanation of why the Qt 4 containers don't offer that feature.) \endomit The following table summarizes the API differences between the two classes: \table \header \o Q3Dict function \o QMultiHash equivalent \row \o Q3Dict::Q3Dict(int size, bool caseSensitive) \o See remarks below \row \o Q3Dict::autoDelete() \o N/A \row \o Q3Dict::count() \o QMultiHash::count() or QMultiHash::size() (equivalent) \row \o Q3Dict::find(const QString &) \o QMultiHash::value(const QString &) \row \o Q3Dict::remove(const QString &) \o QMultiHash::take(const QString &) \row \o Q3Dict::resize(uint) \o QMultiHash::reserve(int) \row \o Q3Dict::setAutoDelete() \o See discussion below \row \o Q3Dict::size() \o QMultiHash::capacity() \row \o Q3Dict::statistics() \o N/A \row \o Q3Dict::operator[](const QString &) \o See remark below \endtable Remarks: \list 1 \o Q3Dict requires the user to allocate a specific number of buckets by passing a prime number (17 by default) to the constructor and/or calling Q3Dict::resize() later on. In contrast, QMultiHash's hash table automatically grows and shrinks as needed, and the constructor doesn't take a prime number. \o Q3Dict supportes case-insensitive lookups by passing false as second argument to the constructor. This feature has no equivalent in QMultiHash. Instead, call QString::toLower() before you insert or lookup a key in the hash. \o Q3Dict::size() and QMultiHash::size() have different semantics. The former returns the number of buckets in the container, whereas the latter returns the number of \e items in the container. \o If there are multiple items with the same key, Q3Dict::remove() removes only the most recently inserted item, whereas QMultiHash::remove() removes all items that share a particular key. To remove only the most recently inserted item, call QMultiHash::take(). \o Q3Dict has only one [] operator (Q3Dict::operator[]()), providing const access to an item's value. QMultiHash also has a non-const overload that can be used on the left side of the assignment operator. If you use the [] operator on a non-const QHash with an unexisting item, QHash will created an element and initialize it to be a null pointer. For that reason, Q3Dict::operator[] should be converted to QMultiHash::value(), not QMultiHash::operator[]. \endlist If you use Q3Dict's auto-delete feature (by calling Q3Dict::setAutoDelete(true)), you need to do some more work. You have two options: Either you call \c delete yourself whenever you remove an item from the container, or you use QMultiHash instead of QMultiHash (i.e. store values directly instead of pointers to values). Here, we'll see when to call \c delete. The following table summarizes the idioms that you need to watch out for if you want to call \c delete yourself. \table \header \o Q3Dict idiom \o QMultiHash idiom \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 9 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 10 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 11 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 12 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 13 (also called from Q3Dict's destructor) \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 14 In 99% of cases, the following idiom also works: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 15 However, it may lead to crashes if \c hash is referenced from the value type's destructor, because \c hash contains dangling pointers until clear() is called. \endtable Be aware that Q3Dict's destructor automatically calls clear(). If you have a Q3Dict data member in a custom class and use the auto-delete feature, you will need to call \c delete on all the items in the container from your class destructor to avoid a memory leak. Finally, \c QDictIterator (renamed Q3DictIterator) must also be ported. There are no fewer than four iterator classes that can be used as a replacement: QHash::const_iterator, QHash::iterator, QHashIterator, and QMutableHashIterator. The most straightforward class to use when porting is QHashIterator. The following table summarizes the API differences: \table \header \o Q3DictIterator functions \o Qt 4 equivalent \row \o Q3DictIterator::count() \o QHash::count() or QHash::size() \row \o Q3DictIterator::current() \o QHashIterator::value() \row \o Q3DictIterator::currentKey() \o QHashIterator::key() \row \o Q3DictIterator::isEmpty() \o QHash::isEmpty() \row \o Q3DictIterator::toFirst() \o QHashIterator::toFront() \row \o Q3DictIterator::operator()() \o QHashIterator::value() \row \o Q3DictIterator::operator*() \o QHashIterator::value() \row \o Q3DictIterator::operator++() \o See remark below \endtable Be aware that QHashIterator has a different way of iterating than Q3DictIterator. A typical loop with Q3DictIterator looks like this: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 16 Here's the equivalent QHashIterator loop: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 17 See \l{Java-style iterators} for details. \section1 QDir The following functions used to have a boolean \c{acceptAbsPath} parameter that defaulted to true: \list \i QDir::filePath() \i QDir::absFilePath() \i QDir::cd() \i QDir::mkdir() \i QDir::rmdir() \i QDir::remove() \i QDir::rename() \i QDir::exists() \endlist In Qt 3, if \c acceptAbsPath is true, a file name starting with '/' is be returned without change; if \c acceptAbsPath is false, an absolute path is prepended to the file name. For example: \table \header \i Current directory \i File name \i \c acceptAbsPath \i File path \row \i{1,2} /home/tsmith \i{1,2} index.html \i true \i /home/tsmith/index.html \row \i false \i /home/tsmith/index.html \row \i{1,2} /home/tsmith \i{1,2} /index.html \i true \i /index.html \row \i false \i /home/tsmith/index.html \endtable In Qt 4, this parameter is no longer available. If you use it in your code, you can check that QDir::isRelativePath() returns false instead. \oldcode QDir dir("/home/tsmith"); QString path = dir.filePath(fileName, false); \newcode QDir dir("/home/tsmith"); QString path; if (dir.isRelativePath(fileName)) path = dir.filePath(fileName); else path = fileName; \endcode QDir::encodedEntryList() has been removed. fileInfoList(), entryInfoList(), and drives() now return a QList and not a QPtrList *. Code using these methods will not work with the Qt3Support library and must be adapted instead. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QDir virtual member functions in Qt 3 that are no longer virtual in Qt 4. QDir::match() now always matches case insensitively. QDir::homeDirPath() has been removed. Use QDir::home() instead, and extract the path separately. \section1 QDns Qt 3 used its own implementation of the DNS protocol and provided a low-level \c QDns class. Qt 4's QHostInfo class uses the system's \c gethostbyname() function from a thread instead. The old \c QDns class has been renamed Q3Dns and moved to the Qt3Support library. The new QHostInfo class has a radically different API: It consists mainly of two static functions, one of which is blocking (QHostInfo::fromName()), the other non-blocking (QHostInfo::lookupHost()). See the QHostInfo class documentation for details. \section1 QDockArea The \c QDockArea class has been renamed Q3DockArea and moved to the Qt3Support library. In Qt 4, QMainWindow handles the dock and toolbar areas itself. See the QMainWindow documentation for details. \section1 QDockWindow The old \c QDockWindow class has been renamed Q3DockWindow and moved to the Qt3Support library. In Qt 4, there is a new QDockWidget class with a different API. See the class documentation for details. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QDockWidget virtual member functions in Qt 3 that are no longer virtual in Qt 4. \note \l{Q3DockWindow}'s \l{Q3DockWindow::setHorizontallyStretchable()}{horizontallyStretchable} property can be achieved in QDockWidget with \l{QWidget#Size Hints and Size Policies}{size policies}. \section1 QDragObject The \c QDragObject class has been renamed Q3DragObject and moved to the Qt3Support library. In Qt 4, it has been replaced by the QMimeData class. See the class documentation for details. Note that the Q3DragObject::DragCopyOrMove drag and drop mode is interpreted differently to Qt 3's QDragObject::DragCopyOrMove mode. In Qt 3, a move operation was performed by default, and the user had to hold down the \key{Ctrl} key to perform a copy operation. In Qt 4, a copy operation is performed by default; the user has to hold down the \key{Shift} key to perform a move operation. See \l{Porting to Qt 4 - Drag and Drop} for a comparison between the drag and drop APIs in Qt 3 and Qt 4. \section1 QDropSite The \c QDropSite class has been renamed Q3DropSite and moved to the Qt3Support library. The QDropSite class has been obsolete ever since Qt 2.0. The only thing it does is call QWidget::setAcceptDrops(true). \oldcode class MyWidget : public QWidget, public QDropSite { public: MyWidget(const QWidget *parent) : QWidget(parent), QDropSite(this) { } ... } \newcode class MyWidget : public QWidget { public: MyWidget(const QWidget *parent) : QWidget(parent) { setAcceptDrops(true); } ... } \endcode See \l{Porting to Qt 4 - Drag and Drop} for a comparison between the drag and drop APIs in Qt 3 and Qt 4. \section1 QEditorFactory The \c QEditorFactory class has been renamed Q3EditorFactory and moved to the Qt3Support library. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QEventLoop In Qt 3, \c QEventLoop combined the Qt event loop and the event dispatching. In Qt 4, these tasks are now assigned to two distinct classes: QEventLoop and QAbstractEventDispatcher. If you subclassed QEventLoop to integrate with another library's event loop, you must subclass QAbstractEventDispatcher instead. See the class documentation for details. Developers using \c{QEventLoop::loopLevel()} in Qt 3 should use QCoreApplication::loopLevel() instead. Note that this function is marked as obsolete, but it is expected to be available for the lifetime of Qt 4. \omit ### mention virtual functions that aren't virtual anymore \endomit \omit \section1 QFile The QFile::readLine(QString&, Q_ULONG) method from qt3 has been removed in qt4, but this change in the QFile interface is not documented in the porting documentation as of qt-4.0.0-b1. \endomit \section1 QFileDialog The QFileDialog class in Qt 4 has been totally rewritten. It provides most of the functionality of the old \c QFileDialog class, but with a different API. Some functionality, such as the ability to preview files, is expected to be added in a later Qt 4 release. The old \c QFileDialog, \c QFileIconProvider, and \c QFilePreview classes has been renamed Q3FileDialog, Q3FileIconProvider, and Q3FilePreview and have been moved to Qt3Support. You can use them if you need some functionality not provided yet by the new QFileDialog class. The following table lists which functions have been renamed or removed in Qt 4. \table \header \o Old function \o Qt 4 equivalent \row \o Q3FileDialog::addFilter(const QString &) \o See remark below \row \o Q3FileDialog::addLeftWidget(QWidget *) \o N/A \row \o Q3FileDialog::addRightWidget(QWidget *) \o N/A \row \o Q3FileDialog::addToolButton(QAbstractButton *, bool separator) \o N/A \row \o Q3FileDialog::addWidgets(QLabel *, QWidget *, QPushButton *) \o N/A \row \o Q3FileDialog::dir() \o QFileDialog::directory() \row \o Q3FileDialog::dirPath() \o QFileDialog::directory().path() \row \o Q3FileDialog::iconProvider() \o N/A \row \o Q3FileDialog::isContentsPreviewEnabled() \o N/A \row \o Q3FileDialog::isInfoPreviewEnabled() \o N/A \row \o Q3FileDialog::previewMode() \o N/A \row \o Q3FileDialog::rereadDir() \o N/A \row \o Q3FileDialog::resortDir() \o N/A \row \o Q3FileDialog::selectAll(bool) \o N/A \row \o Q3FileDialog::setContentsPreview(QWidget *, Q3FilePreview *) \o N/A \row \o Q3FileDialog::setContentsPreviewEnabled(bool) \o N/A \row \o Q3FileDialog::setDir(const QString &) \o QFileDialog::setDirectory(const QString &) \row \o Q3FileDialog::setFilters(const char **) \o Q3FileDialog::setFilters(const QStringList &) \row \o Q3FileDialog::setIconProvider(Q3FileIconProvider *) \o N/A \row \o Q3FileDialog::setInfoPreview(QWidget *, Q3FilePreview *) \o N/A \row \o Q3FileDialog::setInfoPreviewEnabled(bool) \o N/A \row \o Q3FileDialog::setPreviewMode(PreviewMode) \o N/A \row \o Q3FileDialog::setSelectedFilter(const QString &) \o QFileDialog::selectFilter(const QString &) \row \o Q3FileDialog::setSelectedFilter(int) \o See remark below \row \o Q3FileDialog::setSelection(const QString &) \o QFileDialog::selectFile(const QString &) \row \o Q3FileDialog::setShowHiddenFiles(bool) \o showHidden() \row \o Q3FileDialog::setUrl(const QUrlOperator &) \o N/A \row \o Q3FileDialog::showHiddenFiles() \o N/A \row \o Q3FileDialog::url() \o QUrl::fromLocalFile(QFileDialog::directory()) \header \o Old signals \o Qt 4 equivalent \row \o Q3FileDialog::fileHighlighted(const QString &) \o N/A \row \o Q3FileDialog::fileSelected(const QString &) \o QFileDialog::filesSelected(const QStringList &) \row \o Q3FileDialog::dirEntered(const QString &) \o N/A \row \o Q3FileDialog::filterSelected(const QString &) \o N/A \endtable Remarks: \list 1 \o The Q3FileDialog::addFilter(const QString &) function has no direct equivalent in the new QFileDialog. Use QFileDialog::setFilters() instead. \oldcode fileDialog->addFilter(tr("JPEG files (*.jpg *.jpeg)")); \newcode QStringList filters = fileDialog->filters(); filters << tr("JPEG files (*.jpg *.jpeg)"); fileDialog->setFilters(filters); \endcode \o The Q3FileDialog::setSelectedFilter(int) overload has no direct equivalent in the new QFileDialog. Use QFileDialog::selectFilter(const QString &) instead. \oldcode fileDialog->setSelectedFilter(3); \newcode fileDialog->selectFilter(fileDialog->filters().at(3)); \endcode \endlist There are no equivalent virtual functions to the two Q3FileDialog::setSelectedFilter() virtual functions in the QFileDialog API. In addition, these functions have been renamed or removed, as described above. \section1 QFocusData The QFocusData class is not available in Qt 4. Some of its functionality is available via the QWidget::nextInFocusChain() and QWidget::focusNextPrevChild() functions. \section1 QFocusEvent The setReason() function is no longer present in Qt 4. It is necessary to define the reason when constructing a focus event. \section1 QFont \c QFont::Script has been moved to QFontDatabase::WritingSystem. \section1 QFrame The QFrame class has been made more lightweight in Qt 4, by reducing the number of properties and virtual functions. The reduction in the number of virtual functions is significant because QFrame is the base class of many Qt classes. Here's an overview of the changes: \list \o QFrame no longer has a \c margin property (which wasn't honored by Qt's layout managers anyway). \o QFrame no longer has a frameChanged() function, reimplement QFrame::resizeEvent() instead. \o QFrame used to have drawFrame(QPainter *) and drawContents(QPainter *) virtual functions. These are now gone. In Qt 4, the frame is drawn by the QFrame::paintEvent() function. If you want to change the way QFrame paints itself, reimplement this function. To draw the contents of the frame, reimplement QFrame:paintEvent() and call the base class implementation of the function before you use the \l {QWidget::}{contentsRect()} function inherited from QWidget, to retrieve the rectangle to paint on. \endlist To help with porting, the Qt3Support library contains a Q3Frame class that inherits QFrame and provides a similar API to the old QFrame class. If you derived from QFrame in your application, you might want to use Q3Frame as a base class as a first step in the porting process, and later move on to the new QFrame class. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QFrame virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QFtp QFtp no longer inherits from QNetworkProtocol. See the \l{#qnetworkprotocol.section}{section on QNetworkProtocol} for details. The old \c QFtp class has been renamed Q3Ftp and moved to the Qt3Support library. \target qglayoutiterator.section \section1 QGLayoutIterator The QGLayoutIterator class no longer exists in Qt 4. This makes only a difference if you implemented custom layout managers (i.e., QLayout subclasses). The new approach is much simpler: It consists in reimplementing QLayout::itemAt() and QLayout::takeAt(). These functions operate on indexes, eliminating the need for a layout iterator class. \section1 QGrid The \c QGrid class is now only available as Q3Grid in Qt 4. You can achieve the same result as \c QGrid by creating a QWidget with a grid layout: \oldcode QGrid *grid = new QGrid(2, Qt::Horizontal); QPushButton *child1 = new QPushButton(grid); QPushButton *child2 = new QPushButton(grid); QPushButton *child3 = new QPushButton(grid); QPushButton *child4 = new QPushButton(grid); \newcode QWidget *grid = new QWidget; QPushButton *child1 = new QPushButton(grid); QPushButton *child2 = new QPushButton(grid); QPushButton *child3 = new QPushButton(grid); QPushButton *child4 = new QPushButton(grid); QVBoxLayout *layout = new QVBoxLayout; layout->addWidget(child1, 0, 0); layout->addWidget(child2, 0, 1); layout->addWidget(child3, 1, 0); layout->addWidget(child4, 1, 1); grid->setLayout(layout); \endcode \section1 QGridLayout See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QGridLayout virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QGridView The \c QGridView class has been renamed Q3GridView and moved to the Qt3Support library. In Qt 4, we recommend that you use QTableView or QAbstractItemView for presenting tabular data. See \l{Model/View Programming} for an overview of the new item view classes. \target qgroupbox.section \section1 QGroupBox The QGroupBox class has been redesigned in Qt 4. Many of the features of the old \c QGroupBox class can be obtained by using the Q3GroupBox class from the Qt3Support library. The new QGroupBox is more lightweight. It doesn't attempt to duplicate functionality already provided by QGridLayout, and it does not inherit from QFrame. As a result, the following members have been removed: \list \o Q3GroupBox::setColumns(), Q3GroupBox::columns() \o Q3GroupBox::setOrientation(), Q3GroupBox::orientation() \o Q3GroupBox::setInsideMargin(), Q3GroupBox::insideMargin() \o Q3GroupBox::addSpace() \endlist Naturally, the \c columns and \c orientation properties have also been removed. If you rely on some of the missing functionality in your application, you can use Q3GroupBox instead of QGroupBox as a help to porting. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QGroupBox virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QHBox The \c QHBox class is now only available as Q3HBox in Qt 4. You can achieve the same result as \c QHBox by creating a QWidget with an horizontal layout: \oldcode QHBox *hbox = new QHBox; QPushButton *child1 = new QPushButton(hbox); QPushButton *child2 = new QPushButton(hbox); \newcode QWidget *hbox = new QWidget; QPushButton *child1 = new QPushButton; QPushButton *child2 = new QPushButton; QHBoxLayout *layout = new QHBoxLayout; layout->addWidget(child1); layout->addWidget(child2); hbox->setLayout(layout); \endcode Note that child widgets are not automatically placed into the widget's layout; you will need to manually add each widget to the QHBoxLayout. \section1 QHeader The \c QHeader class has been renamed Q3Header and moved to the Qt3Support library. In Qt 4, it is replaced by the QHeaderView class. See \l{Model/View Programming} for an overview of the new item view classes. \section1 QHGroupBox The \c QHGroupBox class has been renamed Q3HGroupBox and moved to the Qt3Support library. Qt 4 does not provide a specific replacement class for \c QHGroupBox since QGroupBox is designed to be a generic container widget. As a result, you need to supply your own layout for any child widgets. See \l{#QGroupBox} for more information about porting code that uses group boxes. \section1 QHttp QHttp no longer inherits from QNetworkProtocol. See the See the \l{#qnetworkprotocol.section}{section on QNetworkProtocol} for details. The old \c QHttp, \c QHttpHeader, \c QHttpRequestHeader, and \c QHttpResponseHeader classes have been renamed Q3Http, Q3HttpHeader, Q3HttpRequestHeader, and Q3HttpResponseHeader and have been moved to the Qt3Support library. \section1 QIconFactory The QIconFactory class is no longer part of Qt. It has been replaced by the QIconEngine class. \section1 QIconSet The QIconSet class is no longer part of Qt. It has been replaced by the QIcon class. \section1 QIconView The \c QIconView, \c QIconViewItem, \c QIconDrag, and \c QIconDragItem classes has been renamed Q3IconView, Q3IconViewItem, Q3IconDrag, and Q3IconDragItem and moved to the Qt3Support library. New Qt applications should use QListWidget or its base class QListView instead, and call QListView::setViewMode(QListView::IconMode) to obtain an "icon view" look. See \l{Model/View Programming} for an overview of the new item view classes. \omit ### \section1 QImage QImage::fromMimeSource(const QString &) -> qImageFromMimeSource(const QString &) \endomit \section1 QImageDrag The \c QImageDrag class has been renamed Q3ImageDrag and moved to the Qt3Support library. In Qt 4, use QMimeData instead and call QMimeData::setImage() to set the image. See \l{Porting to Qt 4 - Drag and Drop} for a comparison between the drag and drop APIs in Qt 3 and Qt 4. \section1 QImageIO The \c QImageIO class has been split into two classes: QImageReader and QImageWriter. The table below shows the correspondance between the two APIs: \table \header \o Qt 3 function \o Qt 4 equivalents \row \o QImageIO::description() \o QImageWriter::text() \row \o QImageIO::fileName() \o QImageReader::fileName() and QImageWriter::fileName() \row \o QImageIO::format() \o QImageReader::format() and QImageWriter::format() \row \o QImageIO::gamma() \o QImageWriter::gamma() \row \o QImageIO::image() \o Return value of QImageReader::read() \row \o QImageIO::inputFormats() \o QImageReader::supportedImageFormats() \row \o QImageIO::ioDevice() \o QImageReader::device() and QImageWriter::device() \row \o QImageIO::outputFormats() \o QImageWriter::supportedImageFormats() \row \o QImageIO::parameters() \o N/A \row \o QImageIO::quality() \o QImageWriter::quality() \row \o QImageIO::read() \o QImageReader::read() \row \o QImageIO::setDescription() \o QImageWriter::setText() \row \o QImageIO::setFileName() \o QImageReader::setFileName() and QImageWriter::setFileName() \row \o QImageIO::setFormat() \o QImageReader::setFormat() and QImageWriter::setFormat() \row \o QImageIO::setGamma() \o QImageWriter::setGamma() \row \o QImageIO::setIODevice() \o QImageReader::setDevice() and QImageWriter::setDevice() \row \o QImageIO::setImage() \o Argument to QImageWriter::write() \row \o QImageIO::setParameters() \o N/A \row \o QImageIO::setQuality() \o QImageWriter::setQuality() \row \o QImageIO::setStatus() \o N/A \row \o QImageIO::status() \o QImageReader::error() and QImageWriter::error() \row \o QImageIO::write() \o QImageWriter::write() \endtable \section1 QIntCache QIntCache has been moved to Qt3Support. It has been replaced by QCache. For details, read the \l{#qcache.section}{section on QCache}, mentally substituting \c int for QString. \section1 QIntDict QIntDict and QIntDictIterator have been moved to Qt3Support. They have been replaced by the more modern QHash and QMultiHash classes and their associated iterator classes. When porting old code that uses QIntDict to Qt 4, there are four classes that you can use: \list \o QMultiHash \o QMultiHash \o QHash \o QHash \endlist For details, read the \l{#qdict.section}{section on QDict}, mentally substituting \c int for QString. \target qiodevice.section \section1 QIODevice The QIODevice class's API has been simplified to make it easier to subclass and to make it work more smoothly with asynchronous devices such as QTcpSocket and QProcess. The following virtual functions have changed name or signature: \table \header \o Qt 3 function \o Comment \row \o QIODevice::at() const \o Renamed QIODevice::pos(). \row \o QIODevice::at(Offset) \o Renamed QIODevice::seek(). \row \o QIODevice::open(int) \o The parameter is now of type QIODevice::OpenMode. \row \o QIODevice::readBlock(char *, Q_ULONG) \o QIODevice::read(char *, qint64) \row \o QIODevice::writeBlock(const char *, Q_ULONG) \o QIODevice::write(const char *, qint64) \endtable \note QIODevice::open(QIODevice::OpenMode) is no longer pure virtual. The following functions are no longer virtual or don't exist anymore: \table \row \o QIODevice::getch() \o Renamed QIODevice::getChar() and implemented in terms of QIODevice::readData(). \row \o QIODevice::putch(int) \o Renamed QIODevice::putChar() and implemented in terms of QIODevice::writeData(). \row \o QIODevice::readAll() \o Implemented in terms of QIODevice::readData(). \row \o QIODevice::readLine(char *, Q_ULONG) \o Implemented in terms of QIODevice::readData() \row \o QIODevice::ungetch(int) \o Renamed QIODevice::ungetChar() and simulated using an internal unget buffer. \endtable The \c IO_xxx flags have been revised, and the protected setFlags() function removed. Most of the flags have been eliminated because errors are best handled by implementing certain functions in QIODevice subclasses rather than through the base classes. The file access flags, such as \c IO_ReadOnly and \c IO_WriteOnly, have been moved to the QIODevice class to avoid polluting the global namespace. The table below shows the correspondence between the Qt 3 \c IO_xxx flags and the Qt 4 API: \table \header \o Qt 3 constant \o Qt 4 equivalent \row \o IO_Direct \o Use !QIODevice::isSequential() instead (notice the \e not). \row \o IO_Sequential \o Use QIODevice::isSequential() instead. \row \o IO_Combined \o N/A \row \o IO_TypeMask \o N/A \row \o IO_Raw \o QIODevice::Unbuffered \row \o IO_Async \o N/A \row \o IO_ReadOnly \o QIODevice::ReadOnly \row \o IO_WriteOnly \o QIODevice::WriteOnly \row \o IO_ReadWrite \o QIODevice::ReadWrite \row \o IO_Append \o QIODevice::Append \row \o IO_Truncate \o QIODevice::Truncate \row \o IO_Translate \o QIODevice::Text \row \o IO_ModeMask \o N/A \row \o IO_Open \o Use QIODevice::isOpen() instead. \row \o IO_StateMask \o N/A \row \o IO_Ok \o N/A \row \o IO_ReadError \o N/A \row \o IO_WriteError \o N/A \row \o IO_FatalError \o N/A \row \o IO_ResourceError \o N/A \row \o IO_OpenError \o N/A \row \o IO_ConnectError \o N/A \row \o IO_AbortError \o N/A \row \o IO_TimeOutError \o N/A \row \o IO_UnspecifiedError \o N/A \endtable \section1 QIODeviceSource The QIODeviceSource class was used internally in Qt 2.x in conjunction with QImageConsumer. It was obsoleted in Qt 3.0. \input porting/porting4-obsoletedmechanism.qdocinc \section1 QLabel QLabel doesn't enable word-wrap automatically anymore when rich text is used. You can enable it by calling QLabel::setWordWrap() or by setting the \l{QLabel::wordWrap}{wordWrap} property. The reason for this change is that the old behavior was confusing to many users. Also, QLabel no longer offers an \c autoResize property. Instead, you can call QWidget::setFixedSize() on the label, with QLabel::sizeHint() as the argument, whenever you change the contents of the QLabel. See also \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of QLabel virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QLayout In Qt 4, margins are always handled by layouts; there is no QLayout::setSupportsMargin() function anymore. The deleteAllItems() function is now only available if \c QT3_SUPPORT is defined. If you maintain a QList of layout items, you can use qDeleteAll() to remove all the items in one go. In Qt 3, it was possible to change the resizing behavior for layouts in top-level widgets by adjusting the layout's \c resizeMode property. In Qt 4, this property has been replaced by the QLayout::sizeConstraint property which provides more control over how the layout behaves when resized. See also the \l{#qlayoutiterator.section}{section on QLayoutIterator} and the \l{#qglayoutiterator.section}{section on QGLayoutIterator}. \target qlayoutiterator.section \section1 QLayoutIterator The QLayoutIterator class is obsoleted in Qt 4. It is available only if \c QT3_SUPPORT is defined. It can be replaced by the QLayout::itemAt() and QLayout::takeAt() functions, which operate on indexes. \oldcode QLayoutIterator it = layout()->iterator(); QLayoutItem *child; while ((child = it.current()) != 0) { if (child->widget() == myWidget) { it.takeCurrent(); return; ++it; } \newcode int i = 0; QLayoutItem *child; while ((child = layout()->itemAt(i)) != 0) { if (child->widget() == myWidget) { layout()->takeAt(i); return; } ++i; } \endcode \section1 QLineEdit See \l{#properties}{Properties} for a list of QLineEdit properties in Qt 3 that have changed in Qt 4. The default value of QLineEdit's \l{QLineEdit::dragEnabled()}{dragEnabled} property was \c true in Qt 3. In Qt 4, the default value is \c false. Note that QLineEdit in Qt 4 is no longer a subclass of QFrame. If you need to visually style a line edit with a frame, we recommend either using a QFrame as a container for a QLineEdit or customizing the line edit with a \l{Qt Style Sheets}{style sheet}. \section1 QListBox The \c QListBox, \c QListBoxItem, \c QListBoxText, and \c QListBoxPixmap classes have been renamed Q3ListBox, Q3ListBoxItem, Q3ListBoxText, and Q3ListBoxPixmap and have been moved to the Qt3Support library. New Qt applications should use QListWidget or its base class QListView instead. See \l{Model/View Programming} for an overview of the new item view classes. \section1 QListView The \c QListView, \c QListViewItem, \c QCheckListItem, and \c QListViewItemIterator classes have been renamed Q3ListView, Q3ListViewItem, Q3CheckListItem, and Q3ListViewItemIterator, and have been moved to the Qt3Support library. New Qt applications should use one of the following four classes instead: QTreeView or QTreeWidget for tree-like structures; QListWidget or the new QListView class for one-dimensional lists. See \l{Model/View Programming} for an overview of the new item view classes. \section1 QLocalFs The \c QLocalFs class is no longer part of the public Qt API. It has been renamed Q3LocalFs and moved to Qt3Support. Use QDir, QFileInfo, or QFile instead. \section1 QMainWindow The QMainWindow class has been redesigned in Qt 4 to provide a more modern look and feel and more flexibility. The API has changed to reflect that. The old \c QMainWindow class has been renamed Q3MainWindow and moved to Qt3Support. See the QMainWindow class documentation for details. \omit ### More detail \endomit \target qmemarray.section \section1 QMemArray QMemArray has been moved to Qt3Support. It has been replaced by the QVector class. The following table summarizes the API differences between the two classes. \table \row \o QMemArray::assign(const QMemArray &) \o QVector::operator=() \row \o QMemArray::assign(const T *, uint) \o See remark below \row \o QMemArray::duplicate(const QMemArray &) \o QVector::operator=() \row \o QMemArray::duplicate(const T *, uint) \o See remark below \row \o QMemArray::setRawData(const T *, uint) \o N/A \row \o QMemArray::resetRawData(const T *, uint) \o N/A \row \o QMemArray::find(const T &, uint) \o QVector::indexOf(const T &, int) \row \o QMemArray::contains(const T &) \o QVector::count(const T &) \row \o QMemArray::sort() \o \l qSort() \row \o QMemArray::bsearch(const T &d) \o \l qBinaryFind() \row \o QMemArray::at(uint) \o QVector::operator[]() \row \o QMemArray::operator const T *() \o QVector::constData() \endtable Remarks: \list 1 \o QMemArray::assign(const T *, uint) and QMemArray::duplicate(const T *, uint) can be replaced by QVector::resize() and qCopy(). \oldcode QMemArray array; ... array.assign(data, size); \newcode QVector vector; ... vector.resize(size); qCopy(data, data + size, vector.begin()); \endcode \o QMemArray is an explicitly shared class, whereas QVector is implicitly shared. See \l{Explicit Sharing} for more information. \endlist \section1 QMenuBar In Qt 3, QMenuBar inherited from QFrame and QMenuData; in Qt 4, it is a direct subclass of QWidget. Applications that provided customized menu bars will need to take advantage of the styling features described in the \l{Qt Style Sheets} document. It is not possible to add widgets to menu bars in Qt 4. \section1 QMenuData In Qt 4, the QMenu class provides a menu widget that can be used in all the places where menus are used in an application. Unlike \c QMenuData, QMenu is designed around the concept of actions, provided by the QAction class, instead of the identifiers used in Qt 3. In Qt 3, it was possible to insert widgets directly into menus by using a specific \c QMenuData::insertItem() overload. In Qt 4.2 and later, the QWidgetAction class can be used to wrap widgets for use in Qt 4's action-based APIs. \section1 QMessageBox The QMessageBox::iconPixmap() function used to return a "const QPixmap *". In Qt 4, it returns a QPixmap. \section1 QMimeSourceFactory The \c QMimeSourceFactory has been renamed Q3MimeSourceFactory and moved to the Qt3Support library. New Qt applications should use Qt 4's \l{Resource System} instead. \section1 QMovie The QMovie API has been revised in Qt 4 to make it more consistent with the other Qt classes (notably QImageReader). The table below summarizes the changes. \table \header \o Qt 3 function \o Qt 4 equivalent \row \o QMovie::connectResize() \o Connect to QMovie::resized() \row \o QMovie::connectStatus() \o Connect to QMovie::stateChanged() \row \o QMovie::connectUpdate() \o Connect to QMovie::updated() \row \o QMovie::disconnectResize() \o Disconnect from QMovie::resized() \row \o QMovie::disconnectStatus() \o Disconnect from QMovie::stateChanged() \row \o QMovie::disconnectUpdate() \o Disconnect from QMovie::updated() \row \o QMovie::finished() \o Use QMovie::state() instead \row \o QMovie::frameImage() \o Use QMovie::currentImage() instead \row \o QMovie::frameNumber() \o Use QMovie::currentFrameNumber() instead \row \o QMovie::framePixmap() \o Use QMovie::currentPixmap() instead \row \o QMovie::getValidRect() \o Use frameRect() instead \row \o QMovie::isNull() \o Use QMovie::isValid() instead \row \o QMovie::pause() \o Use QMovie::setPaused(true) instead \row \o QMovie::paused() \o Use QMovie::state() instead \row \o QMovie::pushData() \o N/A \row \o QMovie::pushSpace() \o N/A \row \o QMovie::restart() \o Use QMovie::jumpToFrame(0) instead \row \o QMovie::running() \o Use QMovie::state() instead \row \o QMovie::step() \o Use QMovie::jumpToFrame() and QMovie::setPaused() instead \row \o QMovie::step() \o Use QMovie::jumpToNextFrame() instead \row \o QMovie::steps() \o Use QMovie::currentFrameNumber() and QMovie::frameCount() instead \row \o QMovie::unpause() \o Use QMovie::setPaused(false) instead \endtable \section1 QMultiLineEdit The \c QMultiLineEdit class in Qt 3 was a convenience QTextEdit subclass that provided an interface compatible with Qt 2's QMultiLineEdit class. In Qt 4, it is called Q3MultiLineEdit, it inherits Q3TextEdit, and it is part of Qt3Support. Use QTextEdit in new code. \target qnetworkprotocol.section \section1 QNetworkProtocol The QNetworkProtocol, QNetworkProtocolFactoryBase, QNetworkProtocolFactory, and QNetworkOperation classes are no longer part of the public Qt API. They have been renamed Q3NetworkProtocol, Q3NetworkProtocolFactoryBase, Q3NetworkProtocolFactory, and Q3NetworkOperation and have been moved to the Qt3Support library. In Qt 4 applications, you can use classes like QFtp and QNetworkAccessManager directly to perform file-related actions on a remote host. \section1 QObject QObject::children() now returns a QObjectList instead of a pointer to a QObjectList. See also the comments on QObjectList below. Use QObject::findChildren() (or qFindChildren() if you need MSVC 6 compatibility) instead of QObject::queryList(). For example: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 18 QObject::killTimers() has been removed because it was unsafe to use in subclass. (A subclass normally doesn't know whether the base class uses timers or not.) The \c QObject::name property has been renamed QObject::objectName. \c QObject::objectTrees() has been removed. If you are primarly interested in widgets, use QApplication::allWidgets() or QApplication::topLevelWidgets(). \section1 QObjectDictionary The QObjectDictionary class is a synonym for QAsciiDict. See the \l{#qasciidict.section}{section on QAsciiDict}. \section1 QObjectList In Qt 3, the QObjectList class was a typedef for QPtrList. In Qt 4, it is a typedef for QList. See the \l{#qptrlist.section}{section on QPtrList}. \section1 QPaintDevice To reimplement painter backends one previously needed to reimplement the virtual function QPaintDevice::cmd(). This function is taken out and should is replaced with the function QPaintDevice::paintEngine() and the abstract class QPaintEngine. QPaintEngine provides virtual functions for all drawing operations that can be performed on a painter backend. bitBlt() and copyBlt() are now only compatibility functions. Use QPainter::drawPixmap() instead. \section1 QPaintDeviceMetrics All functions that used to be provided by the \c QPaintDeviceMetrics class have now been moved to QPaintDevice. \oldcode QPaintDeviceMetrics metrics(widget); int deviceDepth = metrics.depth(); \newcode int deviceDepth = widget->depth(); \endcode For compatibility, the old \c QPaintDeviceMetrics class has been renamed Q3PaintDeviceMetrics and moved to Qt3Support. \section1 QPainter The QPainter class has undergone some changes in Qt 4 because of the way rectangles are drawn. In Qt 4, the result of drawing a QRect with a pen width of 1 pixel is 1 pixel wider and 1 pixel taller than in Qt 3. For compatibility, we provide a Q3Painter class in Qt3Support that provides the old semantics. See the Q3Painter documentation for details and for the reasons why we had to make this change. The \l{http://doc.qt.nokia.com/3.3/qpainter.html#CoordinateMode-enum}{QPainter::CoordinateMode} enum has been removed in Qt 4. All clipping operations are now defined using logical coordinates and are subject to transformation operations. The \l{http://doc.qt.nokia.com/3.3/qpainter.html#RasterOP-enum}{QPainter::RasterOP} enum has been replaced with QPainter::CompositionMode. \section1 QPicture In Qt 3, a QPicture could be saved in the SVG file format. In Qt 4, the SVG support is provided by the QtSvg module, which includes classes for \e displaying the contents of SVG files. If you would like to generate SVG files, you can use the Q3Picture compatibility class or the QSvgGenerator class introduced in Qt 4.3. \section1 QPixmap The mask() function has been changed to return a reference to a QBitmap rather than a pointer. As a result, it is no longer possible simply to test for a null pointer when determining whether a pixmap has a mask. Instead, you need to explicitly test whether the mask bitmap is null or not. \oldcode if (pixmap.mask()) widget->setMask(*pixmap.mask()); \newcode if (!pixmap.mask().isNull()) widget->setMask(pixmap.mask()); \endcode The \c QPixmap::setOptimization() and \c QPixmap::setDefaultOptimization() mechanism is no longer available in Qt 4. \omit QPixmap::fromMimeSource(const QString &) -> qPixmapFromMimeSource(const QString &) \endomit \section1 QPointArray The \c QPointArray class has been renamed QPolygon in Qt 4 and has undergone significant changes. In Qt 3, \c QPointArray inherited from QMemArray. In Qt 4, QPolygon inherits from QVector. Everything mentioned in the \l{#qmemarray.section}{section on QMemArray} apply for QPointArray as well. The Qt3Support library contains a Q3PointArray class that inherits from QPolygon and provides a few functions that existed in \c QPointArray but no longer exist in QPolygon. These functions include Q3PointArray::makeArc(), Q3PointArray::makeEllipse(), and Q3PointArray::cubicBezier(). In Qt 4, we recommend that you use QPainterPath for representing arcs, ellipses, and Bezier curves, rather than QPolygon. The QPolygon::setPoints() and QPolygon::putPoints() functions return \c void in Qt 4. The corresponding Qt 3 functions returned a \c bool indicating whether the array was successfully resized or not. This can now be checked by checking QPolygon::size() after the call. \omit X11 Specific: ::appDisplay() -> QX11Info::display() QPaintDevice::x11Display() -> QX11Info::display() QPaintDevice::x11AppDisplay() -> QX11Info::display() QPaintDevice::x11Screen() -> QX11Info::appScreen() QPaintDevice::x11AppScreen() -> ??? QPaintDevice::x11Depth() -> QX11Info::appDepth() QPaintDevice::x11ColorMap() -> QX11Info::appColorMap() QPaintDevice::x11DefaultColorMap() -> ??? QPaintDevice::x11Visual() -> QX11Info::appVisual() QPaintDevice::x11DefaultVisual() -> ??? QPaintDevice::x11AppDpiX() -> QX11Info::appDpiX() QPaintDevice::x11AppDpiY() -> QX11Info::appDpiY() QPaintDevice::x11SetAppDpiX() -> QX11Info::setAppDpiX() QPaintDevice::x11SetAppDpiY() -> QX11Info::setAppDpiY() QPaintDevice::x11AppDepth() -> ??? QPaintDevice::x11AppCells() -> ??? QPaintDevice::x11AppRootWindow() -> ??? QPaintDevice::x11AppColorMap() -> ??? QPaintDevice::x11AppDefaultColorMap() -> ??? QPaintDevice::x11AppVisual() -> ??? QPaintDevice::x11AppDefaultVisual() -> ??? End of X11 Specific \endomit \section1 QPopupMenu For most purposes, QPopupMenu has been replaced by QMenu in Qt 4. For compatibility with older applications, Q3PopupMenu provides the old API and features that are specific to pop-up menus. Note that, when using Q3PopupMenu, the menu's actions must be \l {Q3Action}s. In Qt 3, it was common practice to add entries to pop-up menus using the insertItem() function, maintaining identifiers for future use; for example, to dynamically change menu items. In Qt 4, menu entries are completely represented by actions for consistency with other user interface components, such as toolbar buttons. Create new menus with the QMenu class, and use the overloaded QMenu::addAction() functions to insert new entries. If you need to manage a set of actions created for a particular menu, we suggest that you construct a QActionGroup and add them to that. The \l{Main Window Examples} provided show how to use Qt's action system to construct menus, toolbars, and other common user interface elements. \section1 QPrinter The QPrinter class now expects printing to be set up from a QPrintDialog. \section1 QProcess The QProcess class has undergone major improvements in Qt 4. It now inherits QIODevice, which makes it possible to combine QProcess with a QTextStream or a QDataStream. The old \c QProcess class has been renamed Q3Process and moved to the Qt3Support library. \section1 QProgressBar The QProgressBar API has been significantly improved in Qt 4. The old \c QProgressBar API is available as Q3ProgressBar in the Qt3Support library. \section1 QProgressDialog The QProgressDialog API has been significantly improved in Qt 4. The old \c QProgressDialog API is available as Q3ProgressDialog in the Qt3Support library. See \l{#properties}{Properties} for a list of QProgressDialog properties in Qt 3 that have changed in Qt 4. \section1 QPtrCollection The \c QPtrCollection abstract base class has been renamed Q3PtrCollection moved to the Qt3Support library. There is no direct equivalent in Qt 4. \omit ### The QPtrCollection entry is unsatisfactory. The xref is missing its list and saying "no direct equivalent" with so suggestions seems feeble. \endomit See \l{Container Classes} for a list of Qt 4 containers. \section1 QPtrDict \c QPtrDict and \c QPtrDictIterator have been renamed Q3PtrDict and Q3PtrDictIterator and have been moved to the Qt3Support library. They have been replaced by the more modern QHash and QMultiHash classes and their associated iterator classes. When porting old code that uses Q3PtrDict to Qt 4, there are four classes that you can use: \list \o QMultiHash \o QMultiHash \o QHash \o QHash \endlist (You can naturally use other types than \c{void *} for the key type, e.g. \c{QWidget *}.) To port Q3PtrDict to Qt 4, read the \l{#qdict.section}{section on QDict}, mentally substituting \c{void *} for QString. \target qptrlist.section \section1 QPtrList QPtrList, QPtrListIterator, and QPtrListStdIterator have been moved to the Qt3Support library. They have been replaced by the more modern QList and QLinkedList classes and their associated iterator classes. When porting to Qt 4, you have the choice of using QList or QLinkedList as alternatives to QValueList. QList has an index-based API and provides very fast random access (QList::operator[]), whereas QLinkedList has an iterator-based API. The following table summarizes the API differences between QPtrList and QList: \table \header \o QPtrList function \o QList equivalent \row \o QPtrList::contains(const T *) \o QList::count(T *) \row \o QPtrList::containsRef(const T *) \o QList::count(T *) \row \o QPtrList::find(const T *) \o See remark below \row \o QPtrList::findRef(const T *) \o See remark below \row \o QPtrList::getFirst() \o QList::first() \row \o QPtrList::getLast() \o QList::last() \row \o QPtrList::inSort(const T *) \o N/A \row \o QPtrList::remove(const T *) \o QList::removeAll(T *) \row \o QPtrList::remove(uint) \o QList::removeAt(int) \row \o QPtrList::removeNode(QLNode *) \o N/A \row \o QPtrList::removeRef(const T *) \o QList::removeAll(T *) \row \o QPtrList::sort() \o See remark below \row \o QPtrList::takeNode(QLNode *) \o N/A \row \o QPtrList::toVector(QGVector *) \o See remark below \endtable Remarks: \list 1 \o QPtrList::toVector(QGVector *) can be replaced by QVector::resize() and qCopy(). \oldcode QPtrList list; ... QPtrVector vector; list.toVector(&vector); \newcode QList list; ... QVector vector; vector.resize(list.size()); qCopy(list.begin(), list.end(), vector.begin()); \endcode \o QPtrList::sort() relied on the virtual compareItems() to sort items. In Qt 4, you can use \l qSort() instead and pass your "compare item" function as an argument. \o QPtrList::find(const T *) returns an iterator, whereas QList::indexOf(T *) returns an index. To convert an index into an iterator, add the index to QList::begin(). \o QPtrList::removeFirst() and QPtrList::removeLast() return a \c bool that indicates whether the element was removed or not. The corresponding QList functions return \c void. You can achieve the same result by calling QList::isEmpty() before attempting to remove an item. \endlist If you use QPtrList's auto-delete feature (by calling QPtrList::setAutoDelete(true)), you need to do some more work. You have two options: Either you call \c delete yourself whenever you remove an item from the container, or you can use QList instead of QList (i.e. store values directly instead of pointers to values). Here, we'll see when to call \c delete. \omit (See \l{What's Wrong with Auto-Delete} for an explanation of why the Qt 4 containers don't offer that feature.) \endomit The following table summarizes the idioms that you need to watch out for if you want to call \c delete yourself. \table \header \o QPtrList idiom \o QList idiom \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 19 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 20 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 21 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 22 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 23 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 24 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 25 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 26 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 27 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 28 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 29 (removes the current item) \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 30 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 31 (also called from QPtrList's destructor) \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 32 In 99% of cases, the following idiom also works: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 33 However, it may lead to crashes if \c list is referenced from the value type's destructor, because \c list contains dangling pointers until clear() is called. \endtable Be aware that QPtrList's destructor automatically calls clear(). If you have a QPtrList data member in a custom class and use the auto-delete feature, you will need to call \c delete on all the items in the container from your class destructor to avoid a memory leak. QPtrList had the concept of a "current item", which could be used for traversing the list without using an iterator. When porting to Qt 4, you can use the Java-style QListIterator (or QMutableListIterator) class instead. The following table summarizes the API differences: \table \header \o QPtrList function \o QListIterator equivalent \row \o QPtrList::at() \o N/A \row \o QPtrList::current() \o QMutableListIterator::value() \row \o QPtrList::currentNode() \o N/A \row \o QPtrList::findNext(const T *) \o QListIterator::findNext(const T *) \row \o QPtrList::findNextRef(const T *) \o QListIterator::findNext(const T *) \row \o QPtrList::first() \o QPtrList::toFront() \row \o QPtrList::last() \o QPtrList::toBack() \row \o QPtrList::next() \o QPtrList::next() \row \o QPtrList::prev() \o QPtrList::previous() \row \o QPtrList::remove() \o QMutableListIterator::remove() \row \o QPtrList::take() \o QMutableListIterator::remove() \endtable Be aware that QListIterator has a different way of iterating than QPtrList. A typical loop with QPtrList looks like this: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 34 Here's the equivalent QListIterator loop: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 35 Finally, QPtrListIterator must also be ported. There are no fewer than four iterator classes that can be used as a replacement: QList::const_iterator, QList::iterator, QListIterator, and QMutableListIterator. The most straightforward class to use when porting is QMutableListIterator (if you modify the list through the iterator) or QListIterator (if you don't). The following table summarizes the API differences: \table \header \o QPtrListIterator function \o Qt 4 equivalent \row \o QPtrListIterator::atFirst() \o !QListIterator::hasPrevious() (notice the \c{!}) \row \o QPtrListIterator::atLast() \o !QListIterator::hasNext() (notice the \c{!}) \row \o QPtrListIterator::count() \o QList::count() or QList::size() \row \o QPtrListIterator::current() \o QMutableListIterator::value() \row \o QPtrListIterator::isEmpty() \o QList::isEmpty() \row \o QPtrListIterator::toFirst() \o QListIterator::toFront() \row \o QPtrListIterator::toLast() \o QListIterator::toBack() \row \o QPtrListIterator::operator() \o QMutableListIterator::value() \row \o QPtrListIterator::operator*() \o QMutableListIterator::value() \endtable Again, be aware that QListIterator has a different way of iterating than QPtrList. A typical loop with QPtrList looks like this: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 36 Here's the equivalent QListIterator loop: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 37 Finally, QPtrListStdIterator must also be ported. This is easy, because QList also provides STL-style iterators (QList::iterator and QList::const_iterator). \section1 QPtrQueue QPtrQueue has been moved to the Qt3Support library. It has been replaced by the more modern QQueue class. The following table summarizes the differences between QPtrQueue and QQueue: \table \header \o QPtrQueue function \o QQueue equivalent \row \o QPtrQueue::autoDelete() \o See discussion below \row \o QPtrQueue::count() \o QQueue::count() or QQueue::size() (equivalent) \row \o QPtrQueue::current() \o QQueue::head() \row \o QPtrQueue::remove() \o QQueue::dequeue() \row \o QPtrQueue::setAutoDelete() \o See discussion below \endtable If you use QPtrQueue's auto-delete feature (by calling QPtrQueue::setAutoDelete(true)), you need to do some more work. You have two options: Either you call \c delete yourself whenever you remove an item from the container, or you can use QQueue instead of QQueue (i.e. store values directly instead of pointers to values). Here, we will show when to call \c delete. \omit (See \l{What's Wrong with Auto-Delete} for an explanation of why the Qt 4 containers don't offer that feature.) \endomit \table \header \o QPtrQueue idiom \o QQueue idiom \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 38 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 39 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 40 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 41 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 42 (also called from QPtrQueue's destructor) \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 43 In 99% of cases, the following idiom also works: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 44 However, it may lead to crashes if \c queue is referenced from the value type's destructor, because \c queue contains dangling pointers until clear() is called. \endtable \section1 QPtrStack QPtrStack has been moved to the Qt3Support library. It has been replaced by the more modern QStack class. The following table summarizes the differences between QPtrStack and QStack: \table \header \o QPtrStack function \o QStack equivalent \row \o QPtrStack::autoDelete() \o See discussion below \row \o QPtrStack::count() \o QStack::count() or QStack::size() (equivalent) \row \o QPtrStack::current() \o QStack::top() \row \o QPtrStack::remove() \o QStack::pop() \row \o QPtrStack::setAutoDelete() \o See discussion below \endtable If you use QPtrStack's auto-delete feature (by calling QPtrStack::setAutoDelete(true)), you need to do some more work. You have two options: Either you call \c delete yourself whenever you remove an item from the container, or you can use QStack instead of QStack (i.e. store values directly instead of pointers to values). Here, we will show when to call \c delete. \omit (See \l{What's Wrong with Auto-Delete} for an explanation of why the Qt 4 containers don't offer that feature.) \endomit \table \header \o QPtrStack idiom \o QStack idiom \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 45 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 46 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 47 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 48 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 49 (also called from QPtrStack's destructor) \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 50 In 99% of cases, the following idiom also works: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 51 However, it may lead to crashes if \c stack is referenced from the value type's destructor, because \c stack contains dangling pointers until clear() is called. \endtable \section1 QPtrVector QPtrVector has been moved to Qt3Support. It has been replaced by the more modern QVector class. When porting to Qt 4, you can use QVector as an alternative to QPtrVector. The APIs of QPtrVector and QVector are somewhat similar. The main issue is that QPtrVector supports auto-delete whereas QVector doesn't. \omit (See \l{What's Wrong with Auto-Delete} for an explanation of why the Qt 4 containers don't offer that feature.) \endomit The following table summarizes the API differences between the two classes: \table \header \o QPtrVector function \o QVector equivalent \row \o QPtrVector::autoDelete() \o See discussion below \row \o QPtrVector::bsearch(const T *) \o \l qBinaryFind() \row \o QPtrVector::contains(const T *) \o QVector::count(T *) \row \o QPtrVector::containsRef(const T *) \o QVector::count(T *) \row \o QPtrVector::count() \o See remark below \row \o QPtrVector::insert(uint, T *) \o See remark below \row \o QPtrVector::isNull() \o N/A \row \o QPtrVector::remove(uint) \o See remark below \row \o QPtrVector::setAutoDelete() \o See discussion below \row \o QPtrVector::sort() \o \l qSort() \row \o QPtrVector::take(uint) \o See remark below \row \o QPtrVector::toList(QGList *) \o QList::QList(const QVector &) \endtable Remarks: \list 1 \o QPtrVector::insert(uint, T *) sets an item to store a certain pointer value. This is \e not the same as QVector::insert(int, T *), which creates space for the item by moving following items by one position. Use \c{vect[i] = ptr} to set a QVector item to a particular value. \o QPtrVector::remove(uint) sets an item to be 0. This is \e not the same as QVector::removeAt(int), which entirely erases the item, reducing the size of the vector. Use \c{vect[i] = 0} to set a QVector item to 0. \o Likewise, QPtrVector::take(uint) sets an item to be 0 and returns the previous value of the item. Again, this is easy to achieve using QVector::operator[](). \o QPtrVector::count() returns the number of non-null items in the vector, whereas QVector::count() (like QVector::size()) returns the number of items (null or non-null) in the vector. Fortunately, it's not too hard to simulate QPtrVector::count(). \oldcode int numValidItems = vect.count(); \newcode int numValidItems = vect.size() - vect.count(0); \endcode \endlist If you use QVector's auto-delete feature (by calling QVector::setAutoDelete(true)), you need to do some more work. You have two options: Either you call \c delete yourself whenever you remove an item from the container, or you use QVector instead of QVector (i.e. store values directly instead of pointers to values). Here, we'll see when to call \c delete. The following table summarizes the idioms that you need to watch out for if you want to call \c delete yourself. \table \header \o QPtrVector idiom \o QVector idiom \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 52 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 53 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 54 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 55 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 56 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 57 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 58 \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 59 \row \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 60 (also called from QPtrVector's destructor) \o \snippet doc/src/snippets/code/doc_src_porting4.qdoc 61 In 99% of cases, the following idiom also works: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 62 However, it may lead to crashes if \c vect is referenced from the value type's destructor, because \c vect contains dangling pointers until clear() is called. \endtable Be aware that QPtrVector's destructor automatically calls clear(). If you have a QPtrVector data member in a custom class and use the auto-delete feature, you will need to call \c delete on all the items in the container from your class destructor to avoid a memory leak. \section1 QPushButton See \l{#properties}{Properties} for a list of QPushButton properties in Qt 3 that have changed in Qt 4. \section1 QRangeControl In Qt 3, various "range control" widgets (QDial, QScrollBar, QSlider, and QSpin) inherited from both QWidget and \c QRangeControl. In Qt 4, \c QRangeControl has been replaced with the new QAbstractSlider and QAbstractSpinBox classes, which inherit from QWidget and provides similar functionality. Apart from eliminating unnecessary multiple inheritance, the new design allows QAbstractSlider to provide signals, slots, and properties. The old \c QRangeControl class has been renamed Q3RangeControl and moved to the Qt3Support library, together with the (undocumented) \c QSpinWidget class. If you use \c QRangeControl as a base class in your application, you can switch to use QAbstractSlider or QAbstractSpinBox instead. \oldcode class VolumeControl : public QWidget, public QRangeControl { ... protected: void valueChange() { update(); emit valueChanged(value()); } void rangeChange() { update(); } void stepChange() { update(); } }; \newcode class VolumeControl : public QAbstractSlider { ... protected: void sliderChange(SliderChange change) { update(); if (change == SliderValueChange) emit valueChanged(value()); } }; \endcode \section1 QRegExp The search() and searchRev() functions have been renamed to indexIn() and lastIndexIn() respectively. \section1 QRegion The following changes have been made to QRegion in Qt 4: \list \o There is no longer any difference between a \e null region and an \e empty region. Use isEmpty() in most places where you would have used a null QRegion. \o QRegion::rects() used to return a QMemArray. It now returns a QVector. \endlist \section1 QScrollBar See \l{#properties}{Properties} for a list of QScrollBar properties in Qt 3 that have changed in Qt 4. \section1 QScrollView The \c QScrollView class has been renamed Q3ScrollView and moved to the Qt3Support library. It has been replaced by the QAbstractScrollArea and QScrollArea classes. Note that Qt 4 in general uses the QScrollArea::widget() function where Qt 3 used QScrollView::viewport(). The rationale for this is that it is no longer possible to draw directly on a scroll area. The QScrollArea::widget() function returns the widget set on the scroll area. \c QScrollView was designed to work around the 16-bit limitation on widget coordinates found on most window systems. In Qt 4, this is done transparently for \e all widgets, so there is no longer a need for such functionality in \c QScrollView. For that reason, the new QAbstractScrollArea and QScrollArea classes are much more lightweight, and concentrate on handling scroll bars. \section1 QServerSocket The \c QServerSocket class has been renamed Q3ServerSocket and moved to the Qt3Support library. In Qt 4, it has been replaced by QTcpServer. With Q3ServerSocket, connections are accepted by reimplementing a virtual function (Q3ServerSocket::newConnection()). With QTcpServer, on the other hand, you don't need to subclass. Instead, simply connect to the QTcpServer::newConnection() signal. \section1 QSettings The QSettings class has been rewritten to be more robust and to respect existing standards (e.g., the INI file format). The API has also been extensively revised. The old API is still provided when Qt 3 support is enabled. Since the format and location of settings have changed between Qt 3 and Qt 4, the Qt 4 version of your application won't recognize settings written using Qt 3. \section1 QShared The \c QShared class has been obsoleted by the more powerful QSharedData and QSharedDataPointer as a means of creating custom implicitly shared classes. It has been renamed Q3Shared and moved to the Qt3Support library. An easy way of porting to Qt 4 is to include this class into your project and to use it instead of \c QShared: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 63 If possible, we recommend that you use QSharedData and QSharedDataPointer instead. They provide thread-safe reference counting and handle all the reference counting behind the scenes, eliminating the risks of forgetting to increment or decrement the reference count. \section1 QSignal The QSignal class has been renamed to Q3Signal and moved to the Qt3Support library. The preferred approach is to create your own QObject subclass with a signal that has the desired signature. Alternatively, you can call QMetaObject::invokeMethod() if you want to invoke a slot. \section1 QSimpleRichText QSimpleRichText has been obsoleted by QTextDocument. It has been renamed Q3SimpleRichText and moved to the Qt3Support library. Previously, you would do the following with Q3SimpleRichText: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 63a However, with QTextDocument, you use the following code instead: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 63b See \l{Rich Text Processing} for an overview of the Qt 4 rich text classes. \section1 QSlider The QSlider::sliderStart() and QSlider::sliderRect() functions have been removed. The slider's rect can now be retrieved using the code snippet below: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 63c In addition, the direction of a vertical QSlider has changed, i.e. the bottom is now the minimum, and the top the maximum. You can use the QAbstractSlider::invertedAppearance property to control this behavior. See \l{#properties}{Properties} for a list of QSlider properties in Qt 3 that have changed in Qt 4. \section1 QSocket The \c QSocket class has been renamed Q3Socket and moved to the Qt3Support library. In Qt 4, it has been replaced by the QTcpSocket class, which inherits most of its functionality from QAbstractSocket. \section1 QSocketDevice The \c QSocketDevice class has been renamed Q3SocketDevice and moved to the Qt3Support library. In Qt 4, there is no direct equivalent to Q3SocketDevice: \list \o If you use Q3SocketDevice in a thread to perform blocking network I/O (a technique encouraged by the \e{Qt Quarterly} article \l{http://doc.qt.nokia.com/qq/qq09-networkthread.html} {Unblocking Networking}), you can now use QTcpSocket, QFtp, or QNetworkAccessManager, which can be used from non-GUI threads. \o If you use Q3SocketDevice for UDP, you can now use QUdpSocket instead. \o If you use Q3SocketDevice for other uses, Qt 4 offers no alternative right now. However, there is a \c QAbstractSocketEngine internal class that offers a low-level socket API similar to Q3SocketDevice. Should the need for such functionality arise in Qt 4 applications, we will consider making this class public in a future release. \endlist \section1 QSortedList The QSortedList class has been deprecated since Qt 3.0. In Qt 4, it has been moved to the Qt3Support library. In new code, we recommend that you use QList instead and use \l qSort() to sort the items. \section1 QSplitter The function setResizeMode() has been moved into Qt3Support. Set the stretch factor in the widget's size policy to get equivalent functionality. The obsolete function drawSplitter() has been removed. Use QStyle::drawPrimitive() to acheive similar functionality. \section1 QSpinBox See \l{#properties}{Properties} for a list of QSpinBox properties in Qt 3 that have changed in Qt 4. \section1 QSqlCursor The \c QSqlCursor class has been renamed Q3SqlCursor and moved to the Qt3Support library. In Qt 4, you can use QSqlQuery, QSqlQueryModel, or QSqlTableModel, depending on whether you want a low-level or a high-level interface for accessing databases. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QSqlDatabase QSqlDatabase is now a smart pointer that is passed around by value. Simply replace all QSqlDatabase pointers by QSqlDatabase objects. \section1 QSqlEditorFactory The \c QSqlEditorFactory class has been renamed Q3SqlEditorFactory and moved to Qt3Support. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QSqlError The enum \c{Type} was renamed to \c{ErrorType}, The values were renamed as well: \list \o None - use NoError instead \o Connection - use ConnectionError instead \o Statement - use StatementError instead \o Transaction - use TransactionError instead \o Unknown - use UnknownError instead \endlist \section1 QSqlFieldInfo The QSqlFieldInfo class has been moved to Qt3Support. Its functionality is now provided by the QSqlField class. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QSqlForm The \c QSqlForm class has been renamed Q3SqlForm and moved to the Qt3Support library. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QSqlPropertyMap The \c QSqlPropertyMap class has been renamed Q3SqlPropertyMap moved to the Qt3Support library. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QSqlQuery QSqlQuery::prev() was renamed to QSqlQuery::previous(). QSqlQuery::prev() remains, but it just calls previous(). QSqlQuery no longer has any virtual methods, i.e., exec(), value(), seek(), next(), prev(), first(), last(), and the destructor are no longer virtual. \section1 QSqlRecord QSqlRecord behaves like a vector now, QSqlRecord::insert() will actually insert a new field instead of replacing the existing one. \section1 QSqlRecordInfo The QSqlRecordInfo class has been moved to Qt3Support. Its functionality is now provided by the QSqlRecord class. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QSqlSelectCursor The \c QSqlSelectCursor class has been renamed Q3SqlSelectCursor and moved to the Qt3Support library. See \l{QtSql Module} for an overview of the new SQL classes. \section1 QStoredDrag The \c QStoredDrag class has been renamed Q3StoredDrag and moved to the Qt3Support library. In Qt 4, use QMimeData instead and call QMimeData::setData() to set the data. See \l{Porting to Qt 4 - Drag and Drop} for a comparison between the drag and drop APIs in Qt 3 and Qt 4. \section1 QStr(I)List The QStrList and QStrIList convenience classes have been deprecated since Qt 2.0. In Qt 4, they have been moved to the Qt3Support library. If you used any of these, we recommend that you use QStringList or QList instead. \section1 QStr(I)Vec The QStrVec and QStrIVec convenience classes have been deprecated since Qt 2.0. In Qt 4, they have been moved to Qt3Support. If you used any of these, we recommend that you use QStringList or QList instead. \section1 QString Here are the main issues to be aware of when porting QString to Qt 4: \list 1 \o The QString::QString(QChar) constructor performed implicit conversion in Qt 3. Now, you will need a cast to convert a QChar to a QString. \o The QString::QString(const QByteArray &) constructor used to stop at the first '\\0' it encountered, for compatibility with Qt 1. This quirk has now been fixed; in Qt 4, the resulting QString always has the same length as the QByteArray that was passed to the constructor. \o The QString::null static constant has been deprecated in Qt 4. For compatibility, Qt 4 provides a QString::null symbol that behaves more or less the same as the old constant. The new idiom is to write QString() instead of QString::null, or to call clear(). \oldcode str1 = QString::null; if (str2 == QString::null) do_something(QString::null); \newcode str1.clear(); if (str2.isNull()) do_something(QString()); \endcode In new code, we recommend that you don't rely on the distinction between a null string and a (non-null) empty string. See \l{Distinction Between Null and Empty Strings} for details. \o QString::latin1() and QString::ascii() have been replaced with QString::toLatin1() and QString::toAscii(), which return a QByteArray instead of a (non-reentrant) \c{const char *}. For consistency, QString::utf8() and QString::local8Bit(), which already returned a QByteArray (actually a \c QCString), have been renamed QString::toUtf8() and QString::toLocal8Bit(). To obtain a \c{const char *} pointer to ASCII or Latin-1 data, use QString::toAscii() or QString::toLatin1() to obtain a QByteArray containing the data, then call QByteArray::constData() to access the character data directly. Note that the pointer returned by this function is only valid for the lifetime of the byte array; you should avoid taking a pointer to the data contained in temporary objects. \snippet doc/src/snippets/code/doc_src_porting4.qdoc 64 In the above example, the \c goodData pointer is valid for the lifetime of the \c asciiData byte array. If you need to keep a copy of the data in a non-Qt data structure, use standard C memory allocation and string copying functions to do so \e before destroying the byte array. \o QString::at() returned a non-const reference, whereas the new QString::at() returns a const value. Code like \snippet doc/src/snippets/code/doc_src_porting4.qdoc 65 will no longer compile. Instead, use QString::operator[]: \snippet doc/src/snippets/code/doc_src_porting4.qdoc 66 \o The QString::contains(\e x) function (where \e x is a character or a string) has been renamed QString::count(\e x). In addition, there now exists a set of QString::contains() functions that returns a boolean value. Replace old calls to contains() with either count() or contains(), depending on whether you care about the specific number of occurrences of a character in the string or only care about whether the string contains that character or not. \o Many functions in QString had a \c bool parameter that specified case sensitivity. In Qt 4, in the interest of code readability and maintainability, the \c bool parameters have been replaced by the Qt::CaseSensitivity enum, which can take the values Qt::CaseSensitive and Qt::CaseInsensitive. \oldcode if (url.startsWith("http:", false)) ... \newcode if (url.startsWith("http:", Qt::CaseInsensitive)) ... \endcode \o The QString::setExpand(uint, QChar) function, which already was obsolete in Qt 3, is no longer available. Use QString::operator[] instead. \oldcode str.setExpand(32, '$'); \newcode str[32] = '$'; \endcode \o The \c QT_NO_ASCII_CAST and \c QT_NO_CAST_ASCII macros have been renamed \c QT_NO_CAST_TO_ASCII and \c QT_NO_CAST_FROM_ASCII, respectively. \o The QString::data() used to return the same as QString::ascii(). It now returns a pointer to the Unicode data stored in the QString object. Call QString::ascii() if you want the old behavior. \o QString::arg() now converts two-digit place markers, allowing up to 99 place markers to be used in any given string. \o Comparisons between QStrings and \c NULL in order to determine whether strings are empty are no longer allowed. Use \l{QString::}{isEmpty()} instead. \endlist \section1 QStringList QStringList now inherits from QList and can no longer be converted to a QValueList. Since QValueList inherits QList a cast will work as expected. This change implies some API incompatibilities for QStringList. For example, at() returns the string, not an iterator. See the \l{#qvaluelist.section}{section on QValueList} for details. The static QStringList::split() function for splitting strings into lists of smaller strings has been replaced by QString::split(), which returns a QStringList. \section1 QStyle The QStyle API has been overhauled and improved. Most of the information on why this change was done is described in \l{The Qt 4 Style API}{the QStyle overview}. Since QStyle is mostly used internally by Qt's widgets and styles and since it is not essential to the good functioning of an application, there is no compatibility path. This means that we have changed many enums and functions and the qt3to4 porting tool will not change much in your qstyle code. To ease the pain, we list some of the major changes here. QStyleOption has taken on a more central role and is no longer an optional argument, please see the QStyleOption documentation for more information. The QStyle::StyleFlags have been renamed QStyle::StateFlags and are now prefixed State_ instead of Style_, in addition the Style_ButtonDefault flag has moved to QStyleOptionButton. The QStyle::PrimitiveElement enumeration has undergone extensive change. Some of the enums were moved to QStyle::ControlElement, some were removed and all were renamed. This renaming is not done by the qt3to4 porting tool, so you must do it yourself. The table below shows how things look now. \table \header \o Old name \o New name \o Remark \row \o \c PE_ButtonCommand \o QStyle::PE_PanelButtonCommand \row \o \c PE_ButtonDefault \o QStyle::PE_FrameDefaultButton \row \o \c PE_ButtonBevel \o QStyle::PE_PanelButtonBevel \row \o \c PE_ButtonTool \o QStyle::PE_PanelButtonTool \row \o \c PE_ButtonDropDown \o QStyle::PE_IndicatorButtonDropDown \row \o \c PE_FocusRect \o QStyle::PE_FrameFocusRect \row \o \c PE_ArrowUp \o QStyle::PE_IndicatorArrowUp \row \o \c PE_ArrowDown \o QStyle::PE_IndicatorArrowDown \row \o \c PE_ArrowRight \o QStyle::PE_IndicatorArrowRight \row \o \c PE_ArrowLeft \o QStyle::PE_IndicatorArrowLeft \row \o \c PE_SpinBoxUp \o QStyle::PE_IndicatorSpinUp \row \o \c PE_SpinBoxDown \o QStyle::PE_IndicatorSpinDown \row \o \c PE_SpinBoxPlus \o QStyle::PE_IndicatorSpinPlus \row \o \c PE_SpinBoxMinus \o QStyle::PE_IndicatorSpinMinus \row \o \c PE_SpinBoxSlider \o QStyle::CE_SpinBoxSlider \o uses QStyle::drawControl() \row \o \c PE_Indicator \o QStyle::PE_IndicatorCheckBox \row \o \c PE_IndicatorMask \o N/A \o use QStyle::styleHint() to retrieve mask \row \o \c PE_ExclusiveIndicator \o QStyle::PE_IndicatorRadioButton \row \o \c PE_ExclusiveIndicatorMask \o N/A \o use QStyle::styleHint() to retrieve mask \row \o \c PE_DockWindowHandle \o QStyle::PE_IndicatorToolBarHandle \row \o \c PE_DockWindowSeparator \o QStyle::PE_Q3DockWindowSeparator \row \o \c PE_DockWindowResizeHandle \o QStyle::PE_IndicatorDockWindowResizeHandle \row \o \c PE_DockWindowTitle \o QStyle::CE_DockWindowTitle \o uses QStyle::drawControl() \row \o \c PE_Splitter \o QStyle::CE_Splitter \o uses QStyle::drawControl() \row \o \c PE_Panel \o QStyle::PE_Frame \row \o \c PE_PanelMenu \o QStyle::PE_FrameMenu \row \o \c PE_PanelMenuBar \o QStyle::PE_PanelMenuBar \row \o \c PE_PanelDockWindow \o QStyle::PE_FrameDockWindow \row \o \c PE_TabBarBase \o QStyle::PE_FrameTabBarBase \row \o \c PE_HeaderSection \o QStyle::CE_HeaderSection \o uses QStyle::drawControl() \row \o \c PE_HeaderArrow \o QStyle::PE_IndicatorHeaderArrow \row \o \c PE_StatusBarSection \o QStyle::PE_FrameStatusBar \row \o \c PE_Separator \o QStyle::PE_Q3Separator \row \o \c PE_SizeGrip \o QStyle::CE_SizeGrip \o uses QStyle::drawControl() \row \o \c PE_CheckMark \o QStyle::PE_IndicatorMenuCheckMark \row \o \c PE_ScrollBarAddLine \o QStyle::CE_ScrollBarAddLine \o uses QStyle::drawControl() \row \o \c PE_ScrollBarSubLine \o QStyle::CE_ScrollBarSubLine \o uses QStyle::drawControl() \row \o \c PE_ScrollBarAddPage \o QStyle::CE_ScrollBarAddPage \o uses QStyle::drawControl() \row \o \c PE_ScrollBarSubPage \o QStyle::CE_ScrollBarSubPage \o uses QStyle::drawControl() \row \o \c PE_ScrollBarSlider \o QStyle::CE_ScrollBarSlider \o uses QStyle::drawControl() \row \o \c PE_ScrollBarFirst \o QStyle::CE_ScrollBarFirst \o uses QStyle::drawControl() \row \o \c PE_ScrollBarLast \o QStyle::CE_ScrollBarLast \o uses QStyle::drawControl() \row \o \c PE_ProgressBarChunk \o QStyle::PE_IndicatorProgressChunk \row \o \c PE_PanelLineEdit \o QStyle::PE_FrameLineEdit \row \o \c PE_PanelTabWidget \o QStyle::PE_FrameTabWidget \row \o \c PE_WindowFrame \o QStyle::PE_FrameWindow \row \o \c PE_CheckListController \o QStyle::PE_Q3CheckListController \row \o \c PE_CheckListIndicator \o QStyle::PE_Q3CheckListIndicator \row \o \c PE_CheckListExclusiveIndicator \o QStyle::PE_Q3CheckListExclusiveIndicator \row \o \c PE_PanelGroupBox \o QStyle::PE_FrameGroupBox \row \o \c PE_TreeBranch \o QStyle::PE_IndicatorBranch \row \o \c PE_RubberBand \o QStyle::CE_RubberBand \o uses QStyle::drawControl() \row \o \c PE_PanelToolBar \o QStyle::PE_PanelToolBar \row \o \c PE_ToolBarHandle \o QStyle::PE_IndicatorToolBarHandle \row \o \c PE_ToolBarSeparator \o QStyle::PE_IndicatorToolBarSeparator \endtable The QStyle::drawControlMask() and QStyle::drawComplexControlMask() functions have been removed. They are replaced with a style hint. The QStyle::drawItem() overloads that took both a pixmap and a string have been removed. Use QStyle::drawItemText() and QStyle::drawItemPixmap() directly. The QStyle::itemRect() overload that took both a pixmap and a string is also removed, use either QStyle::itemTextRect() or QStyle::itemPixmapRect() instead. \section1 QStyleSheet The QStyleSheet and QStyleSheetItem classes have been renamed Q3StyleSheet and Q3StyleSheetItem, and have been moved to the Qt3Support library. See \l{Rich Text Processing} for an overview of the Qt 4 rich text classes, and \l{Qt Style Sheets} for a description of CSS-like style sheet support in Qt 4.2 and above. \section1 QSyntaxHighlighter The \c QSyntaxHighlighter class from Qt 3 has been renamed Q3SyntaxHighlighter and moved to the Qt3Support library. Since Qt 4.1, it has been replaced by a new QSyntaxHighlighter class based on Qt 4's new rich text engine. \section1 QTabBar See \l{#properties}{Properties} for a list of QTabBar properties in Qt 3 that have changed in Qt 4. \section1 QTabDialog The \c QTabDialog class is no longer part of the public Qt API. It has been renamed Q3TabDialog and moved to Qt3Support. In Qt 4 applications, you can easily obtain the same result by combining a QTabWidget with a QDialog and provide \l{QPushButton}s yourself. See also the \l{dialogs/tabdialog} example, which shows how to implement tab dialogs in Qt 4. \section1 QTabWidget See \l{#properties}{Properties} for a list of QTabWidget properties in Qt 3 that have changed in Qt 4. \section1 QTable The \c QTable, \c QTableItem, \c QComboTableItem, \c QCheckTableItem, and \c QTableSelection classes have been renamed Q3Table, Q3TableItem, Q3ComboTableItem, Q3CheckTableItem, and Q3TableSelection and moved to the Qt3Support library. New Qt applications should use the new QTableWidget or QTableView class instead. Some of these classes behave differently with respect to the way they handle \c NULL pointers. For example, Q3TableItem::setPixmap() no longer accepts \c NULL or 0 to indicate that the item should contain a null pixmap; in this case, a null pixmap should be constructed and passed explicitly to the function. See \l{Model/View Programming} for an overview of the new item view classes. \section1 QTextCodec The loadCharmap() and loadCharmapFromFile() functions are no longer available in Qt 4. You need to create your own codec if you want to create a codec based on a POSIX2 charmap definition. \section1 QTextDrag The \c QTextDrag class has been renamed Q3TextDrag and moved to the Qt3Support library. In Qt 4, use QMimeData instead and call QMimeData::setText() to set the data. See \l{Porting to Qt 4 - Drag and Drop} for a comparison between the drag and drop APIs in Qt 3 and Qt 4. \section1 QTextEdit The old QTextEdit and QTextBrowser classes have been renamed Q3TextEdit and Q3TextBrowser, and have been moved to Qt3Support. The new QTextEdit and QTextBrowser have a somewhat different API. The \c QTextEdit::setWrapPolicy() function has been renamed to \l{QTextEdit::setWordWrapMode()}{setWordWrapMode()} and the \c QTextEdit::setWrapColumnOrWidth() function has been renamed to \l{QTextEdit::setLineWrapColumnOrWidth()} {setLineWrapColumnOrWidth()}. The Q3TextEdit::setWrapPolicy() and Q3TextEdit::setWrapColumnOrWidth() still provide this functionality in the Q3TextEdit class. See \l{Rich Text Processing} for an overview of the Qt 4 rich text classes. \section1 QTextIStream The QTextIStream convenience class is no longer provided in Qt 4. Use QTextStream directly instead. \section1 QTextOStream The QTextOStream convenience class is no longer provided in Qt 4. Use QTextStream directly instead. \section1 QTextOStreamIterator The undocumented \c QTextOStreamIterator class has been removed from the Qt library. If you need it in your application, feel free to copy the source code from the Qt 3 \c header file. \section1 QTextStream QTextStream has undergone a number of API and implementation enhancements, and some of the changes affect QTextStream's behavior: \list \o QTextStream now uses buffered writing, which means that you need to call QTextStream::flush(), or use the streaming manipulators \c endl or \c flush if you need QTextStream to flush its write buffer. The stream is flushed automatically if QTextStream is deleted or when the device is closed. \o QTextStream now uses buffered reading, so if you read a line from the stream, QTextStream will read as much as it can from the device to fill up its internal read buffer. This speeds up reading significantly, but Qt 3 code that mixed QTextStream access and direct device access may need to be updated. \o While QTextStream in Qt 3 always translated end-of-line characters from Windows style ("\\r\\n") to Unix style ("\\n") on Windows, QTextStream in Qt 4 only does this on devices opened with the \c{QIODevice::Text} mode (formerly \c{IO_Translate}). \endlist Note that when using a QTextStream on a QFile in Qt 4, calling QIODevice::reset() on the QFile will not have the expected result because QTextStream now buffers the file. Use the QTextStream::seek() function instead. \section1 QTextView The \c QTextView class has been renamed Q3TextView and moved to the Qt3Support library. \section1 QTimeEdit The QTimeEdit class in Qt 4 is a convenience class based on QDateTimeEdit. The old class has been renamed Q3TimeEdit and moved to the Qt3Support library. See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for a list of \c QTimeEdit virtual member functions in Qt 3 that are no longer virtual in Qt 4. \section1 QTimer Windows restricts the granularity of timers, but starting with Qt 4, we emulate a finer time resolution. On Windows XP we use the multimedia timer API, which gives us 1 millisecond resolution for QTimer. Note that Windows 2000 has a lower timer resolution, and that code relying on underlying system timer restrictions encounters no such limitations using Qt 4 (e.g., setting an interval of 0 millisecond results in Qt occupying all of the processor time when no GUI events need processing). \section1 QToolBar The old \c QToolBar class, which worked with the old \c QMainWindow and \c QDockArea classes and inherited from \c QDockWindow, has been renamed Q3ToolBar and moved to Qt3Support. Note that, when using Q3ToolBar, the toolbar's actions must be \l {Q3Action}s. Use the new QToolBar class in new applications. \note \l{Q3ToolBar}'s \l{Q3DockWindow::setHorizontallyStretchable()}{horizontallyStretchable} property can be achieved in QToolBar with \l{QWidget#Size Hints and Size Policies}{size policies}. \section1 QToolButton See \l{#properties}{Properties} for a list of QToolButton properties in Qt 3 that have changed in Qt 4. Note that many of the properties that could previously be set in the constructor must now be set separately. \section1 QToolTip The QToolTip::setGloballyEnabled() function no longer exists. Tooltips can be disabled by \l{QObject::installEventFilter()}{installing an event filter} on qApp (the unique QApplication object) to block events of type QEvent::ToolTip. \section1 QUriDrag The \c QUriDrag class has been renamed Q3UriDrag and moved to the Qt3Support library. In Qt 4, use QMimeData instead and call QMimeData::setUrl() to set the URL. See \l{Porting to Qt 4 - Drag and Drop} for a comparison between the drag and drop APIs in Qt 3 and Qt 4. \section1 QUrl The QUrl class has been rewritten from scratch in Qt 4 to be more standard-compliant. The old QUrl class has been renamed Q3Url and moved to the Qt3Support library. The new QUrl class provides an extensive list of compatibility functions to ease porting from Q3Url to QUrl. A few functions require you to change your code: \list \o Q3Url::Q3Url(const Q3Url &, const QString &, bool) can be simulated by combining the URLs manually (using QString::operator+(), for example). \o Q3Url::setEncodedPathAndQuery(const QString &) is replaced by QUrl::setPath() and QUrl::setEncodedQuery(). \o Q3Url::encodedPathAndQuery() is replaced by QUrl::path() and QUrl::encodedQuery(). \o Q3Url::isLocalFile() can be simulated by checking that QUrl::protocol() is "file". \o Q3Url::toString(bool, bool) is replaced by QUrl::toString(int), where the \c int parameter specifies a combination of \l{QUrl::FormattingOptions}{formatting options}. \endlist \section1 QUrlOperator The \c QUrlOperator class is no longer part of the public Qt API. It has been renamed Q3UrlOperator and moved to Qt3Support. From Qt 4.4, the Network Access API provides a subset of the features provided by \c QUrlOperator that are mostly intended for use with applications that use the HTTP and FTP protocols. See the QNetworkRequest, QNetworkReply, and QNetworkAccessManager documentation for further details. \target qvaluelist.section \section1 QValueList The QValueList class has been replaced by QList and QLinkedList in Qt 4. As a help when porting older Qt applications, the Qt3Support library contains a QValueList class implemented in terms of the new QLinkedList. Similarly, it contains QValueListIterator and QValueListConstIterator classes implemented in terms of QLinkedList::iterator and QLinkedList::const_iterator. When porting to Qt 4, you have the choice of using QList or QLinkedList as alternatives to QValueList. QList has an index-based API and provides very fast random access (QList::operator[]), whereas QLinkedList has an iterator-based API. Here's a list of problem functions: \list \o QValueList(const std::list &) doesn't exist in QList or QLinkedList. You can simulate it by calling \l{QLinkedList::append()}{append()} in a loop. \o QValueList::insert(iterator, size_type, const T& x) doesn't exist in QList or QLinkedList. Call \l{QLinkedList::insert()}{insert()} repeatedly instead. \o QValueList::fromLast() doesn't exist in QList or QLinkedList. Use QValueList::end() instead. \oldcode for (QValueList::iterator i = list.fromLast(); i != list.begin(); --i) do_something(*i); \newcode QLinkedList::iterator i = list.end(); while (i != list.begin()) { --i; // decrement i before using it do_something(*i); } \endcode \o QValueList::append() and QValueList::prepend() return an iterator to the inserted item. QList's and QLinkedList's corresponding functions don't, but it's not a problem because QValueList::prepend() always returns begin() and append() always returns QValueList::end() - 1. \o QValueList::at(\e i) return an iterator to the item at index \e i. This corresponds to QList::begin() + \e i. \o QValueList::contains(const T &) corresponds to QList::count(const T &) and QLinkedList::count(const T &). \endlist \section1 QValueVector The QValueVector class has been replaced by QVector in Qt 4. As a help when porting older Qt applications, the Qt3Support library contains a Q3ValueVector class implemented in terms of the new QVector. When porting from QValueVector to QVector, you might run into the following incompatibilities: \list \o QValueVector(const std::vector &) doesn't exist in QVector. You can simulate it by calling QVector::append()} in a loop. \o QValueVector::resize(int, const T &) doesn't exist in QVector. If you want the new items to be initialized with a particular value, use QVector::insert() instead. \o QValueVector::at() on a non-const vector returns a non-const reference. This corresponds to QVector::operator[](). \o Both QValueVector::at() functions have an \e ok parameter of type \c{bool *} that is set to true if the index is within bounds. This functionality doesn't exist in QVector; instead, check the index against QVector::size() yourself. \endlist See \l{Container Classes} for an overview of the Qt 4 container classes. \section1 QVariant Some changes to the rest of the Qt library have implications on QVariant: \list 1 \o The \c QVariant::ColorGroup enum value is defined only if \c QT3_SUPPORT is defined. \o The \c QVariant::IconSet enum value has been renamed QVariant::Icon. \o The \c QVariant::CString enum value is now a synonym for QVariant::ByteArray. \endlist Also, the QVariant(bool, int) constructor has been replaced by QVariant(bool). Old code like QVariant(true, 0) should be replaced with QVariant(true); otherwise, the QVariant(int, void *) overload might accidentally be triggered. Many of QVariant's convenience functions in Qt 3, such as toColor() and toKeySequence(), have been removed to enable QVariant to be part of the QtCore module. QVariant is still able to hold values of these types. Types which are not supported by any of the QVariant constructors can be stored as variants with the QVariant::fromValue() function. Types with no suitable convenience function for unpacking can be retrieved with the QVariant::value() function or passed directly to classes that implement the QVariant() operator. \table \header \o Qt 3 function \o Qt 4 function \input porting/porting4-removedvariantfunctions.qdocinc \endtable See the QVariant::Type enum for a list of types supported by QVariant. \section1 QVBox The \c QVBox class is now only available as Q3VBox in Qt 4. You can achieve the same result as \c QVBox by creating a QWidget with a vertical layout: \oldcode QVBox *vbox = new QVBox; QPushButton *child1 = new QPushButton(vbox); QPushButton *child2 = new QPushButton(vbox); \newcode QWidget *vbox = new QWidget; QPushButton *child1 = new QPushButton; QPushButton *child2 = new QPushButton; QVBoxLayout *layout = new QVBoxLayout; layout->addWidget(child1); layout->addWidget(child2); vbox->setLayout(layout); \endcode Note that child widgets are not automatically placed into the widget's layout; you will need to manually add each widget to the QVBoxLayout. \section1 QVGroupBox The \c QVGroupBox class has been renamed Q3VGroupBox and moved to the Qt3Support library. Qt 4 does not provide a specific replacement class for \c QVGroupBox since QGroupBox is designed to be a generic container widget. As a result, you need to supply your own layout for any child widgets. See \l{#QGroupBox} for more information about porting code that uses group boxes. \section1 QWhatsThis The QWhatsThis class has been redesigned in Qt 4. The old \c QWhatsThis class is available as Q3WhatsThis in Qt3Support. \section1 QWidget Widget background painting has been greatly improved, supporting flicker-free updates and making it possible to have semi-transparent widgets. This renders the following background handling functions obsolete: \list \o QWidget::repaint(bool noErase) - the \c noErase boolean parameter is gone \o QWidget::setBackgroundMode(BackgroundMode m) \o QWidget::backgroundBrush() const \o QWidget::setBackgroundPixmap(const QPixmap &pm) \o QWidget::backgroundPixmap() const \o QWidget::setBackgroundColor(const QColor &c) \o QWidget::backgroundColor() const \o QWidget::foregroundColor() const \o QWidget::eraseColor() const \o QWidget::setEraseColor(const QColor &c) \o QWidget::erasePixmap() const \o QWidget::setErasePixmap(const QPixmap &p) \o QWidget::paletteForegroundColor() \o QWidget::setPaletteForegroundColor(const QColor &c) \o QWidget::paletteBackgroundColor() \o QWidget::setPaletteBackgroundColor(const QColor &c) \o QWidget::paletteBackgroundPixmap() const \o QWidget::setPaletteBackgroundPixmap(const QPixmap &p) \o QWidget::erase() \o QWidget::erase(const QRect &r) \o QWidget::setBackgroundOrigin( BackgroundOrigin ) \o QWidget::BackgroundOrigin backgroundOrigin() const \o QWidget::backgroundOffset() \endlist Sample code on how to do obtain similar behavior from Qt 4, previously handled by some of the above functions can be found in the \l{http://doc.qt.nokia.com/qwidget-qt3.html}{Qt 3 Support Members for QWidget} page. A widget now receives change events in its QWidget::changeEvent() handler. This makes the following virtual change handlers obsolete: \list \o QWidget::styleChange - use QEvent::StyleChange \o QWidget::enabledChange - use QEvent::EnabledChange \o QWidget::paletteChange - use QEvent::PaletteChange \o QWidget::fontChange - use QEvent::FontChange \o QWidget::windowActivationChange - use QEvent::ActivationChange \o QWidget::languageChange - use QEvent::LanguageChange \endlist The following functions were slots, but are no more: \list \o QWidget::clearFocus() \o QWidget::setMouseTracking() \o QWidget::stackUnder(QWidget*) \o QWidget::move(int x, int y) \o QWidget::move(const QPoint &) \o QWidget::resize(int w, int h) \o QWidget::resize(const QSize &) \o QWidget::setGeometry(int x, int y, int w, int h) \o QWidget::setGeometry(const QRect &) \o QWidget::adjustSize() \o QWidget::update(int x, int y, int w, int h) \o QWidget::update(const QRect&) \o QWidget::repaint(bool erase) \o QWidget::repaint(int x, int y, int w, int h, bool erase) \o QWidget::repaint(const QRect &, bool erase) \o QWidget::repaint(const QRegion &, bool erase) \o QWidget::setCaption(const QString &) \o QWidget::setIcon(const QPixmap &) \o QWidget::setIconText(const QString &) \endlist The following functions were incorrectly marked as virtual: \list \o QWidget::close(bool alsoDelete) \o QWidget::create(WId, bool, bool) \o QWidget::destroy(bool) \o QWidget::move(int x, int y) \o QWidget::reparent(QWidget *parent, WFlags, const QPoint &, bool) \o QWidget::resize(int w, int h) \o QWidget::setAcceptDrops(bool on) \o QWidget::setActiveWindow() \o QWidget::setAutoMask(bool) \o QWidget::setBackgroundColor(const QColor &) \o QWidget::setBackgroundMode(BackgroundMode) \o QWidget::setBackgroundOrigin(BackgroundOrigin) \o QWidget::setBackgroundPixmap(const QPixmap &) \o QWidget::setCaption(const QString &) \o QWidget::setCursor(const QCursor &) \o QWidget::setEnabled(bool) \o QWidget::setEraseColor(const QColor &) \o QWidget::setErasePixmap(const QPixmap &) \o QWidget::setFocus() \o QWidget::setFocusPolicy(FocusPolicy) \o QWidget::setFocusProxy(QWidget *) \o QWidget::setFont(const QFont &) \o QWidget::setGeometry(const QRect &) \o QWidget::setGeometry(int x, int y, int w, int h) \o QWidget::setIcon(const QPixmap &) \o QWidget::setIconText(const QString &) \o QWidget::setKeyCompression(bool) \o QWidget::setMask(const QBitmap &) \o QWidget::setMask(const QRegion &) \o QWidget::setMaximumSize(int maxw, int maxh) \o QWidget::setMicroFocusHint(int x, int y, int w, int h, bool, QFont *f) \o QWidget::setMinimumSize(int minw, int minh) \o QWidget::setMouseTracking(bool enable) \o QWidget::setPalette(const QPalette &) \o QWidget::setPaletteBackgroundColor(const QColor &) \o QWidget::setPaletteBackgroundPixmap(const QPixmap &) \o QWidget::setSizeIncrement(int w, int h) \o QWidget::setSizePolicy(QSizePolicy) \o QWidget::setUpdatesEnabled(bool enable) \o QWidget::setWState(uint) \o QWidget::show() \o QWidget::showFullScreen() \o QWidget::showMaximized() \o QWidget::showMinimized() \o QWidget::showNormal() \o QWidget::sizePolicy() \o QWidget::unsetCursor() \endlist The internal clearWState() function was removed. Use QWidget::setAttribute() instead. setWFlags() was renamed QWidget::setWindowFlags(). clearWFlags() has no direct replacement. You can use QWidget::setAttribute() instead. For example, \c{setAttribute(..., false)} to clear an attribute. More information is available \l{http://doc.qt.nokia.com/qwidget.html#setAttribute}{here}. testWFlags() was renamed to \l{QWidget::testAttribute()}{testAttribute()}. See \l{#properties}{Properties} for a list of QWidget properties in Qt 3 that have changed in Qt 4. \section1 QWidgetFactory The \c QWidgetFactory class has been replaced by QFormBuilder in Qt 4. \section1 QWidgetIntDict The QWidgetIntDict class was a synonym for QIntDict. It is no longer available in Qt 4. If you link against Qt3Support, you can use Q3IntDict instead; otherwise, see the \l{#qdict.section}{section on QDict}. \target qwidgetlist.section \section1 QWidgetList In Qt 3, the QWidgetList class was a typedef for QPtrList. In Qt 4, it is a typedef for QList. See the \l{#qptrlist.section}{section on QPtrList}. \section1 QWidgetPlugin The QWidgetPlugin class is no longer available in Qt 4. To create custom widget plugins, subclass QDesignerCustomWidgetInterface to provide information about the custom widget, and build a plugin in the way described in the \l{designer/customwidgetplugin}{Custom Widget Plugin} example. \section1 QWidgetStack The QWidgetStack class is no longer part of the Qt public API. It has been renamed Q3WidgetStack and moved to Qt3Support. In Qt 4 applications, you can use QStackedWidget instead to obtain the same results. \section1 QWizard The \c QWizard class was reintroduced in Qt 4.3. See the \l{Trivial Wizard Example}, \l{License Wizard Example} and \l{Class Wizard Example} for more details. \section1 QWorkspace The \c QWorkspace in Qt 4 class requires explicit adding of MDI windows with QWorkspace::addWindow(). */ /*! \page porting4-virtual-functions.html \title Porting to Qt 4 - Virtual Functions \contentspage {Porting Guides}{Contents} \previouspage Porting to Qt 4 \nextpage Porting to Qt 4 - Drag and Drop \ingroup porting \brief An overview of changes to virtual functions in Qt 4. \section1 Virtual Functions Virtual functions that changed their signature in Qt 4: \table \header \o Qt 3 function signature \o Qt 4 function signature \input porting/porting4-modifiedvirtual.qdocinc \endtable Virtual functions that are not virtual in Qt 4: \table \header \o Qt 3 function \o Comment \input porting/porting4-removedvirtual.qdocinc \endtable */