Documentation: Add \nullptr macro and use where applicable

Qt for Python users reading the documentation assume that int(0) can
be passed for pointer parameters. Use the newly introduced \nullptr to
disambiguate this.

In a follow-up step, the \nullptr macro can be defined as None
when generating the Qt for Python documentation.

Task-number: PYSIDE-903
Change-Id: I3a45f87175a0668ab5f3f95f0aff409f7e3ef027
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
Reviewed-by: Christian Tismer <tismer@stackless.com>
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

doc/global/macros.qdocconf

@@ -14,6 +14,7 @@ macro.macos             = "macOS"
 macro.menu              = "\\b"
 macro.oslash.HTML       = "ø"
 macro.ouml.HTML         = "ö"
+macro.nullptr           = "\\c{nullptr}"
 macro.QA                = "\\e{Qt Assistant}"
 macro.QD                = "\\e{Qt Designer}"
 macro.QL                = "\\e{Qt Linguist}"

src/gui/accessible/qaccessible.cpp

@@ -654,7 +654,7 @@ void QAccessible::removeActivationObserver(ActivationObserver *observer)
 /*!
     If a QAccessibleInterface implementation exists for the given \a object,
     this function returns a pointer to the implementation; otherwise it
-    returns 0.
+    returns \nullptr.
 
     The function calls all installed factory functions (from most
     recently installed to least recently installed) until one is found
@@ -770,7 +770,7 @@ QAccessible::Id QAccessible::uniqueId(QAccessibleInterface *iface)
 /*!
     Returns the QAccessibleInterface belonging to the \a id.
 
-    Returns 0 if the id is invalid.
+    Returns \nullptr if the id is invalid.
 */
 QAccessibleInterface *QAccessible::accessibleInterface(Id id)
 {
@@ -1119,7 +1119,7 @@ QAccessibleInterface *QAccessibleInterface::focusChild() const
     \fn QAccessibleInterface *QAccessibleInterface::childAt(int x, int y) const
 
     Returns the QAccessibleInterface of a child that contains the screen coordinates (\a x, \a y).
-    If there are no children at this position this function returns 0.
+    If there are no children at this position this function returns \nullptr.
     The returned accessible must be a child, but not necessarily a direct child.
 
     This function is only relyable for visible objects (invisible
@@ -1139,7 +1139,7 @@ QAccessibleInterface *QAccessibleInterface::focusChild() const
 
     Returns the QAccessibleInterface of the parent in the accessible object hierarchy.
 
-    Returns 0 if no parent exists (e.g. for the top level application object).
+    Returns \nullptr if no parent exists (e.g. for the top level application object).
 
     \sa child()
 */
@@ -1150,7 +1150,7 @@ QAccessibleInterface *QAccessibleInterface::focusChild() const
     Returns the accessible child with index \a index.
     0-based index. The number of children of an object can be checked with childCount.
 
-    Returns 0 when asking for an invalid child (e.g. when the child became invalid in the meantime).
+    Returns \nullptr when asking for an invalid child (e.g. when the child became invalid in the meantime).
 
     \sa childCount(), parent()
 */
@@ -1356,7 +1356,7 @@ QAccessibleEvent::~QAccessibleEvent()
     \internal
     Returns the uniqueId of the QAccessibleInterface represented by this event.
 
-    In case the object() function returns 0 this is the only way to access the
+    In case the object() function returns \nullptr, this is the only way to access the
     interface.
 */
 QAccessible::Id QAccessibleEvent::uniqueId() const
@@ -1786,7 +1786,7 @@ QAccessibleInterface *QAccessibleEvent::accessibleInterface() const
     (This means that at least one interface among the ancestors should
     return a valid QWindow pointer).
 
-    The default implementation returns 0.
+    The default implementation returns \nullptr.
   */
 QWindow *QAccessibleInterface::window() const
 {

src/gui/image/qimage.cpp

@@ -113,7 +113,7 @@ QImageData::QImageData()
     \internal
 
     Creates a new image data.
-    Returns 0 if invalid parameters are give or anything else failed.
+    Returns \nullptr if invalid parameters are give or anything else failed.
 */
 QImageData * QImageData::create(const QSize &size, QImage::Format format)
 {

src/gui/itemmodels/qstandarditemmodel.cpp

@@ -879,8 +879,8 @@ QStandardItem::~QStandardItem()
 }
 
 /*!
-  Returns the item's parent item, or 0 if the item has no parent.
-  \note For toplevel items parent() returns 0. To receive toplevel
+  Returns the item's parent item, or \nullptr if the item has no parent.
+  \note For toplevel items parent() returns \nullptr. To receive toplevel
   item's parent use QStandardItemModel::invisibleRootItem() instead.
 
   \sa child(), QStandardItemModel::invisibleRootItem()
@@ -1548,7 +1548,7 @@ QModelIndex QStandardItem::index() const
   Returns the QStandardItemModel that this item belongs to.
 
   If the item is not a child of another item that belongs to the model, this
-  function returns 0.
+  function returns \nullptr.
 
   \sa index()
 */
@@ -1865,7 +1865,7 @@ void QStandardItem::setChild(int row, int column, QStandardItem *item)
 
 /*!
     Returns the child item at (\a row, \a column) if one has been set; otherwise
-    returns 0.
+    returns \nullptr.
 
     \sa setChild(), takeChild(), parent()
 */
@@ -1881,7 +1881,7 @@ QStandardItem *QStandardItem::child(int row, int column) const
 /*!
     Removes the child item at (\a row, \a column) without deleting it, and returns
     a pointer to the item. If there was no child at the given location, then
-    this function returns 0.
+    this function returns \nullptr.
 
     Note that this function, unlike takeRow() and takeColumn(), does not affect
     the dimensions of the child table.
@@ -2283,7 +2283,7 @@ void QStandardItemModel::clear()
     itemPrototype()), and set it in the parent item's child table, if no item
     already exists at that index.
 
-    If \a index is an invalid index, this function returns 0.
+    If \a index is an invalid index, this function returns \nullptr.
 
     \sa indexFromItem()
 */
@@ -2380,7 +2380,7 @@ void QStandardItemModel::setItem(int row, int column, QStandardItem *item)
     \since 4.2
 
     Returns the item for the given \a row and \a column if one has been set;
-    otherwise returns 0.
+    otherwise returns \nullptr.
 
     \sa setItem(), takeItem(), itemFromIndex()
 */
@@ -2453,7 +2453,7 @@ void QStandardItemModel::setHorizontalHeaderItem(int column, QStandardItem *item
     \since 4.2
 
     Returns the horizontal header item for \a column if one has been set;
-    otherwise returns 0.
+    otherwise returns \nullptr.
 
     \sa setHorizontalHeaderItem(), verticalHeaderItem()
 */
@@ -2509,7 +2509,7 @@ void QStandardItemModel::setVerticalHeaderItem(int row, QStandardItem *item)
     \since 4.2
 
     Returns the vertical header item for row \a row if one has been set;
-    otherwise returns 0.
+    otherwise returns \nullptr.
 
     \sa setVerticalHeaderItem(), horizontalHeaderItem()
 */

src/gui/kernel/qevent.cpp

@@ -3072,7 +3072,7 @@ QDropEvent::~QDropEvent()
 /*!
     If the source of the drag operation is a widget in this
     application, this function returns that source; otherwise it
-    returns 0. The source of the operation is the first parameter to
+    returns \nullptr. The source of the operation is the first parameter to
     the QDrag object used instantiate the drag.
 
     This is useful if your widget needs special behavior when dragging
@@ -3514,7 +3514,7 @@ QActionEvent::~QActionEvent()
     \fn QAction *QActionEvent::before() const
 
     If type() is \l ActionAdded, returns the action that should
-    appear before action(). If this function returns 0, the action
+    appear before action(). If this function returns \nullptr, the action
     should be appended to already existing actions on the same
     widget.
 

src/gui/kernel/qguiapplication.cpp

@@ -3747,7 +3747,7 @@ Qt::LayoutDirection QGuiApplication::layoutDirection()
 
     Returns the active application override cursor.
 
-    This function returns 0 if no application cursor has been defined (i.e. the
+    This function returns \nullptr if no application cursor has been defined (i.e. the
     internal cursor stack is empty).
 
     \sa setOverrideCursor(), restoreOverrideCursor()

src/gui/kernel/qopenglcontext.cpp

@@ -1118,7 +1118,7 @@ void QOpenGLContext::swapBuffers(QSurface *surface)
 /*!
     Resolves the function pointer to an OpenGL extension function, identified by \a procName
 
-    Returns 0 if no such function can be found.
+    Returns \nullptr if no such function can be found.
 */
 QFunctionPointer QOpenGLContext::getProcAddress(const QByteArray &procName) const
 {

src/gui/kernel/qplatformcursor.cpp

@@ -84,7 +84,7 @@ QT_BEGIN_NAMESPACE
 
     \a windowCursor is a pointer to the QCursor that should be displayed.
 
-    To unset the cursor of \a window, 0 is passed. This means \a window does not have
+    To unset the cursor of \a window, \nullptr is passed. This means \a window does not have
     a cursor set and the cursor of a the first parent window which has a cursor explicitly
     set or the system default cursor should take effect.
 

src/gui/kernel/qplatformintegration.cpp

@@ -350,7 +350,7 @@ void QPlatformIntegration::destroy()
 /*!
   Returns the platforms input context.
 
-  The default implementation returns 0, implying no input method support.
+  The default implementation returns \nullptr, implying no input method support.
 */
 QPlatformInputContext *QPlatformIntegration::inputContext() const
 {

src/gui/kernel/qplatformscreen.cpp

@@ -370,7 +370,7 @@ QString QPlatformScreen::serialNumber() const
 /*!
     Reimplement this function in subclass to return the cursor of the screen.
 
-    The default implementation returns 0.
+    The default implementation returns \nullptr.
 */
 QPlatformCursor *QPlatformScreen::cursor() const
 {

src/gui/kernel/qwindow.cpp

@@ -2644,7 +2644,7 @@ QOpenGLContext *QWindowPrivate::shareContext() const
     native window, or to embed a native window inside a QWindow.
 
     If foreign windows are not supported or embedding the native window
-    failed in the platform plugin, this function returns 0.
+    failed in the platform plugin, this function returns \nullptr.
 
     \note The resulting QWindow should not be used to manipulate the underlying
     native window (besides re-parenting), or to observe state changes of the

src/gui/painting/qpaintengine.cpp

@@ -913,7 +913,7 @@ void QPaintEngine::setPaintDevice(QPaintDevice *device)
 
 /*!
     Returns the device that this engine is painting on, if painting is
-    active; otherwise returns 0.
+    active; otherwise returns \nullptr.
 */
 QPaintDevice *QPaintEngine::paintDevice() const
 {

src/gui/text/qtextcursor.cpp

@@ -2116,7 +2116,7 @@ QTextList *QTextCursor::createList(QTextListFormat::Style style)
 
 /*!
     Returns the current list if the cursor position() is inside a
-    block that is part of a list; otherwise returns 0.
+    block that is part of a list; otherwise returns \nullptr.
 
     \sa insertList(), createList()
  */
@@ -2176,7 +2176,7 @@ QTextTable *QTextCursor::insertTable(int rows, int cols, const QTextTableFormat
 
 /*!
     Returns a pointer to the current table if the cursor position()
-    is inside a block that is part of a table; otherwise returns 0.
+    is inside a block that is part of a table; otherwise returns \nullptr.
 
     \sa insertTable()
 */
@@ -2213,7 +2213,7 @@ QTextFrame *QTextCursor::insertFrame(const QTextFrameFormat &format)
 }
 
 /*!
-    Returns a pointer to the current frame. Returns 0 if the cursor is invalid.
+    Returns a pointer to the current frame. Returns \nullptr if the cursor is invalid.
 
     \sa insertFrame()
 */

src/gui/text/qtextobject.cpp

@@ -1301,7 +1301,7 @@ const QTextDocument *QTextBlock::document() const
 
 /*!
     If the block represents a list item, returns the list that the item belongs
-    to; otherwise returns 0.
+    to; otherwise returns \nullptr.
 */
 QTextList *QTextBlock::textList() const
 {

src/network/access/qftp.cpp

@@ -2154,7 +2154,7 @@ QFtp::Command QFtp::currentCommand() const
     \internal
     Returns the QIODevice pointer that is used by the FTP command to read data
     from or store data to. If there is no current FTP command being executed or
-    if the command does not use an IO device, this function returns 0.
+    if the command does not use an IO device, this function returns \nullptr.
 
     This function can be used to delete the QIODevice in the slot connected to
     the commandFinished() signal.

src/network/access/qnetworkrequest.cpp

@@ -714,7 +714,7 @@ void QNetworkRequest::setOriginatingObject(QObject *object)
     \since 4.6
 
     Returns a reference to the object that initiated this
-    network request; returns 0 if not set or the object has
+    network request; returns \nullptr if not set or the object has
     been destroyed.
 
     \sa setOriginatingObject()

src/testlib/qtestcase.qdoc

@@ -959,7 +959,7 @@
     \overload
     \since 5.8
 
-    Returns a string containing \c{nullptr}.
+    Returns a string containing \nullptr.
 */
 
 /*!

src/widgets/dialogs/qdialog.cpp

@@ -969,7 +969,7 @@ Qt::Orientation QDialog::orientation() const
 
     Sets the widget, \a extension, to be the dialog's extension,
     deleting any previous extension. The dialog takes ownership of the
-    extension. Note that if 0 is passed any existing extension will be
+    extension. Note that if \nullptr is passed, any existing extension will be
     deleted. This function must only be called while the dialog is hidden.
 
     Instead of using this functionality, we recommend that you simply call

src/widgets/dialogs/qprogressdialog.cpp

@@ -397,7 +397,7 @@ void QProgressDialog::setLabelText(const QString &text)
   Sets the cancel button to the push button, \a cancelButton. The
   progress dialog takes ownership of this button which will be deleted
   when necessary, so do not pass the address of an object that is on
-  the stack, i.e. use new() to create the button.  If 0 is passed then
+  the stack, i.e. use new() to create the button.  If \nullptr is passed,
   no cancel button will be shown.
 
   \sa setCancelButtonText()

src/widgets/effects/qgraphicseffect.cpp

@@ -178,7 +178,7 @@ QRectF QGraphicsEffect::sourceBoundingRect(Qt::CoordinateSystem system) const
 
 /*!
     Returns a pointer to the item if this source is a QGraphicsItem; otherwise
-    returns 0.
+    returns \nullptr.
 
     \sa widget()
 */
@@ -189,7 +189,7 @@ const QGraphicsItem *QGraphicsEffectSource::graphicsItem() const
 
 /*!
     Returns a pointer to the widget if this source is a QWidget; otherwise
-    returns 0.
+    returns \nullptr.
 
     \sa graphicsItem()
 */
@@ -200,7 +200,7 @@ const QWidget *QGraphicsEffectSource::widget() const
 
 /*!
     Returns a pointer to the style options (used when drawing the source) if
-    available; otherwise returns 0.
+    available; otherwise returns \nullptr.
 
     \sa graphicsItem(), widget()
 */

src/widgets/graphicsview/qgraphicsitem.cpp

@@ -1726,8 +1726,8 @@ QGraphicsItem *QGraphicsItem::topLevelItem() const
 /*!
     \since 4.6
 
-    Returns a pointer to the item's parent, cast to a QGraphicsObject. returns 0 if the parent item
-    is not a QGraphicsObject.
+    Returns a pointer to the item's parent, cast to a QGraphicsObject. Returns
+    \nullptr if the parent item is not a QGraphicsObject.
 
     \sa parentItem(), childItems()
 */

src/widgets/graphicsview/qgraphicslayoutitem.cpp

@@ -369,7 +369,7 @@ bool QGraphicsLayoutItemPrivate::hasWidthForHeight() const
     protected constructor, or by calling setParentLayoutItem(). The
     parentLayoutItem() function returns a pointer to the item's layoutItem
     parent. If the item's parent is 0 or if the parent does not inherit
-    from QGraphicsItem, the parentLayoutItem() function then returns 0.
+    from QGraphicsItem, the parentLayoutItem() function then returns \nullptr.
     isLayout() returns \c true if the QGraphicsLayoutItem subclass is itself a
     layout, or false otherwise.
 

src/widgets/itemviews/qabstractitemdelegate.cpp

@@ -240,7 +240,7 @@ QAbstractItemDelegate::~QAbstractItemDelegate()
     model being used. The editor's parent widget is specified by \a parent,
     and the item options by \a option.
 
-    The base implementation returns 0. If you want custom editing you
+    The base implementation returns \nullptr. If you want custom editing you
     will need to reimplement this function.
 
     The returned editor widget should have Qt::StrongFocus;

src/widgets/itemviews/qlistwidget.cpp

@@ -1375,7 +1375,7 @@ void QListWidget::setSelectionModel(QItemSelectionModel *selectionModel)
 
 /*!
     Returns the item that occupies the given \a row in the list if one has been
-    set; otherwise returns 0.
+    set; otherwise returns \nullptr.
 
     \sa row()
 */
@@ -1442,7 +1442,7 @@ void QListWidget::insertItems(int row, const QStringList &labels)
 
 /*!
     Removes and returns the item from the given \a row in the list widget;
-    otherwise returns 0.
+    otherwise returns \nullptr.
 
     Items removed from a list widget will not be managed by Qt, and will need
     to be deleted manually.

src/widgets/itemviews/qtablewidget.cpp

@@ -1936,7 +1936,7 @@ int QTableWidget::column(const QTableWidgetItem *item) const
 
 /*!
     Returns the item for the given \a row and \a column if one has been set; otherwise
-    returns 0.
+    returns \nullptr.
 
     \sa setItem()
 */
@@ -2029,7 +2029,7 @@ QTableWidgetItem *QTableWidget::takeVerticalHeaderItem(int row)
 
 /*!
     Returns the horizontal header item for column, \a column, if one has been
-    set; otherwise returns 0.
+    set; otherwise returns \nullptr.
 */
 QTableWidgetItem *QTableWidget::horizontalHeaderItem(int column) const
 {
@@ -2435,7 +2435,7 @@ int QTableWidget::visualColumn(int logicalColumn) const
 /*!
   \fn QTableWidgetItem *QTableWidget::itemAt(const QPoint &point) const
 
-  Returns a pointer to the item at the given \a point, or returns 0 if
+  Returns a pointer to the item at the given \a point, or returns \nullptr if
   \a point is not covered by an item in the table widget.
 
   \sa item()

src/widgets/itemviews/qtreewidget.cpp

@@ -2688,7 +2688,7 @@ void QTreeWidget::addTopLevelItem(QTreeWidgetItem *item)
 
 /*!
   Removes the top-level item at the given \a index in the tree and
-  returns it, otherwise returns 0;
+  returns it, otherwise returns \nullptr;
 
   \sa insertTopLevelItem(), topLevelItem(), topLevelItemCount()
 */

src/widgets/kernel/qapplication.cpp

@@ -360,7 +360,7 @@ void QApplicationPrivate::createEventDispatcher()
 /*!
     \fn QWidget *QApplication::topLevelAt(const QPoint &point)
 
-    Returns the top-level widget at the given \a point; returns 0 if
+    Returns the top-level widget at the given \a point; returns \nullptr if
     there is no such widget.
 */
 QWidget *QApplication::topLevelAt(const QPoint &pos)
@@ -1226,7 +1226,7 @@ void QApplication::setStyle(QStyle *style)
     "windows", "windowsvista", "fusion", or "macintosh". Style
     names are case insensitive.
 
-    Returns 0 if an unknown \a style is passed, otherwise the QStyle object
+    Returns \nullptr if an unknown \a style is passed, otherwise the QStyle object
     returned is set as the application's GUI style.
 
     \warning To ensure that the application's style is set correctly, it is
@@ -2177,7 +2177,7 @@ void QApplicationPrivate::notifyActiveWindowChange(QWindow *previous)
 
 /*!internal
  * Helper function that returns the new focus widget, but does not set the focus reason.
- * Returns 0 if a new focus widget could not be found.
+ * Returns \nullptr if a new focus widget could not be found.
  * Shared with QGraphicsProxyWidgetPrivate::findFocusChild()
 */
 QWidget *QApplicationPrivate::focusNextPrevChild_helper(QWidget *toplevel, bool next,

src/widgets/kernel/qformlayout.cpp

@@ -1825,7 +1825,7 @@ int QFormLayout::rowCount() const
 
 /*!
     Returns the layout item in the given \a row with the specified \a
-    role (column). Returns 0 if there is no such item.
+    role (column). Returns \nullptr if there is no such item.
 
     \sa QLayout::itemAt(), setItem()
 */

src/widgets/kernel/qwidget.cpp

@@ -10409,7 +10409,7 @@ bool QWidget::hasHeightForWidth() const
 
     Returns the visible child widget at the position (\a{x}, \a{y})
     in the widget's coordinate system. If there is no visible child
-    widget at the specified position, the function returns 0.
+    widget at the specified position, the function returns \nullptr.
 */
 
 /*!
@@ -12373,7 +12373,7 @@ Q_WIDGETS_EXPORT QWidgetPrivate *qt_widget_private(QWidget *widget)
    \since 4.5
 
    Returns the proxy widget for the corresponding embedded widget in a graphics
-   view; otherwise returns 0.
+   view; otherwise returns \nullptr.
 
    \sa QGraphicsProxyWidget::createProxyForChildWidget(),
        QGraphicsScene::addWidget()

src/widgets/styles/qstylefactory.cpp

@@ -77,7 +77,7 @@ Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, loader,
 
 /*!
     Creates and returns a QStyle object that matches the given \a key, or
-    returns 0 if no matching style is found.
+    returns \nullptr if no matching style is found.
 
     Both built-in styles and styles from style plugins are queried for a
     matching style.

src/widgets/util/qundogroup.cpp

@@ -242,7 +242,7 @@ void QUndoGroup::setActiveStack(QUndoStack *stack)
     Returns the active stack of this group.
 
     If none of the stacks are active, or if the group is empty, this function
-    returns 0.
+    returns \nullptr.
 
     \sa setActiveStack(), QUndoStack::setActive()
 */

src/widgets/util/qundoview.cpp

@@ -412,7 +412,7 @@ void QUndoView::setGroup(QUndoGroup *group)
 /*!
     Returns the group displayed by this view.
 
-    If the view is not looking at group, this function returns 0.
+    If the view is not looking at group, this function returns \nullptr.
 
     \sa setGroup(), setStack()
 */

src/widgets/widgets/qabstractbutton.cpp

@@ -805,7 +805,7 @@ bool QAbstractButton::autoExclusive() const
   Returns the group that this button belongs to.
 
   If the button is not a member of any QButtonGroup, this function
-  returns 0.
+  returns \nullptr.
 
   \sa QButtonGroup
 */

src/widgets/widgets/qabstractspinbox.cpp

@@ -692,7 +692,7 @@ QLineEdit *QAbstractSpinBox::lineEdit() const
 
     QAbstractSpinBox takes ownership of the new lineEdit
 
-    If QLineEdit::validator() for the \a lineEdit returns 0, the internal
+    If QLineEdit::validator() for the \a lineEdit returns \nullptr, the internal
     validator of the spinbox will be set on the line edit.
 */
 

src/widgets/widgets/qmenu.cpp

@@ -2283,7 +2283,7 @@ int QMenu::columnCount() const
 }
 
 /*!
-  Returns the item at \a pt; returns 0 if there is no item there.
+  Returns the item at \a pt; returns \nullptr if there is no item there.
 */
 QAction *QMenu::actionAt(const QPoint &pt) const
 {

src/widgets/widgets/qmenubar.cpp

@@ -1581,7 +1581,7 @@ bool QMenuBar::eventFilter(QObject *object, QEvent *event)
 }
 
 /*!
-  Returns the QAction at \a pt. Returns 0 if there is no action at \a pt or if
+  Returns the QAction at \a pt. Returns \nullptr if there is no action at \a pt or if
 the location has a separator.
 
     \sa addAction(), addSeparator()