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>

13 files changed, 30 insertions, 30 deletions

diff --git a/src/gui/accessible/qaccessible.cpp b/src/gui/accessible/qaccessible.cpp
index a3f53e149b..46dec7f28d 100644
--- a/src/gui/accessible/qaccessible.cpp
+++ b/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
 {
diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index 0105f1decd..6801e2e1ea 100644
--- a/src/gui/image/qimage.cpp
+++ b/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)
 {
diff --git a/src/gui/itemmodels/qstandarditemmodel.cpp b/src/gui/itemmodels/qstandarditemmodel.cpp
index 430ba152a9..7afad95bd9 100644
--- a/src/gui/itemmodels/qstandarditemmodel.cpp
+++ b/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()
 */
diff --git a/src/gui/kernel/qevent.cpp b/src/gui/kernel/qevent.cpp
index 53d1ac1fc0..7123c4d8ba 100644
--- a/src/gui/kernel/qevent.cpp
+++ b/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.
 
diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index a63e172461..fd01f8bb7b 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/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()
diff --git a/src/gui/kernel/qopenglcontext.cpp b/src/gui/kernel/qopenglcontext.cpp
index c5d5490ea0..be04513de6 100644
--- a/src/gui/kernel/qopenglcontext.cpp
+++ b/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
 {
diff --git a/src/gui/kernel/qplatformcursor.cpp b/src/gui/kernel/qplatformcursor.cpp
index bab26f6028..76e38ab12d 100644
--- a/src/gui/kernel/qplatformcursor.cpp
+++ b/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.
 
diff --git a/src/gui/kernel/qplatformintegration.cpp b/src/gui/kernel/qplatformintegration.cpp
index 6e285a8fa5..7d1fcd4eeb 100644
--- a/src/gui/kernel/qplatformintegration.cpp
+++ b/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
 {
diff --git a/src/gui/kernel/qplatformscreen.cpp b/src/gui/kernel/qplatformscreen.cpp
index 9614be7f3e..b7b312e89e 100644
--- a/src/gui/kernel/qplatformscreen.cpp
+++ b/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
 {
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index bc2d6e6a17..61ef029cbd 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/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
diff --git a/src/gui/painting/qpaintengine.cpp b/src/gui/painting/qpaintengine.cpp
index 1aee7d5f74..bfe1c9cadf 100644
--- a/src/gui/painting/qpaintengine.cpp
+++ b/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
 {
diff --git a/src/gui/text/qtextcursor.cpp b/src/gui/text/qtextcursor.cpp
index af8fcf369c..7719a2e6da 100644
--- a/src/gui/text/qtextcursor.cpp
+++ b/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()
 */
diff --git a/src/gui/text/qtextobject.cpp b/src/gui/text/qtextobject.cpp
index e2130a09d9..0ed8be8530 100644
--- a/src/gui/text/qtextobject.cpp
+++ b/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
 {