Doc/QtGui: replace some 0 with \nullptr

Replace some 'is 0' or 'are 0' where 0 referes to a nullptr with 'is
\nullptr' and 'are \nullptr'

Change-Id: Ic18d0c8bcf64159b4c8fae8c9499839954a98884
Reviewed-by: André Hartmann <aha_1980@gmx.de>
Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>

src/gui/accessible/qaccessible.cpp

@@ -2029,7 +2029,7 @@ QAccessibleTextInterface::~QAccessibleTextInterface()
     \fn void QAccessibleTextInterface::selection(int selectionIndex, int *startOffset, int *endOffset) const
 
     Returns a selection. The size of the selection is returned in \a startOffset and \a endOffset.
-    If there is no selection both \a startOffset and \a endOffset are 0.
+    If there is no selection both \a startOffset and \a endOffset are \nullptr.
 
     The accessibility APIs support multiple selections. For most widgets though, only one selection
     is supported with \a selectionIndex equal to 0.

src/gui/image/qimage.cpp

@@ -4058,7 +4058,7 @@ void QImage::setText(const QString &key, const QString &value)
     \obsolete
 
     Returns the text recorded for the given \a key in the given \a
-    language, or in a default language if \a language is 0.
+    language, or in a default language if \a language is \nullptr.
 
     Use text() instead.
 
@@ -4085,7 +4085,7 @@ void QImage::setText(const QString &key, const QString &value)
 
     Sets the image text to the given \a text and associate it with the
     given \a key. The text is recorded in the specified \a language,
-    or in a default language if \a language is 0.
+    or in a default language if \a language is \nullptr.
 
     Use setText() instead.
 

src/gui/image/qpixmap.cpp

@@ -813,8 +813,8 @@ bool QPixmap::loadFromData(const uchar *buf, uint len, const char *format, Qt::I
     0 to obtain small compressed files, 100 for large uncompressed
     files, and -1 to use the default settings.
 
-    If \a format is 0, an image format will be chosen from \a fileName's
+    If \a format is \nullptr, an image format will be chosen from
-    suffix.
+    \a fileName's suffix.
 
     \sa {QPixmap#Reading and Writing Image Files}{Reading and Writing
     Image Files}

src/gui/kernel/qevent.cpp

@@ -3366,7 +3366,7 @@ QWhatsThisClickedEvent::~QWhatsThisClickedEvent()
 
     \a action is the action that is changed, added, or removed. If \a
     type is ActionAdded, the action is to be inserted before the
-    action \a before. If \a before is 0, the action is appended.
+    action \a before. If \a before is \nullptr, the action is appended.
 */
 QActionEvent::QActionEvent(int type, QAction *action, QAction *before)
     : QEvent(static_cast<QEvent::Type>(type)), act(action), bef(before)

src/gui/kernel/qopenglcontext.cpp

@@ -941,7 +941,7 @@ GLuint QOpenGLContext::defaultFramebufferObject() const
     The latter may happen if the surface is not exposed, or the graphics
     hardware is not available due to e.g. the application being suspended.
 
-    If \a surface is 0 this is equivalent to calling doneCurrent().
+    If \a surface is \nullptr this is equivalent to calling doneCurrent().
 
     Avoid calling this function from a different thread than the one the
     QOpenGLContext instance lives in. If you wish to use QOpenGLContext from a

src/gui/text/qfontmetrics.cpp

@@ -161,7 +161,7 @@ QFontMetrics::QFontMetrics(const QFont &font)
     Constructs a font metrics object for \a font and \a paintdevice.
 
     The font metrics will be compatible with the paintdevice passed.
-    If the \a paintdevice is 0, the metrics will be screen-compatible,
+    If the \a paintdevice is \nullptr, the metrics will be screen-compatible,
     ie. the metrics you get if you use the font for drawing text on a
     \l{QWidget}{widgets} or \l{QPixmap}{pixmaps},
     not on a QPicture or QPrinter.
@@ -1154,7 +1154,7 @@ QFontMetricsF::QFontMetricsF(const QFont &font)
     Constructs a font metrics object for \a font and \a paintdevice.
 
     The font metrics will be compatible with the paintdevice passed.
-    If the \a paintdevice is 0, the metrics will be screen-compatible,
+    If the \a paintdevice is \nullptr, the metrics will be screen-compatible,
     ie. the metrics you get if you use the font for drawing text on a
     \l{QWidget}{widgets} or \l{QPixmap}{pixmaps},
     not on a QPicture or QPrinter.

src/gui/text/qtextlayout.cpp

@@ -350,7 +350,7 @@ QTextLayout::QTextLayout(const QString& text)
     \a font.
 
     All the metric and layout calculations will be done in terms of
-    the paint device, \a paintdevice. If \a paintdevice is 0 the
+    the paint device, \a paintdevice. If \a paintdevice is \nullptr the
     calculations will be done in screen metrics.
 */