Doc: Qt GUI: Fix documentation warnings

These are minor typos or documentation warnings that snuck in with
new features.

Task-number: QTBUG-71502
Change-Id: I03669cfecc3c3d80168ff7b1ca8bca7571e06d25
Reviewed-by: Martin Smith <martin.smith@qt.io>

src/gui/itemmodels/qstandarditemmodel.cpp

@@ -3013,6 +3013,9 @@ bool QStandardItemModel::setData(const QModelIndex &index, const QVariant &value
 /*!
   \since 5.12
   Removes the data stored in all the roles for the given \a index.
+  Returns \c true if \a index is valid and data was cleared, \c false
+  otherwise.
+
   \sa setData(), data()
 */
 bool QStandardItemModel::clearItemData(const QModelIndex &index)

src/gui/kernel/qplatformgraphicsbufferhelper.cpp

@@ -56,6 +56,12 @@
 
 QT_BEGIN_NAMESPACE
 
+/*!
+    \namespace QPlatformGraphicsBufferHelper
+    \inmodule QtGui
+    \internal
+*/
+
 /*!
     Convenience function to both lock and bind the \a graphicsBuffer to a texture.
     This function will first try to lock with texture read and texture write

src/gui/opengl/qopenglfunctions.cpp

@@ -142,6 +142,7 @@ void CLASS::init(QOpenGLContext *context) \
     \value BlendColor glBlendColor() is available.
     \value BlendEquation glBlendEquation() is available.
     \value BlendEquationSeparate glBlendEquationSeparate() is available.
+    \value BlendEquationAdvanced Advanced blend equations are available.
     \value BlendFuncSeparate glBlendFuncSeparate() is available.
     \value BlendSubtract Blend subtract mode is available.
     \value CompressedTextures Compressed texture functions are available.

src/gui/painting/qcolor.cpp

@@ -1366,7 +1366,7 @@ QRgba64 QColor::rgba64() const Q_DECL_NOTHROW
 
     Sets the RGB64 value to \a rgba, including its alpha.
 
-    \sa \setRgba(), rgba64()
+    \sa setRgba(), rgba64()
 */
 void QColor::setRgba64(QRgba64 rgba) Q_DECL_NOTHROW
 {

src/gui/text/qfont.cpp

@@ -1254,7 +1254,7 @@ QFont::StyleStrategy QFont::styleStrategy() const
 /*!
     Returns the StyleHint.
 
-    The style hint affects the \l{#fontmatching}{font matching algorithm}.
+    The style hint affects the \l{QFont#fontmatching}{font matching algorithm}.
     See \l QFont::StyleHint for the list of available hints.
 
     \sa setStyleHint(), QFont::StyleStrategy, QFontInfo::styleHint()

src/gui/text/qtextdocument.cpp

@@ -153,7 +153,7 @@ bool Qt::mightBeRichText(const QString& text)
 
     This function is defined in the \c <QTextDocument> header file.
 
-    \sa escape(), mightBeRichText()
+    \sa QString::toHtmlEscaped(), mightBeRichText()
 */
 QString Qt::convertFromPlainText(const QString &plain, Qt::WhiteSpaceMode mode)
 {

src/gui/text/qtextformat.cpp

@@ -645,6 +645,7 @@ Q_GUI_EXPORT QDataStream &operator>>(QDataStream &stream, QTextFormat &fmt)
     \value ImageName
     \value ImageWidth
     \value ImageHeight
+    \value ImageQuality
 
     Selection properties
 
@@ -2251,7 +2252,7 @@ QList<QTextOption::Tab> QTextBlockFormat::tabPositions() const
     \fn void QTextBlockFormat::setHeadingLevel(int level)
     \since 5.12
 
-    Sets the paragraph's heading level, where 1 is the highest-level heading
+    Sets the paragraph's heading \a level, where 1 is the highest-level heading
     type (usually with the largest possible heading font size), and increasing
     values are progressively deeper into the document (and usually with smaller
     font sizes). For example when reading an HTML H1 tag, the heading level is