Add missing documentation for QUndoStack properties

They were forgotten in 59e9c4956c.

Task-number: QTBUG-67457
Change-Id: I58c576598d88d3dd1fa320628ad80689d3f8b8de
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>

src/widgets/util/qundostack.cpp

@@ -741,6 +741,17 @@ void QUndoStack::resetClean()
         emit cleanChanged(false);
 }
 
+/*!
+    \since 5.12
+    \property QUndoStack::clean
+    \brief the clean status of this stack.
+
+    This property indicates whether or not the stack is clean. For example, a
+    stack is clean when a document has been saved.
+
+    \sa isClean(), setClean(), resetClean(), cleanIndex()
+*/
+
 /*!
     If the stack is in the clean state, returns \c true; otherwise returns \c false.
 
@@ -939,6 +950,17 @@ void QUndoStack::setIndex(int idx)
     d->setIndex(idx, false);
 }
 
+/*!
+    \since 5.12
+    \property QUndoStack::canUndo
+    \brief whether this stack can undo.
+
+    This property indicates whether or not there is a command that can be
+    undone.
+
+    \sa canUndo(), index(), canRedo()
+*/
+
 /*!
     Returns \c true if there is a command available for undo; otherwise returns \c false.
 
@@ -958,6 +980,17 @@ bool QUndoStack::canUndo() const
     return d->index > 0;
 }
 
+/*!
+    \since 5.12
+    \property QUndoStack::canRedo
+    \brief whether this stack can redo.
+
+    This property indicates whether or not there is a command that can be
+    redone.
+
+    \sa canRedo(), index(), canUndo()
+*/
+
 /*!
     Returns \c true if there is a command available for redo; otherwise returns \c false.
 
@@ -977,6 +1010,17 @@ bool QUndoStack::canRedo() const
     return d->index < d->command_list.size();
 }
 
+/*!
+    \since 5.12
+    \property QUndoStack::undoText
+    \brief the undo text of the next command that is undone.
+
+    This property holds the text of the command which will be undone in the
+    next call to undo().
+
+    \sa undoText(), QUndoCommand::actionText(), redoText()
+*/
+
 /*!
     Returns the text of the command which will be undone in the next call to undo().
 
@@ -993,6 +1037,17 @@ QString QUndoStack::undoText() const
     return QString();
 }
 
+/*!
+    \since 5.12
+    \property QUndoStack::redoText
+    \brief the redo text of the next command that is redone.
+
+    This property holds the text of the command which will be redone in the
+    next call to redo().
+
+    \sa redoText(), QUndoCommand::actionText(), undoText()
+*/
+
 /*!
     Returns the text of the command which will be redone in the next call to redo().