QModelIndex/QAIM: improve const correctness

QAIM::createIndex() takes a non-const void*. It's
typically called from inside QAIM::index(), which is a
const member function. If the data storage wrapped
by the model is const correct, it means that we have
to drop constness somewhere before calling createIndex().

To support this: change createIndex() to take a
const void * instead. This is painless.

Accessing the pointer is a bit more troubling, because
the accessor (QModelIndex::internalPointer()) returns
void *. (Effectively, now it does a const_cast...).
To avoid a massive source break, I've left it alone,
and instead added another function to retrieve a
const void *.

Read-only models can now be fully (deep) const correct.

[ChangeLog][QtCore][QAbstractItemModel] The
createIndex() function now takes a const void *, rather
than a void *.

[ChangeLog][QtCore][QModelIndex] Added the
constInternalPointer() function, to retrieve the
internal pointer as a pointer-to-const.

Change-Id: I108912b6814fcd5fe0c5cb7db6c721ba51e83de0
Reviewed-by: Samuel Gaist <samuel.gaist@idiap.ch>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 26 insertions, 1 deletions

diff --git a/src/corelib/itemmodels/qabstractitemmodel.cpp b/src/corelib/itemmodels/qabstractitemmodel.cpp
index fac7058d29..49b5031559 100644
--- a/src/corelib/itemmodels/qabstractitemmodel.cpp
+++ b/src/corelib/itemmodels/qabstractitemmodel.cpp
@@ -352,6 +352,22 @@ void *QPersistentModelIndex::internalPointer() const
 }
 
 /*!
+    \fn const void *QPersistentModelIndex::constInternalPointer() const
+    \since 6.0
+    \internal
+
+    Returns a \c{const void} \c{*} pointer used by the model to
+    associate the index with the internal data structure.
+*/
+
+const void *QPersistentModelIndex::constInternalPointer() const
+{
+    if (d)
+        return d->index.constInternalPointer();
+    return nullptr;
+}
+
+/*!
     \fn quintptr QPersistentModelIndex::internalId() const
 
     \internal
@@ -1065,6 +1081,15 @@ void QAbstractItemModel::resetInternalData()
 */
 
 /*!
+    \fn const void *QModelIndex::constInternalPointer() const
+
+    Returns a \c{const void} \c{*} pointer used by the model to associate
+    the index with the internal data structure.
+
+    \sa QAbstractItemModel::createIndex()
+*/
+
+/*!
     \fn quintptr QModelIndex::internalId() const
 
     Returns a \c{quintptr} used by the model to associate
@@ -2589,7 +2614,7 @@ bool QAbstractItemModel::setHeaderData(int section, Qt::Orientation orientation,
 }
 
 /*!
-    \fn QModelIndex QAbstractItemModel::createIndex(int row, int column, void *ptr) const
+    \fn QModelIndex QAbstractItemModel::createIndex(int row, int column, const void *ptr) const
 
     Creates a model index for the given \a row and \a column with the internal
     pointer \a ptr.