Fix the API for resetting QAbstractItemModels.

This commit deprecates the QAIM::reset() method, and adds beginResetModel()
and endResetModel() methods, addressing Qt issue 247023.

http://www.qtsoftware.com/developer/task-tracker/index_html?method=entry&id=247023

If models and proxies use QAIM::reset() alone, then proxies will
emit modelAboutToBeReset after its source model is reset. This means that mapToSource
will not behave as expected (Will always return an invalid index) in a slot connected
to modelAboutToBeReset.

The usecase for this is maintaining viewstate (which items are selected, expanded)
when the model is reset. See BrowserWidget::modelChanged here:
http://websvn.kde.org/trunk/KDE/kdepim/akonadi/akonadiconsole/browserwidget.cpp?view=markup

Task-number: 247023
Reviewed-by: Olivier Goffart <ogoffart@trolltech.com>
Merge-request: 1072

1 files changed, 3 insertions, 0 deletions

diff --git a/src/corelib/kernel/qabstractitemmodel.h b/src/corelib/kernel/qabstractitemmodel.h
index b47e4cb..1ca6cbe 100644
--- a/src/corelib/kernel/qabstractitemmodel.h
+++ b/src/corelib/kernel/qabstractitemmodel.h
@@ -293,6 +293,9 @@ protected:
 
     void reset();
 
+    void beginResetModel();
+    void endResetModel();
+
     void changePersistentIndex(const QModelIndex &from, const QModelIndex &to);
     void changePersistentIndexList(const QModelIndexList &from, const QModelIndexList &to);
     QModelIndexList persistentIndexList() const;