QAbstractProxyModel: delay headerDataChanged emissions when inserting/removing rows/columns

33c88f86b5b8714977719a8ccff0f7c15c9cbd44 added some logic to QAPM in
order to have it automatically emit headerDataChanged when rows/columns
were added or removed in the model. This was done as a stopgap measure
to prevent QAPM from asking for illegal indices in order to implement
automatic remapping of the section headings (since there's no
mapSectionToSource).

The commit seems to have introduced a regression in QHeaderView, which
isn't prepared to receive headerDataChanged while a row/column count
change is in progress. When receiving headerDataChanged, QHeaderView
will try to read the row/column count and will store it internally.
When it will then receive the signals for insertion/removal of
rows/columns, it will interpret it as a modification of the previously
stored value -- even if the value it stored was already correct.

Fix this by avoiding to have two signals in flight at the same time;
emit headerDataChanged as a queued invocation.

Task-number: QTBUG-114225
Change-Id: I521465a852b8c7135f22f730ead41dca760ba428
Pick-to: 6.5 6.6
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/src/corelib/itemmodels/qabstractproxymodel.cpp b/src/corelib/itemmodels/qabstractproxymodel.cpp
index c0321ee282..12974b5aaa 100644
--- a/src/corelib/itemmodels/qabstractproxymodel.cpp
+++ b/src/corelib/itemmodels/qabstractproxymodel.cpp
@@ -55,6 +55,13 @@ void QAbstractProxyModelPrivate::_q_sourceModelDestroyed()
     model = QAbstractItemModelPrivate::staticEmptyModel();
 }
 
+static auto emitHeaderDataChanged(QAbstractItemModel *model,
+                                  Qt::Orientation orientation,
+                                  int count)
+{
+    return [=](){ emit model->headerDataChanged(orientation, 0, count); };
+}
+
 void QAbstractProxyModelPrivate::_q_sourceModelRowsAboutToBeInserted(const QModelIndex &parent, int, int)
 {
     if (parent.isValid())
@@ -70,7 +77,7 @@ void QAbstractProxyModelPrivate::_q_sourceModelRowsInserted(const QModelIndex &p
         Q_Q(QAbstractProxyModel);
         const int columnCount = q->columnCount();
         if (columnCount > 0)
-            emit q->headerDataChanged(Qt::Horizontal, 0, columnCount - 1);
+            QMetaObject::invokeMethod(q, emitHeaderDataChanged(q, Qt::Horizontal, columnCount - 1), Qt::QueuedConnection);
     }
 }
 
@@ -83,7 +90,7 @@ void QAbstractProxyModelPrivate::_q_sourceModelRowsRemoved(const QModelIndex &pa
         Q_Q(QAbstractProxyModel);
         const int columnCount = q->columnCount();
         if (columnCount > 0)
-            emit q->headerDataChanged(Qt::Horizontal, 0, columnCount - 1);
+            QMetaObject::invokeMethod(q, emitHeaderDataChanged(q, Qt::Horizontal, columnCount - 1), Qt::QueuedConnection);
     }
 }
 
@@ -102,7 +109,7 @@ void QAbstractProxyModelPrivate::_q_sourceModelColumnsInserted(const QModelIndex
         Q_Q(QAbstractProxyModel);
         const int rowCount = q->rowCount();
         if (rowCount > 0)
-            emit q->headerDataChanged(Qt::Vertical, 0, rowCount - 1);
+            QMetaObject::invokeMethod(q, emitHeaderDataChanged(q, Qt::Vertical, rowCount - 1), Qt::QueuedConnection);
     }
 }
 
@@ -114,7 +121,7 @@ void QAbstractProxyModelPrivate::_q_sourceModelColumnsRemoved(const QModelIndex
         Q_Q(QAbstractProxyModel);
         const int rowCount = q->rowCount();
         if (rowCount > 0)
-            emit q->headerDataChanged(Qt::Vertical, 0, rowCount - 1);
+            QMetaObject::invokeMethod(q, emitHeaderDataChanged(q, Qt::Vertical, rowCount - 1), Qt::QueuedConnection);
     }
 }