QHeaderView: fix visual/logical index corruption when restoring statev5.9.0-rc2v5.9.0

This is a followup to 77a8e90cddcfa1c34518ef846a4838874a7bc0c7 which
didn't handle the case where no columns had been moved.
visualIndices and logicalIndices are empty until initializeIndexMapping()
is called, in which case appending is wrong.

As a result, visualIndex(i) would return -1 for the values over
those added by read(), and an assert would happen at painting time.

The fix is to leave visualIndices and logicalIndices empty if
they are empty already, leaving it to initializeIndexMapping()
to fill them later if necessary (e.g. when moving a column).

Task-number: QTBUG-60837
Change-Id: Ia7e4b9d3122647984acd434dfaa0400df319d065
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/src/widgets/itemviews/qheaderview.cpp b/src/widgets/itemviews/qheaderview.cpp
index e0e993ce77..76f80c680e 100644
--- a/src/widgets/itemviews/qheaderview.cpp
+++ b/src/widgets/itemviews/qheaderview.cpp
@@ -3876,9 +3876,11 @@ bool QHeaderViewPrivate::read(QDataStream &in)
     const int currentCount = (orient == Qt::Horizontal ? model->columnCount(root) : model->rowCount(root));
     if (newSectionItems.count() < currentCount) {
         // we have sections not in the saved state, give them default settings
-        for (int i = newSectionItems.count(); i < currentCount; ++i) {
-            visualIndicesIn.append(i);
-            logicalIndicesIn.append(i);
+        if (!visualIndicesIn.isEmpty() && !logicalIndicesIn.isEmpty()) {
+            for (int i = newSectionItems.count(); i < currentCount; ++i) {
+                visualIndicesIn.append(i);
+                logicalIndicesIn.append(i);
+            }
         }
         const int insertCount = currentCount - newSectionItems.count();
         const int insertLength = defaultSectionSizeIn * insertCount;