QComboBox: unify behavior of setModel() and modelReset

When a new model is set, a valid index is selected. When a model is
reset, this is not the case which is slightly inconsistent. Fix it by
using the same logic to find a valid index when the model is reset

Fixes: QTBUG-80998
Change-Id: I6c167511e199a6664343cf1dc3bcd27c65389bfd
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

3 files changed, 26 insertions, 23 deletions

diff --git a/src/widgets/widgets/qcombobox.cpp b/src/widgets/widgets/qcombobox.cpp
index aa3788c404..95c2bea3fe 100644
--- a/src/widgets/widgets/qcombobox.cpp
+++ b/src/widgets/widgets/qcombobox.cpp
@@ -293,8 +293,7 @@ void QComboBoxPrivate::_q_modelReset()
         lineEdit->setText(QString());
         updateLineEditGeometry();
     }
-    if (currentIndex.row() != indexBeforeChange)
-        _q_emitCurrentIndexChanged(currentIndex);
+    trySetValidIndex();
     modelChanged();
     q->update();
 }
@@ -304,6 +303,25 @@ void QComboBoxPrivate::_q_modelDestroyed()
     model = QAbstractItemModelPrivate::staticEmptyModel();
 }
 
+void QComboBoxPrivate::trySetValidIndex()
+{
+    Q_Q(QComboBox);
+    bool currentReset = false;
+
+    const int rowCount = q->count();
+    for (int pos = 0; pos < rowCount; ++pos) {
+        const QModelIndex idx(model->index(pos, modelColumn, root));
+        if (idx.flags() & Qt::ItemIsEnabled) {
+            setCurrentIndex(idx);
+            currentReset = true;
+            break;
+        }
+    }
+
+    if (!currentReset)
+        setCurrentIndex(QModelIndex());
+}
+
 QRect QComboBoxPrivate::popupGeometry(int screen) const
 {
     return QStylePrivate::useFullScreenForPopup()
@@ -2200,20 +2218,7 @@ void QComboBox::setModel(QAbstractItemModel *model)
 
     setRootModelIndex(QModelIndex());
 
-    bool currentReset = false;
-
-    const int rowCount = count();
-    for (int pos=0; pos < rowCount; pos++) {
-        if (d->model->index(pos, d->modelColumn, d->root).flags() & Qt::ItemIsEnabled) {
-            setCurrentIndex(pos);
-            currentReset = true;
-            break;
-        }
-    }
-
-    if (!currentReset)
-        setCurrentIndex(-1);
-
+    d->trySetValidIndex();
     d->modelChanged();
 }
 
diff --git a/src/widgets/widgets/qcombobox_p.h b/src/widgets/widgets/qcombobox_p.h
index 7a3fcf6e0f..3e78e756a6 100644
--- a/src/widgets/widgets/qcombobox_p.h
+++ b/src/widgets/widgets/qcombobox_p.h
@@ -371,6 +371,7 @@ public:
     void _q_rowsRemoved(const QModelIndex &parent, int start, int end);
     void updateArrow(QStyle::StateFlag state);
     bool updateHoverControl(const QPoint &pos);
+    void trySetValidIndex();
     QRect popupGeometry(int screen = -1) const;
     QStyle::SubControl newHoverControl(const QPoint &pos);
     int computeWidthHint() const;
diff --git a/tests/auto/widgets/widgets/qcombobox/tst_qcombobox.cpp b/tests/auto/widgets/widgets/qcombobox/tst_qcombobox.cpp
index ea1b330152..3878e7ccb2 100644
--- a/tests/auto/widgets/widgets/qcombobox/tst_qcombobox.cpp
+++ b/tests/auto/widgets/widgets/qcombobox/tst_qcombobox.cpp
@@ -2756,10 +2756,7 @@ void tst_QComboBox::resetModel()
     class StringListModel : public QStringListModel
     {
     public:
-        StringListModel(const QStringList &list) : QStringListModel(list)
-        {
-        }
-
+        using QStringListModel::QStringListModel;
         void reset()
         {
             QStringListModel::beginResetModel();
@@ -2767,8 +2764,8 @@ void tst_QComboBox::resetModel()
         }
     };
     QComboBox cb;
-    StringListModel model( QStringList() << "1" << "2");
-    QSignalSpy spy(&cb, SIGNAL(currentIndexChanged(int)));
+    StringListModel model({"1", "2"});
+    QSignalSpy spy(&cb, QOverload<int>::of(&QComboBox::currentIndexChanged));
     QCOMPARE(spy.count(), 0);
     QCOMPARE(cb.currentIndex(), -1); //no selection
 
@@ -2779,7 +2776,7 @@ void tst_QComboBox::resetModel()
 
     model.reset();
     QCOMPARE(spy.count(), 2);
-    QCOMPARE(cb.currentIndex(), -1); //no selection
+    QCOMPARE(cb.currentIndex(), 0); //first item selected
 
 }