QComboBox: emit currentIndexChanged() and currentTextChanged() when the model is cleared

QComboBox uses QPersistentModelIndex to store the current index of the
underlying model. When the model is cleared, that index is automatically
invalidated, so calling QComboBoxPrivate::setCurrentIndex(QModelIndex())
does not result in signals being emitted, because we do not detect the
index change.

This patch uses indexBeforeChange to detect such situation and emit all
necessary signals.

Fixes: QTBUG-103007
Pick-to: 6.4 6.3 6.2
Change-Id: I29326830a30a17900839e8d1737a08bd940081ea
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/widgets/widgets/qcombobox.cpp b/src/widgets/widgets/qcombobox.cpp
index 2da6183a1e..9caac239f9 100644
--- a/src/widgets/widgets/qcombobox.cpp
+++ b/src/widgets/widgets/qcombobox.cpp
@@ -2135,7 +2135,11 @@ void QComboBoxPrivate::setCurrentIndex(const QModelIndex &mi)
         }
         updateLineEditGeometry();
     }
-    if (indexChanged) {
+    // If the model was reset to an empty, currentIndex will be invalidated
+    // (because it's a QPersistentModelIndex), but the index change will never
+    // be advertised. So we need an explicit check for such condition.
+    const bool modelResetToEmpty = !normalized.isValid() && indexBeforeChange != -1;
+    if (indexChanged || modelResetToEmpty) {
         q->update();
         _q_emitCurrentIndexChanged(currentIndex);
     }