QComboBox: style change event should not resets custom item delegates

Regression from 4.4 introduced while fixing task 167106

Autotest: tst_QComboBox::task253944_itemDelegateIsReset()

Task-number: 253944
Reviewed-by: jbache

2 files changed, 19 insertions, 9 deletions

diff --git a/src/gui/widgets/qcombobox.cpp b/src/gui/widgets/qcombobox.cpp
index 09a51fe39f..a5a98d48b9 100644
--- a/src/gui/widgets/qcombobox.cpp
+++ b/src/gui/widgets/qcombobox.cpp
@@ -947,7 +947,7 @@ QComboBoxPrivateContainer* QComboBoxPrivate::viewContainer()
     container = new QComboBoxPrivateContainer(new QComboBoxListView(q), q);
     container->itemView()->setModel(model);
     container->itemView()->setTextElideMode(Qt::ElideMiddle);
-    updateDelegate();
+    updateDelegate(true);
     updateLayoutDirection();
     QObject::connect(container, SIGNAL(itemSelected(QModelIndex)),
                      q, SLOT(_q_itemSelected(QModelIndex)));
@@ -1567,15 +1567,25 @@ bool QComboBox::isEditable() const
     return d->lineEdit != 0;
 }
 
-void QComboBoxPrivate::updateDelegate()
+/*! \internal
+    update the default delegate
+    depending on the style's SH_ComboBox_Popup hint, we use a different default delegate.
+
+    but we do not change the delegate is the combobox use a custom delegate,
+    unless \a force is set to true.
+ */
+void QComboBoxPrivate::updateDelegate(bool force)
 {
     Q_Q(QComboBox);
     QStyleOptionComboBox opt;
     q->initStyleOption(&opt);
-    if (q->style()->styleHint(QStyle::SH_ComboBox_Popup, &opt, q))
-        q->setItemDelegate(new QComboMenuDelegate(q->view(), q));
-    else
-        q->setItemDelegate(new QComboBoxDelegate(q->view(), q));
+    if (q->style()->styleHint(QStyle::SH_ComboBox_Popup, &opt, q)) {
+        if (force || qobject_cast<QComboBoxDelegate *>(q->itemDelegate()))
+            q->setItemDelegate(new QComboMenuDelegate(q->view(), q));
+    } else {
+        if (force || qobject_cast<QComboMenuDelegate *>(q->itemDelegate()))
+            q->setItemDelegate(new QComboBoxDelegate(q->view(), q));
+    }
 }
 
 QIcon QComboBoxPrivate::itemIcon(const QModelIndex &index) const
diff --git a/src/gui/widgets/qcombobox_p.h b/src/gui/widgets/qcombobox_p.h
index c39a23140c..a55b439e8d 100644
--- a/src/gui/widgets/qcombobox_p.h
+++ b/src/gui/widgets/qcombobox_p.h
@@ -256,7 +256,7 @@ private:
 };
 
 class QComboMenuDelegate : public QAbstractItemDelegate
-{
+{ Q_OBJECT
 public:
     QComboMenuDelegate(QObject *parent, QComboBox *cmb) : QAbstractItemDelegate(parent), mCombo(cmb) {}
 
@@ -285,7 +285,7 @@ private:
 // Vista does not use the new theme for combo boxes and there might 
 // be other side effects from using the new class
 class QComboBoxDelegate : public QItemDelegate
-{
+{ Q_OBJECT
 public:
     QComboBoxDelegate(QObject *parent, QComboBox *cmb) : QItemDelegate(parent), mCombo(cmb) {}
 
@@ -367,7 +367,7 @@ public:
     int itemRole() const;
     void updateLayoutDirection();
     void setCurrentIndex(const QModelIndex &index);
-    void updateDelegate();
+    void updateDelegate(bool force = false);
     void keyboardSearchString(const QString &text);
     void modelChanged();