Delete replaced delegates after Component.completed() is emitted

This avoids the issue "Object destroyed during incubation" error.
A proper fix is still required in the QML engine.

Change-Id: I3c168cfe2d8c295662bcb5886e99a0f95748e302
Task-number: QTBUG-50992
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>

src/quicktemplates2/qquickabstractbutton.cpp

@@ -438,7 +438,7 @@ void QQuickAbstractButton::setIndicator(QQuickItem *indicator)
     if (d->indicator == indicator)
         return;
 
-    delete d->indicator;
+    d->deleteDelegate(d->indicator);
     d->indicator = indicator;
     if (indicator) {
         if (!indicator->parentItem())

src/quicktemplates2/qquickcombobox.cpp

@@ -627,7 +627,7 @@ void QQuickComboBox::setIndicator(QQuickItem *indicator)
     if (d->indicator == indicator)
         return;
 
-    delete d->indicator;
+    d->deleteDelegate(d->indicator);
     d->indicator = indicator;
     if (indicator) {
         if (!indicator->parentItem())
@@ -655,7 +655,7 @@ void QQuickComboBox::setPopup(QQuickPopup *popup)
     if (d->popup == popup)
         return;
 
-    delete d->popup;
+    d->deleteDelegate(d->popup);
     if (popup) {
         QQuickPopupPrivate::get(popup)->allowVerticalFlip = true;
         popup->setClosePolicy(QQuickPopup::CloseOnEscape | QQuickPopup::CloseOnPressOutsideParent);

src/quicktemplates2/qquickcontrol.cpp

@@ -717,6 +717,18 @@ QLocale QQuickControlPrivate::calcLocale(const QQuickItem *item)
     return QLocale();
 }
 
+/*
+   Deletes "delegate" if Component.completed() has been emitted,
+   otherwise stores it in pendingDeletions.
+*/
+void QQuickControlPrivate::deleteDelegate(QObject *delegate)
+{
+    if (componentComplete)
+        delete delegate;
+    else
+        extra.value().pendingDeletions.append(delegate);
+}
+
 void QQuickControlPrivate::updateLocale(const QLocale &l, bool e)
 {
     Q_Q(QQuickControl);
@@ -943,7 +955,7 @@ void QQuickControl::setBackground(QQuickItem *background)
     if (d->background == background)
         return;
 
-    delete d->background;
+    d->deleteDelegate(d->background);
     d->background = background;
     if (background) {
         background->setParentItem(this);
@@ -975,7 +987,7 @@ void QQuickControl::setContentItem(QQuickItem *item)
         return;
 
     contentItemChange(item, d->contentItem);
-    delete d->contentItem;
+    d->deleteDelegate(d->contentItem);
     d->contentItem = item;
     if (item) {
         if (!item->parentItem())
@@ -1003,6 +1015,11 @@ void QQuickControl::componentComplete()
     if (!d->accessibleAttached && QAccessible::isActive())
         accessibilityActiveChanged(true);
 #endif
+
+    if (d->extra.isAllocated()) {
+        qDeleteAll(d->extra.value().pendingDeletions);
+        d->extra.value().pendingDeletions.clear();
+    }
 }
 
 QFont QQuickControl::defaultFont() const

src/quicktemplates2/qquickcontrol_p_p.h

@@ -109,9 +109,15 @@ public:
     static void updateLocaleRecur(QQuickItem *item, const QLocale &l);
     static QLocale calcLocale(const QQuickItem *item);
 
+    void deleteDelegate(QObject *object);
+
     struct ExtraData {
         ExtraData();
         QFont font;
+        // This list contains the default delegates which were
+        // replaced with custom ones via declarative assignments
+        // before Component.completed() was emitted. See QTBUG-50992.
+        QVector<QObject*> pendingDeletions;
     };
     QLazilyAllocated<ExtraData> extra;
 

src/quicktemplates2/qquickdial.cpp

@@ -480,6 +480,7 @@ void QQuickDial::setHandle(QQuickItem *handle)
     if (handle == d->handle)
         return;
 
+    d->deleteDelegate(d->handle);
     d->handle = handle;
     if (d->handle && !d->handle->parentItem())
         d->handle->setParentItem(this);

src/quicktemplates2/qquickgroupbox.cpp

@@ -137,7 +137,7 @@ void QQuickGroupBox::setLabel(QQuickItem *label)
     if (d->label == label)
         return;
 
-    delete d->label;
+    d->deleteDelegate(d->label);
     d->label = label;
     if (label && !label->parentItem())
         label->setParentItem(this);

src/quicktemplates2/qquicklabel.cpp

@@ -167,6 +167,18 @@ QAccessible::Role QQuickLabelPrivate::accessibleRole() const
 }
 #endif
 
+/*
+   Deletes "delegate" if Component.completed() has been emitted,
+   otherwise stores it in pendingDeletions.
+*/
+void QQuickLabelPrivate::deleteDelegate(QObject *delegate)
+{
+    if (componentComplete)
+        delete delegate;
+    else
+        pendingDeletions.append(delegate);
+}
+
 QFont QQuickLabel::font() const
 {
     return QQuickText::font();
@@ -205,7 +217,7 @@ void QQuickLabel::setBackground(QQuickItem *background)
     if (d->background == background)
         return;
 
-    delete d->background;
+    d->deleteDelegate(d->background);
     d->background = background;
     if (background) {
         background->setParentItem(this);
@@ -230,6 +242,9 @@ void QQuickLabel::componentComplete()
     if (!d->accessibleAttached && QAccessible::isActive())
         d->accessibilityActiveChanged(true);
 #endif
+
+    qDeleteAll(d->pendingDeletions);
+    d->pendingDeletions.clear();
 }
 
 void QQuickLabel::itemChange(QQuickItem::ItemChange change, const QQuickItem::ItemChangeData &value)

src/quicktemplates2/qquicklabel_p_p.h

@@ -83,9 +83,15 @@ public:
     QAccessible::Role accessibleRole() const override;
 #endif
 
+    void deleteDelegate(QObject *object);
+
     QFont font;
     QQuickItem *background;
     QQuickAccessibleAttached *accessibleAttached;
+    // This list contains the default delegates which were
+    // replaced with custom ones via declarative assignments
+    // before Component.completed() was emitted. See QTBUG-50992.
+    QVector<QObject *> pendingDeletions;
 };
 
 QT_END_NAMESPACE

src/quicktemplates2/qquickrangeslider.cpp

@@ -226,7 +226,7 @@ void QQuickRangeSliderNode::setHandle(QQuickItem *handle)
     if (d->handle == handle)
         return;
 
-    delete d->handle;
+    QQuickControlPrivate::get(d->slider)->deleteDelegate(d->handle);
     d->handle = handle;
     if (handle) {
         if (!handle->parentItem())

src/quicktemplates2/qquickslider.cpp

@@ -411,7 +411,7 @@ void QQuickSlider::setHandle(QQuickItem *handle)
     if (d->handle == handle)
         return;
 
-    delete d->handle;
+    d->deleteDelegate(d->handle);
     d->handle = handle;
     if (handle && !handle->parentItem())
         handle->setParentItem(this);

src/quicktemplates2/qquickspinbox.cpp

@@ -768,8 +768,14 @@ void QQuickSpinButton::setIndicator(QQuickItem *indicator)
     if (d->indicator == indicator)
         return;
 
-    delete d->indicator;
+    QQuickControl *control = qobject_cast<QQuickControl*>(d->parent);
+    if (control)
+        QQuickControlPrivate::get(control)->deleteDelegate(d->indicator);
+    else
+        delete d->indicator;
+
     d->indicator = indicator;
+
     if (indicator) {
         if (!indicator->parentItem())
             indicator->setParentItem(static_cast<QQuickItem *>(parent()));

src/quicktemplates2/qquicktextarea.cpp

@@ -363,6 +363,14 @@ QAccessible::Role QQuickTextAreaPrivate::accessibleRole() const
 }
 #endif
 
+void QQuickTextAreaPrivate::deleteDelegate(QObject *delegate)
+{
+    if (componentComplete)
+        delete delegate;
+    else
+        pendingDeletions.append(delegate);
+}
+
 QFont QQuickTextArea::font() const
 {
     return QQuickTextEdit::font();
@@ -401,7 +409,7 @@ void QQuickTextArea::setBackground(QQuickItem *background)
     if (d->background == background)
         return;
 
-    delete d->background;
+    d->deleteDelegate(d->background);
     d->background = background;
     if (background) {
         background->setParentItem(this);
@@ -497,6 +505,9 @@ void QQuickTextArea::componentComplete()
     if (!d->accessibleAttached && QAccessible::isActive())
         d->accessibilityActiveChanged(true);
 #endif
+
+    qDeleteAll(d->pendingDeletions);
+    d->pendingDeletions.clear();
 }
 
 void QQuickTextArea::itemChange(QQuickItem::ItemChange change, const QQuickItem::ItemChangeData &value)

src/quicktemplates2/qquicktextarea_p_p.h

@@ -102,6 +102,8 @@ public:
     QAccessible::Role accessibleRole() const override;
 #endif
 
+    void deleteDelegate(QObject *object);
+
     QFont font;
     QQuickItem *background;
     QString placeholder;
@@ -109,6 +111,10 @@ public:
     QQuickPressHandler pressHandler;
     QQuickAccessibleAttached *accessibleAttached;
     QQuickFlickable *flickable;
+    // This list contains the default delegates which were
+    // replaced with custom ones via declarative assignments
+    // before Component.completed() was emitted. See QTBUG-50992.
+    QVector<QObject *> pendingDeletions;
 };
 
 QT_END_NAMESPACE

src/quicktemplates2/qquicktextfield.cpp

@@ -239,6 +239,18 @@ QAccessible::Role QQuickTextFieldPrivate::accessibleRole() const
 }
 #endif
 
+/*
+   Deletes "delegate" if Component.completed() has been emitted,
+   otherwise stores it in pendingDeletions.
+*/
+void QQuickTextFieldPrivate::deleteDelegate(QObject *delegate)
+{
+    if (componentComplete)
+        delete delegate;
+    else
+        pendingDeletions.append(delegate);
+}
+
 QFont QQuickTextField::font() const
 {
     return QQuickTextInput::font();
@@ -277,7 +289,7 @@ void QQuickTextField::setBackground(QQuickItem *background)
     if (d->background == background)
         return;
 
-    delete d->background;
+    d->deleteDelegate(d->background);
     d->background = background;
     if (background) {
         background->setParentItem(this);
@@ -365,6 +377,9 @@ void QQuickTextField::componentComplete()
     if (!d->accessibleAttached && QAccessible::isActive())
         d->accessibilityActiveChanged(true);
 #endif
+
+    qDeleteAll(d->pendingDeletions);
+    d->pendingDeletions.clear();
 }
 
 void QQuickTextField::itemChange(QQuickItem::ItemChange change, const QQuickItem::ItemChangeData &value)

src/quicktemplates2/qquicktextfield_p_p.h

@@ -93,12 +93,18 @@ public:
     QAccessible::Role accessibleRole() const override;
 #endif
 
+    void deleteDelegate(QObject *object);
+
     QFont font;
     QQuickItem *background;
     QString placeholder;
     Qt::FocusReason focusReason;
     QQuickPressHandler pressHandler;
     QQuickAccessibleAttached *accessibleAttached;
+    // This list contains the default delegates which were
+    // replaced with custom ones via declarative assignments
+    // before Component.completed() was emitted. See QTBUG-50992.
+    QVector<QObject *> pendingDeletions;
 };
 
 QT_END_NAMESPACE