iOS: Refer to the delegate by id from its background

The backgrounds of the ComboBox and SearchField delegates read the
delegate's properties unqualified, through the delegate's context. When
the model is cleared, the delegate model releases the delegates and
clears their context object first. The count change that follows still
updates the delegates' own isSingleItem, isFirstItem and isLastItem
properties, which in turn re-evaluates the backgrounds' bindings. Those
can't find the names anymore then. Depending on whether the lookups were
cached before, they either throw a ReferenceError or read undefined.

Qualify the accesses with the delegate's id. The id stays valid until
the delegate is actually deleted.

Pick-to: 6.12 6.8
Change-Id: Id7e87d332f795135963e1c0465b3e43260d56479
Reviewed-by: Olivier De Cannière <olivier.decanniere@qt.io>

2 files changed, 18 insertions, 14 deletions

diff --git a/src/quickcontrols/ios/ComboBox.qml b/src/quickcontrols/ios/ComboBox.qml
index b7575160eb..935566dca3 100644
--- a/src/quickcontrols/ios/ComboBox.qml
+++ b/src/quickcontrols/ios/ComboBox.qml
@@ -28,6 +28,8 @@ T.ComboBox {
     rightPadding: padding + (control.mirrored || !indicator || !indicator.visible ? 0 : indicator.width + spacing)
 
     delegate: MenuItem {
+        id: menuItem
+
         width: ListView.view.width
         text: model[control.textRole]
         palette.text: control.palette.text
@@ -45,19 +47,19 @@ T.ComboBox {
         background: Item {
             implicitHeight: 44
             NinePatchImage {
-                y: isLastItem ? -1 : 0
+                y: menuItem.isLastItem ? -1 : 0
                 width: parent.width
-                height: isLastItem ? parent.height + 1 : parent.height
-                rotation: isLastItem ? 180 : 0
-                visible: !(isSingleItem && !control.delegate.pressed)
+                height: menuItem.isLastItem ? parent.height + 1 : parent.height
+                rotation: menuItem.isLastItem ? 180 : 0
+                visible: !(menuItem.isSingleItem && !control.delegate.pressed)
                 source: IOS.url + "menuitem-background"
                 NinePatchImageSelector on source {
                     states: [
-                        {"edge": isFirstItem || isLastItem },
-                        {"single": isSingleItem},
+                        {"edge": menuItem.isFirstItem || menuItem.isLastItem },
+                        {"single": menuItem.isSingleItem},
                         {"light": Application.styleHints.colorScheme === Qt.Light},
                         {"dark": Application.styleHints.colorScheme === Qt.Dark},
-                        {"pressed": down}
+                        {"pressed": menuItem.down}
                     ]
                 }
             }
diff --git a/src/quickcontrols/ios/SearchField.qml b/src/quickcontrols/ios/SearchField.qml
index c332a5c5d6..5d683ff1cf 100644
--- a/src/quickcontrols/ios/SearchField.qml
+++ b/src/quickcontrols/ios/SearchField.qml
@@ -21,6 +21,8 @@ T.SearchField {
     rightPadding: padding + (control.mirrored || !clearIndicator.indicator || !clearIndicator.indicator.visible ? 0 : clearIndicator.indicator.width + spacing)
 
     delegate: MenuItem {
+        id: menuItem
+
         width: ListView.view.width
         text: model[control.textRole]
         palette.text: control.palette.text
@@ -40,19 +42,19 @@ T.SearchField {
         background: Item {
             implicitHeight: 44
             NinePatchImage {
-                y: isLastItem ? -1 : 0
+                y: menuItem.isLastItem ? -1 : 0
                 width: parent.width
-                height: isLastItem ? parent.height + 1 : parent.height
-                rotation: isLastItem ? 180 : 0
-                visible: !(isSingleItem && !control.delegate.pressed)
+                height: menuItem.isLastItem ? parent.height + 1 : parent.height
+                rotation: menuItem.isLastItem ? 180 : 0
+                visible: !(menuItem.isSingleItem && !control.delegate.pressed)
                 source: IOS.url + "menuitem-background"
                 NinePatchImageSelector on source {
                     states: [
-                        {"edge": isFirstItem || isLastItem},
-                        {"single": isSingleItem},
+                        {"edge": menuItem.isFirstItem || menuItem.isLastItem},
+                        {"single": menuItem.isSingleItem},
                         {"light": Application.styleHints.colorScheme === Qt.Light},
                         {"dark": Application.styleHints.colorScheme === Qt.Dark},
-                        {"pressed": down}
+                        {"pressed": menuItem.down}
                     ]
                 }
             }