Fix crash when flicking a ListView-based Tumbler

This only happens in 5.7, and seemingly only when the delegate uses
attached properties (like displacement).

Other fixes required and/or relevant to the patch:
- Fixed some instances of displacementChanged possibly not being
emitted.
- Use QPointer for the attached object's Tumbler pointer, as it
was being accessed while null after this patch.

Change-Id: I7d881d815faf57f1a8bc0ea8e73a7331523d2f9b
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>

1 files changed, 44 insertions, 1 deletions

diff --git a/tests/auto/controls/data/tst_tumbler.qml b/tests/auto/controls/data/tst_tumbler.qml
index 22cde065..401f7537 100644
--- a/tests/auto/controls/data/tst_tumbler.qml
+++ b/tests/auto/controls/data/tst_tumbler.qml
@@ -63,7 +63,8 @@ TestCase {
     }
 
     function cleanup() {
-        tumbler.destroy();
+        if (tumbler)
+            tumbler.destroy();
     }
 
     function tumblerXCenter() {
@@ -234,6 +235,48 @@ TestCase {
         tryCompare(tumbler.dayTumbler, "currentIndex", 27);
     }
 
+    Component {
+        id: timePickerComponent
+
+        Row {
+            property alias minuteTumbler: minuteTumbler
+            property alias amPmTumbler: amPmTumbler
+
+            Tumbler {
+                id: minuteTumbler
+                currentIndex: 6
+                model: 60
+                width: 50
+                height: 150
+            }
+
+            Tumbler {
+                id: amPmTumbler
+                model: ["AM", "PM"]
+                width: 50
+                height: 150
+                contentItem: ListView {
+                    anchors.fill: parent
+                    model: amPmTumbler.model
+                    delegate: amPmTumbler.delegate
+                }
+            }
+        }
+    }
+
+    function test_listViewTimePicker() {
+        tumbler.destroy();
+
+        var root = timePickerComponent.createObject(testCase);
+        verify(root);
+
+        mouseDrag(root.minuteTumbler, root.minuteTumbler.width / 2, root.minuteTumbler.height / 2, 0, 50);
+        // Shouldn't crash.
+        mouseDrag(root.amPmTumbler, root.amPmTumbler.width / 2, root.amPmTumbler.height / 2, 0, 50);
+
+        root.destroy();
+    }
+
     function test_displacement_data() {
         var data = [
             // At 0 offset, the first item is current.