Fix Tumbler not respecting currentIndex changes in onModelChanged

The use case in the referenced bug report looks something like this:

    Tumbler {
        model: 4
        // ...
        onModelChanged: {
            currentIndex = model - 2;
        }
    }

The problem was that setting currentIndex in onModelChanged would cause
the wrap to change to true, which in turn caused the internal view to
change to PathView. This would cause the currentIndex to be set to 0
on successive model changes (i.e ++model).

By keeping track of whether or not the user set the currentIndex during
a model change, we can ignore changes in the internal view's
currentIndex and restore the user's currentIndex afterwards.

Task-number: QTBUG-68737
Change-Id: I25738f36cf58a331d1b8e50b5029b4aa1dd27db5
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

1 files changed, 66 insertions, 0 deletions

diff --git a/tests/auto/controls/data/tst_tumbler.qml b/tests/auto/controls/data/tst_tumbler.qml
index 058cbeca..49fd78cc 100644
--- a/tests/auto/controls/data/tst_tumbler.qml
+++ b/tests/auto/controls/data/tst_tumbler.qml
@@ -1112,4 +1112,70 @@ TestCase {
         var label = row.label;
         compare(label.text, "2");
     }
+
+    Component {
+        id: setCurrentIndexOnImperativeModelChangeComponent
+
+        Tumbler {
+            onModelChanged: currentIndex = model - 2
+        }
+    }
+
+    function test_setCurrentIndexOnImperativeModelChange() {
+        var tumbler = createTemporaryObject(setCurrentIndexOnImperativeModelChangeComponent, testCase);
+        verify(tumbler);
+
+        tumbler.model = 4
+        compare(tumbler.count, 4);
+        tumblerView = findView(tumbler);
+        tryCompare(tumblerView, "count", 4);
+
+        // 4 - 2 = 2
+        compare(tumbler.currentIndex, 2);
+
+        ++tumbler.model;
+        compare(tumbler.count, 5);
+        compare(tumbler.wrap, true);
+        tumblerView = findView(tumbler);
+        tryCompare(tumblerView, "count", 5);
+        // 5 - 2 = 3
+        compare(tumbler.currentIndex, 3);
+    }
+
+    Component {
+        id: setCurrentIndexOnDeclarativeModelChangeComponent
+
+        Item {
+            property alias tumbler: tumbler
+
+            property int setting: 4
+
+            Tumbler {
+                id: tumbler
+                model: setting
+                onModelChanged: currentIndex = model - 2
+            }
+        }
+    }
+
+    function test_setCurrentIndexOnDeclarativeModelChange() {
+        var root = createTemporaryObject(setCurrentIndexOnDeclarativeModelChangeComponent, testCase);
+        verify(root);
+
+        var tumbler = root.tumbler;
+        compare(tumbler.count, 4);
+        compare(tumbler.wrap, false);
+        tumblerView = findView(tumbler);
+        tryCompare(tumblerView, "count", 4);
+        // 4 - 2 = 2
+        compare(tumbler.currentIndex, 2);
+
+        ++root.setting;
+        compare(tumbler.count, 5);
+        compare(tumbler.wrap, true);
+        tumblerView = findView(tumbler);
+        tryCompare(tumblerView, "count", 5);
+        // 5 - 2 = 3
+        compare(tumbler.currentIndex, 3);
+    }
 }