Fix visibility of scroll bars in ScrollView

When imperatively assigning a contentItem, we need to make sure that
we respect the policy of the scroll bars, otherwise they could end up
visible when they shouldn't be, and vice versa.

This patch also sets the ScrollView as the parent item of the
contentItem, as a ListView assigned imperatively may already have a
parent item, and so setContentItem_helper will not set one.
When setting the parent item, we also need to ensure that the
stacking order is correct, otherwise the scroll bars will be
behind the contentItem and can't be interacted with.

Task-number: QTBUG-106118
Change-Id: I88d342282ea6d202cbe0f776a6bf4fb1f9cadc48
Reviewed-by: Oliver Eftevaag <oliver.eftevaag@qt.io>
(cherry picked from commit db8f3607e0fb640b6bc1bb69a81ecd5f937dc184)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 22 insertions, 3 deletions

diff --git a/tests/auto/quickcontrols/controls/data/tst_scrollview.qml b/tests/auto/quickcontrols/controls/data/tst_scrollview.qml
index 355e130d9f..5c9c6f1184 100644
--- a/tests/auto/quickcontrols/controls/data/tst_scrollview.qml
+++ b/tests/auto/quickcontrols/controls/data/tst_scrollview.qml
@@ -617,6 +617,7 @@ TestCase {
         id: bindingToContentItemAndStandaloneFlickable
 
         Item {
+            objectName: "container"
             width: 200
             height: 200
 
@@ -655,7 +656,7 @@ TestCase {
         verify(verticalScrollBar.visible)
         verify(horizontalScrollBar.visible)
 
-        mouseDrag(verticalScrollBar, verticalScrollBar.width / 2, verticalScrollBar.height / 2, 0, 50)
+        mouseWheel(control, control.width / 2, control.height / 2, 0, -120)
         verify(verticalScrollBar.active)
         verify(horizontalScrollBar.active)
     }
@@ -664,6 +665,7 @@ TestCase {
         id: contentItemAssignedImperatively
 
         Item {
+            objectName: "container"
             width: 100
             height: 100
 
@@ -689,11 +691,28 @@ TestCase {
     }
 
     // Tests that a ListView declared before the ScrollView (as the QObject destruction order
-    // is relevant for the bug) and assigned imperatively to ScrollView does not cause a crash
-    // on exit.
+    // is relevant for the bug) and assigned imperatively to ScrollView does not cause:
+    // - a crash on exit
+    // - scroll bars that should be hidden to be visible
     function test_contentItemAssignedImperatively() {
         let root = createTemporaryObject(contentItemAssignedImperatively, testCase)
         verify(root)
+
+        let control = root.scrollView
+        let flickable = control.contentItem
+        compare(flickable.parent, control)
+
+        let horizontalScrollBar = control.ScrollBar.horizontal
+        let verticalScrollBar = control.ScrollBar.vertical
+        // The horizontal ScrollBar's policy is set to AlwaysOff, so it shouldn't ever be visible.
+        verify(!horizontalScrollBar.visible)
+        // The vertical ScrollBar should be visible...
+        verify(verticalScrollBar.visible)
+
+        // ... and it should become active when the ScrollView is scrolled.
+        mouseWheel(control, control.width / 2, control.height / 2, 0, -120)
+        verify(verticalScrollBar.active)
+
         // Shouldn't crash.
     }
 }