chore(DoubleFlickableWithFolding): Inline component moved to separate file

Otherwise it would crash tests under Qt 5.15.2
Additionally Storybook page has been extended by adding footers.

storybook/pages/DoubleFlickableWithFoldingPage.qml

@@ -1,6 +1,7 @@
 import QtQuick 2.15
 import QtQuick.Controls 2.15
 import QtQuick.Layouts 1.15
+import QtQml 2.15
 
 import StatusQ.Core 0.1
 import StatusQ.Core.Utils 0.1
@@ -15,6 +16,8 @@ SplitView {
     readonly property int header1Size: 40
     readonly property int header2Size: 40
 
+    readonly property int footerSize: 60
+
     function fillModel(model, count) {
         const content = []
 
@@ -104,6 +107,29 @@ SplitView {
                         }
                     }
 
+                    footer: Rectangle {
+                        z: 1
+
+                        height: root.footerSize
+                        width: grid1.width
+
+                        Label {
+                            anchors.centerIn: parent
+                            text: "placeholder 1"
+                        }
+
+                        color: "yellow"
+                    }
+
+                    Binding {
+                        target: grid1
+                        property: "footer"
+                        when: !grid1.model || grid1.count !== 0
+                        //when: grid1.count !== 0
+                        value: null
+                        restoreMode: Binding.RestoreBindingOrValue
+                    }
+
                     delegate: Rectangle {
                         width: grid1.cellWidth
                         height: grid1.cellHeight
@@ -156,6 +182,28 @@ SplitView {
                         }
                     }
 
+                    footer: Rectangle {
+                        z: 1
+
+                        height: root.footerSize
+                        width: grid2.width
+
+                        Label {
+                            anchors.centerIn: parent
+                            text: "placeholder 2"
+                        }
+
+                        color: "yellow"
+                    }
+
+                    Binding {
+                        target: grid2
+                        property: "footer"
+                        when: !grid2.model || grid2.count !== 0
+                        value: null
+                        restoreMode: Binding.RestoreBindingOrValue
+                    }
+
                     delegate: Rectangle {
                         width: grid2.cellWidth
                         height: grid2.cellHeight

ui/StatusQ/src/StatusQ/Core/Utils/DoubleFlickableWithFolding.qml

@@ -1,6 +1,8 @@
 import QtQuick 2.15
 import QtQml 2.15
 
+import "internal"
+
 DoubleFlickable {
     readonly property bool flickable1Folded: !d.grid1ContentInViewport
     readonly property bool flickable2Folded: d.grid2HeaderAtEnd || d.model2Blocked
@@ -49,50 +51,22 @@ DoubleFlickable {
         }
     }
 
+    // The Flickable component (ListView or GridView) controls y positioning
+    // of the header and it cannot be effectively overriden. As a solution to
+    // this problem, the header can be reparented to a wrapper compensating
+    // for the y offset.
     HeaderWrapper {
-        id: header1Wrapper
-
         parent: contentItem
         flickable: flickable1
         y: contentY
     }
 
     HeaderWrapper {
-        id: header2Wrapper
-
         parent: contentItem
         flickable: flickable2
         y: contentY + d.grid2HeaderOffset
     }
 
-    // The Flickable component (ListView or GridView) controls y positioning
-    // of the header and it cannot be effectively overriden. As a solution to
-    // this problem, the header can be reparented to a wrapper compensating
-    // for the y offset.
-    component HeaderWrapper: Item {
-        property Flickable flickable
-
-        z: 1
-
-        Binding {
-            when: flickable.headerItem
-            target: flickable.headerItem
-            property: "parent"
-            value: container
-            restoreMode: Binding.RestoreBindingOrValue
-        }
-
-        Binding {
-            when: flickable.headerItem
-            target: container
-            property: "y"
-            value: -flickable.headerItem.y
-            restoreMode: Binding.RestoreBindingOrValue
-        }
-
-        Item { id: container }
-    }
-
     QtObject {
         id: d
 

ui/StatusQ/src/StatusQ/Core/Utils/internal/HeaderWrapper.qml

@@ -0,0 +1,29 @@
+import QtQuick 2.15
+import QtQml 2.15
+
+// This component is implementation detail of DoubleFlickableWithFolding
+// Moved to external file instead of using inline component because a bug
+// in Qt 5.15.2 causing tests crash.
+Item {
+    property Flickable flickable
+
+    z: 1
+
+    Binding {
+        when: flickable.headerItem
+        target: flickable.headerItem
+        property: "parent"
+        value: container
+        restoreMode: Binding.RestoreBindingOrValue
+    }
+
+    Binding {
+        when: flickable.headerItem
+        target: container
+        property: "y"
+        value: -flickable.headerItem.y
+        restoreMode: Binding.RestoreBindingOrValue
+    }
+
+    Item { id: container }
+}

ui/StatusQ/src/statusq.qrc

@@ -181,6 +181,7 @@
         <file>StatusQ/Core/Utils/ClippingWrapper.qml</file>
         <file>StatusQ/Core/Utils/DoubleFlickable.qml</file>
         <file>StatusQ/Core/Utils/DoubleFlickableWithFolding.qml</file>
+        <file>StatusQ/Core/Utils/internal/HeaderWrapper.qml</file>
         <file>StatusQ/Core/Utils/Emoji.qml</file>
         <file>StatusQ/Core/Utils/JSONListModel.qml</file>
         <file>StatusQ/Core/Utils/ModelChangeGuard.qml</file>