Give focus to parent window when focus chain wraps

If the focus chain wraps when tabbing (prev == last && next == first),
we need to give a chance to the parent window to gain focus so that
the focus can be passed to the next/prev object in the focus chain.
To give focus to the prev/next target, override new virtual
setFocusToTarget for QQuickWindowPrivate.

Task-number: QTBUG-121789
Change-Id: Ibe91af53ca622e7fe2b7fc662a95f1a5d7cb479b
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

4 files changed, 57 insertions, 3 deletions

diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index a9a5c4c4a2..75037079fb 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -2470,11 +2470,27 @@ bool QQuickItemPrivate::canAcceptTabFocus(QQuickItem *item)
 */
 bool QQuickItemPrivate::focusNextPrev(QQuickItem *item, bool forward)
 {
-    QQuickItem *next = QQuickItemPrivate::nextPrevItemInTabFocusChain(item, forward);
+    QQuickWindow *window = item->window();
+    const bool wrap = !window || window->isTopLevel();
+
+    QQuickItem *next = QQuickItemPrivate::nextPrevItemInTabFocusChain(item, forward, wrap);
 
     if (next == item)
         return false;
 
+    if (!wrap && !next) {
+        // Focus chain wrapped and we are not top-level window
+        // Give focus to parent window
+        Q_ASSERT(window);
+        Q_ASSERT(window->parent());
+
+        qt_window_private(window->parent())->setFocusToTarget(
+            forward ? QWindowPrivate::FocusTarget::Next
+                    : QWindowPrivate::FocusTarget::Prev);
+        window->parent()->requestActivate();
+        return true;
+    }
+
     next->forceActiveFocus(forward ? Qt::TabFocusReason : Qt::BacktabFocusReason);
 
     return true;
@@ -2524,7 +2540,7 @@ QQuickItem *QQuickItemPrivate::prevTabChildItem(const QQuickItem *item, int star
     return nullptr;
 }
 
-QQuickItem* QQuickItemPrivate::nextPrevItemInTabFocusChain(QQuickItem *item, bool forward)
+QQuickItem* QQuickItemPrivate::nextPrevItemInTabFocusChain(QQuickItem *item, bool forward, bool wrap)
 {
     Q_ASSERT(item);
     qCDebug(lcFocus) << "QQuickItemPrivate::nextPrevItemInTabFocusChain: item:" << item << ", forward:" << forward;
@@ -2618,6 +2634,14 @@ QQuickItem* QQuickItemPrivate::nextPrevItemInTabFocusChain(QQuickItem *item, boo
             }
             current = parent;
         } else if (hasChildren) {
+            if (!wrap && (forward || firstFromItem != from)) {
+                qCDebug(lcFocus) << "QQuickItemPrivate::nextPrevItemInTabFocusChain:"
+                                 << "Focus chain about to wrap.";
+                // If focus chain wraps, we should give the parent window
+                // a chance to get focus, so we should stop here
+                return nullptr;
+            }
+
             // Wrap around after checking all items forward
             if (forward) {
                 current = firstChild;
diff --git a/src/quick/items/qquickitem_p.h b/src/quick/items/qquickitem_p.h
index c2e014b72d..bb238904ca 100644
--- a/src/quick/items/qquickitem_p.h
+++ b/src/quick/items/qquickitem_p.h
@@ -575,7 +575,7 @@ public:
     static bool focusNextPrev(QQuickItem *item, bool forward);
     static QQuickItem *nextTabChildItem(const QQuickItem *item, int start);
     static QQuickItem *prevTabChildItem(const QQuickItem *item, int start);
-    static QQuickItem *nextPrevItemInTabFocusChain(QQuickItem *item, bool forward);
+    static QQuickItem *nextPrevItemInTabFocusChain(QQuickItem *item, bool forward, bool wrap = true);
 
     static bool canAcceptTabFocus(QQuickItem *item);
 
diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index b8c7878e04..09f938a473 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -1853,6 +1853,35 @@ void QQuickWindowPrivate::clearFocusObject()
         da->clearFocusObject();
 }
 
+void QQuickWindowPrivate::setFocusToTarget(FocusTarget target)
+{
+    QQuickItem *newFocusItem = nullptr;
+    if (contentItem) {
+        switch (target) {
+        case FocusTarget::First:
+            newFocusItem = QQuickItemPrivate::nextPrevItemInTabFocusChain(contentItem, true);
+            break;
+        case FocusTarget::Last:
+            newFocusItem = QQuickItemPrivate::nextPrevItemInTabFocusChain(contentItem, false);
+            break;
+        case FocusTarget::Next:
+        case FocusTarget::Prev: {
+            auto da = deliveryAgentPrivate();
+            Q_ASSERT(da);
+            QQuickItem *focusItem = da->focusTargetItem() ? da->focusTargetItem() : contentItem;
+            bool forward = (target == FocusTarget::Next);
+            newFocusItem = QQuickItemPrivate::nextPrevItemInTabFocusChain(focusItem, forward);
+            break;
+        }
+        default:
+            break;
+        }
+    }
+
+    if (newFocusItem)
+        newFocusItem->setFocus(true, Qt::ActiveWindowFocusReason);
+}
+
 /*!
     \qmlproperty list<QtObject> Window::data
     \qmldefault
diff --git a/src/quick/items/qquickwindow_p.h b/src/quick/items/qquickwindow_p.h
index 1b1b12de65..3a70fda3d2 100644
--- a/src/quick/items/qquickwindow_p.h
+++ b/src/quick/items/qquickwindow_p.h
@@ -146,6 +146,7 @@ public:
 #endif
 
     void clearFocusObject() override;
+    void setFocusToTarget(QWindowPrivate::FocusTarget) override;
 
     void dirtyItem(QQuickItem *);
     void cleanup(QSGNode *);