QDialogButtonBox: Don't set focus in a dialog with StrongFocus children

A QDialogButtonBox with the first accept button becoming default, didn't
explicitly set focus on such a button in a QDialog.
d44413d526ec12ed83acd7343c2005782178c7ad implemented this missing
functionality. It set focus to the automatic default button, unless the
QDialog had a focusWidget() set.

That has caused a regression, in cases where
- the QDialog has a QWidget child with a Qt::StrongFocus policy, and
- the QDialog is not yet visible, so focusWidget() returns nullptr.

Amend d44413d526ec12ed83acd7343c2005782178c7ad:

Implement a helper in QWidgetPrivate, that returns true, if a child
with a given focus policy is found.

Do not set focus to a QDialogButtonBox's automatic default button, when
- not located inside a QDialog, or
- a focusWidget() exists, or
- the dialog has QWidget child with Qt::StrongFocus, that is not a
child of the QDialogButtonBox.

Add an autotest function.

Pick-to: 6.7 6.6 6.5
Fixes: QTBUG-121514
Fixes: QTBUG-120049
Change-Id: I3c65ae36b56657f9af4a3a4b42f9b66e8bc5c534
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

3 files changed, 23 insertions, 2 deletions

diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 81c6a6f7d8..ec7b5ce69a 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -13235,6 +13235,24 @@ void QWidgetPrivate::setNetWmWindowTypes(bool skipIfMissing)
 #endif
 }
 
+/*!
+   \internal
+   \return \c true, if a child with \param policy exists and isn't a child of \param excludeChildrenOf.
+   Return false otherwise.
+ */
+bool QWidgetPrivate::hasChildWithFocusPolicy(Qt::FocusPolicy policy, const QWidget *excludeChildrenOf) const
+{
+    Q_Q(const QWidget);
+    const QWidgetList &children = q->findChildren<QWidget *>(Qt::FindChildrenRecursively);
+    for (const auto *child : children) {
+        if (child->focusPolicy() == policy && child->isEnabled()
+            && (!excludeChildrenOf || !excludeChildrenOf->isAncestorOf(child))) {
+            return true;
+        }
+    }
+    return false;
+}
+
 #ifndef QT_NO_DEBUG_STREAM
 
 namespace {
diff --git a/src/widgets/kernel/qwidget_p.h b/src/widgets/kernel/qwidget_p.h
index b677a7eccb..e2e39630de 100644
--- a/src/widgets/kernel/qwidget_p.h
+++ b/src/widgets/kernel/qwidget_p.h
@@ -741,6 +741,7 @@ public:
 
     bool stealKeyboardGrab(bool grab);
     bool stealMouseGrab(bool grab);
+    bool hasChildWithFocusPolicy(Qt::FocusPolicy policy, const QWidget *excludeChildrenOf = nullptr) const;
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(QWidgetPrivate::DrawWidgetFlags)
diff --git a/src/widgets/widgets/qdialogbuttonbox.cpp b/src/widgets/widgets/qdialogbuttonbox.cpp
index 545e8bb6da..30ace89fa8 100644
--- a/src/widgets/widgets/qdialogbuttonbox.cpp
+++ b/src/widgets/widgets/qdialogbuttonbox.cpp
@@ -1029,8 +1029,10 @@ void QDialogButtonBoxPrivate::ensureFirstAcceptIsDefault()
         // focus proxy/first button stealing the default button status
         // immediately when the button box is focused, which is not what
         // we want. Account for this by explicitly making the firstAcceptButton
-        // focused as well, unless an explicit focus widget has been set.
-        if (dialog && !dialog->focusWidget())
+        // focused as well, unless an explicit focus widget has been set, or
+        // a dialog child has Qt::StrongFocus.
+        if (dialog && !(QWidgetPrivate::get(dialog)->hasChildWithFocusPolicy(Qt::StrongFocus, q)
+                        || dialog->focusWidget()))
             firstAcceptButton->setFocus();
     }
 }