Add QWindowPrivate::topLevelWindow() helper function

Might be useful to expose to QWindow in 5.3, but for now it's private
so it can be used by platform plugins.

Change-Id: Iad96d7e249a7b85695668f8d7e8918164ec67442
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

2 files changed, 22 insertions, 0 deletions

diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 2e1d8f9976..4c74a0b834 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -2147,6 +2147,26 @@ void QWindowPrivate::maybeQuitOnLastWindowClosed()
 
 }
 
+QWindow *QWindowPrivate::topLevelWindow() const
+{
+    Q_Q(const QWindow);
+
+    QWindow *window = const_cast<QWindow *>(q);
+
+    while (window) {
+        QWindow *parent = window->parent();
+        if (!parent)
+            parent = window->transientParent();
+
+        if (!parent)
+            break;
+
+        window = parent;
+    }
+
+    return window;
+}
+
 /*!
     Creates a local representation of a window created by another process or by
     using native libraries below Qt.
diff --git a/src/gui/kernel/qwindow_p.h b/src/gui/kernel/qwindow_p.h
index 8d8fca3ce6..8ebbf5d508 100644
--- a/src/gui/kernel/qwindow_p.h
+++ b/src/gui/kernel/qwindow_p.h
@@ -122,6 +122,8 @@ public:
         return offset;
     }
 
+    QWindow *topLevelWindow() const;
+
     virtual QWindow *eventReceiver() { Q_Q(QWindow); return q; }
 
     void updateVisibility();