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>

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.

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();

src/plugins/platforms/ios/qiosviewcontroller.mm

@@ -44,6 +44,9 @@
 #include <QtGui/QGuiApplication>
 #include <QtGui/QWindow>
 #include <QtGui/QScreen>
+
+#include <QtGui/private/qwindow_p.h>
+
 #include "qiosscreen.h"
 #include "qiosglobal.h"
 #include "qioswindow.h"
@@ -105,11 +108,10 @@
     if (hiddenFromPlist)
         return YES;
     QWindow *focusWindow = QGuiApplication::focusWindow();
-    if (!focusWindow || !focusWindow->handle())
+    if (!focusWindow)
         return [UIApplication sharedApplication].statusBarHidden;
 
-    QWindow *topLevel = static_cast<QIOSWindow *>(focusWindow->handle())->topLevelWindow();
-    return topLevel->windowState() == Qt::WindowFullScreen;
+    return qt_window_private(focusWindow)->topLevelWindow()->windowState() == Qt::WindowFullScreen;
 }
 
 @end

src/plugins/platforms/ios/qioswindow.h

@@ -87,8 +87,6 @@ public:
 
     WId winId() const { return WId(m_view); };
 
-    QWindow *topLevelWindow() const;
-
 private:
     void applyGeometry(const QRect &rect);
 

src/plugins/platforms/ios/qioswindow.mm

@@ -636,23 +636,6 @@ void QIOSWindow::setParent(const QPlatformWindow *parentWindow)
     }
 }
 
-QWindow *QIOSWindow::topLevelWindow() const
-{
-    QWindow *window = this->window();
-    while (window) {
-        QWindow *parent = window->parent();
-        if (!parent)
-            parent = window->transientParent();
-
-        if (!parent)
-            break;
-
-        window = parent;
-    }
-
-    return window;
-}
-
 void QIOSWindow::requestActivateWindow()
 {
     // Note that several windows can be active at the same time if they exist in the same