Fix setWindowFlags() for QMdiSubWindow.

It was impossible to hide/show the close button after a QMdiSubWindow
was created.

Task-number: QTBUG-9933
Task-number: QTBUG-27274

[ChangeLog][QtWidgets][QMdiSubWindow] Fixed setWindowFlags() for QMdiSubWindow.

Change-Id: I7db9a1bef5ba8a8ace729acb85682c8b3de9c33c
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

3 files changed, 25 insertions, 15 deletions

diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 6b2f88ce58..596b92e06b 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -9479,27 +9479,36 @@ void QWidget::updateGeometry()
 */
 void QWidget::setWindowFlags(Qt::WindowFlags flags)
 {
-    if (data->window_flags == flags)
-        return;
-
     Q_D(QWidget);
+    d->setWindowFlags(flags);
+}
+
+/*! \internal
+
+    Implemented in QWidgetPrivate so that QMdiSubWindowPrivate can reimplement it.
+*/
+void QWidgetPrivate::setWindowFlags(Qt::WindowFlags flags)
+{
+    Q_Q(QWidget);
+    if (q->data->window_flags == flags)
+        return;
 
-    if ((data->window_flags | flags) & Qt::Window) {
+    if ((q->data->window_flags | flags) & Qt::Window) {
         // the old type was a window and/or the new type is a window
-        QPoint oldPos = pos();
-        bool visible = isVisible();
-        setParent(parentWidget(), flags);
+        QPoint oldPos = q->pos();
+        bool visible = q->isVisible();
+        q->setParent(q->parentWidget(), flags);
 
         // if both types are windows or neither of them are, we restore
         // the old position
-        if (!((data->window_flags ^ flags) & Qt::Window)
-            && (visible || testAttribute(Qt::WA_Moved))) {
-            move(oldPos);
+        if (!((q->data->window_flags ^ flags) & Qt::Window)
+            && (visible || q->testAttribute(Qt::WA_Moved))) {
+            q->move(oldPos);
         }
         // for backward-compatibility we change Qt::WA_QuitOnClose attribute value only when the window was recreated.
-        d->adjustQuitOnCloseAttribute();
+        adjustQuitOnCloseAttribute();
     } else {
-        data->window_flags = flags;
+        q->data->window_flags = flags;
     }
 }
 
diff --git a/src/widgets/kernel/qwidget_p.h b/src/widgets/kernel/qwidget_p.h
index 943b7057b5..5387341a75 100644
--- a/src/widgets/kernel/qwidget_p.h
+++ b/src/widgets/kernel/qwidget_p.h
@@ -489,6 +489,7 @@ public:
     void setWindowTitle_helper(const QString &cap);
     void setWindowFilePath_helper(const QString &filePath);
     void setWindowModified_helper();
+    virtual void setWindowFlags(Qt::WindowFlags windowFlags);
 
     bool setMinimumSize_helper(int &minw, int &minh);
     bool setMaximumSize_helper(int &maxw, int &maxh);
diff --git a/src/widgets/widgets/qmdisubwindow.cpp b/src/widgets/widgets/qmdisubwindow.cpp
index 8e1dcbee18..94674319bc 100644
--- a/src/widgets/widgets/qmdisubwindow.cpp
+++ b/src/widgets/widgets/qmdisubwindow.cpp
@@ -2057,13 +2057,13 @@ void QMdiSubWindowPrivate::restoreFocus()
 
 /*!
     \internal
-    ### Please add QEvent::WindowFlagsChange event
 */
 void QMdiSubWindowPrivate::setWindowFlags(Qt::WindowFlags windowFlags)
 {
     Q_Q(QMdiSubWindow);
+
     if (!parent) {
-        q->setWindowFlags(windowFlags);
+        QWidgetPrivate::setWindowFlags(windowFlags);
         return;
     }
 
@@ -2097,7 +2097,7 @@ void QMdiSubWindowPrivate::setWindowFlags(Qt::WindowFlags windowFlags)
         delete sizeGrip;
 #endif
 
-    q->setWindowFlags(windowFlags);
+    QWidgetPrivate::setWindowFlags(windowFlags);
     updateGeometryConstraints();
     updateActions();
     QSize currentSize = q->size();