Windows: Refactor code registering/unregistering drop sites.

Only top level windows of certain types should be drop sites. Add code to
update drop site registration to setParent().

This ensures the drop site is unregistered for example when winId()
is invoked on a parentless widgets which is later inserted into a layout.

Task-number: QTBUG-33635

Change-Id: Ia3161ecd59753f3f39d2a5967e9cb922cf0b9203
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/plugins/platforms/windows/qwindowswindow.h b/src/plugins/platforms/windows/qwindowswindow.h
index 99c5761a65..1d515fd2fe 100644
--- a/src/plugins/platforms/windows/qwindowswindow.h
+++ b/src/plugins/platforms/windows/qwindowswindow.h
@@ -278,11 +278,12 @@ private:
     inline QWindowsWindowData setWindowFlags_sys(Qt::WindowFlags wt, unsigned flags = 0) const;
     inline bool isFullScreen_sys() const;
     inline void setWindowState_sys(Qt::WindowState newState);
-    inline void setParent_sys(const QPlatformWindow *parent) const;
+    inline void setParent_sys(const QPlatformWindow *parent);
     inline void updateTransientParent() const;
     void destroyWindow();
-    void registerDropSite();
-    void unregisterDropSite();
+    inline bool isDropSiteEnabled() const { return m_dropTarget != 0; }
+    void setDropSiteEnabled(bool enabled);
+    void updateDropSite();
     void handleGeometryChange();
     void handleWindowStateChange(Qt::WindowState state);
     inline void destroyIcon();