Expand a bit of ownership...

dw/ui.hh

@@ -5,6 +5,8 @@
 #   error Do not include this file directly, use "core.hh" instead.
 #endif
 
+#include <memory>
+
 namespace dw {
 namespace core {
 
@@ -427,7 +429,7 @@ protected:
 
    void setEmbed (Embed *embed);
 
-   virtual Platform *createPlatform () = 0;
+   virtual std::unique_ptr< Platform > createPlatform () = 0;
    virtual void setLayout (Layout *layout) = 0;
 
    virtual int reliefXThickness () = 0;