Define BasicUI::WindowPlacement and subclass for wxWidgets...

... An elaborate way to hold a wxWindow* as parent of a window, but avoiding
mention of wxWindow* in the member functions of BasicUI::Services, to be defined
next

libraries/lib-basic-ui/BasicUI.cpp

@@ -13,6 +13,8 @@ Paul Licameli
 #include <vector>
 
 namespace  BasicUI {
+WindowPlacement::~WindowPlacement() = default;
+
 Services::~Services() = default;
 
 static Services *theInstance = nullptr;

libraries/lib-basic-ui/BasicUI.h

@@ -20,6 +20,20 @@ namespace BasicUI {
 
 using Action = std::function<void()>;
 
+//! Subclasses may hold information such as a parent window pointer for a dialog.
+/*! The default-constructed empty value of this base class must be accepted by overrides of methods of
+ Services */
+class BASIC_UI_API WindowPlacement {
+public:
+   WindowPlacement() = default;
+
+   //! Don't slice
+   WindowPlacement( const WindowPlacement& ) PROHIBITED;
+   //! Don't slice
+   WindowPlacement &operator=( const WindowPlacement& ) PROHIBITED;
+   virtual ~WindowPlacement();
+};
+
 //! @}
 
 //! Abstract class defines a few user interface services, not mentioning particular toolkits