GUI and RAII: Cleenup by destructor or window close, Window lifecycle

Question

Say I want to write a wrapper around the windows Window functions. Then I let the Window constructor create a window and associate an internal window procedure which in turn calls virtual function(s).

What is preffered cleanup?

• Following RAII, the destructor of that class should call DestroyWindow. WM_CLOSE then needs to returen 0 and somehow signal the window out of scope (by using a Manager which is not RAII, is it?).

• Do all cleanup in WM_DESTROY by "delete this", forcing the Window to be allocated by new.

Answer 1

The latter approach (delete this) is problematic if you have other clients referencing it (they are now left with invalid pointer), it forces you to allocate your object on heap and require that you introduce some sort of reference counting.

RAII approach is more sensible. After all, it is ok to have object disappear from screen but still being live (i.e. window is hidden). I don't see why the lifetime of window itself has to be tied to the lifetime of the object. You don't need to create the window in the constructor, and you also don't need to destroy it in destructor. Often, this is solved by providing a flag to the constructor, which controls whether the real window will be destroyed automatically in constructor or not - there are scenarios which require one or the other.

There is also the scenario where you want to temporarily attach the window object to an 'external' HWND - in that case you also need to decouple lifetimes of the object and window, so the first approach doesn't work well.

just my 2 cents.