Good, since the introduction of the PlusWnd::RegisterMessageNotification function I saw this as the solution to
my child windows resizing problem. And yes, it was. By registering WM_SIZE and WM_SIZING for my main window I don't need a timer anymore to refresh the size.
However, I still have a timer for my window. This timer is used to update the preview which shows how the countdown will look like. RegisterMessageNotification works for PlusWnd objects, but how can I make it work for a control?
So, for example, when the date of a DateTimeControl is changed (DTN_DATETIMECHANGE), it should trigger a function.
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[?] Registering notifications for a window control
