wxWidgets defines a special identifier value wxID_ANY which is used in the following two situations:
wxID_ANY to let wxWidgets assign an unused identifier to it automatically Another standard special identifier value is wxID_NONE: this is a value which is not matched by any other id.
wxWidgets also defines a few standard command identifiers which may be used by the user code and also are sometimes used by wxWidgets itself. These reserved identifiers are all in the range between wxID_LOWEST and wxID_HIGHEST and, accordingly, the user code should avoid defining its own constants in this range (e.g. by using wxID_ANY and retrieving the control's id after it was created).
Refer to the list of stock items for the subset of standard IDs which are stock IDs as well.