The PAGE_CHANGING events are sent before the current page is changed. It allows the program to examine the current page (which can be retrieved with getOldSelection/1) and to veto the page change by calling wxNotifyEvent:veto/1 if, for example, the current values in the controls of the old page are invalid.
The PAGE_CHANGED events are sent after the page has been changed and the program cannot veto it any more, it just informs it about the page change.
To summarize, if the program is interested in validating the page values before allowing the user to change it, it should process the PAGE_CHANGING event, otherwise PAGE_CHANGED is probably enough. In any case, it is probably unnecessary to process both events at once.
wxWidgets docs: wxBookCtrlEvent
command_notebook_page_changing | choicebook_page_changed |
choicebook_page_changing | treebook_page_changed |
treebook_page_changing | toolbook_page_changed |
toolbook_page_changing | listbook_page_changed |
Returns the page that was selected before the change, wxNOT_FOUND if none was selected.
Sets the id of the page selected before the change.
Sets the selection member variable.