Sets the number of bytes per tab reserved for application-defined data in a tab control. You can send this message explicitly or by using the TabCtrl_SetItemExtra macro.
Number of extra bytes.
- Must be zero.
Returns TRUE if successful, or FALSE otherwise.
By default, the number of extra bytes is four. An application that changes the number of extra bytes cannot use the TCITEM structure to retrieve and set the application-defined data for a tab. Instead, you must define a new structure that consists of the TCITEMHEADER structure followed by application-defined members.
An application should only change the number of extra bytes when a tab control does not contain any tabs.
Minimum supported client
|Windows 2000 Professional [desktop apps only]|
Minimum supported server
|Windows 2000 Server [desktop apps only]|