TCM_SETITEMEXTRA message

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.

Parameters

wParam

Number of extra bytes.

lParam

Must be zero.

Return value

Returns TRUE if successful, or FALSE otherwise.

Remarks

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.

Requirements

Minimum supported client
Windows Vista [desktop apps only]
Minimum supported server
Windows Server 2003 [desktop apps only]
Header
Commctrl.h