http://bugs.winehq.org/show_bug.cgi?id=9795
--- Comment #17 from Pavel rawlik@list.ru 2010-06-23 07:59:20 --- This behavior seems to be documented ... See: owner_drawn_tabs
http://msdn.microsoft.com/en-us/library/bb760550%28VS.85%29.aspx#owner_drawn...
By default, the itemData member of DRAWITEMSTRUCT contains the value of the >lParam member of the TCITEM structure. However, if you change the amount of >application-defined data per tab, itemData contains the ADRESS of the data >instead.
And
http://msdn.microsoft.com/en-us/library/bb760554%28v=VS.85%29.aspx
lParam LPARAM
Application-defined data associated with the tab control item. If more or >less than 4 bytes of application-defined data exist per tab, an application must >define a structure and use it instead of the TCITEM structure. The first member >of the application-defined structure must be a TCITEMHEADER structure.