If you use a TPageControl, and you set certain Tabsheets to invisible, and then you set the OwnerDraw property to true on the PageControl (like the code listed below), you will not get the proper page selected. This is due to a new method, TPageControl.SetTabIndex, that doesn't take visible tabs/pages into account before trying to set the PageControl.ActivePage property. In Delphi 6, this method didn't exist, and everything worked fine. However, in Delphi 2005, things are different. When you set OwnerDraw, the underlying window is recreated. During the destroy of the window, the current tab index is saved off so that it can be restored when the window is later recreated. It is at this point that the new SetTabIndex method is called, and in that method, notice that no effort is made to determine that any tabs have been set invisible, therefore, the wrong page is selected.

The simple workaround is to set OwnerDraw in the DFM, or at the very least, set OwnerDraw prior to setting any tabs to invisible.

Tabsheet2.TabVisible := false;
Pagecontrol1.ActivePage := Tabsheet4;
Pagecontrol1.OwnerDraw := true;

I also submitted this to Quality Central (QC) as issue 11978. You will find a test case in that entry, too.

Lastly, thanks to both Chris Hesik (Borland) for helping me out with some debugger issues, and Rich Werning for helping debug this to the point where we could come up with a valid test case.