Hello,

Just try the following steps:

. Open Lazarus IDE with its empty Form1;
. Put a TabControl1 in the Form1 and add one or more tabs;
. Implement the OnDrawTab event with this code:
  procedure TForm1.TabControl1DrawTab(Control: TCustomTabControl;
    TabIndex: Integer; const Rect: TRect; AActive: Boolean);
  begin
    ShowMessage('OK');
  end;

. Compile and run the project.

You can't see any message.

Now set True in the TabControl1.OwnerDraw and try the tests above again, you can't see any message btw.

So, is the OnDrawTab event working on Windows?

PS. I did this same test on GTK and I found same problem there too.

I commented out the entire definition of (F)OnDrawTab and the LCL still compiled fine.
So, it seems this eventhandler is never invoked at all. (Tested on Windows)

Bart

Hm... I'm going to issue that ...

Done. #29543 <http://bugs.freepascal.org/view.php?id=29543>