[lazarus] Tab generates error

[Tony]

This is odd...

Doubleclicking a control generates three events in this order:

WMLMButtonUp
WMLMButtonDblClk
WMLMButtonUp

This causes me grief because if I use setfocus during the dblclk event, 
the next buttonup event will set the focus to NO control, despite the 
fact that I'm not setting focus within the event handler.  What then 
happens is that if you hit tab after a doubleclick on the TCheckbook 
control, the program crashes saying that you can't focus an invisible 
control.  The crash is generated by the TControl.Tabhandler or something 
like that... not by my code directly.

I've added a workaround to detect if I'm getting the duplicate buttonup 
message immediately following the doubleclick, and set a focus within 
that event to the control I want.

-Tony