procedure TCustomControl.WMPaint(var Message: TLMPaint);
begin
   if (csDestroying in ComponentState) or (not HandleAllocated) then exit;
   Include(FControlState, csCustomPaint);
   inherited WMPaint(Message);
   Exclude(FControlState, csCustomPaint);
end;

Maybe use try-finally here for Exclude?

Just curious:

What use is altering a local variable (i.e. FControlState) when you are calling an inherited code?

I mean, shouldn't you alter ControlState (I am assuming it exist in the 'inherited')?

I don't know any case where this would help.

Mattias