I've now tried various combinations of spoofing a doubleclick when formA makes formB visible, in formB's OnShow() handler, some while later using an asynchronous event, and 100 mSec later using a timer. In all cases, I'm stuck with the behaviour that the first doubleclick on the memo is lost.
This is really only cosmetic and being a debugging facility is most unlikely to be used by anybody except myself, so I'm not putting any more work into it.
I find that Qt works as expected, i.e. the first doubleclick isn't lost. I've not tried any other widgetset.
MarkMLl