Currently the db lookup controls tries to open the dataset linked to
ListSource if is closed at lookup initialization.
The initialization occurs after the control is loaded (streamed) or when
a related db property is changed in the control. This behavior can leads
to opening the dataset at unpredictable time or even twice (if the
programmer opens the dataset after loading of the control). Also it can
trigger events like AfterOpen in improper moments, e.g., data structures
not initialized.
Removing this feature, that is LCL specific, can have side effects in
projects that do not open explicitly the ListSource dataset or closes it
when the lookup control is still in use.
Recently two bugs were reported due to this behavior (see
http://bugs.freepascal.org/view.php?id=22387
http://bugs.freepascal.org/view.php?id=22337
http://lazarus.freepascal.org/index.php/topic,17355.msg96112.html )
So, removing this feature has the benefits of a cleaner code and better
user control when to open the dataset thus avoiding potential bugs and
decreased performance. The drawback is that it can affect programs that
relies in that behavior although it should be easily fixable and if
there's a good moment for such changes is now since 1.0 has already
branched.
Luiz
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