Hi guys,
I've derived a class from qx.ui.form.ComboBox and implemented the
qx.ui.core.ISingleSelection and qx.ui.form.IModelSelection interfaces so
that I can use a qx.data.controller.List to bind the drop down to data
fetched from the server; the idea is that the ComboBox is used for
incremental type-ahead style lookups, where if the user pauses long enough
between keystrokes it goes back to the server to get a new list of items to
go in the ComboBox's drop-down.
Everything works fine, except when I get a second lot of data from the
server and set it as the new model for my qx.data.controller.List - it tries
to preserve the selection but fires changeSelection with the wrong model
element.
AFAICT, qx.data.controller.List._applyModel sees that the new model is
longer and extends the list of ListItems, setting each ListItem's model
property to the appropriate element from the new model. However
q.d.c.List._changeTargetSelection (from q.d.c.MSelection) tries to preserve
the selection based on that of the target, but that just means that if the
n-th item was selected before then the n-th item will be selected afterwards
even if the model has completely changed underneath it.
I'm not sure this is clear, so for example: if the 1st model is [ 'a', 'b',
'c' ] and you select 'a' and then apply a new model with [ 'z', 'a', 'b',
'c' ] you'll get a changeSelection event where the new selection is 'z'.
Preserving the selection based on array index doesn't make sense
q.d.c.List should either erase the selection when a new model is applied, or
(ideally) use some form of comparator (or easily overridden method) to copy
selection between before and after.
Have I missed something? If not, I'd like to suggest that
q.d.c.List._applyModel passes the previous selection to
q.d.c.MSelection._changeTargetSelection, and then derived classes could
override the re-selection mechanism (I'll write the patch if someone will
sponsor it to commit)
John
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