Hi Martin
Oops, I should have thought to try a standard control first (sorry, it was
the end of a long day)
Thanks for your example, it helped me strip down to a much simpler example
and track down what was different to mine.
My widget implements ISingleSelection and I found that because
ISingleSelection and IMultiSelection controls are handled differently, if I
use a SelectBox instead of a List then the SelectBox will always keep the
n-th selection; my demo is http://tinyurl.com/2uz5hz4.
This kind of makes sense for SelectBox because it does not have the concept
of an empty selection, but IMHO the ISingleSelection interface implies that
an empty selection is valid for some types of control, in that it doesn't
specifically exclude empty selections and it has a resetSelection() method.
Could MSelection._updateSelection call target.resetSelection() if there is
nothing to be selected?
Cheers
John
From: Martin Wittemann <[email protected]>
Reply-To: qooxdoo Development <[email protected]>
Date: Fri, 24 Sep 2010 12:51:15 +0200
To: qooxdoo Development <[email protected]>
Subject: Re: [qooxdoo-devel] List controller problem - wrong selection when
changing the model
Hello,
seems like it has something to do with your widget. I just tried the list
and it works as expected, the selection will be removed on the set of a new
model:
http://tinyurl.com/2whzmq9
So maybe it has to do with the model selection which is wrong to the time
the model changes. That would be the first thing i would check if the
bindings are already applied. I had once a bug where the bindings were
executed after the selection changed which caused the list to be the same in
that moment. If you can supply some code, i can try to give you some help
debugging it.
Best,
Martin
Am 23.09.2010 um 21:35 schrieb John Spackman:
> 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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