[Qt-interest] ModelView - how to use proxies to filter this data?

[Stephen Kelly]

On Wed, Dec 2, 2009 at 2:18 PM, Daniel Price <daniel.price at fxhome.com> wrote:
> Can I see the source code for DescendantEntitiesProxyModel? I'm not familiar with KDE underpinnings.
>
> From my experimentation so far, proxy models can only remove items from the model. They cannot change the fundamental structure so if the source is a tree, they will still display a tree.

Hey, sorry for the very late reply. The LGPL code is now here:

http://websvn.kde.org/trunk/KDE/kdepimlibs/akonadi/kdescendantsproxymodel_p.h?view=markup
http://websvn.kde.org/trunk/KDE/kdepimlibs/akonadi/kdescendantsproxymodel.cpp?view=markup

Note that it is also broken in a subtle way because it uses the
internalPointer() of source model indexes. My intention is to replace
it with the even more generic KReparentingProxyModel

http://websvn.kde.org/trunk/KDE/kdepim/akonadi/akonadi_next/kreparentingproxymodel.h?view=markup

It can turn a list into a tree (for email threading for example), a
tree into a list, or a tree into a different tree. So yes, you can
change the fundamental structure of the model, but it's not trivial if
you want to keep up to date with source model changes.

All the best,

Steve.

>
>> -----Original Message-----
>> From: Stephen Kelly [mailto:steveire at gmail.com]
>> Sent: 02 December 2009 13:14
>> To: Daniel Price
>> Subject: Re: [Qt-interest] ModelView - how to use proxies to filter
>> this data?
>>
>> Daniel Price wrote:
>>
>> > I've been playing with this sortfilter approach and it works fine if
>> the
>> > layout of the source matches the output. However, what if my source
>> items
>> > are buried away?
>> >
>> > Eg:
>> >
>> > --Companies
>> > ----Company1
>> > ------Product1
>> > ------Product2
>> > ------Product3
>> > ----Company2
>> > ------Product4
>> >
>> > The above is stored within a QAbstractItemModel and I want to use a
>> proxy
>> > to just pull out all the products to give me this in a table:
>> >
>> > --Product1
>> > --Product2
>> > --Product3
>> > --Product4
>> >
>> > How could I do this using a proxy? If I store a unique identifier in
>> each
>> > of the product rows identifying it as a Product record, could I
>> somehow
>> > use the built-in filtering to get just those rows?
>>
>> You could do this using a proxy. The way I've done it is to flatten the
>> tree
>> into a list, then filter out Company* from the list.
>>
>> Some screenshots here:
>>
>> http://api.kde.org/playground-api/pim-
>> apidocs/akonadi/akonadi_next/html/index.html
>>
>> (Look for DescendantEntitiesProxyModel)
>>
>> All the best,
>>
>> Steve.
>>
>> >
>> >
>> >> -----Original Message-----
>> >> From: qt-interest-bounces at trolltech.com [mailto:qt-interest-
>> >> bounces at trolltech.com] On Behalf Of Sean Harmer
>> >> Sent: 01 December 2009 15:54
>> >> To: qt-interest at trolltech.com
>> >> Subject: Re: [Qt-interest] ModelView - how to use proxies to filter
>> >> this data?
>> >>
>> >> Hi,
>> >>
>> >> On Tuesday 01 December 2009 15:36:18 Daniel Price wrote:
>> >> > Thanks for the info. I hadn't considered using a proxy filter and
>> >> just
>> >> >  accepting/rejecting rows. Does that work with hierarchical data
>> >> though?
>> >>
>> >> Yes it works absolutely fine with hierarchical data as that is what
>> I
>> >> am using.
>> >>
>> >> > I actually QAbstractProxyModel and implemented the mapTo/mapFrom
>> >> functions.
>> >> >  But sorting doesn't seem to work.
>> >>
>> >> Yeah I thought about doing it that way, but then decided that
>> >> QSortFilterProxyModel fitted my needs with a little subclassing.
>> >>
>> >> > BTW it looks like you're storing pointers to your structures in
>> your
>> >> >  variants as integers and casting them back.
>> >>
>> >> No I am storing them as void* in the QModelIndex's internal pointer
>> so
>> >> that is
>> >> why I am casting them back to my specific types. My model's index
>> >> function
>> >> looks like this:
>> >>
>> >> QModelIndex MapsData1DTreeModel::index( int row, int col, const
>> >> QModelIndex&
>> >> parent ) const
>> >> {
>> >>     MapsData1DTreeModelGroupNode* parentItem;
>> >>     if ( !parent.isValid() )
>> >>         parentItem = m_root;
>> >>     else
>> >>         parentItem = static_cast<MapsData1DTreeModelGroupNode*>(
>> >> parent.internalPointer() );
>> >>
>> >>     MapsData1DTreeModelNode* childItem = parentItem->child( row );
>> >>     if ( childItem )
>> >>         return createIndex( row, col, childItem );
>> >>     else
>> >>         return QModelIndex();
>> >> }
>> >>
>> >> Good luck.
>> >>
>> >> Sean
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