[Interest] [External]Re: Proxied view not updating live when source model does
Sean.Murphy at centauricorp.com
Wed Sep 22 20:54:12 CEST 2021
Thanks for the response, but no, that’s not it. Modifying my baseModel’s setData from
emit dataChanged(index, index, QVector<int>() << role);
emit dataChanged(index, index, QVector<int>() << role << Qt::DisplayRole);
changes nothing in the behavior…
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Subject: [External]Re: [Interest] Proxied view not updating live when source model does
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You emit dataChanged with the given role (which is Qt::EditRole), but not for Qt::DisplayRole. Is it that?
Am 20.09.2021 um 19:15 schrieb Murphy, Sean:
I'm having an issue where my proxy model and its associated view aren't updating live when changes
are made in the source model.
My proxy model simply is attempting to invert the rows of the source model. So it inherits from a
QSortFilterProxyModel and implements mapFromSource() and mapToSource() as follows:
QModelIndex invertRowsModel::mapFromSource(const QModelIndex &sourceIndex) const
if(sourceIndex.isValid() && rowCount() > 0)
return this->index(rowCount() - sourceIndex.row() - 1, sourceIndex.column());
QModelIndex invertRowsModel::mapToSource(const QModelIndex &proxyIndex) const
if(proxyIndex.isValid() && sourceModel() && rowCount() > 0)
return sourceModel()->index(rowCount() - proxyIndex.row() - 1, proxyIndex.column());
I load up my source model with some data, connect the models up to their respective views,
connect the source model to the proxy and launch the application. The original views are
correct - the proxied rows are flipped when compared to the source model. But then if the
user makes a change to some of the data in the source model's view, the corresponding index
in proxy model's view is NOT updated automatically. HOWEVER, if the user then clicks within
the proxy view, or clicks outside of my application, the proxy model will then repaint and the
updated information is correctly shown.
I've attached a minimal example that shows the behavior. Things to note:
1. When the source model emits its dataChanged(), this seems to trigger a dataChanged()
emission in the proxy model as well. The weird (at least to me) thing is that both of those
signals have the SAME model index row & column numbers. I would have expected that
when the source model emits data changed, that the proxy model would translate the
source model's indices into the proper proxy model's indices via the mapFromSource()
function and then emit dataChanged() with those indices. I've got debug statements in
my example to illustrate that no dataChanged() translation is happening - if the user
updates data in row 0 in the source model's view, the proxy model also emits that data
changed in its row 0, but that isn't the correct row for the proxy.
2. We discovered that if we connect the proxy model's dataChanged() signal to a custom
slot within the proxy model, and have that slot emit layoutChanged() then we can get
the live update behavior when the source model updates. This is at line 25 of
invertrowsmodel.cpp. It's commented out initially, but if you uncomment it and re-run
the app then proxy view does update instantly. Other similar signals would work as well -
we just need something triggers the proxy view to refresh the data in the proxied view,
but we don't think we should really have to do this...
3. I have a second view attached to the source model and both source model views update
each other live - changes in one source model view are instantly updated in the other
source model view, but not in the proxy model view without further user interaction
(or by emitting that layoutChanged() signal)
Any thoughts as to why the proxy model isn't updating correctly?
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