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());
}
return QModelIndex();
}
QModelIndex invertRowsModel::mapToSource(const QModelIndex &proxyIndex)
const
{
if(proxyIndex.isValid() && sourceModel() && rowCount() > 0)
{
return sourceModel()->index(rowCount() - proxyIndex.row() - 1,
proxyIndex.column());
}
return QModelIndex();
}
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?
Sean
<<attachment: invertRowsModel.zip>>
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