Qt Code:
  1. QModelIndex sourceIndex = QFSMfilenameView->setRootPath(qsPath); // gives a model index on the original model
  2. QModelIndex proxyIndex = filenameSortFilterModel->mapFromSource(sourceIndex); // converts that to an index on the proxy
  3. // do something with the view(s) using the proxy index
  4. ui->filenameListView->setRootIndex(proxyIindex);
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You need the index on the proxy because those are the indexes the view(s) you have attached to the proxy will see and use.