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Details

Type: Bug
Resolution: Done
Priority: P3: Somewhat important
Fix Version/s: 5.3.0
Affects Version/s: 4.8.3, 5.2.1
Component/s: (Inactive) QtQuick (version 1)
Labels:
None

Commits:
f09b12cea1143f1b2763064bb0d3e6592081de2b

Description

If the number of items in a model changes while the item view initialization is not completed, the view does not emit a countChanged notification.

This can cause wrong evaluations in bound properties (e.g. if some text should be hidden if the listview is empty).

This example is a stripped down version of actual code to illustrate the problem. The number of items is displayed as "3" whereas due to the filter it actually is 0.

The bug exists in ListView, GridView, PathView and Repeater and can be fixed by emitting the countChanged signal in the itemsRemoved/itemsInserted slots of the views regardless of the view's component initialization state.

The QtQuick 2.0 implementation in Qt 5.x does not have this problem.

import QtQuick 1.1
import org.test.models 1.0

Rectangle {
  width: 360
  height: 360

  ListModel {
    id: m
    ListElement { filter: "X*" }
  }

  Repeater {
    model: m
    delegate: Column {
      property string mfilter: model.filter
      Text {
        visible: lv.count > 0
        text: "Item count " + lv.count + " (it actually is 0, so you should not see this text)"
      }
      ListView {
        width: 100; height: 100
        FilterModel {
          id: fm
          filter: mfilter
        }
        id: lv
        model: fm
        delegate: Text { text: "entry " + model.display }
      }
    }
  }
}

#ifndef FILTERMODEL_H
#define FILTERMODEL_H

#include <QSortFilterProxyModel>
#include <QStringListModel>
#include <QDebug>

class FilterModel : public QSortFilterProxyModel
{
  Q_OBJECT
  Q_PROPERTY(QString filter READ filter WRITE setFilter NOTIFY filterChanged)

  QString m_filter;

public:
  explicit FilterModel(QObject *parent = 0) :
    QSortFilterProxyModel(parent)
  {
    setSourceModel(new QStringListModel(QStringList() << "AA" << "BB" << "CC", this));
  }

  QString filter() const { return m_filter; }
  void setFilter(const QString &filter)
  {
    qDebug() << "setFilter" << filter;
    if (m_filter != filter) {
      m_filter = filter;
      setFilterWildcard(m_filter);
      emit filterChanged();
    }
    qDebug() << "rowCount" << rowCount();
  }

signals:

  void filterChanged();
};

#endif // FILTERMODEL_H