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avoid a model reset in certain conditions

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should be slightly faster and avoid some of the flickering (items deletion and recreation) in ListView
This commit is contained in:
Marco Martin 2012-02-29 14:37:17 +01:00
parent 191bb2cf57
commit 86908c9c31
1 changed files with 31 additions and 4 deletions
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35
declarativeimports/core/datamodel.cpp
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@ -285,8 +285,29 @@ QString DataModel::sourceFilter() const
void DataModel::setItems(const QString &sourceName, const QVariantList &list)
{
beginResetModel();
const int oldLength = m_items.value(sourceName).count();
const int delta = list.length() - oldLength;
const bool firstRun = m_items.isEmpty();
//At what row number the first item associated to this source starts
int sourceIndex = 0;
QMap<QString, QVector<QVariant> >::const_iterator i;
for (i = m_items.constBegin(); i != m_items.constEnd(); ++i) {
if (i.key() == sourceName) {
break;
}
sourceIndex += i.value().count();
}
//signal as inserted the rows at the end, all the other rows will signal a dataupdated.
//better than a model reset because doesn't cause deletion and re-creation of every list item on a qml ListView, repeaters etc.
//the first run it gets reset because otherwise setRoleNames gets broken
if (firstRun) {
beginResetModel();
} else if (delta > 0) {
beginInsertRows(QModelIndex(), sourceIndex + oldLength, sourceIndex + list.length() - 1);
} else if (delta < 0) {
beginRemoveRows(QModelIndex(), sourceIndex + list.length(), sourceIndex + oldLength - 1);
}
//convert to vector, so data() will be O(1)
m_items[sourceName] = list.toVector();
@ -326,9 +347,15 @@ void DataModel::setItems(const QString &sourceName, const QVariantList &list)
setRoleNames(m_roleNames);
//make the declarative view reload everything,
//would be nice an incremental update but is not possible
endResetModel();
if (firstRun) {
endResetModel();
} else if (delta > 0) {
endInsertRows();
} else if (delta < 0) {
endRemoveRows();
}
emit dataChanged(createIndex(sourceIndex, 0),
createIndex(sourceIndex + qMin(list.length(), oldLength), 0));
}
void DataModel::removeSource(const QString &sourceName)