kde/dolphin
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Runtime optimization for preview sorting: Use 2 different algorithms dependent on the relation between model-rows and preview items. One algorithm is faster when e. g. inserting 10 items into a directory of 2000 items, while the other algorithm is faster when initially loading the directory.

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svn path=/trunk/KDE/kdebase/apps/; revision=820321
This commit is contained in:
Peter Penz 2008-06-13 21:22:13 +00:00
parent b17a5814d0
commit 94fd0e85ff
1 changed files with 45 additions and 22 deletions
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31
src/iconmanager.cpp
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@ -486,14 +486,20 @@ void IconManager::orderItems(KFileItemList& items)
// Order the items in a way that the preview for the visible items
// is generated first, as this improves the feeled performance a lot.
//
// Implementation note: using KDirModel::itemForUrl() would lead to a more
// readable code, but it is slower as iterating all model indicess
// and checking whether the index is part of 'items'.
// Implementation note: 2 different algorithms are used for the sorting.
// Algorithm 1 is faster when having a lot of items in comparison
// to the number of rows in the model. Algorithm 2 is faster
// when having quite less items in comparison to the number of rows in
// the model. Choosing the right algorithm is important when having directories
// with several hundreds or thousands of items.
const int itemCount = items.count();
const int rowCount = m_proxyModel->rowCount();
const QRect visibleArea = m_view->viewport()->rect();
const int rowCount = m_proxyModel->rowCount();
if (itemCount * 10 > rowCount) {
// Algorithm 1: The number of items is > 10 % of the row count. Parse all rows
// and check whether the received row is part of the item list.
for (int row = 0; row < rowCount; ++row) {
const QModelIndex proxyIndex = m_proxyModel->index(row, 0);
const QRect itemRect = m_view->visualRect(proxyIndex);
@ -519,6 +525,23 @@ void IconManager::orderItems(KFileItemList& items)
items.insert(0, item);
}
}
} else {
// Algorithm 2: The number of items is <= 10 % of the row count. In this case iterate
// all items and receive the corresponding row from the item.
for (int i = 0; i < itemCount; ++i) {
const QModelIndex dirIndex = m_dolphinModel->indexForItem(items[i]); // O(n) (n = number of rows)
const QModelIndex proxyIndex = m_proxyModel->mapFromSource(dirIndex);
const QRect itemRect = m_view->visualRect(proxyIndex);
if (itemRect.intersects(visibleArea)) {
// The current item is (at least partly) visible. Move it
// to the front of the list, so that the preview is
// generated earlier.
items.insert(0, items[i]);
items.removeAt(i + 1);
}
}
}
}
#include "iconmanager.moc"