X-Git-Url: https://cloud.milkyroute.net/gitweb/dolphin.git/blobdiff_plain/57179872959ea898e4e640b5392acd13f4951202..6861a876830e301878b65cb4e4574bfda4c73340:/src/iconmanager.cpp

diff --git a/src/iconmanager.cpp b/src/iconmanager.cpp
index b7d75b037..97dac53b7 100644
--- a/src/iconmanager.cpp
+++ b/src/iconmanager.cpp
@@ -32,10 +32,55 @@
 #include <QAbstractItemView>
 #include <QClipboard>
 #include <QColor>
+#include <QListView>
 #include <QPainter>
 #include <QScrollBar>
 #include <QIcon>
 
+/**
+ * If the passed item view is an instance of QListView, expensive
+ * layout operations are blocked in the constructor and are unblocked
+ * again in the destructor.
+ *
+ * This helper class is a workaround for the following huge performance
+ * problem when having directories with several 1000 items:
+ * - each change of an icon emits a dataChanged() signal from the model
+ * - QListView iterates through all items on each dataChanged() signal
+ *   and invokes QItemDelegate::sizeHint()
+ * - the sizeHint() implementation of KFileItemDelegate is quite complex,
+ *   invoking it 1000 times for each icon change might block the UI
+ *
+ * QListView does not invoke QItemDelegate::sizeHint() when the
+ * uniformItemSize property has been set to true, so this property is
+ * set before exchanging a block of icons. It is important to reset
+ * it again before the event loop is entered, otherwise QListView
+ * would not get the correct size hints after dispatching the layoutChanged()
+ * signal.
+ */
+class LayoutBlocker {
+public:
+    LayoutBlocker(QAbstractItemView* view) :
+        m_uniformSizes(false),
+        m_view(qobject_cast<QListView*>(view))
+    {
+        if (m_view != 0) {
+            m_uniformSizes = m_view->uniformItemSizes();
+            m_view->setUniformItemSizes(true);
+        }
+    }
+
+    ~LayoutBlocker()
+    {
+        if (m_view != 0) {
+            m_view->setUniformItemSizes(m_uniformSizes);
+        }
+    }
+
+private:
+    bool m_uniformSizes;
+    QListView* m_view;
+};
+
 IconManager::IconManager(QAbstractItemView* parent, DolphinSortFilterProxyModel* model) :
     QObject(parent),
     m_showPreview(false),
@@ -215,6 +260,7 @@ void IconManager::dispatchPreviewQueue()
             dispatchCount = previewsCount;
         }
 
+        LayoutBlocker blocker(m_view);
         for (int i = 0; i < dispatchCount; ++i) {
             const ItemInfo& preview = m_previews.first();
             replaceIcon(preview.url, preview.pixmap);
@@ -486,37 +532,60 @@ 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 QRect visibleArea = m_view->viewport()->rect();
-
     const int rowCount = m_proxyModel->rowCount();
-    for (int row = 0; row < rowCount; ++row) {
-        const QModelIndex proxyIndex = m_proxyModel->index(row, 0);
-        const QRect itemRect = m_view->visualRect(proxyIndex);
-        const QModelIndex dirIndex = m_proxyModel->mapToSource(proxyIndex);
+    const QRect visibleArea = m_view->viewport()->rect();
 
-        KFileItem item = m_dolphinModel->itemForIndex(dirIndex);  // O(1)
-        const KUrl url = item.url();
+    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);
+            const QModelIndex dirIndex = m_proxyModel->mapToSource(proxyIndex);
+
+            KFileItem item = m_dolphinModel->itemForIndex(dirIndex);  // O(1)
+            const KUrl url = item.url();
+
+            // check whether the item is part of the item list 'items'
+            int index = -1;
+            for (int i = 0; i < itemCount; ++i) {
+                if (items[i].url() == url) {
+                    index = i;
+                    break;
+                }
+            }
 
-        // check whether the item is part of the item list 'items'
-        int index = -1;
-        for (int i = 0; i < itemCount; ++i) {
-            if (items[i].url() == url) {
-                index = i;
-                break;
+            if ((index > 0) && 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.removeAt(index);
+                items.insert(0, item);
             }
         }
-
-        if ((index > 0) && 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.removeAt(index);
-            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);
+            }
         }
     }
 }