(trunk, qt) #4961 -- make the file list more responsive when a torrent has an extreme number of files.

Before this patch, the test torrent I had with ~10k files took 8 seconds to load. After this patch, it takes less than 1 second.

qt/file-tree.cc

@@ -41,16 +41,31 @@ enum
 *****
 ****/
 
+QHash<QString,int>&
+FileTreeItem :: getMyChildRows()
+{
+  // if necessary, revalidate the name-to-row mapping
+  if( myChildRowsDirty ) {
+      myChildRows.clear();
+      for (size_t i=0, n=childCount(); i<n; ++i)
+          myChildRows.insert (child(i)->name(), i);
+      myChildRowsDirty = false;
+    }
+
+  return myChildRows;
+}
+
+
 FileTreeItem :: ~FileTreeItem( )
 {
     assert( myChildren.isEmpty( ) );
 
-    if( myParent ) {
-        const int pos = myParent->myChildren.indexOf( this );
-        if( pos >= 0 )
-            myParent->myChildren.removeAt( pos );
-        else
+    const int pos = row();
+    if( pos < 0 )
         assert (0 && "failed to remove");
+    else {
+        myParent->myChildren.removeAt( pos );
+        myParent->myChildRowsDirty = true;
     }
 }
 
@@ -58,26 +73,35 @@ void
 FileTreeItem :: appendChild( FileTreeItem * child )
 {
     child->myParent = this;
+    const size_t n = childCount();
     myChildren.append (child);
+    myChildRows.insert (child->name(), n);
 }
 
 FileTreeItem *
 FileTreeItem :: child (const QString& filename )
 {
-    foreach( FileTreeItem * c, myChildren )
-        if( c->name() == filename )
-            return c;
+  FileTreeItem * item(0);
 
-    return 0;
+  const int row = getMyChildRows().value (filename, -1);
+  if (row != -1)
+    {
+      item = child (row);
+      assert (filename == item->name());
+    }
+
+  return item;
 }
 
 int
 FileTreeItem :: row( ) const
 {
-    int i(0);
+    int i(-1);
 
     if( myParent )
-        i = myParent->myChildren.indexOf( const_cast<FileTreeItem*>(this) );
+      {
+        i = myParent->getMyChildRows().value (name(), -1);
+      }
 
     return i;
 }

qt/file-tree.h

@@ -17,6 +17,7 @@
 #include <QObject>
 #include <QItemDelegate>
 #include <QList>
+#include <QHash>
 #include <QSet>
 #include <QSize>
 #include <QString>
@@ -43,7 +44,8 @@ class FileTreeItem: public QObject
         FileTreeItem( int fileIndex, const QString& name="" ):
             myIndex(fileIndex), myParent(0), myName(name),
             myPriority(0), myIsWanted(0),
-            myHaveSize(0), myTotalSize(0) { }
+            myHaveSize(0), myTotalSize(0),
+            myChildRowsDirty(false) { }
 
     public:
         void appendChild( FileTreeItem *child );
@@ -72,11 +74,14 @@ class FileTreeItem: public QObject
         int myIndex;
         FileTreeItem * myParent;
         QList<FileTreeItem*> myChildren;
+        QHash<QString,int> myChildRows;
+        QHash<QString,int>& getMyChildRows();
         const QString myName;
         int myPriority;
         bool myIsWanted;
         uint64_t myHaveSize;
         uint64_t myTotalSize;
+        bool myChildRowsDirty;
 };
 
 class FileTreeModel: public QAbstractItemModel