private void ProcessChanges(RequestIndex index)
{
// When the UI thread acquires the lock, it should update the front
// buffer only if there has been changes. Otherwise, it would block
// the UI for too long on each update.
_isBackBufferDirty = index.Modifications.Count > 0 ||
index.Insertions.Count > 0;
// apply changes to the data in the back buffer
if (index.Modifications.Count > 0)
{
var groupHead = 0;
for (var i = 0; i < _backBuffer.Count; ++i)
{
Trace.Assert(groupHead <= i, $"{nameof(groupHead)} <= {nameof(i)}");
var group = _backBuffer[i];
// update items in the group
var head = 0;
for (var j = 0; j < group.Items.Count; ++j)
{
Trace.Assert(head <= j, $"{nameof(head)} <= {nameof(j)}");
var item = group.Items[j];
if (!index.Modifications.TryGetValue(item.FullPath, out var req))
{
// this item has not changed
group.Items[head] = item;
++head;
}
else if (req is RemoveRequest)
{
_removed.Add(item);
}
else if (req is MoveRequest moveReq)
{
item.Data.ChangePath(moveReq.NewPath);
var key = Query.GetGroup(item.Data);
var list = GetOrAddList(key, index.Insertions);
list.Add(item);
}
else if (req is ModifyRequest modReq)
{
// replace the item but do not throw away its thumbnail
item = new EntityView(modReq.Value, item.Thumbnail);
var key = Query.GetGroup(item.Data);
var list = GetOrAddList(key, index.Insertions);
list.Add(item);
}
}
group.Items.RemoveRange(head, group.Items.Count - head);
// remove the group if it is empty
if (group.Items.Count > 0)
{
_backBuffer[groupHead] = group;
++groupHead;
}
}
_backBuffer.RemoveRange(groupHead, _backBuffer.Count - groupHead);
}
// add new groups
if (index.Insertions.Count > 0)
{
// merge items of existing groups
for (var i = 0; i < _backBuffer.Count; ++i)
{
var group = _backBuffer[i];
if (!index.Insertions.TryGetValue(group.Key, out var list))
{
continue;
}
list.Sort(Comparer);
group.Items = group.Items.Merge(list, Comparer);
index.Insertions.Remove(group.Key);
}
// add brand new groups
var addedGroups = index.Insertions
.Select(pair => new Group(pair.Key)
{
Items = pair.Value
})
.ToList();
addedGroups.Sort();
foreach (var view in addedGroups)
{
view.Items.Sort(Comparer);
}
_backBuffer = _backBuffer.Merge(addedGroups, Comparer <Group> .Default);
}
}
/// <inheritdoc />
/// <summary>
/// Create a new drop event arguments.
/// </summary>
/// <param name="entity">Entity on which the data was dropped. This can be null.</param>
/// <param name="allowedEffect">Allowed effect of the drop operation.</param>
/// <param name="data">Data dropped on the entity</param>
/// <exception cref="ArgumentNullException"><paramref name="data"/> is null</exception>
public DropEventArgs(EntityView entity, DragDropEffects allowedEffect, IDataObject data)
{
Entity = entity;
AllowedEffect = allowedEffect;
Data = data ?? throw new ArgumentNullException(nameof(data));
}
public AddRequest(EntityView value)
{
Value = value ?? throw new ArgumentNullException(nameof(value));
}
public EntityEventArgs(EntityView entity)
{
Entity = entity ?? throw new ArgumentNullException(nameof(entity));
}
public EntityView FindLastItemBelow(EntityView currentItem)
{
return(_view.FindLastItemBelow(currentItem));
}
public EntityView FindFirstItemAbove(EntityView currentItem)
{
return(_view.FindFirstItemAbove(currentItem));
}
public EntityView FindItem(EntityView currentItem, Point delta)
{
return(_view.FindItem(currentItem, delta));
}
public void EnsureItemVisible(EntityView item)
{
_view.EnsureItemVisible(item);
}
