/// <summary>
/// Expand part of the specified lazy box.
/// Todo: implement firstItemToExpand, limItemToExpand.
/// </summary>
internal void ExpandItems(LazyBox <T> source, int firstItemToExpand, int limItemToExpand,
int topOfFirstItemToExpand, int bottomOfLastItemToExpand)
{
var root = ContainingBox.Root;
int oldRootHeight = root.Height;
var builder = ContainingBox.Builder;
builder.CurrentHookup = this;
var objects = new T[limItemToExpand - firstItemToExpand];
source.Items.CopyTo(firstItemToExpand, objects, 0, limItemToExpand - firstItemToExpand);
int insertAt = Children.IndexOf(source); // default, insert in place of source (or before it).
if (firstItemToExpand > 0)
{
// we will keep source to represent the unexpanded items at the start.
insertAt += 1; // insert right after source.
if (limItemToExpand < source.Items.Count)
{
// We will have to make a new lazy box to insert after the expanded items
var newLazyBox = new LazyBox <T>(source.Style, this,
source.Items.Skip(limItemToExpand));
Children.Insert(insertAt, newLazyBox);
ContainingBox.InsertBox(newLazyBox, source);
// We will still insert the expanded items after source, before newLazyBox.
}
// Remove the items no longer considered part of source.
source.RemoveItems(firstItemToExpand, source.Items.Count - firstItemToExpand);
}
else if (limItemToExpand < source.Items.Count)
{
// We will keep source to represent the unexpanded items at the end.
source.RemoveItems(0, limItemToExpand);
}
else
{
// Everything is being expanded: get rid of source altogether.
ContainingBox.RemoveBoxes(source, source);
Children.RemoveAt(insertAt); // get rid of the lazy box from hookup collection
}
// Generate the new items.
for (int i = 0; i < objects.Length; i++)
{
BuildAnItemDisplay(builder, objects[i], insertAt + i);
}
using (var gh = ContainingBox.Root.Site.DrawingInfo)
{
ContainingBox.RelayoutWithParents(gh, true);
}
// Notify root of changed overall size and possibly scroll position.
root.RaiseLazyExpanded(new RootBox.LazyExpandedEventArgs()
{
EstimatedTop = topOfFirstItemToExpand,
EstimatedBottom = bottomOfLastItemToExpand, DeltaHeight = root.Height - oldRootHeight
});
}
