/// <summary>
/// Computes the next visible TreeViewItem in order from top to bottom.
/// Wraps around when it gets to the bottom-most item.
/// </summary>
/// <param name="treeViewItem">The starting item.</param>
/// <returns>The next item in the traversal.</returns>
private static TreeViewItem NextVisibleTreeViewItem(TreeViewItem treeViewItem)
{
// First child
if (treeViewItem.IsExpanded && treeViewItem.HasItems && treeViewItem.Items.Count > 0)
{
return(treeViewItem.ItemContainerGenerator.ContainerFromIndex(0) as TreeViewItem);
}
while (true)
{
var parent = treeViewItem.FindVisualAncestor <TreeViewItem>();
ItemContainerGenerator itemContainerGenerator;
if (parent == null)
{
var treeView = treeViewItem.FindVisualAncestor <TreeView>();
itemContainerGenerator = treeView.ItemContainerGenerator;
}
else
{
itemContainerGenerator = parent.ItemContainerGenerator;
}
var childIndex = itemContainerGenerator.IndexFromContainer(treeViewItem);
if (childIndex >= 0 && (childIndex + 1) < itemContainerGenerator.Items.Count)
{
// Next sibling
return(itemContainerGenerator.ContainerFromIndex(childIndex + 1) as TreeViewItem);
}
// No more siblings
if (parent == null)
{
// Reached the end. Start at the top again.
return(itemContainerGenerator.ContainerFromIndex(0) as TreeViewItem);
}
// Go to the parent and find its next sibling.
treeViewItem = parent;
}
}
