Run HelloTreeView, go to the checked tab, and collapse / expand the root node - note the graphics disappear.
From a quick analysis, this appears to be due to the item count changing in TreeViewSkin, which results in new cells being built, but I think the graphics are being updated in both the old and new cells (with the same graphic), so they are being removed automatically by the scenegraph to avoid duplication.
From a quick analysis, this appears to be due to the item count changing in TreeViewSkin, which results in new cells being built, but I think the graphics are being updated in both the old and new cells (with the same graphic), so they are being removed automatically by the scenegraph to avoid duplication.