>
> Is it that the existing code recreates all the QT items from scratch every 
> time there is a redraw? And your code can add/remove a much smaller subset 
> of QT items because of your set operations?
>
>
Yes, that's the difference.
 

> I didn't quite follow your example about expanding a node. When a node is 
> expanded, then the children or descendants must appear in the display. How 
> does that relate to the "set of links" you are using to represent the 
> outline structure?
>
> In my code, all nodes both visible and invisible are added to the tree 
once. Expanding and collapsing is done by the QTreeWidget and there is no 
need to add any node for this operation to work. Currently when user clicks 
in the "plus icon" in tree, Leo redraws all visible items and adds those 
previously invisible nodes. To allow user to expand clones separately Leo 
currently uses the following scheme. If a node p.v is a clone then it is 
expanded only if it has expanded bit set on the v-node and 
v.expandedPositions contains a copy of p. However, keeping copies of 
positions in v.expandedPositions is error prone. Some structural changes of 
the outline, like inserting or deleting a node make those cached positions 
invalid and the information about expanded/collapsed state is lost. This 
scheme also doesn't allow to separately expand children of clones. If you 
try to expand one child of a clone, then it is expanded in all other clones 
of its parent. In the new scheme every position has its own item in the 
QTreeWidget and every item keeps track of its expanded/collapsed state. 

I hope this clears a bit what I meant by this example.

Vitalije

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