Performance tips?

[davidbrochart]

Thanks for this great library. I am using it in https://github.com/davidbrochart/nbterm, a Jupyter Notebook in the terminal. So far it works great, but I'm not sure I'm using prompt-toolkit right, and maybe I am abusing its flexibility at the cost of a loss in performance.
In nbterm, the complexity of the layout is directly linked to the number of cells in the notebook, and I have seen that it doesn't scale very well. I would have thought that cells not visible on the screen would not matter (because not rendered), but it looks like it does, e.g. if I have 100 cells but only 10 fit on the screen, then it's "as slow as" rendering these 100 cells. Even focusing on a cell gets slow (using up and down arrows), even if the layout doesn't have to be re-rendered.
Maybe I am doing something wrong, or my application is not well structured. So I was wondering, is there any common mistake you know of, that could explain this loss in performance? Or tips that generally help?
Thanks again!

[davidbrochart]

@joouha has implemented a really nice ScrollingContainer that would be a great contribution to prompt-toolkit, see joouha/euporie#6.