The solution here is to draw only visible elements, we keep them in a list which is regularly refreshed ( zoom, drag ...).

I have not yet measure the speed gain, but it is obvious.

The gain is during the visualization, not during the layouting.

MCHttpRepository
    location: 'http://smalltalkhub.com/mc/MathieuDehouck/RoassalAlgorithm/main'
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package: RoassalScalability

Regards

Mathieu