I'm not sure I have clearly expressed my question. So I'd better give some background. In our project, we use processing to display kind of information in different ways. In one of these displaying method, we use a hierarchical tree like way to display from left to right. As there are so many info to be displayed in bottom of the structure, we write a scroll bar to display part of this structure according to users' interests. And actually inside the void draw() method, we have drawn all the whole structure, but only displayed part of it according to the scroll bar and window size.

My question is it displays really slow if there are too many elements. (the most shapes we draw here is rectangle and lines.)

If there is a way to only draw part of the shapes?