If you have a page full of writing, all sorts of things get slow. I do a lot of digital writing, and have encountered a number of strange slowdowns, even in ap

If you have a page full of writing, all sorts of things get slow. I do a lot of digital writing, and have encountered a number of strange slowdowns, even in apps designed for the purpose. In particular, selecting a large number of strokes can be quite a problem. There are minimum bounding circle algorithms that are O(n) where n is the number of points, but n can get big enough that you may not want to be doing that in an interactive program. You can put objects in a quadtree or similar to look them up quickly, and that may let you discard entire strokes in e.g. Welzl's bounding circle algorithm, but with stroke or curve data you'll still need to search along each one somehow for the extreme points by whatever measure you're using (and a Bezier curve has uncountably infinitely many points, so maybe you can only find an approximate bounding circle?).