Grouping only overlapping points into stacks

Question

I have n number of files on a ScrollView. Every time a file is added, x/y coordinates are stored in an array. The user is able to drag and drop the files anywhere they like. Overlapping files (e.g. distance between center less than 100 points) will form a stack, see screenshot.

At the moment, my implementation is not good. I don't come from a computer science background, so I was wondering which algorithm I should take a look at to improve the performance of this function.

var stacksSet: Set<Controller.File.View> = .init()

for fileView in fileViews {
    for compareTo in fileViews {
        comparisons += 1
        
        if fileView == compareTo { continue }
        
        let pointA = fileView.file.relativePosition
        let pointB = compareTo.file.relativePosition
        
        let distance = hypotf(Float(pointA.x - pointB.x), Float(pointA.y - pointB.y)) * Float(zoomViewSize.width)
        
        if distance < 100 {
            stacksSet.insert(fileView)
            stacksSet.insert(compareTo)
        }
    }
}