Soft scroll animation NSScrollView scrollToPoint:

Question

I want to create soft animation between transitions in simply UI:

Answer 1

I know, it's a little bit off topic, but I wanted to have a similar method to scroll to a rectangle with animation like in UIView's scrollRectToVisible(_ rect: CGRect, animated: Bool) for my NSView. I was happy to find this post, but apparently the accepted answer doesn't always work correctly. It turns out that there is a problem with bounds.origin of the clipview. If the view is getting resized (e.g. by resizing the surrounding window) bounds.origin is somehow shifted against the true origin of the visible rectangle in y-direction. I could not figure out why and by how much. Well, there is also this statement in the Apple docs not to manipulate the clipview directly since its main purpose is to function internally as a scrolling machine for views.

But I do know the true origin of the visible area. It’s part of the clipview’s documentVisibleRect. So I take that origin for the calculation of the scrolled origin of the visibleRect and shift the bounds.origin of the clipview by the same amount, and voilà: that works even if the view is getting resized.

Here is my implementation of the new method of my NSView:

   func scroll(toRect rect: CGRect, animationDuration duration: Double) {
        if let scrollView = enclosingScrollView {           // we do have a scroll view
            let clipView = scrollView.contentView           // and thats its clip view
            var newOrigin = clipView.documentVisibleRect.origin // make a copy of the current origin
            if newOrigin.x > rect.origin.x {                // we are too far to the right
                newOrigin.x = rect.origin.x                 // correct that
            }
            if rect.origin.x > newOrigin.x + clipView.documentVisibleRect.width - rect.width {  // we are too far to the left
                newOrigin.x = rect.origin.x - clipView.documentVisibleRect.width + rect.width   // correct that
            }
            if newOrigin.y > rect.origin.y {                // we are too low
                newOrigin.y = rect.origin.y                 // correct that
            }
            if rect.origin.y > newOrigin.y + clipView.documentVisibleRect.height - rect.height {    // we are too high
                newOrigin.y = rect.origin.y - clipView.documentVisibleRect.height + rect.height // correct that
            }
            newOrigin.x += clipView.bounds.origin.x - clipView.documentVisibleRect.origin.x  // match the new origin to bounds.origin
            newOrigin.y += clipView.bounds.origin.y - clipView.documentVisibleRect.origin.y
            NSAnimationContext.beginGrouping()              // create the animation
            NSAnimationContext.current.duration = duration  // set its duration
            clipView.animator().setBoundsOrigin(newOrigin)  // set the new origin with animation
            scrollView.reflectScrolledClipView(clipView)    // and inform the scroll view about that
            NSAnimationContext.endGrouping()                // finaly do the animation
        }
    }

Please note, that I use flipped coordinates in my NSView to make it match the iOS behaviour. BTW: the animation duration in the iOS version scrollRectToVisible is 0.3 seconds.

https://www.fpposchmann.de/animate-nsviews-scrolltovisible/