CODEWITHSUNDEEP
cocoansscrollview
Lupurus
Lupurus

Reputation: 4209

NSClipView bounds - Problems to find out the scroll position

I try to find out, when the user scrolls to the end of a NSTableView. So of course, the tableview is embedded as usual in a NSClipView an this is embedded in a NSScrollView. There are no more changes except the fact of adding insets to the ClipView (Top: 20, Left/Right: 20, Bottom: 0).

To get notified about the scrolling, I connected an outlet of the NSClipView.

So I use this code:

self.clipView.postsBoundsChangedNotifications = true
NotificationCenter.default.addObserver(self,
                                       selector: #selector(scrollViewDidScroll(notification:)),
                                       name: NSView.boundsDidChangeNotification,
                                       object: self.clipView)

...

@objc func scrollViewDidScroll(notification: Notification) {
    print("\(self.clipView.contentInsets.bottom) - \(self.clipView.contentInsets.top)")
    print(self.clipView.bounds)
}

If I'm at the top of the ScrollView, the print-results look like this:

0.0 - 20.0
(-20.0, -20.0, 600.0, 556.0)
// x      y    width  height

This seems ok for me. But if I'm at the bottom, it looks like this:

0.0 - 20.0
(-20.0, 595.0, 600.0, 556.0)

In my understanding, the y-value should be 536, not 595. Where is this difference coming from?

Upvotes: 1

Views: 475

Answers (1)

Lupurus
Lupurus

Reputation: 4209

I found the solution by my one by observing the different values especially after resizing the window. So:

clipView.documentVisibleRect is that, what you really can see. Of course I cannot use the height value of this part. The origin value tells me about the position in the ScrollView.

So necessary is the height of the total content. Therefore I have to use clipView.documentRect.

Now it's very easy: If the visibleRects y-position + the height of the visible rect is the same as the height of the total clipview, we are at the end. This code works:

@objc func scrollViewDidScroll(notification: Notification) {
    let scrollY = self.clipView.documentVisibleRect.origin.y
    let visibleHeight = self.clipView.documentVisibleRect.size.height
    let totalHeight = self.clipView.documentRect.size.height

    if scrollY + visibleHeight >= totalHeight {
        print("end")
    }
}

Upvotes: 1

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