Is it possible to change value by scrolling OSX trackpad (Swift)? - macos

Question

Is it possible to change a value in Cocoa depending on the direction of the trackpad scroll/ magic mouse 'wheel' scroll etc.
For example
var value = 0
func startsScrolling() {
if direction == up {
value += 5
} else if direction == down {
value -= 5
}
}
This would continuous so as you scroll up on the trackpad the direction is down and so it takes 5 off every time the fingers move up, and vice versa.
Thanks and sorry for the bad pseudo code.

Answer 1

You can create a custom window and override scrollWheel NSEvent. You can check the scrollingDeltaX and scrollingDeltaY properties.
class CustomWindow: NSWindow {
override func scrollWheel(theEvent: NSEvent) {
println( "Mouse Scroll scrollingDeltaX = \(theEvent.scrollingDeltaX)" )
println( "Mouse Scroll scrollingDeltaY = \(Int(theEvent.scrollingDeltaY))" )
}
}
If you are using storyboards you have to override scrollWheel NSEvent of your viewController:
import Cocoa
class ViewController: NSViewController {
#IBOutlet weak var strDeltaX: NSTextField!
#IBOutlet weak var strDeltaY: NSTextField!
#IBOutlet weak var strScrollingDeltaX: NSTextField!
#IBOutlet weak var strScrollingDeltaY: NSTextField!
#IBOutlet weak var strValueX: NSTextField!
#IBOutlet weak var strValueY: NSTextField!
var xValue:CGFloat = 0
var yValue:CGFloat = 0
override func viewDidLoad() {
super.viewDidLoad()
}
override var representedObject: AnyObject? {
didSet {
}
}
override func scrollWheel(theEvent: NSEvent) {
strDeltaX.stringValue = "deltaX: \(theEvent.deltaX)"
strDeltaY.stringValue = "deltaY: \(theEvent.deltaY)"
strScrollingDeltaX.stringValue = "scrollingDeltaX: \(theEvent.scrollingDeltaX)"
strScrollingDeltaY.stringValue = "scrollingDeltaY: \(theEvent.scrollingDeltaY)"
xValue += theEvent.scrollingDeltaX
yValue += theEvent.scrollingDeltaY
strValueX.stringValue = "xValue: \(xValue)"
strValueY.stringValue = "yValue: \(yValue)"
}
}

Answer 2

First you need to add a scroll view to your ViewController and link it. You can make it transparent if you don't want it to show. If you have buttons on your ViewController you can send it to back. I've converted code from objective-c. More power to you :)
var pointNow: CGPoint?
func scrollViewWillBeginDragging(scrollView: UIScrollView) {
pointNow = scrollView.contentOffset
}
func scrollViewDidScroll(scrollView: UIScrollView) {
if scrollView.contentOffset.y < pointNow!.y {
println("down")
}
else {
if scrollView.contentOffset.y > pointNow!.y {
println("up")
}
}
}