I have a custom NSView
subclass with (for example) the following methods:
override func mouseDown(with event: NSEvent) { Swift.print("mouseDown") }
override func mouseDragged(with event: NSEvent) { Swift.print("mouseDragged") }
override func mouseUp(with event: NSEvent) { Swift.print("mouseUp") }
As long as the mouse (button) is pressed, dragged and released all inside the view, this works fine. However, when the mouse is depressed inside the view, moved outside the view, and only then released, I never receive the mouseUp
event.
P.S.: Calling the super
implementations does not help.
The Handling Mouse Dragging Operations section of Apple's mouse events documentation provided a solution: Apparently, we do receive the mouseUp
event when tracking events with a mouse-tracking loop.
Here's a variant of the sample code from the documentation, adapted for Swift 3:
override func mouseDown(with event: NSEvent) {
var keepOn = true
mouseDownImpl(with: event)
// We need to use a mouse-tracking loop as otherwise mouseUp events are not delivered when the mouse button is
// released outside the view.
while true {
guard let nextEvent = self.window?.nextEvent(matching: [.leftMouseUp, .leftMouseDragged]) else { continue }
let mouseLocation = self.convert(nextEvent.locationInWindow, from: nil)
let isInside = self.bounds.contains(mouseLocation)
switch nextEvent.type {
case .leftMouseDragged:
if isInside {
mouseDraggedImpl(with: nextEvent)
}
case .leftMouseUp:
mouseUpImpl(with: nextEvent)
return
default: break
}
}
}
func mouseDownImpl(with event: NSEvent) { Swift.print("mouseDown") }
func mouseDraggedImpl(with event: NSEvent) { Swift.print("mouseDragged") }
func mouseUpImpl(with event: NSEvent) { Swift.print("mouseUp") }