CODEWITHSUNDEEP
cocoaevent-handlingnsviewappkitmouseup
MrMage
MrMage

Reputation: 7487

NSView does not receive mouseUp: event when mouse button is released outside of view

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.

Upvotes: 6

Views: 3978

Answers (2)

soundGuy33
soundGuy33

Reputation: 59

Am posting this as an answer to a similar question that I had where I needed to know that the user had stopped using a slider. I needed to capture the mouseUp event from NSSlider or actually NSView. The solution that worked out for me was to simply capture the mouseDown event and add some code when it exited and does the job that I needed. Hope that this is of use to somebody else who needs to do a similar thing. Code written using XCode 11.3.1 Swift 5

import Cocoa

class SMSlider: NSSlider {

    var calledOnExit:(()->())?

    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)
    }

    override func mouseDown(with event: NSEvent) {
        super.mouseDown(with: event)
        if self.calledOnExit != nil {
            self.calledOnExit!()
        }
    }    
}

// In my main swift app
func sliderStopped() {
    print("Slider stopped moving")
}

//...
if slider == nil {
    slider = SMSlider()
}
slider?.isContinuous = true
slider?.target = self
slider?.calledOnExit = sliderStopped
//...

Upvotes: -1

MrMage
MrMage

Reputation: 7487

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") }

Upvotes: 14

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