DraggableView.swift

// A view that you can drag to move the underlying window around,
// but other mouse events are still handled by the view.
class DraggableView: NSView {
    var dragStart: Date? = nil
    
    // This alone would be sufficient except that the final mouseUp
    // after a drag gets handled by the view instead of ignored,
    // so the user will accidentally click a button if they happened
    // to start (thus end) their drag on one.
    override var mouseDownCanMoveWindow: Bool { return true }
    
    // Timestamp the start of any drag.
    override func mouseDragged(with event: NSEvent) {
        if dragStart == nil {
            dragStart = Date()
        }
    }
    
    // Figure out if the mouseUp terminated a drag or not.
    // Also consider tiny drags (<100ms) to be clicks.
    override func mouseUp(with event: NSEvent) {
        if let dragStart = dragStart {
            let milliseconds = (Date().timeIntervalSince1970 - dragStart.timeIntervalSince1970) * 1000
            //print("delta", delta)
            if milliseconds > 100 {
                self.dragStart = nil
                return
            }
        }
        
        super.mouseUp(with: event)
    }
}