Revert "refactor: SpringMotionProtocol for NSWindow and NSPanel confo…

…rmance"

This reverts commit f552afb.

Sources/Model/SpringMotionPhysics.swift

@@ -10,7 +10,7 @@ import Foundation
 /// Implements the physics of spring motion.
 ///
 /// The math is inspired by [this great post](https://www.ryanjuckett.com/damped-springs).
-public final class SpringMotionPhysics {
+final class SpringMotionPhysics {
 
     private let posPosCoef: Double
     private let posVelCoef: Double

Sources/Model/SpringMotionState.swift

@@ -7,7 +7,7 @@
 
 import Foundation
 
-public final class SpringMotionState {
+final class SpringMotionState {
 
     struct Velocity {
 

Sources/SpringMotionPanel.swift

@@ -6,46 +6,124 @@
 //
 
 #if canImport(AppKit)
-import AppKit
 
-open class SpringMotionPanel: NSPanel, SpringMotionWindowProtocol {
-    /// Implement the shared protocol in the NSPanel subclass.
-
+
+open class SpringMotionPanel: NSPanel {
+
+    /// Configuration that adjusts the spring physics behind the animation.
     public var configuration: SpringConfiguration = .default {
         didSet {
             motionPhysics = .init(configuration: configuration, timeStep: 0.008)
         }
     }
-
-    public var destinationPoint: NSPoint? {
+
+    // MARK: Private
+    private var destinationPoint: NSPoint? {
         didSet {
             startMotion()
         }
     }
-    lazy public var motionPhysics = SpringMotionPhysics(configuration: configuration, timeStep: 0.008)
-    public var currentMotionState: SpringMotionState?
-    public var displayLink: CVDisplayLink?
-    public var anchorWindowFrameObservation: NSKeyValueObservation?
+
+    private lazy var motionPhysics = SpringMotionPhysics(configuration: configuration, timeStep: 0.008)
+    private var currentMotionState: SpringMotionState?
+    private var displayLink: CVDisplayLink?
+    private var anchorWindowFrameObservation: NSKeyValueObservation?
 }
 
-// MARK: - Mouse events
-extension SprintMotionPanel {
+// MARK: - API
+public extension SpringMotionPanel {
 
-    override open func mouseDown(with event: NSEvent) {
+    /// Moves the window to the specified point with spring animation.
+    ///
+    /// - Parameter point: a `CGPoint` that defines the window's destination and represents the window's center point.
+    func move(to point: NSPoint) {
+        destinationPoint = point
+    }
+
+    /// Starts following the given window with a certain offset from its center.
+    ///
+    /// - Parameter anchorWindow: an `NSWindow` that this window will follow.
+    /// - Parameter offsetFromCenter: the difference between this window's center and the anchor window's center.
+    func pinToWindow(_ anchorWindow: NSWindow, offsetFromCenter: NSPoint) {
+        unpinFromWindow()
+        move(to: anchorWindow.frame.center + offsetFromCenter)
+        anchorWindowFrameObservation = anchorWindow.observe(\.frame, changeHandler: { [weak self] _, _ in
+            self?.move(to: anchorWindow.frame.center + offsetFromCenter)
+        })
+    }
+
+    /// Stops following a previously followed window, if any.
+    func unpinFromWindow() {
+        anchorWindowFrameObservation?.invalidate()
+        anchorWindowFrameObservation = nil
+    }
+}
+
+// MARK: - Mouse events
+public extension SpringMotionPanel {
+
+    override func mouseDown(with event: NSEvent) {
         super.mouseDown(with: event)
-        /// Stop window from moving if the user grabbed it.
+        // Stop window from moving if the user grabbed it.
         if isMovableByWindowBackground {
             stopMotion()
         }
     }
-    
-    override open func mouseUp(with event: NSEvent) {
+
+    override func mouseUp(with event: NSEvent) {
         super.mouseUp(with: event)
-        /// Continue movement after the user lets go.
+        // Continue movement after the user lets go.
         if isMovableByWindowBackground {
             startMotion()
         }
     }
 }
 
+// MARK: - Start/stop motion
+private extension SpringMotionPanel {
+
+    func startMotion() {
+        guard displayLink == nil,
+              let screenDescription = NSScreen.main?.deviceDescription,
+              let screenNumber = screenDescription[.init("NSScreenNumber")] as? NSNumber else { return }
+
+        CVDisplayLinkCreateWithCGDisplay(screenNumber.uint32Value, &displayLink)
+        guard let displayLink else { return }
+
+        CVDisplayLinkSetOutputHandler(displayLink) { [weak self] _, inNow, _, _, _ in
+            DispatchQueue.main.async { [weak self] in
+                guard let self, let destinationPoint else {
+                    self?.stopMotion()
+                    return
+                }
+
+                let currentState = currentMotionState ?? .init(position: frame.center, velocity: .zero)
+                let nextState = motionPhysics.calculateNextState(from: currentState, destinationPoint: destinationPoint)
+
+                if abs(nextState.velocity.horizontal) < 0.01 && abs(nextState.velocity.vertical) < 0.01 {
+                    stopMotion()
+                    return
+                }
+
+                self.setFrame(.init(x: nextState.position.x - frame.width / 2,
+                                    y: nextState.position.y - frame.height / 2,
+                                    width: frame.width,
+                                    height: frame.height), display: false)
+                currentMotionState = nextState
+            }
+
+            return kCVReturnSuccess
+        }
+
+        CVDisplayLinkStart(displayLink)
+    }
+
+    func stopMotion() {
+        guard let link = displayLink else { return }
+        CVDisplayLinkStop(link)
+        displayLink = nil
+        currentMotionState = nil
+    }
+}
+
 #endif

Sources/SpringMotionWindow.swift

@@ -9,8 +9,122 @@
 
 import AppKit
 
-open class SpringMotionWindow: SpringMotionBase {
-    /// This class inherits all functionality from SpringMotionBase.
+open class SpringMotionWindow: NSWindow {
+
+    /// Configuration that adjusts the spring physics behind the animation.
+    public var configuration: SpringConfiguration = .default {
+        didSet {
+            motionPhysics = .init(configuration: configuration, timeStep: 0.008)
+        }
+    }
+
+    // MARK: Private
+    private var destinationPoint: NSPoint? {
+        didSet {
+            startMotion()
+        }
+    }
+
+    private lazy var motionPhysics = SpringMotionPhysics(configuration: configuration, timeStep: 0.008)
+    private var currentMotionState: SpringMotionState?
+    private var displayLink: CVDisplayLink?
+    private var anchorWindowFrameObservation: NSKeyValueObservation?
+}
+
+// MARK: - API
+public extension SpringMotionWindow {
+
+    /// Moves the window to the specified point with spring animation.
+    ///
+    /// - Parameter point: a `CGPoint` that defines the window's destination and represents the window's center point.
+    func move(to point: NSPoint) {
+        destinationPoint = point
+    }
+
+    /// Starts following the given window with a certain offset from its center.
+    ///
+    /// - Parameter anchorWindow: an `NSWindow` that this window will follow.
+    /// - Parameter offsetFromCenter: the difference between this window's center and the anchor window's center.
+    func pinToWindow(_ anchorWindow: NSWindow, offsetFromCenter: NSPoint) {
+        unpinFromWindow()
+        move(to: anchorWindow.frame.center + offsetFromCenter)
+        anchorWindowFrameObservation = anchorWindow.observe(\.frame, changeHandler: { [weak self] _, _ in
+            self?.move(to: anchorWindow.frame.center + offsetFromCenter)
+        })
+    }
+
+    /// Stops following a previously followed window, if any.
+    func unpinFromWindow() {
+        anchorWindowFrameObservation?.invalidate()
+        anchorWindowFrameObservation = nil
+    }
+}
+
+// MARK: - Mouse events
+extension SpringMotionWindow {
+
+    override open func mouseDown(with event: NSEvent) {
+        super.mouseDown(with: event)
+        // Stop window from moving if the user grabbed it.
+        if isMovableByWindowBackground {
+            stopMotion()
+        }
+    }
+
+    override open func mouseUp(with event: NSEvent) {
+        super.mouseUp(with: event)
+        // Continue movement after the user lets go.
+        if isMovableByWindowBackground {
+            startMotion()
+        }
+    }
+}
+
+// MARK: - Start/stop motion
+private extension SpringMotionWindow {
+
+    func startMotion() {
+        guard displayLink == nil,
+              let screenDescription = NSScreen.main?.deviceDescription,
+              let screenNumber = screenDescription[.init("NSScreenNumber")] as? NSNumber else { return }
+
+        CVDisplayLinkCreateWithCGDisplay(screenNumber.uint32Value, &displayLink)
+        guard let displayLink else { return }
+
+        CVDisplayLinkSetOutputHandler(displayLink) { [weak self] _, inNow, _, _, _ in
+            DispatchQueue.main.async { [weak self] in
+                guard let self = self, let destinationPoint = self.destinationPoint else {
+                    self?.stopMotion()
+                    return
+                }
+
+                let currentState = self.currentMotionState ?? .init(position: self.frame.center, velocity: .zero)
+                let nextState = self.motionPhysics.calculateNextState(from: currentState, destinationPoint: destinationPoint)
+
+                if abs(nextState.velocity.horizontal) < 0.01 && abs(nextState.velocity.vertical) < 0.01 {
+                    self.stopMotion()
+                    return
+                }
+
+                self.setFrame(.init(x: nextState.position.x - self.frame.width / 2,
+                                    y: nextState.position.y - self.frame.height / 2,
+                                    width: self.frame.width,
+                                    height: self.frame.height), display: false)
+                self.currentMotionState = nextState
+            }
+
+            return kCVReturnSuccess
+        }
+
+        CVDisplayLinkStart(displayLink)
+    }
+
+    func stopMotion() {
+        guard let link = displayLink else { return }
+        CVDisplayLinkStop(link)
+        displayLink = nil
+        currentMotionState = nil
+    }
 }
 
 #endif