CanTheAlmighty · May 24, 2025 06:45 · Aug 19, 2016 · Aug 19, 2016
diff --git a/DisplayLink.swift b/DisplayLink.swift
@@ -18,7 +18,7 @@ class DisplayLink
 
     var callback : Optional<() -> ()> = nil
 
-    var running : Bool { return !source.isCancelled }
+    var running : Bool { return CVDisplayLinkIsRunning(timer) }
 
     /**
      Creates a new DisplayLink that gets executed on the given queue

diff --git a/DisplayLink.swift b/DisplayLink.swift
@@ -0,0 +1,114 @@
+//
+//  DisplayLink.swift
+//  MetalMac
+//
+//  Created by Jose Canepa on 8/18/16.
+//  Copyright © 2016 Jose Canepa. All rights reserved.
+//
+
+import AppKit
+
+/**
+ Analog to the CADisplayLink in iOS.
+ */
+class DisplayLink
+{
+    let timer  : CVDisplayLink
+    let source : DispatchSourceUserDataAdd
+
+    var callback : Optional<() -> ()> = nil
+
+    var running : Bool { return !source.isCancelled }
+
+    /**
+     Creates a new DisplayLink that gets executed on the given queue
+
+     - Parameters:
+        - queue: Queue which will receive the callback calls
+     */
+    init?(onQueue queue: DispatchQueue = DispatchQueue.main)
+    {
+        // Source
+        source = DispatchSource.makeUserDataAddSource(queue: queue)
+
+        // Timer
+        var timerRef : CVDisplayLink? = nil
+
+        // Create timer
+        var successLink = CVDisplayLinkCreateWithActiveCGDisplays(&timerRef)
+
+        if let timer = timerRef
+        {
+            // Set Output
+            successLink = CVDisplayLinkSetOutputCallback(timer,
+            {
+                (timer : CVDisplayLink, currentTime : UnsafePointer<CVTimeStamp>, outputTime : UnsafePointer<CVTimeStamp>, _ : CVOptionFlags, _ : UnsafeMutablePointer<CVOptionFlags>, sourceUnsafeRaw : UnsafeMutableRawPointer?) -> CVReturn in
+
+                // Un-opaque the source
+                if let sourceUnsafeRaw = sourceUnsafeRaw
+                {
+                    // Update the value of the source, thus, triggering a handle call on the timer
+                    let sourceUnmanaged = Unmanaged<DispatchSourceUserDataAdd>.fromOpaque(sourceUnsafeRaw)
+                    sourceUnmanaged.takeUnretainedValue().add(data: 1)
+                }
+
+                return kCVReturnSuccess
+
+            }, Unmanaged.passUnretained(source).toOpaque())
+
+            guard successLink == kCVReturnSuccess else
+            {
+                NSLog("Failed to create timer with active display")
+                return nil
+            }
+
+            // Connect to display
+            successLink = CVDisplayLinkSetCurrentCGDisplay(timer, CGMainDisplayID())
+
+            guard successLink == kCVReturnSuccess else
+            {
+                NSLog("Failed to connect to display")
+                return nil
+            }
+
+            self.timer = timer
+        }
+        else
+        {
+            NSLog("Failed to create timer with active display")
+            return nil
+        }
+
+        // Timer setup
+        source.setEventHandler(handler:
+        {
+            [weak self] in self?.callback?()
+        })
+    }
+
+    /// Starts the timer
+    func start()
+    {
+        guard !running else { return }
+
+        CVDisplayLinkStart(timer)
+        source.resume()
+    }
+
+    /// Cancels the timer, can be restarted aftewards
+    func cancel()
+    {
+        guard running else { return }
+
+        CVDisplayLinkStop(timer)
+        source.cancel()
+    }
+
+    deinit
+    {
+        if running
+        {
+            cancel()
+        }
+    }
+}
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