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CADisplayLinkTicker.cs
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CADisplayLinkTicker.cs
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using System;
using System.Collections.Concurrent;
using System.Threading;
using Foundation;
using Xamarin.Forms.Internals;
using CoreVideo;
using AppKit;
using CoreAnimation;
namespace Xamarin.Forms.Platform.MacOS
{
// ReSharper disable once InconsistentNaming
internal class CADisplayLinkTicker : Ticker
{
readonly BlockingCollection<Action> _queue = new BlockingCollection<Action>();
CVDisplayLink _link;
public CADisplayLinkTicker()
{
var thread = new Thread(StartThread);
thread.Start();
}
internal new static CADisplayLinkTicker Default => Ticker.Default as CADisplayLinkTicker;
public void Invoke(Action action)
{
_queue.Add(action);
}
protected override void DisableTimer()
{
_link?.Stop();
_link?.Dispose();
_link = null;
}
protected override void EnableTimer()
{
_link = new CVDisplayLink();
_link.SetOutputCallback(DisplayLinkOutputCallback);
_link.Start();
}
public CVReturn DisplayLinkOutputCallback(CVDisplayLink displayLink, ref CVTimeStamp inNow,
ref CVTimeStamp inOutputTime, CVOptionFlags flagsIn, ref CVOptionFlags flagsOut)
{
// There is no autorelease pool when this method is called because it will be called from a background thread
// It's important to create one or you will leak objects
// ReSharper disable once UnusedVariable
using (var pool = new NSAutoreleasePool())
{
Device.BeginInvokeOnMainThread(() => SendSignals());
}
return CVReturn.Success;
}
void StartThread()
{
while (true)
{
Action action = _queue.Take();
bool previous = NSApplication.CheckForIllegalCrossThreadCalls;
NSApplication.CheckForIllegalCrossThreadCalls = false;
CATransaction.Begin();
action.Invoke();
while (_queue.TryTake(out action))
action.Invoke();
CATransaction.Commit();
NSApplication.CheckForIllegalCrossThreadCalls = previous;
}
// ReSharper disable once FunctionNeverReturns
}
}
}