From ed7a9f881319ec7a535334a2cc6fdf92d398aaec Mon Sep 17 00:00:00 2001
From: Nikita Tsukanov <keks9n@gmail.com>
Date: Mon, 17 Jul 2023 17:26:19 +0600
Subject: [PATCH] Special handling for macos dispatcher quirks

---
 .../Threading/Dispatcher.Queue.cs             | 20 +++++++++++++------
 .../Threading/Dispatcher.Timers.cs            |  2 +-
 src/Avalonia.Base/Threading/Dispatcher.cs     |  3 +++
 .../Threading/DispatcherFrame.cs              |  8 ++++++--
 4 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/src/Avalonia.Base/Threading/Dispatcher.Queue.cs b/src/Avalonia.Base/Threading/Dispatcher.Queue.cs
index 829ab4cf87..1644332aea 100644
--- a/src/Avalonia.Base/Threading/Dispatcher.Queue.cs
+++ b/src/Avalonia.Base/Threading/Dispatcher.Queue.cs
@@ -9,7 +9,9 @@ public partial class Dispatcher
     private readonly DispatcherPriorityQueue _queue = new();
     private bool _signaled;
     private bool _explicitBackgroundProcessingRequested;
-    private const int MaximumTimeProcessingBackgroundJobs = 50;
+    private const int MaximumInputStarvationTimeInFallbackMode = 50;
+    private const int MaximumInputStarvationTimeInExplicitProcessingExplicitMode = 50;
+    private int _maximumInputStarvationTime;
     
     void RequestBackgroundProcessing()
     {
@@ -35,8 +37,8 @@ public partial class Dispatcher
         lock (InstanceLock)
         {
             _explicitBackgroundProcessingRequested = false;
-            ExecuteJobsCore();
         }
+        ExecuteJobsCore(true);
     }
 
     /// <summary>
@@ -130,10 +132,10 @@ public partial class Dispatcher
         lock (InstanceLock)
             _signaled = false;
 
-        ExecuteJobsCore();
+        ExecuteJobsCore(false);
     }
 
-    void ExecuteJobsCore()
+    void ExecuteJobsCore(bool fromExplicitBackgroundProcessingCallback)
     {
         long? backgroundJobExecutionStartedAt = null;
         while (true)
@@ -151,7 +153,6 @@ public partial class Dispatcher
             if (job.Priority > DispatcherPriority.Input)
             {
                 ExecuteJob(job);
-                backgroundJobExecutionStartedAt = null;
             }
             // If platform supports pending input query, ask the platform if we can continue running low priority jobs
             else if (_pendingInputImpl?.CanQueryPendingInput == true)
@@ -164,6 +165,13 @@ public partial class Dispatcher
                     return;
                 }
             }
+            // We can't ask if the implementation has pending input, so we should let it to call us back
+            // Once it thinks that input is handled
+            else if (_backgroundProcessingImpl != null && !fromExplicitBackgroundProcessingCallback)
+            {
+                RequestBackgroundProcessing();
+                return;
+            }
             // We can't check if there is pending input, but still need to enforce interactivity
             // so we stop processing background jobs after some timeout and start a timer to continue later
             else
@@ -171,7 +179,7 @@ public partial class Dispatcher
                 if (backgroundJobExecutionStartedAt == null)
                     backgroundJobExecutionStartedAt = Now;
                 
-                if (Now - backgroundJobExecutionStartedAt.Value > MaximumTimeProcessingBackgroundJobs)
+                if (Now - backgroundJobExecutionStartedAt.Value > _maximumInputStarvationTime)
                 {
                     _signaled = true;
                     RequestBackgroundProcessing();
diff --git a/src/Avalonia.Base/Threading/Dispatcher.Timers.cs b/src/Avalonia.Base/Threading/Dispatcher.Timers.cs
index bb252b7f55..51408daad1 100644
--- a/src/Avalonia.Base/Threading/Dispatcher.Timers.cs
+++ b/src/Avalonia.Base/Threading/Dispatcher.Timers.cs
@@ -127,7 +127,7 @@ public partial class Dispatcher
         if (needToPromoteTimers)
             PromoteTimers();
         if (needToProcessQueue)
-            ExecuteJobsCore();
+            ExecuteJobsCore(false);
         UpdateOSTimer();
     }
     
diff --git a/src/Avalonia.Base/Threading/Dispatcher.cs b/src/Avalonia.Base/Threading/Dispatcher.cs
index f257072dc8..46c6699b5a 100644
--- a/src/Avalonia.Base/Threading/Dispatcher.cs
+++ b/src/Avalonia.Base/Threading/Dispatcher.cs
@@ -34,6 +34,9 @@ public partial class Dispatcher : IDispatcher
         _controlledImpl = _impl as IControlledDispatcherImpl;
         _pendingInputImpl = _impl as IDispatcherImplWithPendingInput;
         _backgroundProcessingImpl = _impl as IDispatcherImplWithExplicitBackgroundProcessing;
+        _maximumInputStarvationTime = _backgroundProcessingImpl == null ?
+            MaximumInputStarvationTimeInFallbackMode :
+            MaximumInputStarvationTimeInExplicitProcessingExplicitMode;
         if (_backgroundProcessingImpl != null)
             _backgroundProcessingImpl.ReadyForBackgroundProcessing += OnReadyForExplicitBackgroundProcessing;
     }
diff --git a/src/Avalonia.Base/Threading/DispatcherFrame.cs b/src/Avalonia.Base/Threading/DispatcherFrame.cs
index e826432475..1a80740420 100644
--- a/src/Avalonia.Base/Threading/DispatcherFrame.cs
+++ b/src/Avalonia.Base/Threading/DispatcherFrame.cs
@@ -38,10 +38,14 @@ public class DispatcherFrame
     ///        for their important criteria to be met.  These frames
     ///        should have a timeout associated with them.
     /// </param>
-    public DispatcherFrame(bool exitWhenRequested)
+    public DispatcherFrame(bool exitWhenRequested) : this(Dispatcher.UIThread, exitWhenRequested)
     {
-        Dispatcher = Dispatcher.UIThread;
         Dispatcher.VerifyAccess();
+    }
+
+    internal DispatcherFrame(Dispatcher dispatcher, bool exitWhenRequested)
+    {
+        Dispatcher = dispatcher;
         _exitWhenRequested = exitWhenRequested;
         _continue = true;
     }