From 14fc68059c5d533669d9d476814368feb9c49047 Mon Sep 17 00:00:00 2001
From: Sam Pepose <sampepose@gmail.com>
Date: Sun, 8 Jun 2025 17:13:42 -0400
Subject: [PATCH] Add video renderer pool prewarming API

- Add VideoRendererConfiguration public API for prewarming video renderers
- Add internal configure method to VideoRendererPool for capacity management
- Fix thread safety issue in ReusePool initialization
- Eliminates 150-200ms UI hangs when video views are first created
---
 .../StreamVideoSwiftUI/Utils/ReusePool.swift  | 21 +++++++++++---
 .../VideoRendererPool/VideoRendererPool.swift | 19 ++++++++++++
 .../VideoRendererConfiguration.swift          | 29 +++++++++++++++++++
 3 files changed, 65 insertions(+), 4 deletions(-)
 create mode 100644 Sources/StreamVideoSwiftUI/VideoRendererConfiguration.swift

diff --git a/Sources/StreamVideoSwiftUI/Utils/ReusePool.swift b/Sources/StreamVideoSwiftUI/Utils/ReusePool.swift
index 24884793c..e6ebb0068 100644
--- a/Sources/StreamVideoSwiftUI/Utils/ReusePool.swift
+++ b/Sources/StreamVideoSwiftUI/Utils/ReusePool.swift
@@ -30,10 +30,12 @@ final class ReusePool<Element: AnyObject & Hashable> {
         self.initialCapacity = initialCapacity
         self.factory = factory
 
-        // Initialize the pool with a set number of elements
-        for _ in 0..<initialCapacity {
-            let element = factory()
-            available.append(element)
+        // Initialize the pool with a set number of elements (thread-safe)
+        queue.sync {
+            for _ in 0..<initialCapacity {
+                let element = factory()
+                available.append(element)
+            }
         }
     }
 
@@ -94,4 +96,15 @@ final class ReusePool<Element: AnyObject & Hashable> {
             }
         }
     }
+
+    /// Adds a pre-created element to the available pool.
+    /// Used for prewarming to add elements beyond initial capacity.
+    ///
+    /// - Parameter element: The pre-created element to add to the pool.
+    func addToAvailable(_ element: Element) {
+        queue.sync {
+            available.append(element)
+            log.debug("Added prewarmed \(type(of: element)):\(String(describing: element)) to available pool.")
+        }
+    }
 }
diff --git a/Sources/StreamVideoSwiftUI/Utils/VideoRendererPool/VideoRendererPool.swift b/Sources/StreamVideoSwiftUI/Utils/VideoRendererPool/VideoRendererPool.swift
index 359e725b2..132d9dcf1 100644
--- a/Sources/StreamVideoSwiftUI/Utils/VideoRendererPool/VideoRendererPool.swift
+++ b/Sources/StreamVideoSwiftUI/Utils/VideoRendererPool/VideoRendererPool.swift
@@ -47,6 +47,25 @@ final class VideoRendererPool: @unchecked Sendable {
     func releaseRenderer(_ renderer: VideoRenderer) {
         pool.release(renderer)
     }
+
+    /// Configures the global video renderer pool with the specified initial capacity.
+    /// This method is intended for internal use by StreamVideo.
+    ///
+    /// - Parameter initialCapacity: The number of video renderers to pre-create.
+    @MainActor
+    static func configure(initialCapacity: Int) async {
+        // Create pool with 0 initial capacity first
+        currentValue = VideoRendererPool(initialCapacity: 0)
+        
+        // Then add renderers one by one with yielding
+        for _ in 0..<initialCapacity {
+            let renderer = VideoRenderer(frame: CGRect(origin: .zero, size: .zero))
+            currentValue.pool.addToAvailable(renderer)
+            
+            // Yield to allow other main thread work between renderer creations
+            await Task.yield()
+        }
+    }
 }
 
 /// - Note: I have no other way of satisfying the compiler here.
diff --git a/Sources/StreamVideoSwiftUI/VideoRendererConfiguration.swift b/Sources/StreamVideoSwiftUI/VideoRendererConfiguration.swift
new file mode 100644
index 000000000..9c0e3899c
--- /dev/null
+++ b/Sources/StreamVideoSwiftUI/VideoRendererConfiguration.swift
@@ -0,0 +1,29 @@
+//
+// Copyright © 2025 Stream.io Inc. All rights reserved.
+//
+
+import Foundation
+
+/// Configuration options for video rendering performance optimization.
+public enum VideoRendererConfiguration {
+    
+    /// Prewarms video renderers to avoid UI blocking when video views are first created.
+    /// This should be called early in your app lifecycle, before any video views appear.
+    /// Safe to call from any thread - will never block the caller.
+    ///
+    /// - Parameter count: The number of video renderers to pre-create (default is 2).
+    ///
+    /// ## Usage
+    /// ```swift
+    /// // Early in app lifecycle - simple call, never blocks
+    /// VideoRendererConfiguration.prewarm(count: 5)
+    ///
+    /// // Then later initialize StreamVideo as usual
+    /// let streamVideo = StreamVideo(apiKey: apiKey, user: user, token: token)
+    /// ```
+    public static func prewarm(count: Int = 2) {
+        Task.detached {
+            await VideoRendererPool.configure(initialCapacity: count)
+        }
+    }
+}
\ No newline at end of file