Batch thread updates

Session.xcodeproj/project.pbxproj

@@ -509,6 +509,7 @@
 		C3548F0824456AB6009433A8 /* UIView+Wrapping.swift in Sources */ = {isa = PBXBuildFile; fileRef = C3548F0724456AB6009433A8 /* UIView+Wrapping.swift */; };
 		C354E75A23FE2A7600CE22E3 /* BaseVC.swift in Sources */ = {isa = PBXBuildFile; fileRef = C354E75923FE2A7600CE22E3 /* BaseVC.swift */; };
 		C35D0DB525AE5F1200B6BF49 /* UIEdgeInsets.swift in Sources */ = {isa = PBXBuildFile; fileRef = C35D0DB425AE5F1200B6BF49 /* UIEdgeInsets.swift */; };
+		C35D76DB26606304009AA5FB /* ThreadUpdateBatcher.swift in Sources */ = {isa = PBXBuildFile; fileRef = C35D76DA26606303009AA5FB /* ThreadUpdateBatcher.swift */; };
 		C35E8AAE2485E51D00ACB629 /* IP2Country.swift in Sources */ = {isa = PBXBuildFile; fileRef = C35E8AAD2485E51D00ACB629 /* IP2Country.swift */; };
 		C374EEE225DA26740073A857 /* LinkPreviewModal.swift in Sources */ = {isa = PBXBuildFile; fileRef = C374EEE125DA26740073A857 /* LinkPreviewModal.swift */; };
 		C374EEEB25DA3CA70073A857 /* ConversationTitleView.swift in Sources */ = {isa = PBXBuildFile; fileRef = C374EEEA25DA3CA70073A857 /* ConversationTitleView.swift */; };
@@ -1487,6 +1488,7 @@
 		C3548F0724456AB6009433A8 /* UIView+Wrapping.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "UIView+Wrapping.swift"; sourceTree = "<group>"; };
 		C354E75923FE2A7600CE22E3 /* BaseVC.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BaseVC.swift; sourceTree = "<group>"; };
 		C35D0DB425AE5F1200B6BF49 /* UIEdgeInsets.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UIEdgeInsets.swift; sourceTree = "<group>"; };
+		C35D76DA26606303009AA5FB /* ThreadUpdateBatcher.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ThreadUpdateBatcher.swift; sourceTree = "<group>"; };
 		C35E8AA22485C72300ACB629 /* SwiftCSV.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = SwiftCSV.framework; path = ThirdParty/Carthage/Build/iOS/SwiftCSV.framework; sourceTree = "<group>"; };
 		C35E8AAD2485E51D00ACB629 /* IP2Country.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = IP2Country.swift; sourceTree = "<group>"; };
 		C374EEE125DA26740073A857 /* LinkPreviewModal.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LinkPreviewModal.swift; sourceTree = "<group>"; };
@@ -3145,6 +3147,7 @@
 				C33FDB32255A580A00E217F9 /* SSKIncrementingIdFinder.swift */,
 				C3A3A170256E1D25004D228D /* SSKReachabilityManager.swift */,
 				C3ECBF7A257056B700EA7FCE /* Threading.swift */,
+				C35D76DA26606303009AA5FB /* ThreadUpdateBatcher.swift */,
 				C33FDB5F255A580E00E217F9 /* YapDatabaseConnection+OWS.h */,
 				C33FDB43255A580C00E217F9 /* YapDatabaseConnection+OWS.m */,
 				C33FDA88255A57FD00E217F9 /* YapDatabaseTransaction+OWS.h */,
@@ -4680,6 +4683,7 @@
 				B8856CEE256F1054001CE70E /* OWSAudioPlayer.m in Sources */,
 				C32C5EDC256DF501003C73A2 /* YapDatabaseConnection+OWS.m in Sources */,
 				C3BBE0762554CDA60050F1E3 /* Configuration.swift in Sources */,
+				C35D76DB26606304009AA5FB /* ThreadUpdateBatcher.swift in Sources */,
 				B8B32033258B235D0020074B /* Storage+Contacts.swift in Sources */,
 				B8856D69256F141F001CE70E /* OWSWindowManager.m in Sources */,
 				C3D9E3BE25676AD70040E4F3 /* TSAttachmentPointer.m in Sources */,

SessionMessagingKit/Sending & Receiving/MessageReceiver+Handling.swift

@@ -25,9 +25,7 @@ extension MessageReceiver {
         // Touch the thread to update the home screen preview
         let storage = SNMessagingKitConfiguration.shared.storage
         guard let threadID = storage.getOrCreateThread(for: message.sender!, groupPublicKey: message.groupPublicKey, openGroupID: openGroupID, using: transaction) else { return }
-        let transaction = transaction as! YapDatabaseReadWriteTransaction
-        guard let thread = TSThread.fetch(uniqueId: threadID, transaction: transaction) else { return }
-        thread.touch(with: transaction)
+        ThreadUpdateBatcher.shared.touch(threadID)
     }
 
     

SessionMessagingKit/Utilities/ThreadUpdateBatcher.swift

@@ -0,0 +1,31 @@
+
+final class ThreadUpdateBatcher {
+    private var threadIDs: Set<String> = []
+
+    private lazy var timer = Timer.scheduledTimer(withTimeInterval: 0.25, repeats: true) { [weak self] _ in self?.touch() }
+
+    static let shared = ThreadUpdateBatcher()
+
+    private init() {
+        DispatchQueue.main.async {
+            SessionUtilitiesKit.touch(self.timer)
+        }
+    }
+
+    deinit { timer.invalidate() }
+
+    func touch(_ threadID: String) {
+        threadIDs.insert(threadID)
+    }
+
+    @objc private func touch() {
+        let threadIDs = self.threadIDs
+        self.threadIDs.removeAll()
+        Storage.write { transaction in
+            for threadID in threadIDs {
+                guard let thread = TSThread.fetch(uniqueId: threadID, transaction: transaction) else { return }
+                thread.touch(with: transaction)
+            }
+        }
+    }
+}

SessionUtilitiesKit/General/General.swift

@@ -1,4 +1,11 @@
 
+/// Does nothing, but is never inlined and thus evaluating its argument will never be optimized away.
+///
+/// Useful for forcing the instantiation of lazy properties like globals.
+@inline(never)
+public func touch<Value>(_ value: Value) { /* Do nothing */ }
+
+
 /// Returns `f(x!)` if `x != nil`, or `nil` otherwise.
 public func given<T, U>(_ x: T?, _ f: (T) throws -> U) rethrows -> U? { return try x.map(f) }