fix(ui): batch UI updates for bulk mark-as-read to prevent UI freeze (#786)

Wino.Core/Requests/Folder/MarkFolderAsReadRequest.cs

@@ -13,22 +13,26 @@ public record MarkFolderAsReadRequest(MailItemFolder Folder, List<MailCopy> Mail
 {
     public override void ApplyUIChanges()
     {
+        if (MailsToMarkRead == null || MailsToMarkRead.Count == 0) return;
+
         foreach (var item in MailsToMarkRead)
         {
             item.IsRead = true;
-
-            WeakReferenceMessenger.Default.Send(new MailUpdatedMessage(item));
         }
+
+        WeakReferenceMessenger.Default.Send(new BulkMailUpdatedMessage(MailsToMarkRead));
     }
 
     public override void RevertUIChanges()
     {
+        if (MailsToMarkRead == null || MailsToMarkRead.Count == 0) return;
+
         foreach (var item in MailsToMarkRead)
         {
             item.IsRead = false;
-
-            WeakReferenceMessenger.Default.Send(new MailUpdatedMessage(item));
         }
+
+        WeakReferenceMessenger.Default.Send(new BulkMailUpdatedMessage(MailsToMarkRead));
     }
 
     public List<Guid> SynchronizationFolderIds => [Folder.Id];

Wino.Mail.ViewModels/MailBaseViewModel.cs

@@ -1,4 +1,5 @@
-using CommunityToolkit.Mvvm.Messaging;
+using System.Collections.Generic;
+using CommunityToolkit.Mvvm.Messaging;
 using Wino.Core.Domain.Entities.Mail;
 using Wino.Core.Domain.Entities.Shared;
 using Wino.Core.Domain.Models.Folders;
@@ -11,6 +12,7 @@ public class MailBaseViewModel : CoreBaseViewModel,
     IRecipient<MailAddedMessage>,
     IRecipient<MailRemovedMessage>,
     IRecipient<MailUpdatedMessage>,
+    IRecipient<BulkMailUpdatedMessage>,
     IRecipient<MailDownloadedMessage>,
     IRecipient<DraftCreated>,
     IRecipient<DraftFailed>,
@@ -21,6 +23,17 @@ public class MailBaseViewModel : CoreBaseViewModel,
     protected virtual void OnMailAdded(MailCopy addedMail) { }
     protected virtual void OnMailRemoved(MailCopy removedMail) { }
     protected virtual void OnMailUpdated(MailCopy updatedMail) { }
+
+    protected virtual void OnMailUpdated(IReadOnlyList<MailCopy> updatedMails)
+    {
+        if (updatedMails == null) return;
+
+        foreach (var mail in updatedMails)
+        {
+            OnMailUpdated(mail);
+        }
+    }
+
     protected virtual void OnMailDownloaded(MailCopy downloadedMail) { }
     protected virtual void OnDraftCreated(MailCopy draftMail, MailAccount account) { }
     protected virtual void OnDraftFailed(MailCopy draftMail, MailAccount account) { }
@@ -31,6 +44,7 @@ public class MailBaseViewModel : CoreBaseViewModel,
     void IRecipient<MailAddedMessage>.Receive(MailAddedMessage message) => OnMailAdded(message.AddedMail);
     void IRecipient<MailRemovedMessage>.Receive(MailRemovedMessage message) => OnMailRemoved(message.RemovedMail);
     void IRecipient<MailUpdatedMessage>.Receive(MailUpdatedMessage message) => OnMailUpdated(message.UpdatedMail);
+    void IRecipient<BulkMailUpdatedMessage>.Receive(BulkMailUpdatedMessage message) => OnMailUpdated(message.UpdatedMails);
     void IRecipient<MailDownloadedMessage>.Receive(MailDownloadedMessage message) => OnMailDownloaded(message.DownloadedMail);
 
     void IRecipient<DraftMapped>.Receive(DraftMapped message) => OnDraftMapped(message.LocalDraftCopyId, message.RemoteDraftCopyId);

Wino.Mail.ViewModels/MailListPageViewModel.cs

@@ -685,6 +685,37 @@ public partial class MailListPageViewModel : MailBaseViewModel,
         await ExecuteUIThread(() => { SetupTopBarActions(); });
     }
 
+    protected override async void OnMailUpdated(IReadOnlyList<MailCopy> updatedMails)
+    {
+        base.OnMailUpdated(updatedMails);
+
+        if (updatedMails == null || updatedMails.Count == 0) return;
+
+        // Bulk update: do all changes in a single UI-thread invocation to avoid UI lockups when
+        // thousands of MailUpdatedMessage events would otherwise be processed one by one.
+        await ExecuteUIThread(() =>
+        {
+            foreach (var mail in updatedMails)
+            {
+                if (mail == null) continue;
+
+                // Avoid work for items not in the list.
+                if (!MailCollection.MailCopyIdHashSet.Contains(mail.UniqueId))
+                    continue;
+
+                var container = MailCollection.GetMailItemContainer(mail.UniqueId);
+
+                if (container?.ItemViewModel != null)
+                {
+                    container.ItemViewModel.MailCopy = mail;
+                    container.ThreadViewModel?.NotifyPropertyChanges();
+                }
+            }
+
+            SetupTopBarActions();
+        });
+    }
+
     protected override async void OnMailRemoved(MailCopy removedMail)
     {
         base.OnMailRemoved(removedMail);

Wino.Mail.ViewModels/MailRenderingPageViewModel.cs

@@ -596,13 +596,22 @@ public partial class MailRenderingPageViewModel : MailBaseViewModel,
         // This is done with UniqueId to include FolderId into calculations.
         if (initializedMailItemViewModel.UniqueId != updatedMail.UniqueId) return;
 
-        // Mail operation might change the mail item like mark read/unread or change flag.
-        // So we need to update the mail item view model when this happens.
-        // Also command bar items must be re-initialized since the items loaded based on the mail item.
-
         await ExecuteUIThread(() => { InitializeCommandBarItems(); });
     }
 
+    protected override async void OnMailUpdated(IReadOnlyList<MailCopy> updatedMails)
+    {
+        base.OnMailUpdated(updatedMails);
+
+        if (initializedMailItemViewModel == null || updatedMails == null || updatedMails.Count == 0) return;
+
+        // Only care about the currently rendered item.
+        if (updatedMails.Any(m => m?.UniqueId == initializedMailItemViewModel.UniqueId))
+        {
+            await ExecuteUIThread(() => { InitializeCommandBarItems(); });
+        }
+    }
+
     [RelayCommand]
     private async Task OpenAttachmentAsync(MailAttachmentViewModel attachmentViewModel)
     {

Wino.Messages/UI/BulkMailUpdatedMessage.cs

@@ -0,0 +1,6 @@
+using System.Collections.Generic;
+using Wino.Core.Domain.Entities.Mail;
+
+namespace Wino.Messaging.UI;
+
+public record BulkMailUpdatedMessage(IReadOnlyList<MailCopy> UpdatedMails) : UIMessageBase<BulkMailUpdatedMessage>;