fix(board): skip the refresh when the card editor wrote nothing

Every editor close rebuilt all columns, so opening a card and cancelling
reset each column's scroll position. The editor now reports whether it
saved the card or created a tag in the nested picker, and the board only
refreshes in that case.

YKanBan.Tests/ViewModels/BoardViewModelTests.cs

@@ -204,6 +204,66 @@ public class BoardViewModelTests
         Assert.AreEqual(card.Id, board.Columns[0].Cards.Single().Card.Id);
     }
 
+    [TestMethod]
+    public async Task EditorThatWroteNothingLeavesTheColumnsAlone()
+    {
+        using var fixture = new Fixture();
+        ColumnModel column = fixture.Repository.AddColumn("A", "");
+        fixture.Repository.AddCard(column.Id, "t", "", []);
+        BoardViewModel board = fixture.CreateBoard();
+        ColumnViewModel shown = board.Columns.Single();
+        int writes = 0;
+        board.DataWritten += (_, _) => writes++;
+
+        // Cancel a new card, confirm an unchanged existing card, confirm an empty new card.
+        fixture.Dialogs.Script = dialog => dialog is CardEditorDialogViewModel editor
+            ? editor.RequestCancelAsync()
+            : Task.CompletedTask;
+        await shown.AddCardCommand.ExecuteAsync(null);
+        fixture.Dialogs.Script = dialog =>
+        {
+            (dialog as CardEditorDialogViewModel)?.ConfirmCommand.Execute(null);
+            return Task.CompletedTask;
+        };
+        await shown.Cards.Single().EditCommand.ExecuteAsync(null);
+        await shown.AddCardCommand.ExecuteAsync(null);
+
+        Assert.AreSame(shown, board.Columns.Single());
+        Assert.AreEqual(0, writes);
+    }
+
+    [TestMethod]
+    public async Task TagCreatedInACancelledEditRefreshesTheBoard()
+    {
+        using var fixture = new Fixture();
+        fixture.Repository.AddColumn("A", "");
+        BoardViewModel board = fixture.CreateBoard();
+        ColumnViewModel shown = board.Columns.Single();
+        int writes = 0;
+        board.DataWritten += (_, _) => writes++;
+        fixture.Dialogs.Script = async dialog =>
+        {
+            switch (dialog)
+            {
+                case CardEditorDialogViewModel editor:
+                    await editor.AddTagCommand.ExecuteAsync(null);
+                    editor.Tags.Clear();
+                    await editor.RequestCancelAsync();
+                    break;
+                case TagPickerDialogViewModel picker:
+                    picker.NewName = "fresh";
+                    picker.NewColor = "#123456";
+                    picker.CreateCommand.Execute(null);
+                    break;
+            }
+        };
+
+        await shown.AddCardCommand.ExecuteAsync(null);
+
+        Assert.AreNotSame(shown, board.Columns.Single());
+        Assert.AreEqual(1, writes);
+    }
+
     [TestMethod]
     public void UnchangedEditConfirmationWritesNothing()
     {

YKanBan/ViewModels/Board/BoardViewModel.cs

@@ -274,9 +274,7 @@ public sealed partial class BoardViewModel : ViewModelBase
         var editor = CardEditorDialogViewModel.ForNewCard(
             _repository, _dialogs, columnId, _config.Confirmations.DiscardEdit);
         await _dialogs.ShowAsync(editor);
-
-        // Refresh even after a cancel: the nested picker may have created tags.
-        await RefreshAfterWriteAsync();
+        await RefreshAfterEditorAsync(editor);
     }
 
     /// <summary>
@@ -306,9 +304,20 @@ public sealed partial class BoardViewModel : ViewModelBase
         var editor = CardEditorDialogViewModel.ForExistingCard(
             _repository, _dialogs, card, _config.Confirmations.DiscardEdit);
         await _dialogs.ShowAsync(editor);
-        await RefreshAfterWriteAsync();
+        await RefreshAfterEditorAsync(editor);
     }
 
+    /// <summary>
+    /// Refreshes after the card editor closes, but only when it wrote something:
+    /// a saved card, or a tag created in the nested picker even if the edit was
+    /// cancelled. An editor that wrote nothing leaves the columns, and so their
+    /// scroll positions, untouched.
+    /// </summary>
+    /// <param name="editor">The closed editor.</param>
+    /// <returns>A task completing after the refresh, if any.</returns>
+    private Task RefreshAfterEditorAsync(CardEditorDialogViewModel editor) =>
+        editor.WroteToWorkspace ? RefreshAfterWriteAsync() : Task.CompletedTask;
+
     /// <summary>
     /// Deletes a card, asking first when that confirmation is enabled.
     /// </summary>

YKanBan/ViewModels/Dialogs/CardEditorDialogViewModel.cs

@@ -118,6 +118,12 @@ public sealed partial class CardEditorDialogViewModel : DialogViewModelBase
     /// </summary>
     public CardModel? SavedCard { get; private set; }
 
+    /// <summary>
+    /// Gets whether this edit session wrote anything: the card on confirmation,
+    /// or a tag created in the nested picker (kept even when the edit is cancelled).
+    /// </summary>
+    public bool WroteToWorkspace { get; private set; }
+
     /// <summary>
     /// Gets or sets the card title; the empty string means "no title".
     /// </summary>
@@ -169,9 +175,11 @@ public sealed partial class CardEditorDialogViewModel : DialogViewModelBase
             return;
         }
 
-        if (await _dialogs.ShowAsync(picker) && picker.PickedTag is { } picked)
+        bool picked = await _dialogs.ShowAsync(picker);
+        WroteToWorkspace |= picker.CreatedTag;
+        if (picked && picker.PickedTag is { } tag)
         {
-            Tags.Add(new TagBadgeViewModel(picked));
+            Tags.Add(new TagBadgeViewModel(tag));
         }
     }
 
@@ -202,6 +210,7 @@ public sealed partial class CardEditorDialogViewModel : DialogViewModelBase
             SavedCard = _existing is null
                 ? _repository.AddCard(_columnId, CardTitle, Content, tagIds)
                 : _repository.UpdateCard(_existing.Id, CardTitle, Content, tagIds);
+            WroteToWorkspace = true;
         }
         catch (Exception exception)
         {

YKanBan/ViewModels/Dialogs/TagPickerDialogViewModel.cs

@@ -48,6 +48,11 @@ public sealed partial class TagPickerDialogViewModel : DialogViewModelBase
     /// </summary>
     public TagModel? PickedTag { get; private set; }
 
+    /// <summary>
+    /// Gets whether <see cref="PickedTag"/> was newly created, i.e. written to the workspace.
+    /// </summary>
+    public bool CreatedTag { get; private set; }
+
     /// <summary>
     /// Gets the available tags matching <see cref="FilterText"/>.
     /// </summary>
@@ -127,6 +132,7 @@ public sealed partial class TagPickerDialogViewModel : DialogViewModelBase
         try
         {
             PickedTag = _repository.AddTag(NewName, color, NewDescription);
+            CreatedTag = true;
         }
         catch (Exception exception)
         {

docs/ACCEPTANCE.md

@@ -75,6 +75,7 @@
 - [ ] 列宽：窄 240 / 标准 320 / 宽 480 / 手动 160–720；全局生效，重启保持
 - [ ] 排序：id 升序 / 最后修改时间降序 / 标题升序（空标题在前）；只影响卡片，列始终 id 序；重启保持
 - [ ] 大数据量：用脚本向一列灌入约 10000 张卡片，滚动流畅、打开工作区无明显卡顿（虚拟化）
+- [ ] 长列滚动到中部后打开某张卡片，不改动就取消或确认 → 各列滚动位置不变（未写库不刷新看板）
 - [ ] 所有模态在父窗口居中；使用系统原生标题栏
 - [ ] 打开带输入框的模态时，第一个输入框自动获得焦点并全选