Address PR #46915 review feedback from zadjii-msft

- Null-coalesce MonitorConfigs in PopulateMonitorConfigs for SequenceEqual safety
- Remove over-qualified Dock.DockWindowManager in ShellPage.xaml.cs
- Disambiguate MonitorInfo via using alias in DockWindow.xaml.cs
- Add debug log in MonitorService.NotifyMonitorsChanged
- Move side resolution to DockSettings.GetSideForMonitor() helper
- Merge _dockWindows/_dockViewModels into single _docks dictionary
- Make _syncing atomic with Interlocked.CompareExchange
- Reconciler: use DeviceId dictionary for O(1) lookups, remove mutable copy, clarify Phase 2 comment
- Simplify bands resolution in CommandProviderWrapper
- Expand activeSt/activeCt abbreviations in DockViewModel
- Remove ShowLabels migration code and tests (separate PR)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: michaeljolley

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/CommandProviderWrapper.cs

@@ -505,35 +505,26 @@ public void PinDockBand(string commandId, IServiceProvider serviceProvider, Dock
         // Prevent duplicate pins — check the target destination's bands.
         // When pinning to a specific monitor, check that monitor's resolved bands
         // (which include forked-from-global bands). Otherwise, check global bands.
-        bool alreadyPinned;
+        DockMonitorConfig? targetConfig = null;
         if (monitorDeviceId is not null)
         {
-            var configs = dockSettings.MonitorConfigs ?? System.Collections.Immutable.ImmutableList<DockMonitorConfig>.Empty;
-            DockMonitorConfig? targetConfig = null;
-            foreach (var cfg in configs)
+            foreach (var cfg in dockSettings.MonitorConfigs)
             {
-                if (string.Equals(cfg.MonitorDeviceId, monitorDeviceId, System.StringComparison.OrdinalIgnoreCase))
+                if (string.Equals(cfg.MonitorDeviceId, monitorDeviceId, StringComparison.OrdinalIgnoreCase))
                 {
                     targetConfig = cfg;
                     break;
                 }
             }
+        }
 
-            // Resolve the bands for the target monitor (per-monitor if customized, else global)
-            var resolvedStart = targetConfig?.ResolveStartBands(dockSettings.StartBands) ?? dockSettings.StartBands;
-            var resolvedCenter = targetConfig?.ResolveCenterBands(dockSettings.CenterBands) ?? dockSettings.CenterBands;
-            var resolvedEnd = targetConfig?.ResolveEndBands(dockSettings.EndBands) ?? dockSettings.EndBands;
+        var resolvedStart = targetConfig?.ResolveStartBands(dockSettings.StartBands) ?? dockSettings.StartBands;
+        var resolvedCenter = targetConfig?.ResolveCenterBands(dockSettings.CenterBands) ?? dockSettings.CenterBands;
+        var resolvedEnd = targetConfig?.ResolveEndBands(dockSettings.EndBands) ?? dockSettings.EndBands;
 
-            alreadyPinned = resolvedStart.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId) ||
+        var alreadyPinned = resolvedStart.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId) ||
                             resolvedCenter.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId) ||
                             resolvedEnd.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId);
-        }
-        else
-        {
-            alreadyPinned = dockSettings.StartBands.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId) ||
-                            dockSettings.CenterBands.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId) ||
-                            dockSettings.EndBands.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId);
-        }
 
         if (alreadyPinned)
         {

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Dock/DockViewModel.cs

@@ -368,10 +368,10 @@ private void SaveSettings()
     public void SyncBandPosition(DockBandViewModel band, DockPinSide targetSide, int targetIndex)
     {
         var bandId = band.Id;
-        var (activeSt, activeCt, activeEnd) = GetActiveBands();
+        var (activeStart, activeCenter, activeEnd) = GetActiveBands();
 
-        var bandSettings = activeSt.FirstOrDefault(b => b.CommandId == bandId)
-                        ?? activeCt.FirstOrDefault(b => b.CommandId == bandId)
+        var bandSettings = activeStart.FirstOrDefault(b => b.CommandId == bandId)
+                        ?? activeCenter.FirstOrDefault(b => b.CommandId == bandId)
                         ?? activeEnd.FirstOrDefault(b => b.CommandId == bandId);
 
         if (bandSettings == null)
@@ -380,8 +380,8 @@ public void SyncBandPosition(DockBandViewModel band, DockPinSide targetSide, int
         }
 
         // Remove from all active band lists
-        var newStart = activeSt.RemoveAll(b => b.CommandId == bandId);
-        var newCenter = activeCt.RemoveAll(b => b.CommandId == bandId);
+        var newStart = activeStart.RemoveAll(b => b.CommandId == bandId);
+        var newCenter = activeCenter.RemoveAll(b => b.CommandId == bandId);
         var newEnd = activeEnd.RemoveAll(b => b.CommandId == bandId);
 
         // Add to target list at the correct index
@@ -417,10 +417,10 @@ public void SyncBandPosition(DockBandViewModel band, DockPinSide targetSide, int
     public void MoveBandWithoutSaving(DockBandViewModel band, DockPinSide targetSide, int targetIndex)
     {
         var bandId = band.Id;
-        var (activeSt, activeCt, activeEnd) = GetActiveBands();
+        var (activeStart, activeCenter, activeEnd) = GetActiveBands();
 
-        var bandSettings = activeSt.FirstOrDefault(b => b.CommandId == bandId)
-                        ?? activeCt.FirstOrDefault(b => b.CommandId == bandId)
+        var bandSettings = activeStart.FirstOrDefault(b => b.CommandId == bandId)
+                        ?? activeCenter.FirstOrDefault(b => b.CommandId == bandId)
                         ?? activeEnd.FirstOrDefault(b => b.CommandId == bandId);
 
         if (bandSettings == null)
@@ -430,8 +430,8 @@ public void MoveBandWithoutSaving(DockBandViewModel band, DockPinSide targetSide
         }
 
         // Remove from all sides (settings)
-        var newStart = activeSt.RemoveAll(b => b.CommandId == bandId);
-        var newCenter = activeCt.RemoveAll(b => b.CommandId == bandId);
+        var newStart = activeStart.RemoveAll(b => b.CommandId == bandId);
+        var newCenter = activeCenter.RemoveAll(b => b.CommandId == bandId);
         var newEnd = activeEnd.RemoveAll(b => b.CommandId == bandId);
 
         // Remove from UI collections
@@ -678,21 +678,21 @@ private void RebuildUICollectionsFromSnapshot()
             return;
         }
 
-        var (activeSt, activeCt, activeEnd) = GetActiveBands();
+        var (activeStart, activeCenter, activeEnd) = GetActiveBands();
 
         StartItems.Clear();
         CenterItems.Clear();
         EndItems.Clear();
 
-        foreach (var bandSettings in activeSt)
+        foreach (var bandSettings in activeStart)
         {
             if (_snapshotBandViewModels.TryGetValue(bandSettings.CommandId, out var bandVM))
             {
                 StartItems.Add(bandVM);
             }
         }
 
-        foreach (var bandSettings in activeCt)
+        foreach (var bandSettings in activeCenter)
         {
             if (_snapshotBandViewModels.TryGetValue(bandSettings.CommandId, out var bandVM))
             {
@@ -711,7 +711,7 @@ private void RebuildUICollectionsFromSnapshot()
 
     private void RebuildUICollections()
     {
-        var (activeSt, activeCt, activeEnd) = GetActiveBands();
+        var (activeStart, activeCenter, activeEnd) = GetActiveBands();
 
         // Create a lookup of all current band ViewModels
         var allBands = StartItems.Concat(CenterItems).Concat(EndItems).ToDictionary(b => b.Id);
@@ -720,15 +720,15 @@ private void RebuildUICollections()
         CenterItems.Clear();
         EndItems.Clear();
 
-        foreach (var bandSettings in activeSt)
+        foreach (var bandSettings in activeStart)
         {
             if (allBands.TryGetValue(bandSettings.CommandId, out var bandVM))
             {
                 StartItems.Add(bandVM);
             }
         }
 
-        foreach (var bandSettings in activeCt)
+        foreach (var bandSettings in activeCenter)
         {
             if (allBands.TryGetValue(bandSettings.CommandId, out var bandVM))
             {
@@ -789,7 +789,7 @@ public void AddBandToSection(TopLevelViewModel topLevel, DockPinSide targetSide)
         // Create settings for the new band
         var bandSettings = new DockBandSettings { ProviderId = topLevel.CommandProviderId, CommandId = bandId };
         var dockSettings = _settings;
-        var (activeSt, activeCt, activeEnd) = GetActiveBands();
+        var (activeStart, activeCenter, activeEnd) = GetActiveBands();
 
         // Create the band view model
         var bandVm = CreateBandItem(bandSettings, topLevel.ItemViewModel);
@@ -798,15 +798,15 @@ public void AddBandToSection(TopLevelViewModel topLevel, DockPinSide targetSide)
         switch (targetSide)
         {
             case DockPinSide.Start:
-                _settings = WithActiveBands(activeSt.Add(bandSettings), activeCt, activeEnd);
+                _settings = WithActiveBands(activeStart.Add(bandSettings), activeCenter, activeEnd);
                 StartItems.Add(bandVm);
                 break;
             case DockPinSide.Center:
-                _settings = WithActiveBands(activeSt, activeCt.Add(bandSettings), activeEnd);
+                _settings = WithActiveBands(activeStart, activeCenter.Add(bandSettings), activeEnd);
                 CenterItems.Add(bandVm);
                 break;
             case DockPinSide.End:
-                _settings = WithActiveBands(activeSt, activeCt, activeEnd.Add(bandSettings));
+                _settings = WithActiveBands(activeStart, activeCenter, activeEnd.Add(bandSettings));
                 EndItems.Add(bandVm);
                 break;
         }
@@ -829,12 +829,12 @@ public void AddBandToSection(TopLevelViewModel topLevel, DockPinSide targetSide)
     public void UnpinBand(DockBandViewModel band)
     {
         var bandId = band.Id;
-        var (activeSt, activeCt, activeEnd) = GetActiveBands();
+        var (activeStart, activeCenter, activeEnd) = GetActiveBands();
 
         // Remove from settings
         _settings = WithActiveBands(
-            activeSt.RemoveAll(b => b.CommandId == bandId),
-            activeCt.RemoveAll(b => b.CommandId == bandId),
+            activeStart.RemoveAll(b => b.CommandId == bandId),
+            activeCenter.RemoveAll(b => b.CommandId == bandId),
             activeEnd.RemoveAll(b => b.CommandId == bandId));
 
         // Remove from UI collections
@@ -899,13 +899,13 @@ private void EmitDockConfiguration()
         var isDockEnabled = _settingsService.Settings.EnableDock;
         var dockSide = isDockEnabled ? GetEffectiveSide().ToString().ToLowerInvariant() : "none";
 
-        var (activeSt, activeCt, activeEnd) = GetActiveBands();
+        var (activeStart, activeCenter, activeEnd) = GetActiveBands();
 
         static string FormatBands(ImmutableList<DockBandSettings> bands) =>
             string.Join("\n", bands.Select(b => $"{b.ProviderId}/{b.CommandId}"));
 
-        var startBands = isDockEnabled ? FormatBands(activeSt) : string.Empty;
-        var centerBands = isDockEnabled ? FormatBands(activeCt) : string.Empty;
+        var startBands = isDockEnabled ? FormatBands(activeStart) : string.Empty;
+        var centerBands = isDockEnabled ? FormatBands(activeCenter) : string.Empty;
         var endBands = isDockEnabled ? FormatBands(activeEnd) : string.Empty;
 
         WeakReferenceMessenger.Default.Send(new TelemetryDockConfigurationMessage(

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Services/SettingsService.cs

@@ -89,8 +89,6 @@ private void ApplyMigrations()
                     DeprecatedHotkeyGoesHomeKey,
                     (ref SettingsModel model, bool goesHome) => model = model with { AutoGoHomeInterval = goesHome ? TimeSpan.Zero : Timeout.InfiniteTimeSpan },
                     JsonSerializationContext.Default.Boolean);
-
-                migratedAny |= TryMigrateBandShowLabels(root, ref _settings);
             }
         }
         catch (Exception ex)
@@ -136,106 +134,4 @@ private static bool TryMigrate<T>(
 
         return false;
     }
-
-    /// <summary>
-    /// Migrates per-band <c>ShowLabels</c> to <c>ShowTitles</c> and <c>ShowSubtitles</c>.
-    /// The old <c>ShowLabels</c> property on <see cref="DockBandSettings"/> was renamed to
-    /// <c>ShowTitles</c> (with <c>ShowSubtitles</c> added). Because the legacy property is
-    /// <c>[JsonIgnore]</c>, old JSON values are lost during deserialization. This migration
-    /// reads the raw JSON to recover them.
-    /// </summary>
-    private static bool TryMigrateBandShowLabels(JsonObject root, ref SettingsModel model)
-    {
-        try
-        {
-            if (root[nameof(SettingsModel.DockSettings)] is not JsonObject dockSettingsNode)
-            {
-                return false;
-            }
-
-            var migrated = false;
-            var ds = model.DockSettings;
-
-            var newStart = MigrateBandList(dockSettingsNode, nameof(DockSettings.StartBands), ds.StartBands, ref migrated);
-            var newCenter = MigrateBandList(dockSettingsNode, nameof(DockSettings.CenterBands), ds.CenterBands, ref migrated);
-            var newEnd = MigrateBandList(dockSettingsNode, nameof(DockSettings.EndBands), ds.EndBands, ref migrated);
-
-            if (migrated)
-            {
-                model = model with
-                {
-                    DockSettings = ds with
-                    {
-                        StartBands = newStart,
-                        CenterBands = newCenter,
-                        EndBands = newEnd,
-                    },
-                };
-            }
-
-            return migrated;
-        }
-        catch (Exception ex)
-        {
-            Logger.LogError("Error during band ShowLabels migration.", ex);
-            return false;
-        }
-    }
-
-    /// <summary>
-    /// Scans a single band array in the raw JSON for <c>ShowLabels</c> entries that
-    /// need migrating to <c>ShowTitles</c> / <c>ShowSubtitles</c>.
-    /// </summary>
-    private static ImmutableList<DockBandSettings> MigrateBandList(
-        JsonObject dockSettingsNode,
-        string bandKey,
-        ImmutableList<DockBandSettings> bands,
-        ref bool anyMigrated)
-    {
-        if (dockSettingsNode[bandKey] is not JsonArray jsonBands)
-        {
-            return bands;
-        }
-
-        var builder = bands.ToBuilder();
-        var listChanged = false;
-
-        for (var i = 0; i < builder.Count && i < jsonBands.Count; i++)
-        {
-            if (jsonBands[i] is not JsonObject jsonBand)
-            {
-                continue;
-            }
-
-            // Only migrate if old key exists and new key does not
-            if (!jsonBand.ContainsKey("ShowLabels") || jsonBand.ContainsKey("ShowTitles"))
-            {
-                continue;
-            }
-
-            var showLabelsNode = jsonBand["ShowLabels"];
-            if (showLabelsNode is null)
-            {
-                continue;
-            }
-
-            var showLabels = showLabelsNode.GetValue<bool>();
-            var band = builder[i];
-            band = band with
-            {
-                ShowTitles = band.ShowTitles ?? showLabels,
-                ShowSubtitles = band.ShowSubtitles ?? showLabels,
-            };
-            builder[i] = band;
-            listChanged = true;
-        }
-
-        if (listChanged)
-        {
-            anyMigrated = true;
-            return builder.ToImmutable();
-        }
-
-        return bands;
-    }
 }

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Settings/DockSettings.cs

@@ -105,6 +105,23 @@ public ImmutableList<DockMonitorConfig> MonitorConfigs
         init => _monitorConfigs = value ?? ImmutableList<DockMonitorConfig>.Empty;
     }
 
+    /// <summary>
+    /// Gets the dock side override for a specific monitor, or <c>null</c> if the
+    /// monitor has no override (inherits global <see cref="Side"/>).
+    /// </summary>
+    public DockSide? GetSideForMonitor(string deviceId)
+    {
+        foreach (var cfg in MonitorConfigs)
+        {
+            if (string.Equals(cfg.MonitorDeviceId, deviceId, StringComparison.OrdinalIgnoreCase))
+            {
+                return cfg.Side;
+            }
+        }
+
+        return null;
+    }
+
     [JsonIgnore]
     public IEnumerable<(string ProviderId, string CommandId)> AllPinnedCommands
     {