Made dragging the splitter in the chat smooth (#978)

app/MindWork AI Studio/Pages/Chat.razor

@@ -36,7 +36,7 @@
     </CascadingValue>
     @if (this.AreWorkspacesVisible)
     {
-        <MudSplitter Dimension="@this.ReadSplitterPosition" DimensionChanged="this.SplitterChanged" EnableSlide="@this.AreWorkspacesVisible" EnableMargin="@false" StartContentStyle="margin-right: 1em;" BarStyle="" EndContentStyle="margin-left: 1em;">
+        <MudSplitter Dimension="@this.ReadSplitterPosition" DimensionChanged="this.SplitterChanged" Sensitivity="0.05" EnableSlide="@this.AreWorkspacesVisible" EnableMargin="@false" StartContentStyle="margin-right: 1em;" BarStyle="" EndContentStyle="margin-left: 1em;">
             <StartContent>
                 @if (this.SettingsManager.ConfigurationData.Workspace.DisplayBehavior is WorkspaceDisplayBehavior.TOGGLE_SIDEBAR && this.SettingsManager.ConfigurationData.Workspace.IsSidebarVisible)
                 {

app/MindWork AI Studio/Pages/Chat.razor.cs

@@ -27,6 +27,7 @@ public partial class Chat : MSGComponentBase
     private string currentWorkspaceName = string.Empty;
     private Workspaces? workspaces;
     private double splitterPosition = 30;
+    private bool skipRenderAfterSplitterChange;
     private readonly ChatComposerState composerState = new();
     
     private readonly Timer splitterSaveTimer = new(TimeSpan.FromSeconds(1.6));
@@ -39,6 +40,16 @@ public partial class Chat : MSGComponentBase
         
         this.splitterPosition = this.SettingsManager.ConfigurationData.Workspace.SplitterPosition;
         this.splitterSaveTimer.AutoReset = false;
+        //
+        // Mind that this handler deliberately stays off the renderer thread, although it writes the
+        // configuration data from a thread pool thread. The position is a single double, and every
+        // target we ship is 64 bit, so the write cannot tear -- and the worst a lost one could do is
+        // a splitter standing somewhere else after the next start. What a jump to the dispatcher
+        // would cost instead is paid by the user: storing the settings serializes all of them and
+        // writes two files, and it would do that in the very queue which draws the drag they are in
+        // the middle of. The splitter then stutters under their hand. Whoever synchronizes the
+        // configuration data one day should do it without moving that work onto the renderer.
+        //
         this.splitterSaveTimer.Elapsed += (_, _) =>
         {
             this.SettingsManager.ConfigurationData.Workspace.SplitterPosition = this.splitterPosition;
@@ -47,7 +58,31 @@ public partial class Chat : MSGComponentBase
         
         await base.OnInitializedAsync();
     }
-    
+
+    /// <summary>
+    /// Decides whether this page renders again.
+    /// </summary>
+    /// <remarks>
+    /// Dragging the splitter reports every movement, and Blazor renders this page after each of
+    /// them. That render is pure waste: all it would contribute is the position the splitter just
+    /// reported, and the splitter has it already -- it renders itself after its own event, which is
+    /// what resizes the two panels. What this page rebuilds instead is everything else it holds,
+    /// the workspace tree above all, which has no render guard of its own and draws an item with
+    /// three buttons for every chat. That is what the user sees stutter while they drag.<br/><br/>
+    /// Dropping that one render costs nothing, because the splitter never needed it. Should a
+    /// message from the bus ask for a render in the very same moment, this swallows it -- both sit
+    /// on the same dispatcher and the render of a movement follows it without a gap, so the window
+    /// is as good as closed, and the next render brings the message along anyway.
+    /// </remarks>
+    protected override bool ShouldRender()
+    {
+        if (!this.skipRenderAfterSplitterChange)
+            return true;
+
+        this.skipRenderAfterSplitterChange = false;
+        return false;
+    }
+
     #endregion
     
     private string WorkspaceSidebarToggleIcon => this.SettingsManager.ConfigurationData.Workspace.IsSidebarVisible ? Icons.Material.Filled.ArrowCircleLeft : Icons.Material.Filled.ArrowCircleRight;
@@ -75,6 +110,7 @@ public partial class Chat : MSGComponentBase
         this.splitterPosition = position;
         this.splitterSaveTimer.Stop();
         this.splitterSaveTimer.Start();
+        this.skipRenderAfterSplitterChange = true;
     }
     
     private void ToggleWorkspacesOverlay()