Merge pull request #226 from ClaudioESSilva/feature/auto-scrolling

implements #225

Author: erikdarlingdata

src/PlanViewer.App/Controls/PlanViewerControl.axaml.cs

@@ -141,6 +141,7 @@ public PlanViewerControl()
         var layoutTransform = this.FindControl<Avalonia.Controls.LayoutTransformControl>("PlanLayoutTransform")!;
         _zoomTransform = (ScaleTransform)layoutTransform.LayoutTransform!;
 
+        Helpers.DataGridBehaviors.Attach(StatementsGrid);
     }
 
     /// <summary>

src/PlanViewer.App/Controls/QueryStoreGridControl.axaml.cs

@@ -63,6 +63,7 @@ public QueryStoreGridControl(ServerConnection serverConnection, ICredentialServi
         _slicerDaysBack = AppSettingsService.Load().QueryStoreSlicerDays;
         InitializeComponent();
         ResultsGrid.ItemsSource = _filteredRows;
+        Helpers.DataGridBehaviors.Attach(ResultsGrid);
         EnsureFilterPopup();
         SetupColumnHeaders();
         PopulateDatabaseBox(databases, initialDatabase);

src/PlanViewer.App/Dialogs/QueryStoreHistoryWindow.axaml.cs

@@ -104,6 +104,8 @@ public QueryStoreHistoryWindow(string connectionString, string queryHash,
         _maxHoursBack = slicerDaysBack * 24;
         InitializeComponent();
 
+        Helpers.DataGridBehaviors.Attach(HistoryDataGrid);
+
         QueryIdentifierText.Text = $"Query Store History: {queryHash} in [{database}]";
         QueryTextBox.Text = queryText;
 

src/PlanViewer.App/Helpers/DataGridBehaviors.cs

@@ -0,0 +1,111 @@
+using System;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
+using Avalonia.Input;
+using Avalonia.Interactivity;
+using Avalonia.VisualTree;
+
+namespace PlanViewer.App.Helpers;
+
+/// <summary>
+/// Attaches middle-mouse-button pan behavior to a DataGrid.
+/// </summary>
+public static class DataGridBehaviors
+{
+    /// <summary>Attach middle-click pan behavior to <paramref name="grid"/>.</summary>
+    public static void Attach(DataGrid grid)
+    {
+        AttachMiddleClickPan(grid);
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Middle-mouse-button drag → pan (scroll) the grid
+    // ─────────────────────────────────────────────────────────────────────────
+
+    private static void AttachMiddleClickPan(DataGrid grid)
+    {
+        Point  panStart    = default;
+        double scrollStartH = 0, scrollStartV = 0;
+        bool   panning     = false;
+        ScrollBar? hBar    = null, vBar = null;
+        bool   barsResolved = false;
+
+        // Avalonia's DataGrid has no ScrollViewer in its template — it manages scrolling
+        // itself via PART_HorizontalScrollbar and PART_VerticalScrollbar. Resolve them
+        // lazily (visual tree isn't populated until after TemplateApplied).
+        void ResolveScrollBars()
+        {
+            if (barsResolved) return;
+            barsResolved = true;
+            foreach (var d in grid.GetVisualDescendants())
+            {
+                if (d is not ScrollBar sb) continue;
+                if      (sb.Name == "PART_HorizontalScrollbar") hBar = sb;
+                else if (sb.Name == "PART_VerticalScrollbar")   vBar = sb;
+                if (hBar != null && vBar != null) break;
+            }
+        }
+
+        // Re-resolve scroll bars if the template is ever re-applied.
+        grid.TemplateApplied += (_, _) => { barsResolved = false; hBar = null; vBar = null; };
+
+        // RoutingStrategies.Direct|Bubble + handledEventsToo:true ensures the handler fires
+        // even though DataGrid rows/cells mark PointerPressed handled (for row selection).
+        grid.AddHandler(InputElement.PointerPressedEvent, (object? _, PointerPressedEventArgs e) =>
+        {
+            if (e.GetCurrentPoint(grid).Properties.PointerUpdateKind != PointerUpdateKind.MiddleButtonPressed) return;
+
+            ResolveScrollBars();
+
+            panning      = true;
+            panStart     = e.GetPosition(grid);
+            scrollStartH = hBar?.Value ?? 0;
+            scrollStartV = vBar?.Value ?? 0;
+            e.Pointer.Capture(grid);
+            grid.Cursor  = new Cursor(StandardCursorType.SizeAll);
+            e.Handled    = true;
+        }, RoutingStrategies.Direct | RoutingStrategies.Bubble, handledEventsToo: true);
+
+        grid.AddHandler(InputElement.PointerMovedEvent, (object? _, PointerEventArgs e) =>
+        {
+            if (!panning) return;
+
+            // Release pan if the middle button was lifted outside a PointerReleased event.
+            if (!e.GetCurrentPoint(grid).Properties.IsMiddleButtonPressed)
+            {
+                panning = false;
+                e.Pointer.Capture(null);
+                grid.Cursor = null;
+                return;
+            }
+
+            var delta = e.GetPosition(grid) - panStart;
+
+            if (hBar is not null)
+            {
+                hBar.Value = Math.Clamp(scrollStartH - delta.X, hBar.Minimum, hBar.Maximum);
+                // Raise Thumb.DragDeltaEvent on the scrollbar — a public routed event whose
+                // ScrollBar class handler calls OnScroll → fires Scroll event → DataGrid
+                // processes the new Value without any reflection on private members.
+                hBar.RaiseEvent(new VectorEventArgs { RoutedEvent = Thumb.DragDeltaEvent });
+            }
+            if (vBar is not null)
+            {
+                vBar.Value = Math.Clamp(scrollStartV - delta.Y, vBar.Minimum, vBar.Maximum);
+                vBar.RaiseEvent(new VectorEventArgs { RoutedEvent = Thumb.DragDeltaEvent });
+            }
+
+            e.Handled = true;
+        }, RoutingStrategies.Direct | RoutingStrategies.Bubble, handledEventsToo: true);
+
+        grid.AddHandler(InputElement.PointerReleasedEvent, (object? _, PointerReleasedEventArgs e) =>
+        {
+            if (!panning) return;
+            panning = false;
+            e.Pointer.Capture(null);
+            grid.Cursor = null;
+            e.Handled   = true;
+        }, RoutingStrategies.Direct | RoutingStrategies.Bubble, handledEventsToo: true);
+    }
+}