Add mouse drag support to SplitterControl with mouse capture

- Implement IMouseAwareControl on SplitterControl for click-and-drag
  column resizing via ProcessMouseEvent (press/drag/release lifecycle)
- Add mouse capture mechanism to WindowEventDispatcher so drag/release
  events route to the originating control regardless of cursor position
- Fix MouseEventArgs.HasFlag/HasAnyFlag to use bitwise checking instead
  of exact equality, supporting both X10 (separate list entries) and SGR
  (combined flag values) mouse formats
- Place capture check before enter/leave tracking to prevent synthetic
  MouseEnter/MouseLeave events from interfering with active drags
- Use WindowPosition for stable delta computation since the splitter
  physically moves during resize, making control-relative coords unreliable

Author: nickprotop

SharpConsoleUI/Controls/SplitterControl.cs

@@ -14,14 +14,16 @@
 using System.Drawing;
 using Color = Spectre.Console.Color;
 
+using SharpConsoleUI.Drivers;
+using SharpConsoleUI.Events;
 using SharpConsoleUI.Extensions;
 namespace SharpConsoleUI.Controls
 {
 	/// <summary>
 	/// A vertical splitter control that allows users to resize adjacent columns in a <see cref="HorizontalGridControl"/>.
 	/// Supports keyboard-based resizing with arrow keys and provides visual feedback during focus and dragging.
 	/// </summary>
-	public class SplitterControl : IWindowControl, IInteractiveControl, IFocusableControl, IDOMPaintable
+	public class SplitterControl : IWindowControl, IInteractiveControl, IFocusableControl, IDOMPaintable, IMouseAwareControl
 	{
 		private const int DEFAULT_WIDTH = 1;
 		private const float MIN_COLUMN_PERCENTAGE = 0.1f; // Minimum 10% width for any column
@@ -39,6 +41,8 @@ public class SplitterControl : IWindowControl, IInteractiveControl, IFocusableCo
 		private bool _hasFocus;
 		private bool _isDragging;
 		private bool _isEnabled = true;
+		private bool _isMouseDragging = false;
+		private int _lastMouseX = 0;
 
 		// References to the columns on either side of this splitter
 		private ColumnContainer? _leftColumn;
@@ -239,6 +243,11 @@ public bool HasFocus
 		/// </summary>
 		public bool IsDragging => _isDragging;
 
+		/// <summary>
+		/// Gets a value indicating whether the splitter is currently being dragged by the mouse.
+		/// </summary>
+		public bool IsMouseDragging => _isMouseDragging;
+
 		/// <inheritdoc/>
 		public bool IsEnabled
 		{
@@ -447,6 +456,84 @@ public void PaintDOM(CharacterBuffer buffer, LayoutRect bounds, LayoutRect clipR
 
 		#endregion
 
+		#region IMouseAwareControl Implementation
+
+		/// <inheritdoc/>
+		public bool WantsMouseEvents => IsEnabled;
+
+		/// <inheritdoc/>
+		public bool CanFocusWithMouse => true;
+
+		#pragma warning disable CS0067
+		/// <inheritdoc/>
+		public event EventHandler<MouseEventArgs>? MouseClick;
+
+		/// <inheritdoc/>
+		public event EventHandler<MouseEventArgs>? MouseDoubleClick;
+
+		/// <inheritdoc/>
+		public event EventHandler<MouseEventArgs>? MouseEnter;
+
+		/// <inheritdoc/>
+		public event EventHandler<MouseEventArgs>? MouseLeave;
+
+		/// <inheritdoc/>
+		public event EventHandler<MouseEventArgs>? MouseMove;
+		#pragma warning restore CS0067
+
+		/// <inheritdoc/>
+		public bool ProcessMouseEvent(MouseEventArgs args)
+		{
+			if (!IsEnabled) return false;
+
+			// Ignore synthetic enter/leave events — they carry the original press/drag
+			// flags and would incorrectly start or process a drag.
+			if (args.HasAnyFlag(MouseFlags.MouseEnter, MouseFlags.MouseLeave))
+				return false;
+
+			// Use WindowPosition for delta computation because the splitter physically
+			// moves as it resizes, making control-relative Position unreliable.
+			int mouseX = args.WindowPosition.X;
+
+			// Handle drag-in-progress
+			if (_isMouseDragging && args.HasAnyFlag(MouseFlags.Button1Dragged, MouseFlags.Button1Pressed))
+			{
+				int deltaX = mouseX - _lastMouseX;
+				if (deltaX != 0 && _leftColumn != null && _rightColumn != null)
+				{
+					MoveSplitter(deltaX);
+					_lastMouseX = mouseX;
+				}
+				args.Handled = true;
+				return true;
+			}
+
+			// Handle drag end
+			if (args.HasFlag(MouseFlags.Button1Released) && _isMouseDragging)
+			{
+				_isMouseDragging = false;
+				_isDragging = false;
+				Container?.Invalidate(true);
+				args.Handled = true;
+				return true;
+			}
+
+			// Handle press to start drag
+			if (args.HasFlag(MouseFlags.Button1Pressed) && !_isMouseDragging)
+			{
+				_isMouseDragging = true;
+				_lastMouseX = mouseX;
+				_isDragging = true;
+				Container?.Invalidate(true);
+				args.Handled = true;
+				return true;
+			}
+
+			return false;
+		}
+
+		#endregion
+
 		/// <summary>
 		/// Sets the columns that this splitter will resize
 		/// </summary>
@@ -480,6 +567,7 @@ public void SetFocus(bool focus, FocusReason reason = FocusReason.Programmatic)
 			if (!focus && _isDragging)
 			{
 				_isDragging = false;
+				_isMouseDragging = false;
 				Container?.Invalidate(true);  // Force redraw with normal colors
 			}
 

SharpConsoleUI/Events/MouseEventArgs.cs

@@ -60,19 +60,24 @@ public MouseEventArgs(List<MouseFlags> flags, Point position, Point absolutePosi
 		}
 
 		/// <summary>
-		/// Convenience method to check if specific mouse flags are present
+		/// Convenience method to check if specific mouse flags are present.
+		/// Uses bitwise checking to support both separate list entries (X10)
+		/// and combined flag values (SGR).
 		/// </summary>
 		public bool HasFlag(MouseFlags flag)
 		{
-			return Flags.Contains(flag);
+			if (flag == MouseFlags.None) return false;
+			return Flags.Any(f => (f & flag) == flag);
 		}
 
 		/// <summary>
-		/// Convenience method to check if any of the specified flags are present
+		/// Convenience method to check if any of the specified flags are present.
+		/// Uses bitwise checking to support both separate list entries (X10)
+		/// and combined flag values (SGR).
 		/// </summary>
 		public bool HasAnyFlag(params MouseFlags[] flags)
 		{
-			return flags.Any(flag => Flags.Contains(flag));
+			return flags.Any(flag => Flags.Any(f => (f & flag) == flag));
 		}
 
 		/// <summary>

SharpConsoleUI/Windows/WindowEventDispatcher.cs

@@ -34,6 +34,9 @@ public class WindowEventDispatcher
 		private DateTime _lastClickTime;
 		private Point _lastClickPosition;
 
+		// Mouse capture: routes drag/release events to the control that received Button1Pressed
+		private IWindowControl? _mouseCaptureControl;
+
 		// Escape key tracking: remembers control for Tab restore after Escape
 		private IInteractiveControl? _escapedFromControl;
 
@@ -90,6 +93,26 @@ public bool ProcessMouseEvent(Events.MouseEventArgs args)
 				// Ensure layout is current before processing mouse events
 				UpdateControlLayout();
 
+				// Route drag/release events to the captured control (mouse capture).
+				// This must run before enter/leave tracking to prevent synthetic
+				// enter/leave events from interfering with active drags.
+				// Include Button1Pressed because SGR mouse format uses Button1Pressed+ReportMousePosition
+				// for drag events (without Button1Dragged flag).
+				if (_mouseCaptureControl != null && args.HasAnyFlag(MouseFlags.Button1Pressed, MouseFlags.Button1Dragged, MouseFlags.Button1Released))
+				{
+					var capturedControl = _mouseCaptureControl;
+
+					if (args.HasFlag(MouseFlags.Button1Released))
+						_mouseCaptureControl = null;
+
+					if (capturedControl is Controls.IMouseAwareControl mouseCapture && mouseCapture.WantsMouseEvents)
+					{
+						var controlPosition = GetControlRelativePosition(capturedControl, args.WindowPosition);
+						var controlArgs = args.WithPosition(controlPosition);
+						return mouseCapture.ProcessMouseEvent(controlArgs);
+					}
+				}
+
 				// Find the control at the current mouse position
 				Controls.IWindowControl? currentControl = null;
 				if (IsClickInWindowContent(args.WindowPosition))
@@ -201,6 +224,10 @@ public bool ProcessMouseEvent(Events.MouseEventArgs args)
 						// Propagate mouse event to control if applicable
 						if (targetControl != null && targetControl is Controls.IMouseAwareControl mouseAware && mouseAware.WantsMouseEvents)
 						{
+							// Set mouse capture on Button1Pressed so drag/release events route here
+							if (args.HasFlag(MouseFlags.Button1Pressed))
+								_mouseCaptureControl = targetControl;
+
 							var controlPosition = GetControlRelativePosition(targetControl, args.WindowPosition);
 							var controlArgs = args.WithPosition(controlPosition);