Fixes #4456 - Clear MouseGrabView in App.End (#4460)

* Fixed MouseGrabView bug.

Added extensive test coverage for `Keyboard`, `Mouse`, `Timeout`, and `Popover` functionalities, including edge cases and concurrent access. Introduced parameterized and data-driven tests to reduce redundancy and improve clarity.

Refactored codebase for modularity and maintainability,
introducing new namespaces and reorganizing classes. Enhanced `MouseImpl`, `KeyboardImpl`, and `Runnable` implementations with improved event handling, thread safety, and support for the Terminal.Gui Cancellable Work Pattern (CWP).

Removed deprecated code and legacy tests, such as `LogarithmicTimeout` and `SmoothAcceleratingTimeout`. Fixed bugs related to mouse grabbing during drag operations and unbalanced `ApplicationImpl.Begin/End` calls. Improved documentation and code readability with modern C# features.

* Code cleanup.

* Update Tests/UnitTestsParallelizable/Application/Runnable/RunnableIntegrationTests.cs

Co-authored-by: Copilot <[email protected]>

* Improve null handling and simplify test setup

In `MouseImpl.cs`, added an early `return` after the `UngrabMouse()`
call within the `if (view is null)` block to prevent further execution
when `view` is `null`, improving null reference handling.

In `RunnableIntegrationTests.cs`, removed the initialization of the
`IApplication` object (`app`) from the `MultipleRunnables_IndependentResults`
test method, simplifying the test setup and focusing on runnable behavior.

* Code cleanup

* API doc link cleanup

---------

Co-authored-by: Copilot <[email protected]>

Author: tig

Terminal.Gui/App/ApplicationImpl.Run.cs

@@ -368,6 +368,8 @@ public void End (SessionToken token)
             previousRunnable.RaiseIsModalChangedEvent (true);
         }
 
+        Mouse?.UngrabMouse ();
+
         runnable.RaiseIsRunningChangedEvent (false);
 
         token.Result = runnable.Result;

Terminal.Gui/App/Mouse/MouseImpl.cs

@@ -266,11 +266,17 @@ public void ResetState ()
     /// <inheritdoc/>
     public void GrabMouse (View? view)
     {
-        if (view is null || RaiseGrabbingMouseEvent (view))
+        if (RaiseGrabbingMouseEvent (view))
         {
             return;
         }
 
+        if (view is null)
+        {
+            UngrabMouse();
+            return;
+        }
+
         RaiseGrabbedMouseEvent (view);
 
         // MouseGrabView is only set if the application is initialized.

Terminal.Gui/ViewBase/Adornment/Border.Arrangment.cs

@@ -1,4 +1,3 @@
-using System.ComponentModel;
 using System.Diagnostics;
 
 namespace Terminal.Gui.ViewBase;
@@ -766,6 +765,17 @@ internal void HandleDragOperation (MouseEventArgs mouseEvent)
         }
     }
 
+    /// <summary>
+    ///     Cancels <see cref="IMouseGrabHandler.GrabbingMouse"/> events during an active drag to prevent other views from
+    ///     stealing the mouse grab mid-operation.
+    /// </summary>
+    /// <remarks>
+    ///     During an Arrange Mode drag (<see cref="_dragPosition"/> has a value), Border owns the mouse grab and
+    ///     must receive all mouse events until Button1Released. If another view (e.g., scrollbar, slider) were allowed
+    ///     to grab the mouse, the drag would freeze, leaving Border in an inconsistent state with no cleanup.
+    ///     Canceling follows the CWP pattern, ensuring Border maintains exclusive mouse control until it explicitly
+    ///     releases via <see cref="IMouseGrabHandler.UngrabMouse"/> in <see cref="OnMouseEvent"/>.
+    /// </remarks>
     private void Application_GrabbingMouse (object? sender, GrabMouseEventArgs e)
     {
         if (App?.Mouse.MouseGrabView == this && _dragPosition.HasValue)
@@ -774,25 +784,14 @@ private void Application_GrabbingMouse (object? sender, GrabMouseEventArgs e)
         }
     }
 
-    private void Application_UnGrabbingMouse (object? sender, GrabMouseEventArgs e)
-    {
-        if (App?.Mouse.MouseGrabView == this && _dragPosition.HasValue)
-        {
-            e.Cancel = true;
-        }
-    }
-
     #endregion Mouse Support
 
-
-
     /// <inheritdoc/>
     protected override void Dispose (bool disposing)
     {
         if (App is { })
         {
             App.Mouse.GrabbingMouse -= Application_GrabbingMouse;
-            App.Mouse.UnGrabbingMouse -= Application_UnGrabbingMouse;
         }
 
         _dragPosition = null;

Terminal.Gui/ViewBase/Adornment/Border.cs

@@ -111,7 +111,6 @@ public override void BeginInit ()
         if (App is { })
         {
             App.Mouse.GrabbingMouse += Application_GrabbingMouse;
-            App.Mouse.UnGrabbingMouse += Application_UnGrabbingMouse;
         }
 
         if (Parent is null)

Terminal.Gui/ViewBase/Runnable/Runnable.cs renamed to Terminal.Gui/Views/Runnable/Runnable.cs

@@ -1,4 +1,4 @@
-namespace Terminal.Gui.ViewBase;
+namespace Terminal.Gui.Views;
 
 /// <summary>
 ///     Base implementation of <see cref="IRunnable"/> for views that can be run as blocking sessions without returning a result.

Terminal.Gui/ViewBase/Runnable/RunnableTResult.cs renamed to Terminal.Gui/Views/Runnable/RunnableTResult.cs

@@ -1,4 +1,4 @@
-namespace Terminal.Gui.ViewBase;
+namespace Terminal.Gui.Views;
 
 /// <summary>
 ///     Base implementation of <see cref="IRunnable{TResult}"/> for views that can be run as blocking sessions.

Terminal.Gui/ViewBase/Runnable/RunnableWrapper.cs renamed to Terminal.Gui/Views/Runnable/RunnableWrapper.cs

@@ -1,4 +1,4 @@
-namespace Terminal.Gui.ViewBase;
+namespace Terminal.Gui.Views;
 
 /// <summary>
 ///     Wraps any <see cref="View"/> to make it runnable with a typed result, similar to how

Terminal.Gui/ViewBase/Runnable/ViewRunnableExtensions.cs renamed to Terminal.Gui/Views/Runnable/ViewRunnableExtensions.cs

@@ -1,4 +1,4 @@
-namespace Terminal.Gui.ViewBase;
+namespace Terminal.Gui.Views;
 
 /// <summary>
 ///     Extension methods for making any <see cref="View"/> runnable with typed results.

Tests/UnitTests/View/Mouse/MouseTests.cs

@@ -49,8 +49,10 @@ public void ButtonPressed_In_Border_Starts_Drag (int marginThickness, int border
 
         Application.RaiseMouseEvent (new () { ScreenPosition = new (xy + 1, xy + 1), Flags = MouseFlags.Button1Pressed | MouseFlags.ReportMousePosition });
         AutoInitShutdownAttribute.RunIteration ();
-
         Assert.Equal (expectedMoved, new Point (5, 5) == testView.Frame.Location);
+        // The above grabbed the mouse. Need to ungrab.
+        Application.Mouse.UngrabMouse ();
+
         top.Dispose ();
     }
 

Tests/UnitTests/View/ViewCommandTests.cs

@@ -152,6 +152,9 @@ public void Button_CanFocus_False_Raises_Accepted_Correctly ()
         Assert.Equal (1, btnAcceptedCount);
         Assert.Equal (0, wAcceptedCount);
 
+        // The above grabbed the mouse. Need to ungrab.
+        Application.Mouse.UngrabMouse ();
+
         w.Dispose ();
         Application.ResetState (true);
     }