Optimize View drawing logic and update ClearViewport tests

Refactored the `View` class to include a `NeedsDraw` check in
multiple drawing methods, improving rendering efficiency.
Adjusted `OnDrewText` and `DrewText` event handling for
consistency. Removed unused code and redundant tests.

Rewrote and reorganized `ClearViewportTests` for clarity and
compatibility with the new `NeedsDraw` logic. Added new tests
to validate `ClearViewport` behavior under various conditions,
including transparent viewports, event cancellations, and
content-only clearing.

Updated namespaces for better alignment, disabled a noisy
`ComboBoxTests` test, and improved code formatting and
maintainability across files.

Tests/UnitTestsParallelizable/ViewBase/Draw/ClearViewportTests.cs

@@ -0,0 +1,339 @@
+using Moq;
+using UnitTests;
+using Xunit.Abstractions;
+
+namespace ViewBaseTests.Viewport;
+
+[Trait ("Category", "Output")]
+public class ClearViewportTests (ITestOutputHelper output)
+{
+    public class TestableView : View
+    {
+        public TestableView ()
+        {
+            Frame = new Rectangle (0, 0, 10, 10);
+        }
+
+        public bool TestOnClearingViewport () { return OnClearingViewport (); }
+
+        public int OnClearingViewportCalled { get; set; }
+        public bool CancelOnClearingViewport { get; set; }
+
+        protected override bool OnClearingViewport ()
+        {
+            OnClearingViewportCalled++;
+
+            return CancelOnClearingViewport;
+        }
+
+        public int OnClearedViewportCalled { get; set; }
+        protected override void OnClearedViewport () { OnClearedViewportCalled++; }
+    }
+
+    [Fact]
+    public void DoClearViewport_ViewportIsTransparent_DoesNotClear ()
+    {
+        // Arrange
+        Mock<TestableView> view = new () { CallBase = true };
+        view.Object.ViewportSettings = ViewportSettingsFlags.Transparent;
+
+        // Act
+        view.Object.DoClearViewport ();
+
+        // Assert
+        Assert.Equal (0, view.Object.OnClearingViewportCalled);
+        Assert.Equal (0, view.Object.OnClearedViewportCalled);
+    }
+
+    [Fact]
+    public void DoClearViewport_OnClearingViewportReturnsTrue_DoesNotClear ()
+    {
+        // Arrange
+        Mock<TestableView> view = new () { CallBase = true };
+        view.Object.CancelOnClearingViewport = true;
+
+        // Act
+        view.Object.DoClearViewport ();
+
+        // Assert
+        Assert.Equal (0, view.Object.OnClearedViewportCalled);
+    }
+
+    [Fact]
+    public void DoClearViewport_ClearingViewportEventCancelled_DoesNotClear ()
+    {
+        // Arrange
+        Mock<TestableView> view = new () { CallBase = true };
+        view.Object.ClearingViewport += (sender, e) => e.Cancel = true;
+
+        // Act
+        view.Object.DoClearViewport ();
+
+        // Assert
+        Assert.Equal (0, view.Object.OnClearedViewportCalled);
+    }
+
+    [Fact]
+    public void DoClearViewport_ClearsViewport ()
+    {
+        // Arrange
+        Mock<TestableView> view = new () { CallBase = true };
+
+        // Act
+        view.Object.SetNeedsDraw ();
+        view.Object.DoClearViewport ();
+
+        // Assert
+        Assert.Equal (1, view.Object.OnClearedViewportCalled);
+    }
+
+    [Fact]
+    public void DoClearViewport_RaisesClearingViewportEvent ()
+    {
+        // Arrange
+        Mock<TestableView> view = new () { CallBase = true };
+        var eventRaised = false;
+        view.Object.ClearingViewport += (sender, e) => eventRaised = true;
+
+        // Act
+        view.Object.SetNeedsDraw ();
+        view.Object.DoClearViewport ();
+
+        // Assert
+        Assert.True (eventRaised);
+    }
+
+    [Fact]
+    public void Clear_ClearsEntireViewport ()
+    {
+        using IApplication? app = Application.Create ();
+        app.Init ("Fake");
+
+        var superView = new Runnable
+        {
+            Width = Dim.Fill (), Height = Dim.Fill ()
+        };
+
+        var view = new View
+        {
+            Text = "X",
+            X = 1, Y = 1,
+            Width = 3, Height = 3,
+            BorderStyle = LineStyle.Single
+        };
+        superView.Add (view);
+        app.Begin (superView);
+        superView.LayoutSubViews ();
+        superView.Draw ();
+
+        DriverAssert.AssertDriverContentsWithFrameAre (
+                                                       @"
+ ┌─┐
+ │X│
+ └─┘",
+                                                       output,
+                                                       app.Driver);
+
+        // On Draw exit the view is excluded from the clip, so this will do nothing.
+        view.ClearViewport ();
+
+        DriverAssert.AssertDriverContentsWithFrameAre (
+                                                       @"
+ ┌─┐
+ │X│
+ └─┘",
+                                                       output,
+                                                       app.Driver);
+
+
+        view.SetClipToScreen ();
+
+        view.ClearViewport ();
+
+        DriverAssert.AssertDriverContentsWithFrameAre (
+                                                       @"
+ ┌─┐
+ │ │
+ └─┘",
+                                                       output,
+                                                       app.Driver);
+    }
+
+    [Fact]
+    public void Clear_WithClearVisibleContentOnly_ClearsVisibleContentOnly ()
+    {
+        using IApplication? app = Application.Create ();
+        app.Init ("Fake");
+
+        var superView = new Runnable
+        {
+            Width = Dim.Fill (), Height = Dim.Fill ()
+        };
+
+        var view = new View
+        {
+            Text = "X",
+            X = 1, Y = 1,
+            Width = 3, Height = 3,
+            BorderStyle = LineStyle.Single,
+            ViewportSettings = ViewportSettingsFlags.ClearContentOnly
+        };
+        superView.Add (view);
+        app.Begin (superView);
+        superView.LayoutSubViews ();
+
+        superView.Draw ();
+
+        DriverAssert.AssertDriverContentsWithFrameAre (
+                                                       @"
+ ┌─┐
+ │X│
+ └─┘",
+                                                       output,
+                                                       app.Driver);
+        view.SetClipToScreen ();
+        view.ClearViewport ();
+
+        DriverAssert.AssertDriverContentsWithFrameAre (
+                                                       @"
+ ┌─┐
+ │ │
+ └─┘",
+                                                       output,
+                                                       app.Driver);
+    }
+
+    [Fact]
+    public void Clear_Viewport_Can_Use_Driver_AddRune_Or_AddStr_Methods ()
+    {
+        using IApplication? app = Application.Create ();
+        app.Init ("Fake");
+        var view = new FrameView {  Width = Dim.Fill (), Height = Dim.Fill (), BorderStyle = LineStyle.Single };
+
+        view.DrawingContent += (s, e) =>
+                               {
+                                   Region? savedClip = view.AddViewportToClip ();
+
+                                   for (var row = 0; row < view.Viewport.Height; row++)
+                                   {
+                                       app.Driver?.Move (1, row + 1);
+
+                                       for (var col = 0; col < view.Viewport.Width; col++)
+                                       {
+                                           app.Driver?.AddStr ($"{col}");
+                                       }
+                                   }
+
+                                   view.SetClip (savedClip);
+                                   e.Cancel = true;
+                               };
+        var top = new Runnable ();
+        top.Add (view);
+        app.Begin (top);
+        app.Driver!.SetScreenSize (20, 10);
+        app.LayoutAndDraw ();
+
+        var expected = @"
+┌──────────────────┐
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+└──────────────────┘
+"
+            ;
+
+        Rectangle pos = DriverAssert.AssertDriverContentsWithFrameAre (expected, output, app.Driver);
+        Assert.Equal (new (0, 0, 20, 10), pos);
+
+        view.FillRect (view.Viewport);
+
+        expected = @"
+┌──────────────────┐
+│                  │
+│                  │
+│                  │
+│                  │
+│                  │
+│                  │
+│                  │
+│                  │
+└──────────────────┘
+"
+            ;
+
+        pos = DriverAssert.AssertDriverContentsWithFrameAre (expected, output, app.Driver);
+        top.Dispose ();
+    }
+
+    [Fact]
+    public void Clear_Can_Use_Driver_AddRune_Or_AddStr_Methods ()
+    {
+        using IApplication? app = Application.Create ();
+        app.Init ("Fake");
+        var view = new FrameView { Width = Dim.Fill (), Height = Dim.Fill (), BorderStyle = LineStyle.Single };
+
+        view.DrawingContent += (s, e) =>
+                               {
+                                   Region? savedClip = view.AddViewportToClip ();
+
+                                   for (var row = 0; row < view.Viewport.Height; row++)
+                                   {
+                                       app.Driver?.Move (1, row + 1);
+
+                                       for (var col = 0; col < view.Viewport.Width; col++)
+                                       {
+                                           app.Driver?.AddStr ($"{col}");
+                                       }
+                                   }
+
+                                   view.SetClip (savedClip);
+                                   e.Cancel = true;
+                               };
+        var top = new Runnable ();
+        top.Add (view);
+        app.Begin (top);
+        app.Driver!.SetScreenSize (20, 10);
+        app.LayoutAndDraw ();
+
+        var expected = @"
+┌──────────────────┐
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+│012345678910111213│
+└──────────────────┘
+"
+            ;
+
+        Rectangle pos = DriverAssert.AssertDriverContentsWithFrameAre (expected, output, app.Driver);
+        Assert.Equal (new (0, 0, 20, 10), pos);
+
+        view.FillRect (view.Viewport);
+
+        expected = @"
+┌──────────────────┐
+│                  │
+│                  │
+│                  │
+│                  │
+│                  │
+│                  │
+│                  │
+│                  │
+└──────────────────┘
+";
+
+        pos = DriverAssert.AssertDriverContentsWithFrameAre (expected, output, app.Driver);
+
+        top.Dispose ();
+    }
+}

Tests/UnitTestsParallelizable/ViewBase/Draw/ViewDrawTextAndLineCanvasTests.cs

@@ -205,34 +205,6 @@ public class ViewDrawTextAndLineCanvasTests () : FakeDriverBase
         Assert.True (eventRaised);
     }
 
-    [Fact]
-    public void DrewText_Event_Raised ()
-    {
-        IDriver driver = CreateFakeDriver (80, 25);
-        driver.Clip = new Region (driver.Screen);
-
-        bool eventRaised = false;
-
-        var view = new View
-        {
-            X = 10,
-            Y = 10,
-            Width = 20,
-            Height = 20,
-            Driver = driver,
-            Text = "Test"
-        };
-        view.BeginInit ();
-        view.EndInit ();
-        view.LayoutSubViews ();
-
-        view.DrewText += (s, e) => eventRaised = true;
-
-        view.Draw ();
-
-        Assert.True (eventRaised);
-    }
-
     #endregion
 
     #region LineCanvas Tests