Fixes #4453. Regression in wide glyph rendering on all drivers (#4458)

Examples/UICatalog/Scenarios/WideGlyphs.cs

@@ -0,0 +1,129 @@
+#nullable enable
+
+using System.Text;
+
+namespace UICatalog.Scenarios;
+
+[ScenarioMetadata ("WideGlyphs", "Demonstrates wide glyphs with overlapped views & clipping")]
+[ScenarioCategory ("Unicode")]
+[ScenarioCategory ("Drawing")]
+
+public sealed class WideGlyphs : Scenario
+{
+    private Rune [,]? _codepoints;
+
+    public override void Main ()
+    {
+        // Init
+        Application.Init ();
+
+        // Setup - Create a top-level application window and configure it.
+        Window appWindow = new ()
+        {
+            Title = GetQuitKeyAndName (),
+            BorderStyle = LineStyle.None
+        };
+
+        // Build the array of codepoints once when subviews are laid out
+        appWindow.SubViewsLaidOut += (s, e) =>
+        {
+            View? view = s as View;
+            if (view is null)
+            {
+                return;
+            }
+
+            // Only rebuild if size changed or array is null
+            if (_codepoints is null || 
+                _codepoints.GetLength (0) != view.Viewport.Height || 
+                _codepoints.GetLength (1) != view.Viewport.Width)
+            {
+                _codepoints = new Rune [view.Viewport.Height, view.Viewport.Width];
+
+                for (int r = 0; r < view.Viewport.Height; r++)
+                {
+                    for (int c = 0; c < view.Viewport.Width; c += 2)
+                    {
+                        _codepoints [r, c] = GetRandomWideCodepoint ();
+                    }
+                }
+            }
+        };
+
+        // Fill the window with the pre-built codepoints array
+        appWindow.DrawingContent += (s, e) =>
+        {
+            View? view = s as View;
+            if (view is null || _codepoints is null)
+            {
+                return;
+            }
+
+            // Traverse the Viewport, using the pre-built array
+            for (int r = 0; r < view.Viewport.Height && r < _codepoints.GetLength (0); r++)
+            {
+                for (int c = 0; c < view.Viewport.Width && c < _codepoints.GetLength (1); c += 2)
+                {
+                    Rune codepoint = _codepoints [r, c];
+                    if (codepoint != default (Rune))
+                    {
+                        view.AddRune (c, r, codepoint);
+                    }
+                }
+            }
+        };
+
+        Line verticalLineAtEven = new Line ()
+        {
+            X = 10,
+            Orientation = Orientation.Vertical,
+            Length = Dim.Fill ()
+        };
+        appWindow.Add (verticalLineAtEven);
+
+        Line verticalLineAtOdd = new Line ()
+        {
+            X = 25,
+            Orientation = Orientation.Vertical,
+            Length = Dim.Fill ()
+        };
+        appWindow.Add (verticalLineAtOdd);
+
+        View arrangeableViewAtEven = new ()
+        {
+            CanFocus = true,
+            Arrangement = ViewArrangement.Movable | ViewArrangement.Resizable,
+            X = 30,
+            Y = 5,
+            Width = 15,
+            Height = 5,
+            BorderStyle = LineStyle.Dashed,
+        };
+        appWindow.Add (arrangeableViewAtEven);
+
+        View arrangeableViewAtOdd = new ()
+        {
+            CanFocus = true,
+            Arrangement = ViewArrangement.Movable | ViewArrangement.Resizable,
+            X = 31,
+            Y = 11,
+            Width = 15,
+            Height = 5,
+            BorderStyle = LineStyle.Dashed,
+        };
+        appWindow.Add (arrangeableViewAtOdd);
+        // Run - Start the application.
+        Application.Run (appWindow);
+        appWindow.Dispose ();
+
+        // Shutdown - Calling Application.Shutdown is required.
+        Application.Shutdown ();
+    }
+
+    private Rune GetRandomWideCodepoint ()
+    {
+        Random random = new ();
+        int codepoint = random.Next (0x4E00, 0x9FFF);
+        return new Rune (codepoint);
+    }
+}