Expand TabCompositionTests to cover all 4 sides and thicknesses 1, 2, 3

Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs

@@ -394,10 +394,124 @@ public void Merge (LineCanvas lineCanvas)
             AddLine (line);
         }
 
-        if (lineCanvas._exclusionRegion is { })
+        if (lineCanvas._exclusionRegion is null)
         {
-            _exclusionRegion ??= new ();
-            _exclusionRegion.Union (lineCanvas._exclusionRegion);
+            return;
+        }
+
+        _exclusionRegion ??= new Region ();
+        _exclusionRegion.Union (lineCanvas._exclusionRegion);
+    }
+
+    /// <summary>
+    ///     Merges one line canvas into this one, excluding lines (or portions of lines) that fall
+    ///     within <paramref name="exclude"/>. Lines that partially overlap the exclusion region are
+    ///     split into segments that skip the excluded cells. The exclusion is applied at the line level
+    ///     so that excluded cells do not participate in auto-join intersection resolution.
+    /// </summary>
+    /// <param name="lineCanvas">The source canvas to merge from.</param>
+    /// <param name="exclude">
+    ///     The region to exclude. Cells of incoming lines that fall within this region will not be merged.
+    ///     Pass <see langword="null"/> for default merge behavior (no exclusion).
+    /// </param>
+    public void Merge (LineCanvas lineCanvas, Region? exclude)
+    {
+        if (exclude is null || exclude.IsEmpty ())
+        {
+            Merge (lineCanvas);
+
+            return;
+        }
+
+        Rectangle excludeBounds = exclude.GetBounds ();
+        Rectangle [] excludeRects = exclude.GetRectangles ();
+
+        foreach (StraightLine line in lineCanvas._lines)
+        {
+            AddLineExcluding (line, excludeBounds, excludeRects);
+        }
+
+        if (lineCanvas._exclusionRegion is null)
+        {
+            return;
+        }
+
+        _exclusionRegion ??= new Region ();
+        _exclusionRegion.Union (lineCanvas._exclusionRegion);
+
+        return;
+
+        // Adds segments of `line` that do not overlap with the exclusion rectangles.
+        void AddLineExcluding (StraightLine line, Rectangle exBounds, Rectangle [] exRects)
+        {
+            Rectangle bounds = line.Bounds;
+
+            // Fast path: if the line doesn't intersect the exclusion bounds at all, add it whole.
+            if (!bounds.IntersectsWith (exBounds))
+            {
+                AddLine (line);
+
+                return;
+            }
+
+            // Walk cells along the line's axis, building non-excluded segments.
+            bool isHorizontal = line.Orientation == Orientation.Horizontal;
+            int axisStart = isHorizontal ? bounds.X : bounds.Y;
+            int axisEnd = axisStart + (isHorizontal ? bounds.Width : bounds.Height);
+            int fixedCoord = isHorizontal ? bounds.Y : bounds.X;
+
+            int segStart = -1;
+
+            for (int i = axisStart; i < axisEnd; i++)
+            {
+                int x = isHorizontal ? i : fixedCoord;
+                int y = isHorizontal ? fixedCoord : i;
+
+                if (!ContainedInAny (exRects, x, y))
+                {
+                    if (segStart < 0)
+                    {
+                        segStart = i;
+                    }
+
+                    continue;
+                }
+
+                // Cell is excluded — flush any pending segment.
+                if (segStart < 0)
+                {
+                    continue;
+                }
+
+                EmitSegment (line, isHorizontal, fixedCoord, segStart, i - segStart);
+                segStart = -1;
+            }
+
+            // Flush trailing segment.
+            if (segStart >= 0)
+            {
+                EmitSegment (line, isHorizontal, fixedCoord, segStart, axisEnd - segStart);
+            }
+        }
+
+        static bool ContainedInAny (Rectangle [] rects, int x, int y)
+        {
+            for (var i = 0; i < rects.Length; i++)
+            {
+                if (rects [i].Contains (x, y))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        void EmitSegment (StraightLine original, bool isHorizontal, int fixedCoord, int segAxisStart, int segLength)
+        {
+            Point start = isHorizontal ? new Point (segAxisStart, fixedCoord) : new Point (fixedCoord, segAxisStart);
+
+            AddLine (new StraightLine (start, segLength, original.Orientation, original.Style, original.Attribute));
         }
     }
 

Terminal.Gui/ViewBase/Adornment/Border.cs

@@ -25,10 +25,10 @@ protected override AdornmentView CreateView ()
         return bv;
     }
 
-    /// <inheritdoc />
+    /// <inheritdoc/>
     public override Rectangle GetFrame () => Parent is { } ? Parent.Margin.Thickness.GetInside (Parent!.Margin.GetFrame ()) : Rectangle.Empty;
 
-    /// <inheritdoc />
+    /// <inheritdoc/>
     protected override void OnThicknessChanged ()
     {
         base.OnThicknessChanged ();
@@ -48,7 +48,8 @@ protected override void OnThicknessChanged ()
 
     /// <summary>
     ///     Sets the style of the lines drawn in the <see cref="Border"/>. If not set, will inherit the style from
-    ///     the <see cref="IAdornment.Parent"/>'s <see cref="View.SuperView"/>'s <see cref="View.BorderStyle"/>. If set, will cause <see cref="IAdornment.View"/>
+    ///     the <see cref="IAdornment.Parent"/>'s <see cref="View.SuperView"/>'s <see cref="View.BorderStyle"/>. If set, will
+    ///     cause <see cref="IAdornment.View"/>
     ///     to be created.
     /// </summary>
     public LineStyle? LineStyle
@@ -63,7 +64,7 @@ public LineStyle? LineStyle
 
             field = value;
 
-            if (field is not null)
+            if (field is { })
             {
                 GetOrCreateView ();
             }
@@ -82,9 +83,87 @@ public BorderSettings Settings
             {
                 return;
             }
+
             field = value;
 
+            if (field.HasFlag (BorderSettings.Tab))
+            {
+                GetOrCreateView ();
+            }
+
+            SettingsChanged?.Invoke (this, EventArgs.Empty);
             Parent?.SetNeedsLayout ();
         }
     } = BorderSettings.Title;
+
+    /// <summary>Fired when <see cref="Settings"/> changes.</summary>
+    public event EventHandler? SettingsChanged;
+
+    /// <summary>
+    ///     Gets or sets which side the Tab protrudes from. Only used when <see cref="BorderSettings.Tab"/> is set.
+    /// </summary>
+    public Side TabSide
+    {
+        get;
+        set
+        {
+            if (field == value)
+            {
+                return;
+            }
+
+            field = value;
+            Parent?.SetNeedsLayout ();
+        }
+    } = Side.Top;
+
+    /// <summary>
+    ///     Gets or sets the offset along the border edge where the Tab starts (columns for Top/Bottom,
+    ///     rows for Left/Right). Only used when <see cref="BorderSettings.Tab"/> is set.
+    /// </summary>
+    public int TabOffset
+    {
+        get;
+        set
+        {
+            if (field == value)
+            {
+                return;
+            }
+
+            field = value;
+            Parent?.SetNeedsLayout ();
+        }
+    }
+
+    /// <summary>
+    ///     Gets or sets the total length of the tab parallel to the border edge (including border cells).
+    ///     If <see langword="null"/> the length will be determined based on <see cref="View.Title"/>.
+    ///     Only used when <see cref="BorderSettings.Tab"/> is set.
+    /// </summary>
+    public int? TabLength
+    {
+        get
+        {
+            if (field is { } || !Settings.HasFlag (BorderSettings.Tab))
+            {
+                return field;
+            }
+
+            int titleColumns = Settings.HasFlag (BorderSettings.Title) ? Parent?.TitleTextFormatter.FormatAndGetSize ().Width ?? 0 : 0;
+
+            // Two vertical border lines + title text width (2 when no title)
+            return titleColumns + 2;
+        }
+        set
+        {
+            if (field == value)
+            {
+                return;
+            }
+
+            field = value;
+            Parent?.SetNeedsLayout ();
+        }
+    }
 }

Terminal.Gui/ViewBase/Adornment/BorderSettings.cs

@@ -20,4 +20,12 @@ public enum BorderSettings
     /// Use <see cref="GradientFill"/> to draw the border.
     /// </summary>
     Gradient = 2,
+
+    /// <summary>
+    ///     Draw a Tab on one side of the border. The <see cref="View.Title"/> will be displayed in the Tab. Configure with
+    ///     <see cref="Border.TabSide"/>, <see cref="Border.TabOffset"/>,
+    ///     <see cref="Border.TabLength"/>.
+    /// </summary>
+    Tab = 4,
 }
+