Removed MaxOverhang and fixed MeasuredOverhang to work out both left and right overhang

SandboxDriver/SandboxDriver.cs

@@ -230,12 +230,30 @@ namespace SandboxDriver
 
             if (_textBlock.MeasuredOverhang.Left > 0)
             {
-                using (var paint = new SKPaint() { Color = new SKColor(0xFFf0f0f0), StrokeWidth = 1 })
+                using (var paint = new SKPaint() { Color = new SKColor(0xFF00fff0), StrokeWidth = 1 })
                 {
                     canvas.DrawLine(new SKPoint(margin - _textBlock.MeasuredOverhang.Left, 0), new SKPoint(margin - _textBlock.MeasuredOverhang.Left, (float)canvasHeight), paint);
                 }
             }
 
+            if (_textBlock.MeasuredOverhang.Right > 0)
+            {
+                using (var paint = new SKPaint() { Color = new SKColor(0xFF00ff00), StrokeWidth = 1 })
+                {
+                    float x;
+                    if (_textBlock.MaxWidth.HasValue)
+                    {
+                        x = margin + _textBlock.MaxWidth.Value;
+                    }
+                    else
+                    {
+                        x = margin + _textBlock.MeasuredWidth;
+                    }
+                    x += _textBlock.MeasuredOverhang.Right;
+                    canvas.DrawLine(new SKPoint(x, 0), new SKPoint(x, (float)canvasHeight), paint);
+                }
+            }
+
             _textBlock.Paint(canvas, new SKPoint(margin, margin), options);
 
             if (ci != null)

Topten.RichTextKit/FontRun.cs

@@ -419,13 +419,18 @@ namespace Topten.RichTextKit
         internal Buffer<int> CodePointBuffer;
 
         /// <summary>
-        /// Calculate how by how much text at the left margin overhangs the margin
+        /// Calculate any overhang for this text line
         /// </summary>
-        /// <returns>The amount of overhang</returns>
-        internal float CalculateRequiredLeftMargin()
+        /// <param name="right"></param>
+        /// <param name="leftOverhang"></param>
+        /// <param name="rightOverhang"></param>
+        internal void UpdateOverhang(float right, ref float leftOverhang, ref float rightOverhang)
         {
+            if (RunKind == FontRunKind.TrailingWhitespace)
+                return;
+
             if (Glyphs.Length == 0)
-                return 0;
+                return;
 
             using (var paint = new SKPaint())
             {
@@ -450,18 +455,25 @@ namespace Topten.RichTextKit
                 {
                     fixed (ushort* pGlyphs = Glyphs.Underlying)
                     {
-                        paint.GetGlyphWidths((IntPtr)(pGlyphs + Start), sizeof(ushort), out var bounds);
-                        if (bounds != null && bounds.Length >= 1)
+                        paint.GetGlyphWidths((IntPtr)(pGlyphs + Start), sizeof(ushort) * Glyphs.Length, out var bounds);
+                        if (bounds != null)
                         {
-                            var lhs = XCoord + bounds[0].Left;
-                            if (lhs < 0)
-                                return -lhs;
+                            for (int i = 0; i < bounds.Length; i++)
+                            {
+                                float gx = GlyphPositions[i].X;
+
+                                var loh = -(gx + bounds[i].Left);
+                                if (loh > leftOverhang)
+                                    leftOverhang = loh;
+
+                                var roh = (gx + bounds[i].Right + 1) - right;
+                                if (roh > rightOverhang) 
+                                    rightOverhang = roh;
+                            }
                         }
                     }
                 }
             }
-
-            return 0;
         }
 
         /// <summary>

Topten.RichTextKit/TextBlock.cs

@@ -245,8 +245,8 @@ namespace Topten.RichTextKit
             _caretIndicies.Clear();
             _measuredHeight = 0;
             _measuredWidth = 0;
-            _minLeftMargin = 0;
-            _requiredLeftMargin = null;
+            _leftOverhang = null;
+            _rightOverhang = null;
 
             // Only layout if actually have some text
             if (_codePoints.Length != 0)
@@ -445,39 +445,11 @@ namespace Topten.RichTextKit
         }
 
 
-        /// <summary>
-        /// Returns the maximum possible overhang based on the fonts used in this text block
-        /// </summary>
-        /// <remarks>
-        /// Some font's can overhang the left and right margins.  eg: a lowercase 'j' at 
-        /// the start of a line will often overhang to the left of the left margin.
-        /// 
-        /// This property returns the maximum overhang in each direction based on the fonts 
-        /// used, but not the actual text or final layout.  This can be useful to get a 
-        /// consistent maximum possible overhang, although the returned value is often 
-        /// excessive (depending on the font).
-        /// 
-        /// Currently only the left overhang is calculated.
-        /// 
-        /// The return rectangle describes overhang amounts for each edge - not rectangle 
-        /// co-ordinates.
-        /// </remarks>
-        public SKRect MaxOverhang
-        {
-            get
-            {
-                Layout();
-                return new SKRect(_minLeftMargin, 0, 0, 0);
-            }
-        }
-
         /// <summary>
         /// Gets the actual measured overhang in each direction based on the 
         /// fonts used, and the supplied text.
         /// </summary>
         /// <remarks>
-        /// Currently only the left overhang is calculated.
-        /// 
         /// The return rectangle describes overhang amounts for each edge - not 
         /// rectangle co-ordinates.
         /// </remarks>
@@ -486,23 +458,19 @@ namespace Topten.RichTextKit
             get
             {
                 Layout();
-                if (!_requiredLeftMargin.HasValue)
+                if (!_leftOverhang.HasValue)
                 {
-                    float required = 0;
+                    var right = _maxWidth ?? MeasuredWidth;
+                    float leftOverhang = 0;
+                    float rightOverhang = 0;
                     foreach (var l in _lines)
                     {
-                        if (l.Runs.Count == 0)
-                            continue;
-                        var r = l.Runs[0];
-                        if (r.RunKind == FontRunKind.TrailingWhitespace)
-                            continue;
-                        var m = r.CalculateRequiredLeftMargin();
-                        if (m > required)
-                            required = m;
+                        l.UpdateOverhang(right, ref leftOverhang, ref rightOverhang);
                     }
-                    _requiredLeftMargin = required;
+                    _leftOverhang = leftOverhang;
+                    _rightOverhang = rightOverhang;
                 }
-                return new SKRect(_requiredLeftMargin.Value, 0, 0, 0);
+                return new SKRect(_leftOverhang.Value, 0, _rightOverhang.Value, 0);
             }
         }
 
@@ -779,14 +747,14 @@ namespace Topten.RichTextKit
         float _measuredWidth;
 
         /// <summary>
-        /// The minimum left margin
+        /// The required left overhang
         /// </summary>
-        float _minLeftMargin;
+        float? _leftOverhang = null;
 
         /// <summary>
-        /// The required left margin
+        /// The required left overhang
         /// </summary>
-        float? _requiredLeftMargin = null;
+        float? _rightOverhang = null;
 
         /// <summary>
         /// The final laid out set of lines
@@ -953,11 +921,6 @@ namespace Topten.RichTextKit
             var shaper = TextShaper.ForTypeface(typeface);
             var shaped = shaper.Shape(_textShapingBuffers, codePoints, style, direction, codePoints.Start);
 
-            // Update minimum required left margin
-            if (shaped.XMin < 0 && -shaped.XMin > _minLeftMargin)
-            {
-                _minLeftMargin = -shaped.XMin;
-            }
 
             // Create the run
             var fontRun = FontRun.Pool.Get();

Topten.RichTextKit/TextLine.cs

@@ -293,6 +293,14 @@ namespace Topten.RichTextKit
             }
         }
 
+        internal void UpdateOverhang(float right, ref float leftOverhang, ref float rightOverhang)
+        {
+            foreach (var r in Runs)
+            {
+                r.UpdateOverhang(right, ref leftOverhang, ref rightOverhang);
+            }
+        }
+
         /// <summary>
         /// Internal List of runs
         /// </summary>