Add StringIndex and GraphemeIndex to GlyphBounds

src/SixLabors.Fonts/GlyphBounds.cs

@@ -15,10 +15,14 @@ public readonly struct GlyphBounds
     /// </summary>
     /// <param name="codePoint">The Unicode codepoint for the glyph.</param>
     /// <param name="bounds">The glyph bounds.</param>
-    public GlyphBounds(CodePoint codePoint, in FontRectangle bounds)
+    /// <param name="graphemeIndex">The index of the grapheme in original text.</param>
+    /// <param name="stringIndex">The index of the codepoint in original text..</param>
+    public GlyphBounds(CodePoint codePoint, in FontRectangle bounds, int graphemeIndex, int stringIndex)
     {
         this.Codepoint = codePoint;
         this.Bounds = bounds;
+        this.GraphemeIndex = graphemeIndex;
+        this.StringIndex = stringIndex;
     }
 
     /// <summary>
@@ -31,6 +35,16 @@ public GlyphBounds(CodePoint codePoint, in FontRectangle bounds)
     /// </summary>
     public FontRectangle Bounds { get; }
 
+    /// <summary>
+    /// Gets grapheme index of glyph in original text.
+    /// </summary>
+    public int GraphemeIndex { get; }
+
+    /// <summary>
+    /// Gets string index of glyph in original text.
+    /// </summary>
+    public int StringIndex { get; }
+
     /// <inheritdoc/>
     public override string ToString()
         => $"Codepoint: {this.Codepoint}, Bounds: {this.Bounds}.";

src/SixLabors.Fonts/GlyphLayout.cs

@@ -19,7 +19,9 @@ internal GlyphLayout(
         float advanceWidth,
         float advanceHeight,
         GlyphLayoutMode layoutMode,
-        bool isStartOfLine)
+        bool isStartOfLine,
+        int graphemeIndex,
+        int stringIndex)
     {
         this.Glyph = glyph;
         this.CodePoint = glyph.GlyphMetrics.CodePoint;
@@ -30,6 +32,8 @@ internal GlyphLayout(
         this.AdvanceY = advanceHeight;
         this.LayoutMode = layoutMode;
         this.IsStartOfLine = isStartOfLine;
+        this.GraphemeIndex = graphemeIndex;
+        this.StringIndex = stringIndex;
     }
 
     /// <summary>
@@ -78,6 +82,16 @@ internal GlyphLayout(
     /// </summary>
     public bool IsStartOfLine { get; }
 
+    /// <summary>
+    /// Gets grapheme index of glyph in original text.
+    /// </summary>
+    public int GraphemeIndex { get; }
+
+    /// <summary>
+    /// Gets string index of glyph in original text.
+    /// </summary>
+    public int StringIndex { get; }
+
     /// <summary>
     /// Gets a value indicating whether the glyph represents a whitespace character.
     /// </summary>

src/SixLabors.Fonts/TextLayout.cs

@@ -420,7 +420,9 @@ private static IEnumerable<GlyphLayout> LayoutLineHorizontal(
                     data.ScaledAdvance,
                     advanceY,
                     GlyphLayoutMode.Horizontal,
-                    i == 0 && j == 0));
+                    i == 0 && j == 0,
+                    data.GraphemeIndex,
+                    data.StringIndex));
 
                 j++;
             }
@@ -556,7 +558,9 @@ private static IEnumerable<GlyphLayout> LayoutLineVertical(
                     advanceX,
                     data.ScaledAdvance,
                     GlyphLayoutMode.Vertical,
-                    i == 0 && j == 0));
+                    i == 0 && j == 0,
+                    data.GraphemeIndex,
+                    data.StringIndex));
 
                 j++;
             }
@@ -689,7 +693,9 @@ private static IEnumerable<GlyphLayout> LayoutLineVerticalMixed(
                         advanceX,
                         data.ScaledAdvance,
                         GlyphLayoutMode.VerticalRotated,
-                        i == 0 && j == 0));
+                        i == 0 && j == 0,
+                        data.GraphemeIndex,
+                        data.StringIndex));
 
                     j++;
                 }
@@ -712,7 +718,9 @@ private static IEnumerable<GlyphLayout> LayoutLineVerticalMixed(
                         advanceX,
                         data.ScaledAdvance,
                         GlyphLayoutMode.Vertical,
-                        i == 0 && j == 0));
+                        i == 0 && j == 0,
+                        data.GraphemeIndex,
+                        data.StringIndex));
 
                     j++;
                 }
@@ -895,6 +903,7 @@ private static TextBox BreakLines(
         List<TextLine> textLines = new();
         TextLine textLine = new();
         int glyphCount = 0;
+        int stringIndex = 0;
 
         // No glyph should contain more than 64 metrics.
         // We do a sanity check below just in case.
@@ -1205,12 +1214,15 @@ private static TextBox BreakLines(
                         graphemeIndex,
                         codePointIndex,
                         isRotated,
-                        isDecomposed);
+                        isDecomposed,
+                        stringIndex);
                 }
 
                 codePointIndex++;
                 graphemeCodePointIndex++;
             }
+
+            stringIndex += graphemeEnumerator.Current.Length;
         }
 
         // Add the final line.
@@ -1268,7 +1280,8 @@ public void Add(
             int graphemeIndex,
             int offset,
             bool isRotated,
-            bool isDecomposed)
+            bool isDecomposed,
+            int stringIndex)
         {
             // Reset metrics.
             // We track the maximum metrics for each line to ensure glyphs can be aligned.
@@ -1288,7 +1301,8 @@ public void Add(
                 graphemeIndex,
                 offset,
                 isRotated,
-                isDecomposed));
+                isDecomposed,
+                stringIndex));
         }
 
         public TextLine SplitAt(LineBreak lineBreak, bool keepAll)
@@ -1627,7 +1641,8 @@ public GlyphLayoutData(
                 int graphemeIndex,
                 int offset,
                 bool isRotated,
-                bool isDecomposed)
+                bool isDecomposed,
+                int stringIndex)
             {
                 this.Metrics = metrics;
                 this.PointSize = pointSize;
@@ -1640,6 +1655,7 @@ public GlyphLayoutData(
                 this.Offset = offset;
                 this.IsRotated = isRotated;
                 this.IsDecomposed = isDecomposed;
+                this.StringIndex = stringIndex;
             }
 
             public readonly CodePoint CodePoint => this.Metrics[0].CodePoint;
@@ -1668,6 +1684,8 @@ public GlyphLayoutData(
 
             public bool IsDecomposed { get; }
 
+            public int StringIndex { get; }
+
             public readonly bool IsNewLine => CodePoint.IsNewLine(this.CodePoint);
 
             private readonly string DebuggerDisplay => FormattableString

src/SixLabors.Fonts/TextMeasurer.cs

@@ -265,7 +265,7 @@ internal static bool TryGetCharacterAdvances(IReadOnlyList<GlyphLayout> glyphLay
             GlyphLayout glyph = glyphLayouts[i];
             FontRectangle bounds = new(0, 0, glyph.AdvanceX * dpi, glyph.AdvanceY * dpi);
             hasSize |= bounds.Width > 0 || bounds.Height > 0;
-            characterBoundsList[i] = new GlyphBounds(glyph.Glyph.GlyphMetrics.CodePoint, in bounds);
+            characterBoundsList[i] = new GlyphBounds(glyph.Glyph.GlyphMetrics.CodePoint, in bounds, glyph.GraphemeIndex, glyph.StringIndex);
         }
 
         characterBounds = characterBoundsList;
@@ -290,7 +290,7 @@ internal static bool TryGetCharacterSizes(IReadOnlyList<GlyphLayout> glyphLayout
             bounds = new(0, 0, bounds.Width, bounds.Height);
 
             hasSize |= bounds.Width > 0 || bounds.Height > 0;
-            characterBoundsList[i] = new GlyphBounds(g.Glyph.GlyphMetrics.CodePoint, in bounds);
+            characterBoundsList[i] = new GlyphBounds(g.Glyph.GlyphMetrics.CodePoint, in bounds, g.GraphemeIndex, g.StringIndex);
         }
 
         characterBounds = characterBoundsList;
@@ -312,7 +312,7 @@ internal static bool TryGetCharacterBounds(IReadOnlyList<GlyphLayout> glyphLayou
             GlyphLayout g = glyphLayouts[i];
             FontRectangle bounds = g.BoundingBox(dpi);
             hasSize |= bounds.Width > 0 || bounds.Height > 0;
-            characterBoundsList[i] = new GlyphBounds(g.Glyph.GlyphMetrics.CodePoint, in bounds);
+            characterBoundsList[i] = new GlyphBounds(g.Glyph.GlyphMetrics.CodePoint, in bounds, g.GraphemeIndex, g.StringIndex);
         }
 
         characterBounds = characterBoundsList;

tests/SixLabors.Fonts.Tests/TextLayoutTests.cs

@@ -3,7 +3,6 @@
 
 using System.Globalization;
 using System.Numerics;
-using System.Text;
 using SixLabors.Fonts.Tests.Fakes;
 using SixLabors.Fonts.Unicode;
 
@@ -241,10 +240,10 @@
         const string text = "a b\nc";
         GlyphBounds[] expectedGlyphMetrics =
         {
-            new(new CodePoint('a'), new FontRectangle(10, 0, 10, 10)),
-            new(new CodePoint(' '), new FontRectangle(40, 0, 30, 10)),
-            new(new CodePoint('b'), new FontRectangle(70, 0, 10, 10)),
-            new(new CodePoint('c'), new FontRectangle(10, 30, 10, 10)),
+            new(new CodePoint('a'), new FontRectangle(10, 0, 10, 10), 0, 0),
+            new(new CodePoint(' '), new FontRectangle(40, 0, 30, 10), 1, 1),
+            new(new CodePoint('b'), new FontRectangle(70, 0, 10, 10), 2, 2),
+            new(new CodePoint('c'), new FontRectangle(10, 30, 10, 10), 3, 3),
         };
         Font font = CreateFont(text);
 
@@ -778,7 +777,7 @@
         }
     }
 
     public static TheoryData<char, FontRectangle> OpenSans_Data
         = new()
         {
             { '!', new(0, 0, 2, 8) },
@@ -996,11 +995,78 @@
         }
     }
 
+    [Fact]
+    public void DoesMeasureCharacterLayoutIncludeStringIndex()
+    {
+        FontFamily family = new FontCollection().Add(TestFonts.OpenSansFile);
+        family.TryGetMetrics(FontStyle.Regular, out FontMetrics metrics);
+
+        TextOptions options = new(family.CreateFont(metrics.UnitsPerEm))
+        {
+            LineSpacing = 1.5F
+        };
+
+        const string text = "The quick👩🏽‍🚒 brown fox jumps over \r\n the lazy dog";
+
+        Assert.True(TextMeasurer.TryMeasureCharacterAdvances(text, options, out ReadOnlySpan<GlyphBounds> advances));
+        Assert.True(TextMeasurer.TryMeasureCharacterSizes(text, options, out ReadOnlySpan<GlyphBounds> sizes));
+        Assert.True(TextMeasurer.TryMeasureCharacterBounds(text, options, out ReadOnlySpan<GlyphBounds> bounds));
+
+        Assert.Equal(advances.Length, sizes.Length);
+        Assert.Equal(advances.Length, bounds.Length);
+
+        int stringIndex = -1;
+
+        for (int i = 0; i < advances.Length; i++)
+        {
+            GlyphBounds advance = advances[i];
+            GlyphBounds size = sizes[i];
+            GlyphBounds bound = bounds[i];
+
+            Assert.Equal(bound.StringIndex, advance.StringIndex);
+            Assert.Equal(bound.StringIndex, size.StringIndex);
+
+            Assert.Equal(bound.GraphemeIndex, advance.GraphemeIndex);
+            Assert.Equal(bound.GraphemeIndex, size.GraphemeIndex);
+
+            if (bound.Codepoint == new CodePoint("k"[0]))
+            {
+                stringIndex = text.IndexOf("k", StringComparison.InvariantCulture);
+                Assert.Equal(stringIndex, bound.StringIndex);
+                Assert.Equal(stringIndex, bound.GraphemeIndex);
+            }
+
+            // after emoji
+            if (bound.Codepoint == new CodePoint("b"[0]))
+            {
+                stringIndex = text.IndexOf("b", StringComparison.InvariantCulture);
+                Assert.NotEqual(bound.StringIndex, bound.GraphemeIndex);
+                Assert.Equal(stringIndex, bound.StringIndex);
+                Assert.Equal(11, bound.GraphemeIndex);
+            }
+        }
+
+        SpanGraphemeEnumerator graphemeEnumerator = new(text);
+        int graphemeCount = 0;
+        while (graphemeEnumerator.MoveNext())
+        {
+            graphemeCount += 1;
+        }
+
+        GlyphBounds firstBound = bounds[0];
+        Assert.Equal(0, firstBound.StringIndex);
+        Assert.Equal(0, firstBound.GraphemeIndex);
+
+        GlyphBounds lastBound = bounds[^1];
+        Assert.Equal(text.Length - 1, lastBound.StringIndex);
+        Assert.Equal(graphemeCount - 1, lastBound.GraphemeIndex);
+    }
+
     private static readonly Font OpenSansTTF = new FontCollection().Add(TestFonts.OpenSansFile).CreateFont(10);
     private static readonly Font OpenSansWoff = new FontCollection().Add(TestFonts.OpenSansFile).CreateFont(10);
 
 #if OS_WINDOWS
     public static TheoryData<char, FontRectangle> SegoeUi_Data
         = new()
         {
             { '!', new(0, 0, 2, 8) },