Ensure we never add empty text lines

src/SixLabors.Fonts/TextLayout.cs

@@ -1066,7 +1066,7 @@ private static TextBox BreakLines(
                     else if (shouldWrap && lineAdvance + glyphAdvance >= wrappingLength)
                     {
                         // Forced wordbreak
-                        if (breakAll)
+                        if (breakAll && textLine.Count > 0)
                         {
                             textLines.Add(textLine.Finalize());
                             glyphCount += textLine.Count;
@@ -1086,7 +1086,7 @@ private static TextBox BreakLines(
                                     lineAdvance = split.ScaledLineAdvance;
                                 }
                             }
-                            else
+                            else if (textLine.Count > 0)
                             {
                                 textLines.Add(textLine.Finalize());
                                 glyphCount += textLine.Count;
@@ -1123,15 +1123,15 @@ private static TextBox BreakLines(
                                 textLine = split;
                                 lineAdvance = split.ScaledLineAdvance;
                             }
-                            else if (breakWord)
+                            else if (breakWord && textLine.Count > 0)
                             {
                                 textLines.Add(textLine.Finalize());
                                 glyphCount += textLine.Count;
                                 textLine = new();
                                 lineAdvance = 0;
                             }
                         }
-                        else if (breakWord)
+                        else if (breakWord && textLine.Count > 0)
                         {
                             textLines.Add(textLine.Finalize());
                             glyphCount += textLine.Count;

tests/SixLabors.Fonts.Tests/Issues/Issues_383.cs

@@ -0,0 +1,94 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+#if OS_WINDOWS
+using System.Numerics;
+
+namespace SixLabors.Fonts.Tests.Issues;
+
+public class Issues_383
+{
+    [Fact]
+    public void CanBreakLinesWithShortWrappingLength()
+    {
+        FontFamily fontFamily = SystemFonts.Get("Yu Gothic");
+        Font font = fontFamily.CreateFont(20.0F);
+
+        TextOptions textOption = new(font)
+        {
+            WrappingLength = 10.0F,
+            WordBreaking = WordBreaking.BreakAll
+        };
+
+        // OK
+        TextRenderer.RenderTextTo(new DummyGlyphRenderer(), "i", textOption);
+
+        // OK
+        TextRenderer.RenderTextTo(new DummyGlyphRenderer(), "v", textOption);
+
+        // raise ArgumentOutOfRangeException
+        TextRenderer.RenderTextTo(new DummyGlyphRenderer(), "a", textOption);
+
+        textOption.WrappingLength = 9.0F;
+
+        // OK
+        TextRenderer.RenderTextTo(new DummyGlyphRenderer(), "i", textOption);
+
+        // raise ArgumentOutOfRangeException
+        TextRenderer.RenderTextTo(new DummyGlyphRenderer(), "v", textOption);
+
+        // OK
+        TextRenderer.RenderTextTo(new DummyGlyphRenderer(), "i\r\nv", textOption);
+
+        // raise ArgumentOutOfRangeException
+        TextRenderer.RenderTextTo(new DummyGlyphRenderer(), "v\r\ni", textOption);
+    }
+}
+
+internal class DummyGlyphRenderer : IGlyphRenderer
+{
+    public void BeginFigure()
+    {
+    }
+
+    public bool BeginGlyph(in FontRectangle bounds, in GlyphRendererParameters parameters) => true;
+
+    public void BeginText(in FontRectangle bounds)
+    {
+    }
+
+    public void CubicBezierTo(Vector2 secondControlPoint, Vector2 thirdControlPoint, Vector2 point)
+    {
+    }
+
+    public TextDecorations EnabledDecorations() => TextDecorations.None;
+
+    public void EndFigure()
+    {
+    }
+
+    public void EndGlyph()
+    {
+    }
+
+    public void EndText()
+    {
+    }
+
+    public void LineTo(Vector2 point)
+    {
+    }
+
+    public void MoveTo(Vector2 point)
+    {
+    }
+
+    public void QuadraticBezierTo(Vector2 secondControlPoint, Vector2 point)
+    {
+    }
+
+    public void SetDecoration(TextDecorations textDecorations, Vector2 start, Vector2 end, float thickness)
+    {
+    }
+}
+#endif