AvaloniaUI/Avalonia · error · ArgumentNullException

glyphRun

Error message

glyphRun

What it means

DrawGlyphRun throws ArgumentNullException(nameof(glyphRun)) when the IImmutableGlyphRunReference is null. The context dereferences glyphRun.GlyphRun, so a null reference is rejected up front.

Source

Thrown at src/Avalonia.Base/Media/ImmediateDrawingContext.cs:190

                return;
            }

            var originX = center.X - radiusX;
            var originY = center.Y - radiusY;
            var width = radiusX * 2;
            var height = radiusY * 2;

            PlatformImpl.DrawEllipse(brush, pen, new Rect(originX, originY, width, height));
        }

        /// <summary>
        /// Draws a glyph run.
        /// </summary>
        /// <param name="foreground">The foreground brush.</param>
        /// <param name="glyphRun">The glyph run.</param>
        public void DrawGlyphRun(IImmutableBrush foreground, IImmutableGlyphRunReference glyphRun)
        {
            _ = glyphRun ?? throw new ArgumentNullException(nameof(glyphRun));
            if (glyphRun.GlyphRun != null)
                PlatformImpl.DrawGlyphRun(foreground, glyphRun.GlyphRun.Item);
        }

        /// <summary>
        /// Draws a filled rectangle.
        /// </summary>
        /// <param name="brush">The brush.</param>
        /// <param name="rect">The rectangle bounds.</param>
        /// <param name="cornerRadius">The corner radius.</param>
        public void FillRectangle(IImmutableBrush brush, Rect rect, float cornerRadius = 0.0f)
        {
            DrawRectangle(brush, null, rect, cornerRadius, cornerRadius);
        }

        public readonly record struct PushedState : IDisposable
        {
            private readonly int _level;

View on GitHub (pinned to 11c5427268)

Solutions

1. Null-check the glyph run before drawing.
2. Skip the draw call when the text run is empty.
3. Ensure GlyphRun objects are built before being wrapped as references.

Example fix

// before
context.DrawGlyphRun(foreground, glyphRunRef); // may be null

// after
if (glyphRunRef is not null)
    context.DrawGlyphRun(foreground, glyphRunRef);

if (glyphRun is null) return;
context.DrawGlyphRun(foreground, glyphRun);

When it happens

Trigger: Calling context.DrawGlyphRun(foreground, null) — e.g. a text rendering path that produced no glyph run or passed a reference before it was built.

Common situations: Custom text controls drawing before the glyph run is computed; formatted text with no characters yielding null; partial initialization of a GlyphRunReference.

Related errors

• source
• ImmediateDrawingContext
• DrawingContext
• Wrong Push/Pop state order
• Transform container stack is non-empty

AI-assisted analysis of AvaloniaUI/Avalonia@11c5427268 (2026-08-13). Data as JSON: /api/errors/356ea698322e8383. Report an issue: GitHub.