AvaloniaUI/Avalonia · error · ArgumentNullException

glyphRun

Error message

glyphRun

What it means

Thrown by PlatformDrawingContext.DrawGlyphRun when the GlyphRun argument is null. The drawing context dereferences glyphRun.PlatformImpl immediately, so a null reference cannot proceed; the explicit guard produces a clear ArgumentNullException instead of a NullReferenceException deeper in the stack.

Source

Thrown at src/Avalonia.Base/Media/PlatformDrawingContext.cs:60

        _impl.DrawBitmap(source.Item, opacity, sourceRect, destRect);

    public override void Custom(ICustomDrawOperation custom)
    {
        using var immediateDrawingContext = new ImmediateDrawingContext(_impl, false);
        try
        {
            custom.Render(immediateDrawingContext);
        }
        catch (Exception e)
        {
            Logger.TryGet(LogEventLevel.Error, LogArea.Visual)
                ?.Log(custom, $"Exception in {custom.GetType().Name}.{nameof(ICustomDrawOperation.Render)} {{0}}", e);
        }
    }

    public override void DrawGlyphRun(IBrush? foreground, GlyphRun glyphRun)
    {
        _ = glyphRun ?? throw new ArgumentNullException(nameof(glyphRun));

        if (foreground != null) 
            _impl.DrawGlyphRun(foreground, glyphRun.PlatformImpl.Item);
    }

    protected override void PushClipCore(RoundedRect rect) => _impl.PushClip(rect);

    protected override void PushClipCore(Rect rect) => _impl.PushClip(rect);

    protected override void PushGeometryClipCore(Geometry clip) =>
        _impl.PushGeometryClip(clip.PlatformImpl ?? throw new ArgumentException());

    protected override void PushOpacityCore(double opacity) => 
        _impl.PushOpacity(opacity, null);

    protected override void PushOpacityMaskCore(IBrush mask, Rect bounds) =>
        _impl.PushOpacityMask(mask, bounds);

View on GitHub (pinned to 11c5427268)

Solutions

1. Pass null for the foreground brush to draw nothing, or simply skip the DrawGlyphRun call when there is no glyph run.
2. Ensure the GlyphRun is constructed from a valid GlyphTypeface and non-empty metrics before drawing.
3. Guard: if (glyphRun is not null) context.DrawGlyphRun(foreground, glyphRun);

Example fix

// before
context.DrawGlyphRun(foreground, null);

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

if (glyphRun is not null)
    context.DrawGlyphRun(foreground, glyphRun);

static bool HasGlyphRun(GlyphRun? run) => run is not null;

When it happens

Trigger: Calling DrawGlyphRun(foreground, null) directly, or passing a GlyphRun field/property that was never constructed.

Common situations: Rendering text where the GlyphRun was built from a null glyph typeface or zero-length text and ended up null; conditional text rendering that passes null when 'no text' was intended.

Related errors

• dictionary
• items
• array
• collection
• geometryContext

AI-assisted analysis of AvaloniaUI/Avalonia@11c5427268 (2026-08-13). Data as JSON: /api/errors/00bb4afce5d686eb. Report an issue: GitHub.