Changing FontRenderingEmSize with DocumentColorizingTransformer causing incorrect rendering

[gebodal]

Using SetFontRenderingEmSize(double) to change the size of text on an individual line in the editor using DocumentColorizingTransformer does not render correctly.

Current Behaviour (AvaloniaEdit 11.0.6)

The line height is not being set correctly, and the text baseline is offset from its expected position. However the actual fontsize seems to be correct, and text decorations are still being correctly placed relative to the scaled glyphs.

Expected Behaviour (AvalonEdit 6.3.0.90)

Example Code

public class ExampleFontSizeTransformer : DocumentColorizingTransformer {
    protected override void ColorizeLine(DocumentLine line) {
        string chars = CurrentContext.GetText(line.Offset, Math.Min(1, line.Length)).Text;

        if (!chars.StartsWith("#")) { return; }

        float multiplier = 3f;

        foreach (VisualLineElement elem in CurrentContext.VisualLine.Elements) {
            ChangeVisualElements(
                elem.VisualColumn, // startOffset
                elem.VisualColumn + elem.VisualLength, // endOffset
                (VisualLineElement element) => {
                    double initial = element.TextRunProperties.FontRenderingEmSize;
                    element.TextRunProperties.SetFontRenderingEmSize(initial * multiplier);
                });
        }
    }
}

And then during initialization:

textEditor.TextArea.TextView.LineTransformers.Add(new ExampleFontSizeTransformer());

Notes

Same behaviour with FontFamily set to: Roboto Mono, Consolas, Times New Roman.