Question

I am writing a custom software using avalon edit and I am looking for a way to make the space (height) between lines bigger. At the moment I am forced to add an empty line every time the user has ended writing a line and wants to write another.

I have started looking into the TextView Class where defaultLineHeight seems to be calculated but the only thing I was able to affect is the height of the visual caret but not the content itself.

At the moment I am looking at making every pair line invisible but I am hoping there is an easier way to achieve the simple operation of adding more space between lines.

Here is the method from class TextView I am inspecting at the moment. Any tips or hints would be welcome.

void CalculateDefaultTextMetrics()
{
    if (defaultTextMetricsValid)
    {
        return;
    }

    defaultTextMetricsValid = true;
    if (formatter != null)
    {
        var textRunProperties = CreateGlobalTextRunProperties();
        using (
            var line = formatter.FormatLine(
                new SimpleTextSource("x", textRunProperties),
                0,
                32000,
                new VisualLineTextParagraphProperties { defaultTextRunProperties = textRunProperties },
                null))
        {
            wideSpaceWidth = Math.Max(1, line.WidthIncludingTrailingWhitespace);
            defaultBaseline = Math.Max(1, line.Baseline);
            defaultLineHeight = Math.Max(1, line.Height);
        }
    }
    else
    {
        wideSpaceWidth = FontSize / 2;
        defaultBaseline = FontSize;
        **defaultLineHeight = FontSize + 3; // bigger value only affects caret height :(**
    }

    // Update heightTree.DefaultLineHeight, if a document is loaded.
    if (heightTree != null)
    {
        heightTree.DefaultLineHeight = defaultLineHeight;
    }
}

Thanks

Answer 1

The DefaultLineHeight is the height of a line in the default font, which is used as an initial assumption for the each line’s height. (e.g. for calculating the scroll bar position)

Whenever a line gets actually measured (TextView.BuildVisualLine), the measured height gets stored in the height tree, overwriting the default height. This is because word wrapping (or a line transformer changing the font size) can cause each line to have a different height.

Inter-line spacing isn’t really supported at the moment. If you want to add that, you can try changing the height calculation of the VisualLine, e.g. by changing VisualLine.SetTextLines().