How to justify text in a label

Question

I have a label that displays on more than a line and I would like to justify the text in it (align left and right). What is the best way to achieve that?

Answer 1

This is an implementation of the solution proposed by TaW. It is just the base code for the implementation - no automatic re-adjustments, etc.

public void Justify(System.Windows.Forms.Label label)
{
    string text = label.Text;
    string[] lines = text.Split(new[]{"\r\n"}, StringSplitOptions.None).Select(l => l.Trim()).ToArray();

    List<string> result = new List<string>();

    foreach (string line in lines)
    {
        result.Add(StretchToWidth(line, label));
    }

    label.Text = string.Join("\r\n", result);
}

private string StretchToWidth(string text, Label label)
{
    if (text.Length < 2)
        return text;

    // A hair space is the smallest possible non-visible character we can insert
    const char hairspace = '\u200A';

    // If we measure just the width of the space we might get too much because of added paddings so we have to do it a bit differently
    double basewidth = TextRenderer.MeasureText(text, label.Font).Width;
    double doublewidth = TextRenderer.MeasureText(text + text, label.Font).Width;
    double doublewidthplusspace = TextRenderer.MeasureText(text + hairspace + text, label.Font).Width;
    double spacewidth = doublewidthplusspace - doublewidth;

    //The space we have to fill up with spaces is whatever is left
    double leftoverspace = label.Width - basewidth;

    //Calculate the amount of spaces we need to insert
    int approximateInserts = Math.Max(0, (int)Math.Floor(leftoverspace / spacewidth));

    //Insert spaces
    return InsertFillerChar(hairspace, text, approximateInserts);
}

private static string InsertFillerChar(char filler, string text, int inserts)
{
    string result = "";
    int inserted = 0;

    for (int i = 0; i < text.Length; i++)
    {
        //Add one character of the original text
        result += text[i];

        //Only add spaces between characters, not at the end
        if (i >= text.Length - 1) continue;

        //Determine how many characters should have been inserted so far
        int shouldbeinserted = (int)(inserts * (i+1) / (text.Length - 1.0));
        int insertnow = shouldbeinserted - inserted;
        for (int j = 0; j < insertnow; j++)
            result += filler;
        inserted += insertnow;
    }

    return result;
}

In action: