Question

I’m creating a GroupBox at runtime and setting its Text property. Usually, the text is only on one line, but sometimes it wraps. The problem is that the controls contained in the GroupBox cover up the GroupBox’s text.

What I’d like to do is determine if and when the text wraps. Specifically, I’d like to determine how much extra height the wrapped text takes up as compared to a single line. That way, I can reposition the GroupBox’s controls and adjust its height.

Initially, I thought I’d do this by calling the GroupBox’s CreateGraphics() method, and using the Graphics to measure the string. Something like this:

private void SetGroupBoxText(GroupBox grp, string text)
{
    const int somePadding = 10;

    Graphics g = grp.CreateGraphics();
    SizeF textSize = g.MeasureString(text, grp.Font);
    if (textSize.Width > (grp.Width - somePadding))
    {
        // Adjust height, etc.
    }
}

The problem is that the size generated by g.MeasureString(text, grp.Font) doesn’t seem to be accurate. I determined that it wasn’t accurate by putting enough of a single character to cause a wrap, then measuring the resulting string.

For example, it took 86 pipes (|) to until a wrap happened. When I measured that string, its width was ~253. And it took 16 capital W’s to force a wrap – its string had a width of ~164. These were the two extremes that I tested. My GroupBox’s width was 189. (a’s took 29 and had a width of ~180, O’s took 22 and had a width of ~189)

Does anyone have any ideas? (hacks, WinAPI, etc. are welcome solutions)

Answer 1

This code was derived from the Reference Source, it should be very close. It returns the number of pixels added to the text height when it displays more than one line of text:

    public static int GetGroupboxTextHeightExtra(GroupBox box) {
        TextFormatFlags flags = TextFormatFlags.Default | TextFormatFlags.TextBoxControl | TextFormatFlags.WordBreak | TextFormatFlags.PreserveGraphicsTranslateTransform | TextFormatFlags.PreserveGraphicsClipping;
        Rectangle rc = new Rectangle(0, 0, box.Width - 2 * 7, box.Height);
        Size size;
        using (Graphics gr = Application.OpenForms[0].CreateGraphics()) {
            size = TextRenderer.MeasureText(gr, box.Text, box.Font, rc.Size, flags);
        }
        return size.Height - box.Font.Height;
    }