LinkLabel needing more space than TextRenderer.MeasureText says

Question

If I give TextRenderer.MeasureText some text to measure and width to use it will return the height needed to display that text.

private static int CalculateHeight(string text, Font font, int width)
{
    Size size = TextRenderer.MeasureText(text, font, new Size(width, Int32.MaxValue), TextFormatFlags.NoClipping | TextFormatFlags.WordBreak);
    return size.Height;
}

If I give that text, width and height to a LinkLabel it would display the text in the width and height provided with nothing clipped off.

However, if I put a Link into the LinkLabel.Links collection, the LinkLabel will draw the text with what appears to be a little more spacing between the characters and at times this will cause the end of the text to be clipped. Is there anyway to prevent this? I've tried adding padding when there is a link, but there's no reliable way to know exactly how much more space will be needed. Are there any other ways to do this?

Answer 1

You should use Control.GetPreferredSize method to calculate width or height needed for control (LinkLabel in your case). You should not use MeasureText for such purposes, more detailed explanation you can find here (Accuracy of TextRenderer.MeasureText results.)

Answer 2

If a LinkLabel contains more than one link, or there are parts of text which are nor in a link, then the control uses Graphics.DrawString/MeasureString instead of TextRenderer.DrawText/MeasureText. You can easily see it in action, the biggest difference in rendering is with the small L letter:

linkLabel1.Text = new string('l', 100); // 100 x small L
linkLabel1.LinkArea = new LinkArea(0, 50);
linkLabel2.Text = new string('l', 100); // 100 x small L 

Answer 3

TextRenderer.MeasureText is a managed wrapper for the DrawTextEx API. The value returned comes from the lprc struct. You might want to look at that API for more details.

Answer 4

I guess you could remove the style that makes it underline. linkLabel.Styles.Add("text-decoration", "none"); but then of course it wouldn't look like a link. :-/

Another solution would be to add the padding yourself I guess.

int heightBefore = linkLabel.Height;
int fontHeight = CalculateHeight(linkLabel.Text, linkLabel.Font, linkLabel.Width);
int paddingHeight = heightBefore - fontHeight;
linkLabel.Font = otherFont;
linkLabel.Height = CalculateHeight(linkLabel.Text, otherFont, linkLabel.Width);
linkLabel.Height += paddingHeight;

Not the prettiest of solutions, but I would guess it works.