Measure String inside RichTextBox Control

Question

Hi All

Can somebody please explain how I would go about measuring the string inside a richtextbox control so that the I can automatically resize the richtextbox control according to its content?

Thank you

Edit:

I've thought about it, and since the below answer won't work if there are different fonts in the RichTextBox Control, what if, I could get the upper-left coords of the richtextbox control and then get the bottom-right coords of the very last line of text inside the rtb. That would essentially give me the Width and Height of the string inside the RichTextBox Control. Is this possible? Or is this a bad idea to do it this way?

Answer 1

You can measure a string by calling TextRenderer.MeasureText.

However, if the text contains multiple fonts, this will not work.

EDIT: You're looking for the GetPositionFromCharIndex method.
Note that if there are multiple lines, you should take the max of the X coordinates of the last character on each line.

Answer 2

Assuming that someone is typing into the control, you could use an event to fire every time a character is entered (increment counter) and decrement when it is deleted. This would give you a true count.

Edit:

Have you tried this to adjust the height?

richTextBox1.Height = (int)(1.5 * richTextBox1.Font.Height) + richTextBox1.GetLineFromCharIndex(richTextBox1.Text.Length + 1) * richTextBox1.Font.Height + 1 + richTextBox1.Margin.Vertical;

richTextBox1.SelectionStart = 0;

richTextBox1.SelectionStart = richTextBox1.Text.Length;

Or you can do this using Width:

Graphics g = Graphics.FromHwnd(richTextBox1.Handle);

SizeF f = g.MeasureString(richTextBox1.Text, richTextBox1.Font);
richTextBox1.Width = (int)(f.Width)+5;

Answer 3

Try calling GetPreferredSize(Size.Empty). It is defined in the Control class, and if overriden property by the RichTextBoxControl, ought to give you what you are looking for.

If you pass something other than Size.Empty into the method, then it will use that value as a maximum constraint. Using Size.Empty means that the potential size is unbounded.