Problem with richTextBox colour

Federico Ramirez

Hi, im trying to make a very simple syntax highlighter, just highlight some keywords, but i cant get it to work, this is the code i hav so far

private void richTextBox1_TextChanged(object sender, EventArgs e)
        {
            Regex r = new Regex("\\n");
            String [] lines = r.Split(richTextBox1.Text);
            foreach (string l in lines)
            {
                ParseLine(l);
            }
        }
        
        void ParseLine(string line)
        {
            Regex r = new Regex("[\\s\\t\\n{}():;]");
            String[] tokens = r.Split(line);
            foreach (string token in tokens)
            {
                richTextBox1.SelectionColor = Color.Black;

                String[] keywords = { "program", "begin", "end" };

                for (int i = 0; i < keywords.Length; i++)
                {
                    if (keywords[i] == token)
                    {
                        //richTextBox1.SelectionStart = richTextBox1.Text.Length - keywords[i].Length;
                        //richTextBox1.SelectionLength = keywords[i].Length;
                        richTextBox1.SelectionColor = Color.Blue;
                    }
                }
            }
        }
It seems i have to select the text to colour it, but when i do it then starts from the beggining of the keyword...

2 Replies

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Federico Ramirez18y ago

thanks, its kind of working, the problem is that when it finds that word, it selects it and changes the color, but then when i press space it goes back to the beggining of the word, or if i put the cursor at the end and press space, the cursor goes after the first letter, it seems the if is still executing...

void ParseLine(string line)
        {
            Regex r = new Regex("[\\s\\t\\n{}():;]");
            String[] tokens = r.Split(line);
            foreach (string token in tokens)
            {
                richTextBox1.SelectionColor = Color.Black;

                String[] keywords = { "program", "begin", "end" };

                for (int i = 0; i < keywords.Length; i++)
                {
                    if (keywords[i] == token)
                    {
                        //richTextBox1.SelectionStart = richTextBox1.Text.Length - keywords[i].Length;
                        richTextBox1.Select(richTextBox1.Text.Length - keywords[i].Length, keywords[i].Length);
                        //richTextBox1.SelectionLength = keywords[i].Length;
                        richTextBox1.SelectionColor = Color.Blue;
                        richTextBox2.Text = Convert.ToString(richTextBox1.Text.Length);
                        richTextBox1.DeselectAll();
                    }
                }
            }
        }

Scott Lysle18y ago
To select a word from a rich text box control, you use richtextbox.Select(startPosition, Length). Once you have selected it, you can operate on the selection; the following will cycle between bold and unbolded for example:

if (!(rtbDoc.SelectionFont == null))

{

System.Drawing.Font currentFont = rtbDoc.SelectionFont;

System.Drawing.FontStyle newFontStyle;

newFontStyle = rtbDoc.SelectionFont.Style ^ FontStyle.Bold;

rtbDoc.SelectionFont = new Font(currentFont.FontFamily, currentFont.Size,

newFontStyle);

}

To change the selection's color, you'd do something like this (this shows using a color dialog):

ColorDialog1.Color = rtbDoc.ForeColor;

if (ColorDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK)

{

rtbDoc.SelectionColor = ColorDialog1.Color;

}