Displaying ToolTip to MouseHover Text

Question

Related to this question: Displaying tooltip on mouse hover of a text

How can I do the same thing on a keyword in the RichTextBox but not a link?

In RichTextBox I type:

Hello World, How are You?

I set hovering the word "World" for tooltip and when it hovers ToolTip will appear saying "this is world"!

But if it hovers out of the RichTextBox or in the word "World" itself, tooltip will disappear.

Answer 1

It's a little simple. You have to use the GetCharIndexFromPosition method of your RichTextBox to get the Char index under the Mouse Pointer, make some simple loops to find the whole word and then show it in a Tooltip popup normally. Here is the code:

    string punctuations = " ,.;!?'\")]}\n";
    //This saves your words with their corresponding definitions/details
    Dictionary<string, string> dict = new Dictionary<string, string>(StringComparer.CurrentCultureIgnoreCase);
    ToolTip tt = new ToolTip();
    int k;
    int lineBreakIndex = 60;
    int textHeight;
    //MouseMove event handler for your richTextBox1
    private void richTextBox1_MouseMove(object sender, MouseEventArgs e){
        if (richTextBox1.TextLength == 0) return;
        Point lastCharPoint = richTextBox1.GetPositionFromCharIndex(richTextBox1.TextLength - 1);
        if (e.Y > textHeight ||  (e.Y  >= lastCharPoint.Y && e.X > lastCharPoint.X + textHeight - lastCharPoint.Y))            
        {
            tt.Hide(richTextBox1);
            k = -1;
            return;
        } 
        int i = richTextBox1.GetCharIndexFromPosition(e.Location);            
        int m = i, n = i;
        while (m>-1&&!punctuations.Contains(richTextBox1.Text[m])) m--;            
        m++;
        while (n<richTextBox1.TextLength&&!punctuations.Contains(richTextBox1.Text[n])) n++;
        if (n > m){
            string word = richTextBox1.Text.Substring(m, n - m);
            if (dict.ContainsKey(word)){
                if (k != m){
                    tt.ToolTipTitle = word;
                    tt.Show(dict[word], richTextBox1, e.X, e.Y + 10);
                    k = m;
                }
            }
            else{
                tt.Hide(richTextBox1);
                k = -1;
            }
        }
    }
    //This will get the entry text with lines broken.
    private string GetEntryText(string key){
        string s = dict[key];
        int lastLineEnd = lineBreakIndex;
        for (int i = lastLineEnd; i < s.Length; i += lineBreakIndex)
        {
            while (s[i] != ' '){
                if (--i < 0) break;                    
            }
            i++;
            s = s.Insert(i, "\n");
            lastLineEnd = i+1;
        }
        return s;
    }
    //MouseLeave event handler for your richTextBox1
    private void richTextBox1_MouseLeave(object sender, EventArgs e){
        tt.Hide(richTextBox1);
        k = -1;
    }
    //ContentsResized event handler for your richTextBox1
    private void richTextBox1_ContentsResized(object sender, ContentsResizedEventArgs e)
    {
        textHeight = e.NewRectangle.Height;
    }
    //Here are some sample words with definitions:
    dict.Add("world", "- World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth.");
    dict.Add("geek", "- A person who is single-minded or accomplished in scientific or technical pursuits but is felt to be socially inept");