How to get specific text value from a textbox based upon the mouse position

Question

I have a multi-line text box that displays some values based on data it gets given, (Generally one value per line).

(For the purpose of having a tool tip popup with some 'alternative' data) I would like to get the word (or at the very least the line) that the mouse is hovering over so I can then find what alternative to display.

I have a few ideas of how to do this with calculations based on the text box and font sizes but I do not what to go down this road as the sizes and fonts may change frequently.

So... Is there any way of using the mouses position to grab specific text box text?

Answer 1

Here's an alternate solution. Add this MouseMove event to your TextBox:

private void txtHoverWord_MouseMove(object sender, MouseEventArgs e)
{
    if (!(sender is TextBox)) return;
    var targetTextBox = sender as TextBox;
    if(targetTextBox.TextLength < 1) return;

    var currentTextIndex = targetTextBox.GetCharIndexFromPosition(e.Location);

    var wordRegex = new Regex(@"(\w+)");
    var words = wordRegex.Matches(targetTextBox.Text);
    if(words.Count < 1) return;

    var currentWord = string.Empty;
    for (var i = words.Count - 1; i >= 0; i--)
    {
        if (words[i].Index <= currentTextIndex)
        {
            currentWord = words[i].Value;
            break;
        }
    }
    if(currentWord == string.Empty) return;
    toolTip.SetToolTip(targetTextBox, currentWord);
}